Research Article Liquid-Phase Ethanol Oxidation and...

Research ArticleLiquid-Phase Ethanol Oxidation and Gas-Phase CO OxidationReactions over M Doped (M = Ag Au Pd and Ni) and MM1015840

Codoped CeO2 Nanoparticles

Yohan Park1 Yulri Na1 Debabrata Pradhan2 and Youngku Sohn1

1Department of Chemistry Yeungnam University Gyeongsan 38541 Republic of Korea2Materials Science Centre Indian Institute of Technology Kharagpur 721302 India

Correspondence should be addressed to Youngku Sohn youngkusohnynuackr

Received 14 October 2016 Revised 13 November 2016 Accepted 22 November 2016

Academic Editor Stojan Stavber

Copyright copy 2016 Yohan Park et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Transition metal doped metal oxides have been studied extensively for potential applications to environments and chemicalindustry HereinMdoped (M=Ag Au Pd andNi) andMM1015840 codopedCeO

2nanoparticles (NPs) were prepared by a hydrothermal

method and their liquid-phase ethanol and gas-phase CO oxidation performances were examined by UV-visible absorptionspectroscopy and temperature programmed mass spectrometry respectively The ethanol and CO oxidation performances wereenhanced greatly by metal-doping and were dependent on the relative concentration of codoped metals For ethanol oxidationthe concentration of acetaldehyde became saturated at low levels while that of ethyl acetate continuously increased to become afinal major product For M doped CeO

2NPs the ethanol oxidation performance showed an order of Ni lt Ag lt Pd ≪ Au For

MM1015840 codoped CeO2NPs the activity of Au doped CeO

2deteriorated drastically upon adding other metals (Ag Ni and Pd) as a

cocatalyst

1 Introduction

The hybridization of metal oxides with transition metals hasbeen performed extensively to increase the catalytic (eg COoxidation) efficiency of the oxides [1ndash12] Among the manymetal oxides a reducible CeO

2support has been studied

extensively as a model oxidation catalyst because of its con-vertible redox states (Ce4+Ce3+) and oxygen releasestorageproperties [13ndash17] Doped transition metals include Au andAg [1 5 18ndash32] Because Au and Ag have the same crystalstructure as well as similar lattice constants and metallicbond lengths they can easily form alloys which can promotecatalytic activity [18 19 21] For CO oxidation over AuCeO

2

catalysts Chen et al reported that the oxidation reactivityof adsorbed CO was independent of the Au particle sizewhereas the decomposition reactivity of carbonate bicarbon-ate and formate species was dependent on the particle size itwas higher for larger Au particles [20] To identify the activesites for AuCO

2 Nie et al prepared thiol-protected Au and

observed enhanced CO oxidation activity compared to bareAu [1] Based on this result they concluded that the activesite was the perimeter of Au Au nanoparticles aggregateeasily by sintering at high temperature which can resultin deactivation of Au To avoid the aggregation of Au Qiet al synthesized core-shell AuCeO

2nanocomposites and

observed remarkably enhanced CO oxidation activity [5]Liu et al prepared Ag

119909Au1minus119909

CeO2coreshell nanospheres

by galvanic replacement and observed the catalytic COoxidation activity in the order of AuCeO

2lt AgCeO

2≪

Ag041

Au059

CeO2ltAg064

Au036

CeO2[21] No catalyst

shows the best performance in all reaction systems Fiorenzaet al tested AuCeO

2 AgCeO

2 CuCeO

2 AuAgCeO

2

and AuCuCeO2

catalysts on the oxidation of volatileorganic compounds (2-propanol ethanol and toluene)Theyreported that AuCeO

2was most active for the oxidation

of alcohols AgCeO2showed the best efficiency for total

toluene oxidation and AuAgCeO2and AuCuCeO

2showed

the highest selectivity to partial oxidation [24] Studying

Hindawi Publishing CorporationJournal of ChemistryVolume 2016 Article ID 2176576 11 pageshttpdxdoiorg10115520162176576

2 Journal of Chemistry

alcohol oxidation is very important to understanding of thereaction mechanisms involved in many industrial organicsynthetic processes because of its importance as a fuel [3233] Zhang et al prepared plum-pudding type PdCeO

2

and used it as a visible light photocatalyst for selectiveoxidation of benzylic alcohols to corresponding aldehydesin a process in which photogenerated electron producedsuperoxide radicals thereby facilitating the oxidation [34]Maldotti et al emphasized that Au-H species is an importantintermediate for alcohol oxidation when Au-CeO

2catalyst is

used [32]Motivated by these studies this study examined the

catalytic activity of M doped (M = Ag Au Pd and Ni) andMM1015840 codoped CeO

2for both liquid ethanol and gas-phase

COoxidation reactionsThe catalysts were reacted in a streamof gas-phase CO and liquid-phase ethanol CO oxidation isthe simplest model system understood by a simplified CO +[O]lowast rarr CO

2mechanism while for CH

3CH2OH oxidation

on an oxide support the reactions are very complicatedCH3CH2OH rarr CH

3CH2O(ad) + H(ad) CH

3CH2O(ad) +

[O]lowast rarr CH3CHO CH

3CHO + [O]lowast rarr CH

3COOH and

ethyl acetate (CH3COOCH

2CH3) formation via aldehyde

and hemiacetal (CH3CH(OH)OC

2H5) Because the two oxi-

dation reactions have different mechanisms two systemstogether were investigated to determine the role of dopedmetals and the relative concentrations of two differentmetals

2 Experimental

Cerium oxide (CeO2) nanoparticles (NPs) were synthesized

by a hydrothermal method which is described briefly asfollows 10mL of 01M Ce(NO

3)3sdot6H2O (Sigma-Aldrich

99) was added to 15mL of deionized water in a Teflonbottle Subsequently 20mL of ammonia (28sim30) solutionwas added The solution was fully mixed and the bottlewas tightly capped and placed in an oven (120∘C) for 12 hrsFor the synthesis of metal (Ag Au Pd and Ni) doped andcodoped CeO

2 stoichiometric amounts (MM1015840 = 50mol

14mol 2525mol 41mol and 05mol relative toCe ions) of two differentmetal solutions were added to the Cenitrate solution before capping the bottle and placing it intothe oven Upon the reaction for 12 hrs the final products werecooled naturally and washed repeatedly with deionized waterand ethanol several times The finally collected samples werefully dried in a conventional oven (80∘C)

The morphologies of the samples were examined bytransmission electron microscopy (TEM Hitachi H-7600)operated at 100 kV For this the samples were mountedonto carbon-coated Cu grids X-ray diffraction (XRD PAN-alytical XrsquoPert Pro MPD) was performed to examine thecrystal structures of the dried powder samples using CuK120572 radiation at 40 kV and 30mA The UV-visible (UV-VisSCINCO Neosys-2000) absorption spectra of the powdersamples were recorded The Fourier transform infrared (FT-IR) spectra were obtained using a Thermo Scientific NicoletiS10 spectrometer in ZnSe attenuated total reflection mode

Temperature programmed reduction (TPR) was per-formed to examine the reducibility of the catalyst powder

samples using a Quantachrome CHEMBET equipped with athermal conductivity detector The samples were degassed at150∘C for 2 hrs under nitrogen before being tested by TPRTPR was performed at a heating rate of 20∘Cmin and aflow rate of 40mLmin under 5 H

2N2gas stream CO

oxidation tests were performed in a U-tube (inner diameterof 40mm) quartz reactor loaded with 10mg of the catalystThe temperature heating rate was set to 10∘CminThemixedCO(10)O

2(25)N

2gas was fed to the reactor at a flow

rate of 40mLmin The final gas reaction products weremonitored using a RGA 200 quadrupole mass spectrometer(Stanford Research Systems USA)

The liquid-phase ethanol oxidation reaction was per-formed as follows 10mg of the catalyst and 15mL of ethanolsolvent were mixed in a test tube after which the tube wastightly capped The test tube was then placed in an oven at80∘C (or 40∘C) without stirring Since we tightly capped thetube the oxygen supply will be limited at a certain reactionlevel After a desired reaction time in the oven we took theUV-visible absorption spectrum of the solution in the testtube To detect the final products after the ethanol oxidationwe introduced the solution via a leak valve into the UHVchamber and recorded a mass spectrum

3 Results and Discussion

The metal (Ag Au Pd and Ni) codoped (M and M1015840 = 25and 25mol resp) CeO

2catalysts were examined by TEM

Figure 1 reveals two different (big and small) size distribu-tions one was lt20 nm and the other was lt5 nm The largerand smaller particles could be attributed to bulk CeO

2and

doped metal nanoparticles which could be further clearlyidentified by energy dispersive X-ray spectroscopy and highresolution transmissionmicroscopyThe smaller metal parti-cles could be active sites for the catalytic reactions The AgAu doped sample showed much higher aggregation and theaggregation was found to be in the order of AgAu gtAuNi simAuPd gt NiPd

Material characterization and CO oxidation were focusedonly for Ag and Au doped and codoped CeO

2NPs Figure 2

presents the powder XRD patterns of undoped CeO2and

Au and Ag doped and codoped (05 41 2525 14 and50mol resp) CeO

2catalysts For undoped Ce oxide

several major peaks (red filled circles) were observed at 2120579 =285∘ 330∘ 474∘ 563∘ 590∘ and 693∘ which were assignedto the (111) (200) (220) (311) (222) and (400) planes of thecubic (Fm-3m) structure (JCPDS 034-0394) of CeO

2 respec-

tively [11 12] The major peak at 2120579 = 285∘ showed no criticaldifference in peak position for all the samples This meansthat the crystal lattice of the CeO

2support was not critically

affected by metal-doping On the other hand the broadnessof the peak was somewhat different indicating a differencein particle size The particle sizes of the undoped 5molAg 41mol of AgAu 2525mol of AgAu 14mol ofAgAu and 5mol of Au doped CeO

2were calculated

(using the peak at 2120579 = 285∘) using Scherrerrsquos equation tobe 130 140 124 80 100 and 86 nm respectively For themetal doped samples new peaks (green filled circles) were

Journal of Chemistry 3

Ag 25 Au 25 25mol

Au 25 Ni 2520nm 20nm

20nm20nm mol Nimol Au 25 mol

mol Pd 25 mol mol Pd 25 mol

Figure 1 Typical TEM image of AuAg AuNi AuPd and NiPd codoped (25 and 25mol resp) CeO2catalysts

Cou

nt ra

te (a

rb u

nit)

(111

)(200

)

(111

)

(002

)(220

)

(311

)(222

)

(022

)

(400

)

= 5 0

4 1

25 25

1 4

= 0 5

CeO2

2120579 (degree)70605040302010

Ag Au

Ag Au

Ag Au (mol)Doped

Figure 2 Power X-ray diffraction patterns of undoped CeO2and Au and Ag doped and codoped (05 41 2525 14 and 50mol resp)

CeO2catalysts The red and green filled circles are of cubic CeO

2and Au phases respectively


Abso

rban

ce (a

rb u

nit)

CeO2Ag = 5mol

Au = 5mol

Wavelength (nm)800600400200

1mol 4mol25 mol 25 mol

4mol 1mol

Doped Ag Au

Figure 3 UV-visible diffuse reflectance spectra (expressed in termsof KubelkandashMunk absorbance arbitrary unit) of undoped CeO

2and

Au and Ag doped and codoped (50 05 41 2525 and 14mol)CeO2catalysts Optical microscopy images (inset) show the colors

of the corresponding samples

observed at 2120579 = 381∘ 443∘ and 646∘ corresponding tothe (111) (002) and (022) planes of cubic phase metallic Au[5] The new peaks were the most intense for the AgAu(14mol) doped sample which was attributed to the highercrystallinity No Ag peaks were observed indicating well-dispersed small amorphous states

TheUV-Vis diffuse reflectance characteristics of themetaldoped samples were examined to determine the metal-doping states as shown in Figure 3 For undoped CeO

2

no significant visible light absorption was observed and theabsorption edge was positioned at sim29 eV Upon metal-doping the absorption in the visible region was increasedsignificantly For Ag (5mol) doped CeO

2 the color of the

powder sample became yellow The color became reddish asthe amount of Au was increased and the UV-Vis absorp-tion in the visible region also increased For Au (5mol)doped CeO

2 a broad absorption peak was observed at

approximately 530 nm which was attributed to the surfaceplasmon resonance absorption of Au nanoparticles [30] Forthe AgAu (41 2525 and 14mol) doped samples theabsorption in the longer wavelength region was attributed tothe formation of larger particles

Figure 4 presents the FT-IR spectra of undopedCeO2and

Au and Ag doped and codoped (50 05 41 2525 and 14mol) CeO

2nanoparticles A broad peak was commonly

observed at 3400 cmminus1 which was attributed to the adsorbedsurface OH andor H

2O species The maximum of the broad

peak was shifted to a shorter wavenumber with increasing theamount of Au The complicated vibrational peaks observed

Tran

smitt

ance

(arb

uni

t)

CeO2

Ag = 5mol

Au = 5mol

Wavenumber (cmminus1)1000200030004000

Doped Ag Au

1mol 4mol

25 mol 25 mol

4mol 1mol

Figure 4 FT-IR spectra of undoped CeO2and Au and Ag doped

and codoped (50 05 41 2525 and 14mol) CeO2

H2

cons

umpt

ion

(arb

uni

t)

CeO2

Au = 5mol

H2-TPR

100800600400200

Temperature (∘C)

1mol 4mol

25 mol 25 mol

4mol 1mol

Doped Ag Au

Ag = 5mol

Figure 5 TPR profiles of undoped CeO2and Au and Ag doped and

codoped (50 05 41 2525 and 14mol) CeO2catalysts

between 1300 and 1800 cmminus1 were assigned to C=O C=C andCOO- functional groups [5] which were dependent on thesample states

Figure 5 shows the temperature programmed hydrogenreduction (TPR) profiles of the bare and metal doped CeO

2

catalysts For bare CeO2 two broad peaks were observed at

around 550 and 900∘C The higher temperature peak wasattributed to the reduction of bulk oxygen of CeO

2 The

lower temperature peak was assigned to the reduction ofsurface oxygen The reduction peak for bulk oxygen is


commonly observed for metal doped CeO2 but at a lower

temperature (by sim50∘C) In addition the strong peaks newlyappeared below 400∘C for the metal doped CeO

2 The peak

intensityposition and broadness were dependent on theinteractions between the dopedmetal and the lattice of CeO

2

Because doped Ag and Au are present as the metallic statethe doped metallic nanoparticles could cause the spillover oflattice oxygen by forming AundashOndashCe state to result in easyreduction [19 24] Ce3+ can be formed from Ce4+ by formingAundashO bond and charge transfer from Au to Ce [27] For Au(5mol) doped CeO

2 the lower TPR peak was observed at

approximately 300∘C For AgAu (14 and 2525mol)doped CeO

2 the peak was observed at a somewhat

higher temperature with different intensities For AgAu(41 and 50mol) doped CeO

2 the peak was observed

at lower temperatures indicating stronger interactions withCeO2

Figure 6 presents the 1st and 2nd run CO oxidationconversion profiles for undoped CeO

2and Au and Ag

doped and codoped (50 05 41 2525 and 14mol)CeO2catalysts The CO conversion () was calculated using

([CO]inndash[CO]out)[CO]in times 100 [35 36] T10 is definedas the temperature corresponding to CO conversion of 10As seen in the spectra the CO oxidation onset position wasdramatically different in all samples For the 1st and 2nd runsof bare CeO

2 T10 was observed at 405∘C Upon metal-

dopingT10 was lowered dramatically In the 1st runT

10 ofthe 5mol Au and Ag doped samples was observed at240∘C and 352∘C respectively Compared to that of bareCeO2 T10 was lowered by 165∘C and 53∘C respectively

(bottom left of Figure 6) As the amount of Au was increasedT10 was observed at a lower temperature The order of

catalytic activity was found to be bare CeO2lt AgAu

(50mol) lt AgAu (41mol) lt AgAu (2525mol)lt AgAu (14mol) lt AgAu (05mol) In the 2nd runT10 was drastically changed for the metal doped samples

T10 of the 5mol Au and Ag doped samples was observed

at 295∘C and 262∘C respectively The Au doped sampleshowed a 55∘C increase in T

10 while Ag doped sampleshowed a 90∘C decrease in T

10 The order of the catalyticactivity was bare CeO

2lt AgAu (2525mol) lt AgAu

(05mol) asymp AgAu (41mol) lt AgAu (50mol) ltAgAu (14mol)The AgAu (14mol) showed the high-est activity Compared to T

10 in the 1st run the AgAu(50mol) and AgAu (14mol) samples showed a lowerT10 while other samples showed a higher T

10 in the 2ndrun as shown in the bottom right of Figure 6 In the 2nd runboth the sintering of Au nanoparticles and alloying of twodifferent metals were expected to play a role in determiningthe activity because the sample had already experienced ahigh temperature up to 700∘C The colors of the sampleswere significantly changed after the CO oxidation reactionsParticularly the colors of the AgAu (41mol) AgAu(2525mol) andAgAu (05mol) became dark grey (orblack) after the CO oxidation unlike other three samplesThe corresponding catalysts showed catalyst deactivation inthe 2nd run compared with the 1st run (Figure 6(d)) Thisindicates that change in oxidation state carbon residues

after reaction and sinteringalloying of loaded metals areimportant factors for the determination of catalytic activitySasirekha et al examined CO oxidation under hydrogen-rich conditions for Au and Ag doped and codoped CeO

2

catalysts and reported that the Ag-Ag (5 5) doped sampleshowed the highest CO conversion and selectivity [19] Theenhancement was attributed to bimetallic alloy formation[19 24] On the other hand in the present study the AgAu(2525mol) sample showed the poorest activity amongthe metal doped samples in the 2nd run This suggests thatother factors (eg size and relative distributions) are alsoimportant for determining the activity CO oxidation hascommonly been understood by CO(ad) + [O]lowast rarr CO

2(g)

where [O]lowast is the active surface oxygen The surface oxygenis replenished by molecular oxygen present in air AdsorbedCO is plausibly present at the interface of doped metal andCeO2 on top of metal andor defect sites [31]The crystalline

size (reflecting the surface area) of the samples was estimatedusing the full width at half maximum of the (111) peak andScherrerrsquos equation [12] The order of the size was found tobe AgAu (2525mol) 80 nm lt AgAu (05mol)86 nm lt AgAu (14mol) 100 nm lt AgAu (41mol)124 nm lt bare CeO

2 130 nm lt AgAu (50mol) and

140 nm Based on this the size was not linearly related withthe catalytic activity For this reason the metal-loading isimportant and themetal-support interactions play significantroles in the catalytic activity [37] In the present study T

50for all the samples was observed to be gt300∘C Zhang et alreported significantly lower T

50 for AuCeO2prepared by a

deposition-precipitation method [37] They reported T50 of

63 35 and 17∘C for untreatedH2 andH

2-O2treated samples

respectively They concluded that the surface interactionbetween Au and CeO

2was the most important factor for

the catalytic activity Li et al reported T50 of lt150∘C for

crystalline Cu-CeO2(5ndash8 nm) nanopowders synthesized by a

hydrothermal method [38] The formic acid-treated Co3O4-

CeO2catalysts were reported to show T

50 at 695∘C for COoxidation [39]The CO oxidation catalytic activities for otherCeO2-based catalysts were summarized elsewhere [11]

Ethanol oxidation reaction performances were fullyexamined for all M doped (M=Ag Au Pd andNi) andMM1015840codoped CeO

2NPs by UV-visible absorption spectroscopy

Figure 7 shows the UV-Vis absorption spectra of the ethanolsolutions reacted at 80∘C for 5 days with and without cat-alysts and with different metal-doping concentration statesTwo broad absorption peaks were commonly observed ataround 220 and 280 nm which were tentatively attributedto ethyl acetate (CH

3COOCH

2CH3 EA) and acetaldehyde

(CH3CHO AcA) respectively for the oxidation products

of ethanol Further details were discussed below The EApeak became stronger and increased more sharply than theAcA peak with reaction time The AcA absorption peakintensity increased slightly gradually reaching a certain lowconcentration levelThe presence of EA as amajor andAcA asaminor productwas further confirmedbymass spectrometry(or UV-visible absorption) as discussed in detail belowTo examine the temperature effect we conducted ethanoloxidation experiments at 40∘C and 80∘C As expected theabsorbance of the two peaks was dramatically enhanced upon


1st run

CeO2

Ag = 5molAu = 5mol

Temperature (∘C)700600500400300200100

00

20

40

60

80

100CO

conv

ersio

n (

)

1 mol 4 mol25 mol 25 mol

4 mol 1molDoped Ag Au

(a)

2nd run

Temperature (∘C)700600500400300200100

00

20

40

60

80

100

CO co

nver

sion

()

CeO2

Ag = 5molAu = 5mol1 mol 4 mol25 mol 25 mol


(b)

1st run2nd run

Au=

5mol

14m

ol

25

25m

ol

41m

ol

Ag

=5m

ol

0

minus50

minus100

minus150

T10

(MC

eO2)

minusT

10(b

are)

(c)

Au = 5 mol

14 mol

2525 mol

41 mol

Ag = 5mol

T10

(2nd

)minusT

10

minus100

minus50

0

50

100

(1st)

(d)

Au = 5 mol14 mol2525 mol41 molAg = 5molCeO2

bf C

O o

xaf

CO

ox

(e)

Figure 6 1st (a) and 2nd (b) run temperature programmed CO oxidation conversion () profiles (a b) of undoped CeO2and Au and Ag

doped and codoped (50 05 41 2525 and 14mol) CeO2catalysts The difference (c) in T

10 between the metal doped and bare CeO2

for the 1st and 2nd runs The difference (d) in T10 between the 1st and 2nd runs for the metal doped CeO

2catalysts Optical microscope

images showed the color of the powder samples before and after CO oxidation reactions


Rxn in 5 daysat 80∘C


Wavelength (nm)

350300250Wavelength (nm)

350300250

Doped Ag AuAb

sorb

ance

(arb

uni

t)

10

05

00

15

00

01

02

03

04

Abso

rban

ce (a

rb u

nit)

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)

With reaction timeat 80

∘C5 days4 days3 days2 days1 day (24h)8 h4hAu-(5mol) CeO2

Au = 5molNo catalyst

Ag = 5 molCeO21 mol 4 mol

25 mol 25 mol

4 mol 1 mol

O

O

O

(a)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Ni Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15


Ni = 5 mol4 mol 1 mol

(b)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Pd Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15


Pd = 5 mol4 mol 1 mol

(c)

O

O

O

Au = 5mol


at 80∘C


Wavelength (nm)

350300250

Doped Ni Pd

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Pd = 5 molNi = 5 mol

4 mol 1 mol

(d)

Figure 7 UV-visible absorption spectra of the ethanol oxidation with no catalyst undoped CeO2 M doped (M = Ag Au Pd and Ni) and

MM1015840 codoped (AgAu (a) NiAu (b) PdAu (c) and NiPd (d)) CeO2catalysts at 80∘C for 5 days The left inset in (a) shows the magnified

spectra of the grey shadowed region The right inset in (a) shows the UV-Vis absorption spectra of ethanol oxidation with the 5mol Audoped CeO

2catalyst at 80∘C according to the reaction time

increasing reaction temperatureWithout catalysts no signif-icant ethanol oxidation occurred even at high temperatureFor further ethanol oxidation experiments we selected areaction temperature of 80∘C and a total metal-doping levelof 5mol

For Ag and Au doped and codoped samples (Figure 7(a))a strong absorption peak (below 250 nm) was observed forthe Au (5mol) and AuAg (14mol) doped CeO

2cata-

lysts Without a catalyst no significant absorption peak was

observed even after 5 days The absorption peak (shown inthe right inset of Figure 7(a)) increased with increasingreaction time This was attributed to an increase in reactionproducts that contain C=C andor C=O functional groupsFor the other metal doped samples the absorption peakswere much weaker In addition to the strong absorptionpeak a weaker peak at 280 nm was also observed (in theleft inset of Figure 7) The results suggest that at least tworeaction products (EA and AcA as mentioned above) were


present in the ethanol solution The catalytic activity wasobserved to be in the order of bare CeO

2asymp 2525 lt 41 lt

50 ≪ 14 lt 05 (AgAumol) When the concentration ofAu was the same as or lower than that of Ag the activitydeteriorated drastically For Au and Ni doped and codopedsamples (Figure 7(b)) the catalytic activity was decreasedupon adding Ni as a cocatalyst The activity was found to bein the order of 50 lt 41≪ 2525 lt 14 lt 05 (NiAumol)For Au and Pd doped and codoped samples (Figure 7(c))the oxidation performance was more greatly decreased uponadding Pd as a cocatalyst and found to be in the order of 41 le2525asymp 14asymp 50≪ 05 (PdAumol) ForNi and Pd dopedand codoped samples (Figure 7(d)) the catalytic activity wasobserved to be in the order of 50 lt 05≪ 41 asymp 14 le 2525(NiPdmol) The catalytic activity of the NiPd codopedsamples showed much higher catalytic activity than those ofthe single M- (Ni and Pd) doped samples For comparisonof the catalytic activities of single M doped CeO

2NPs the

ethanol oxidation performance showed an order of undopedasympNi ltAg lt Pd≪Au Interestingly the Ni-doping showed noincrease in catalytic activity for ethanol oxidation

For ethanol oxidation on a metal doped CeO2power

sample since the reaction mechanism was much more com-plicated than expected on a single crystal surface we proposethe following simplified mechanisms which are discussed ingreater detail below [32]

Acetaldehyde hemiacetal and ethyl acetate formationfrom ethanol is as follows

CH3CH2OndashH 997888rarr CH

3CH2O (ad) +H (ad) (1)

CH3CH2O (ad) +O species

997888rarr CH3CHO (ad) +OH (ad)

(2)

CH3CH2O (ad) ndashM

997888rarr CH3CHO (minor) +MH hydride shift

(3)

CH3CHO +O (ad) 997888rarr CH

3COO (ad) +H (ad)

997888rarr CH3COOH

(4)

CH3COOH (ad) + CH3CH2OH (ad)

997888rarr CH3COOCH

2CH3+H2O

(5)

2CH3CHO (ad) 997888rarr CH

3COOCH

2CH3 (6)

CH3CHO (ad) + CH3CH2OH (ad)

997888rarr CH3CH (OH)OC

2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)

The rate constant for each step is controlled by the surfacearea and metal-support interaction (or surface activity) Inreaction (1) the OndashH bond of ethanol dissociates to formCH3CH2O which may be mainly adsorbed onto the doped

metal siteThis then turns into adsorbedCH3CHOvia nearby

active oxygen species in (2) or the adsorbed CH3CH2O on

metal desorbs as CH3CHO (acetaldehyde) in response to a

hydride shift reaction in (3) [32 40] Although we have nodirect evidence of the hydride shift reaction the reactionprocess is highly plausible The acetaldehyde in (4) furtherprecedes oxidation reactions to form CH

3COOH (acetic

acid) if active oxygen species are available nearby Otherwisethe CH

3COOH with ethanol in (5) and 2CH

3CHO in (6)

react to form CH3COOCH

2CH3(ethyl acetate) In reaction

(7) CH3CHO and ethanol formCH

3CH(OH)OC

2H5(hemi-

acetal) which is converted to ethyl acetate Consequentlyethyl acetate (CH

3COOCH

2CH3) is formed as a final oxi-

dation product which was confirmed by mass spectrometryIn the present UV-Vis spectra two products of ethyl acetate(major) and acetaldehyde (minor) were observed For alcoholoxidation on the Au-CeO

2catalyst Maldotti et al reported

that the Au-H species is an important intermediate [32] Thisindicates that the hydride shift reaction is facilitated by activedopedmetalsThe present study showed that the Au-rich cat-alyst produced much higher oxidation products and the Auspecies is more active than other metal species (Ag Ni andPd)The reference UV-Vis spectra (Figure 8(a)) were checkedfor four plausible ethanol oxidation products acetaldehydeethyl acetate acetone and acetic acid and the stronger andweaker peak positions near 220 and 280 nm were assignedto the UV-Vis absorptions of ethyl acetate and acetaldehyderespectively Figure 8(b) displays the mass spectrum of thesolution sample after reaction relative to those of the referencesolvents (ethyl acetate and ethanol) As shown in the massspectrum the oxidation product in ethanol matched thatof the reference ethyl acetate well In addition the smell ofthe two samples was very similar As a result we concludedthat the final major product was ethyl acetate For someother extra mass fragmentation signals (59 73 and 75 amu)although no reference data were available the fragmentationsappeared to form from the hemiacetal as shown in reaction(7) Abad et al extensively studied oxidation of alcoholscatalyzed by AuCeO

2[40] and proposed a reaction of (7)

mentioned above in which hemiacetal was detected by H-NMR We have excluded diethyl ether as a major producteven though it could be formed by 2C

2H5OHrarrC

2H5OC2H5

+ H2O because the UV-visible absorption intensity (even

measuredwith 50 solution) was extremely low (Figure 8(a))when compared with that of the sample We also detected nofragmentation signals of diethyl ether by mass spectrometryThe acetone formation reaction 2CH

3CHOrarr CH

3COCH

3

(acetone) + CO2+ H2 was excluded due to absence of the

mass signal Acetic acid as a major product was also excludedbecause the solution is not acidic the mass signal is absentand it did not smell like acetic acid Table 1 summarizes thesizes of the metal-loaded CeO

2estimated using Scherrerrsquos

equation As for the CO oxidation the ethanol oxidationactivity was also found to be more loaded metal (and therelative concentrations) dependent than the size-dependent

4 Conclusion

To increase the catalytic activity of bare CeO2 the CeO

2

matrix was doped and codoped with Ag Au Pd and Ni bya hydrothermal method The novelty of the present study


Table 1 Particles sizes of the metal-loaded CeO2estimated using Scherrerrsquos equation

Loaded MM1015840 50mol (nm) 41mol (nm) 2525mol (nm) 14mol (nm) 05mol (nm)Ag Au 140 124 80 100 86Ni Au 152 123 106 82 86Pd Au 151 127 121 90 86Ni Pd 152 111 147 121 151

Catalysts without stirring

Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50

Different smellAcetaldehyde sim1

Acetone sim1

Different smellAcetic acid 01

Ethyl acetate 01


(a)

Ethyl acetate(reference)

O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

OH Before reaction(ETOH)

50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce

250 300Wavelength (nm)

(b)

Figure 8 UV-Vis absorption spectra (a) of standard samples of acetaldehyde (1) acetone (1) acetic acid (01) and ethyl acetate (01)Mass spectra (b) of reference samples (ethyl acetate and ethanol) and the solution sample after reactionThe inset shows theUV-Vis absorptionspectrum of the corresponding sample solution Blue and red lowast indicate the peak positions for acetaldehyde and ethyl acetate respectively

was that the catalytic efficiency of doped and codoped CeO2

was tested for both gas-phase CO and liquid-phase ethanoloxidation reactions For the 1st and 2nd runs of bare CeO

2

T10 was observed at 405∘C T

10 of bare CeO2for CO oxi-

dation was lowered significantly by 165∘C uponmetal (AgAu= 14mol) doping There were some synergic effects uponcodoping for the CO oxidation The CO oxidation activityvaries with the relative concentrations of two differentmetalsSintering and alloying of two different metals were found toplay important roles in the CO oxidation activity

For liquid-phase ethanol oxidation two liquid productsof ethyl acetate (major 120582max = 220 nm) and acetaldehyde(minor 120582max = 280 nm) were observed by UV-Vis absorptionspectroscopyThe concentration of acetaldehyde (CH

3CHO)

reached a saturation point while that of ethyl acetate(CH3COOCH

2CH3) dramatically increased with reaction

time These findings indicate that acetaldehyde speciespromptly undergo further reaction to form a major productethyl acetate whichwas confirmed bymass spectrometry andUV-visible absorption Undoped CeO

2produces negligible

acetaldehyde which is direct evidence that a hydride shiftreaction CH

3CH2O(ad)-MrarrCH

2CHO+MH is an impor-

tant step for acetaldehyde production for metal-loaded CeO2

catalysts For M- (single) doped CeO2NPs the ethanol

oxidation performance showed an order of Ni lt Ag lt Pd ≪Au For MM1015840 codoped CeO

2NPs the activity of Au doped

CeO2deteriorated drastically upon adding another metals

(Ag Ni and Pd) as cocatalyst The Au-rich CeO2catalyst

showed higher catalytic activity On the other hand the NiPd codoped sample showed much higher catalytic activitycompared with the single M- (Ni and Pd) doped samplesThis study provides further insights into the development ofcatalysts applicable to a range of oxidation reactions

Competing Interests

The authors declare no conflict of interests

Acknowledgments

This study was supported by the 2015 Yeungnam UniversityResearch Grant

References

[1] X Nie H Qian Q Ge H Xu and R Jin ldquoCO oxidationcatalyzed by oxide-supported Au

25(SR)18

nanoclusters and


identification of perimeter sites as active centersrdquo ACS Nanovol 6 no 7 pp 6014ndash6022 2012

[2] H-F Li N Zhang P Chen M-F Luo and J-Q Lu ldquoHigh sur-face area AuCeO

2catalysts for low temperature formaldehyde

oxidationrdquoApplied Catalysis B Environmental vol 110 pp 279ndash285 2011

[3] K Y Ho and K L Yeung ldquoEffects of ozone pretreatment on theperformance of AuTiO

2catalyst for CO oxidation reactionrdquo

Journal of Catalysis vol 242 no 1 pp 131ndash141 2006[4] K Y Ho and K L Yeung ldquoProperties of TiO

2support and the

performance of AuTiO2catalyst for CO oxidation reactionrdquo

Gold Bulletin vol 40 no 1 pp 15ndash30 2007[5] J Qi J Chen G Li S Li Y Gao and Z Tang ldquoFacile

synthesis of core-shell AuCeO2nanocomposites with remark-

ably enhanced catalytic activity for CO oxidationrdquo Energy andEnvironmental Science vol 5 no 10 pp 8937ndash8941 2012

[6] D Jiang W Wang L Zhang Y Zheng and Z Wang ldquoInsightsinto the surface-defect dependence of photoreactivity overCeO2nanocrystals with well-defined crystal facetsrdquo ACS Catal-

ysis vol 5 no 8 pp 4851ndash4858 2015[7] W Lei T Zhang L Gu et al ldquoSurface-structure sensitivity

of CeO2nanocrystals in photocatalysis and enhancing the

reactivity with nanogoldrdquo ACS Catalysis vol 5 no 7 pp 4385ndash4393 2015

[8] B Li T Gu T Ming J Wang P Wang and J C Yu ldquoGoldcore)(ceria shell) nanostructures for plasmon-enhanced cat-alytic reactions under visible lightrdquo ACS Nano vol 8 no 8 pp8152ndash8162 2014

[9] P Lu B Qiao N Lu et al ldquoPhotochemical deposition of highlydispersed Pt nanoparticles on porous CeO

2nanofibers for the

water-gas shift reactionrdquoAdvanced FunctionalMaterials vol 25no 26 pp 4153ndash4162 2015

[10] L Meng A-P Jia J-Q Lu L-F Luo W-X Huang and M-FLuo ldquoSynergetic effects of PdO species on CO oxidation overPdO-CeO

2catalystsrdquo Journal of Physical Chemistry C vol 115

no 40 pp 19789ndash19796 2011[11] Y Park S K Kim D Pradhan and Y Sohn ldquoThermal H

2-

treatment effects on COCO2conversion over Pd-doped CeO

2

comparison with Au and Ag-doped CeO2rdquo Reaction Kinetics

Mechanisms and Catalysis vol 113 no 1 pp 85ndash100 2014[12] Y Park S K Kim D Pradhan and Y Sohn ldquoSurface treatment

effects on CO oxidation reactions over Co Cu and Ni-dopedand codopedCeO

2catalystsrdquoChemical Engineering Journal vol

250 pp 25ndash34 2014[13] B Xu Q Zhang S YuanM Zhang and T Ohno ldquoMorphology

control and photocatalytic characterization of yttrium-dopedhedgehog-like CeO

2rdquo Applied Catalysis B Environmental vol

164 pp 120ndash127 2015[14] W Huang and Y Gao ldquoMorphology-dependent surface chem-

istry and catalysis of CeO2nanocrystalsrdquo Catalysis Science and

Technology vol 4 no 11 pp 3772ndash3784 2014[15] Y Gao W Wang S Chang and W Huang ldquoMorphology

effect of CeO2support in the preparation metal-support

interaction and catalytic performance of PtCeO2catalystsrdquo

ChemCatChem vol 5 no 12 pp 3610ndash3620 2013[16] Y Zhang N Zhang Z-R Tang and Y-J Xu ldquoA unique

silk mat-like structured PdCeO2as an efficient visible light

photocatalyst for green organic transformation in waterrdquo ACSSustainable Chemistry amp Engineering vol 1 no 10 pp 1258ndash1266 2013

[17] W G Shin H J Jung H G Sung H S Hyun and YSohn ldquoSynergic CO oxidation activities of boron-CeO

2hybrid

materials prepared by dry and wet milling methodsrdquo CeramicsInternational vol 40 no 8 pp 11511ndash11517 2014

[18] H Wu P Wang H He and Y Jin ldquoControlled synthesisof porous AgAu bimetallic hollow nanoshells with tunableplasmonic and catalytic propertiesrdquo Nano Research vol 5 no2 pp 135ndash144 2012

[19] N Sasirekha P Sangeetha and Y-W Chen ldquoBimetallic AundashAgCeO

2catalysts for preferential oxidation ofCO inhydrogen-

rich stream effect of calcination temperaturerdquo The Journal ofPhysical Chemistry C vol 118 no 28 pp 15226ndash15233 2014

[20] S Chen L Luo Z Jiang and W Huang ldquoSize-dependent reac-tion pathways of low-temperature CO oxidation on AuCeO

2

catalystsrdquo ACS Catalysis vol 5 no 3 pp 1653ndash1662 2015[21] D LiuW Li X Feng andY Zhang ldquoGalvanic replacement syn-

thesis of Ag119909Au1minus119909

CeO2(0 le x le 1) coreshell nanospheres

with greatly enhanced catalytic performancerdquoChemical Sciencevol 6 pp 7015ndash7019 2015

[22] Y Kang M Sun and A Li ldquoStudies of the catalytic oxidationof CO over AgCeO

2catalystrdquo Catalysis Letters vol 142 no 12

pp 1498ndash1504 2012[23] S Chang M Li Q Hua et al ldquoShape-dependent inter-

play between oxygen vacancies and AgndashCeO2interaction in

AgCeO2catalysts and their influence on the catalytic activityrdquo

Journal of Catalysis vol 293 pp 195ndash204 2012[24] R Fiorenza C Crisafulli G G Condorelli F Lupo and S Scire

ldquoAu-AgCeO2and Au-CuCeO

2Catalysts for volatile organic

compounds oxidation and CO preferential oxidationrdquo CatalysisLetters vol 145 no 9 pp 1691ndash1702 2015

[25] J Zhang L Li X Huang and G Li ldquoFabrication of AgndashCeO2

core-shell nanospheres with enhanced catalytic performancedue to strengthening of the interfacial interactionsrdquo Journal ofMaterials Chemistry vol 22 no 21 pp 10480ndash10487 2012

[26] A Leyva-Perez D Combita-Merchan J R Cabrero-AntoninoS I Al-Resayes and A Corma ldquoOxyhalogenation of activatedarenes with nanocrystalline ceriardquo ACS Catalysis vol 3 no 2pp 250ndash258 2013

[27] Y Liu H Li J Yu DMao andG Lu ldquoElectronic storage capac-ity of ceria role of peroxide inAux supported onCeO

2(111) facet

and CO adsorptionrdquo Physical Chemistry Chemical Physics vol17 no 41 pp 27758ndash27768 2015

[28] D Jiang WWang S Sun L Zhang and Y Zheng ldquoEquilibrat-ing the plasmonic and catalytic roles of metallic nanostructuresin photocatalytic oxidation over Au-modified CeO

2rdquo ACS

Catalysis vol 5 no 2 pp 613ndash621 2015[29] M M Khan S A Ansari M O Ansari B K Min J Lee and

M H Cho ldquoBiogenic fabrication of AuCeO2nanocomposite

with enhanced visible light activityrdquo Journal of Physical Chem-istry C vol 118 no 18 pp 9477ndash9484 2014

[30] A Tanaka K Hashimoto and H Kominami ldquoPreparation ofAuCeO

2exhibiting strong surface plasmon resonance effective

for selective or chemoselective oxidation of alcohols to alde-hydes or ketones in aqueous suspensions under irradiation bygreen lightrdquo Journal of the American Chemical Society vol 134no 35 pp 14526ndash14533 2012

[31] H Y Kim H M Lee and G Henkelman ldquoCO oxidationmechanism on CeO

2-supported Au nanoparticlesrdquo Journal of

the American Chemical Society vol 134 no 3 pp 1560ndash15702012

[32] A Maldotti A Molinari R Juarez and H Garcia ldquoPhotoin-duced reactivity of AundashH intermediates in alcohol oxidation by


gold nanoparticles supported on ceriardquoChemical Science vol 2no 9 pp 1831ndash1834 2011

[33] L Vivier andDDuprez ldquoCeria-based solid catalysts for organicchemistryrdquo ChemSusChem vol 3 no 6 pp 654ndash678 2010

[34] N Zhang S Liu X Fu and Y-J Xu ldquoA simple strategy forfabrication of ldquoplum-puddingrdquo type PdCeO

2semiconductor

nanocomposite as a visible-light-driven photocatalyst for selec-tive oxidationrdquo Journal of Physical Chemistry C vol 115 no 46pp 22901ndash22909 2011

[35] Y Sohn ldquoSiO2nanospheres modified by Ag nanoparticles sur-

face charging and CO oxidation activityrdquo Journal of MolecularCatalysis A Chemical vol 379 pp 59ndash67 2013

[36] W J Kim D Pradhan and Y Sohn ldquoFundamental natureand CO oxidation activities of indium oxide nanostructures1D-wires 2D-plates and 3D-cubes and donutsrdquo Journal ofMaterials Chemistry A vol 1 no 35 pp 10193ndash10202 2013

[37] R-R Zhang L-H Ren A-H Lu and W-C Li ldquoInfluence ofpretreatment atmospheres on the activity of AuCeO

2catalyst

for low-temperature CO oxidationrdquo Catalysis Communicationsvol 13 no 1 pp 18ndash21 2011

[38] Y Li Y Cai X Xing N Chen D Deng and YWang ldquoCatalyticactivity for CO oxidation of CundashCeO

2composite nanoparticles

synthesized by a hydrothermal methodrdquo Analytical Methodsvol 7 no 7 pp 3238ndash3245 2015

[39] R Shang Y Duan X Zhong W Xie Y Luo and L HuangldquoFormic acid modified Co

3O4-CeO

2catalysts for CO oxida-

tionrdquo Catalysts vol 6 no 3 p 48 2016[40] A Abad P Concepcion A Corma and H Garcıa ldquoA collab-

orative effect between gold and a support induces the selectiveoxidation of alcoholsrdquo Angewandte ChemiemdashInternational Edi-tion vol 44 no 26 pp 4066ndash4069 2005

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


alcohol oxidation is very important to understanding of thereaction mechanisms involved in many industrial organicsynthetic processes because of its importance as a fuel [3233] Zhang et al prepared plum-pudding type PdCeO

2

and used it as a visible light photocatalyst for selectiveoxidation of benzylic alcohols to corresponding aldehydesin a process in which photogenerated electron producedsuperoxide radicals thereby facilitating the oxidation [34]Maldotti et al emphasized that Au-H species is an importantintermediate for alcohol oxidation when Au-CeO

2catalyst is

used [32]Motivated by these studies this study examined the

catalytic activity of M doped (M = Ag Au Pd and Ni) andMM1015840 codoped CeO

2for both liquid ethanol and gas-phase

COoxidation reactionsThe catalysts were reacted in a streamof gas-phase CO and liquid-phase ethanol CO oxidation isthe simplest model system understood by a simplified CO +[O]lowast rarr CO

2mechanism while for CH

3CH2OH oxidation

on an oxide support the reactions are very complicatedCH3CH2OH rarr CH

3CH2O(ad) + H(ad) CH

3CH2O(ad) +

[O]lowast rarr CH3CHO CH

3CHO + [O]lowast rarr CH

3COOH and

ethyl acetate (CH3COOCH

2CH3) formation via aldehyde

and hemiacetal (CH3CH(OH)OC

2H5) Because the two oxi-

dation reactions have different mechanisms two systemstogether were investigated to determine the role of dopedmetals and the relative concentrations of two differentmetals

2 Experimental

Cerium oxide (CeO2) nanoparticles (NPs) were synthesized

by a hydrothermal method which is described briefly asfollows 10mL of 01M Ce(NO

3)3sdot6H2O (Sigma-Aldrich

99) was added to 15mL of deionized water in a Teflonbottle Subsequently 20mL of ammonia (28sim30) solutionwas added The solution was fully mixed and the bottlewas tightly capped and placed in an oven (120∘C) for 12 hrsFor the synthesis of metal (Ag Au Pd and Ni) doped andcodoped CeO

2 stoichiometric amounts (MM1015840 = 50mol

14mol 2525mol 41mol and 05mol relative toCe ions) of two differentmetal solutions were added to the Cenitrate solution before capping the bottle and placing it intothe oven Upon the reaction for 12 hrs the final products werecooled naturally and washed repeatedly with deionized waterand ethanol several times The finally collected samples werefully dried in a conventional oven (80∘C)

The morphologies of the samples were examined bytransmission electron microscopy (TEM Hitachi H-7600)operated at 100 kV For this the samples were mountedonto carbon-coated Cu grids X-ray diffraction (XRD PAN-alytical XrsquoPert Pro MPD) was performed to examine thecrystal structures of the dried powder samples using CuK120572 radiation at 40 kV and 30mA The UV-visible (UV-VisSCINCO Neosys-2000) absorption spectra of the powdersamples were recorded The Fourier transform infrared (FT-IR) spectra were obtained using a Thermo Scientific NicoletiS10 spectrometer in ZnSe attenuated total reflection mode

Temperature programmed reduction (TPR) was per-formed to examine the reducibility of the catalyst powder

samples using a Quantachrome CHEMBET equipped with athermal conductivity detector The samples were degassed at150∘C for 2 hrs under nitrogen before being tested by TPRTPR was performed at a heating rate of 20∘Cmin and aflow rate of 40mLmin under 5 H

2N2gas stream CO

oxidation tests were performed in a U-tube (inner diameterof 40mm) quartz reactor loaded with 10mg of the catalystThe temperature heating rate was set to 10∘CminThemixedCO(10)O

2(25)N

2gas was fed to the reactor at a flow

rate of 40mLmin The final gas reaction products weremonitored using a RGA 200 quadrupole mass spectrometer(Stanford Research Systems USA)

The liquid-phase ethanol oxidation reaction was per-formed as follows 10mg of the catalyst and 15mL of ethanolsolvent were mixed in a test tube after which the tube wastightly capped The test tube was then placed in an oven at80∘C (or 40∘C) without stirring Since we tightly capped thetube the oxygen supply will be limited at a certain reactionlevel After a desired reaction time in the oven we took theUV-visible absorption spectrum of the solution in the testtube To detect the final products after the ethanol oxidationwe introduced the solution via a leak valve into the UHVchamber and recorded a mass spectrum

3 Results and Discussion

The metal (Ag Au Pd and Ni) codoped (M and M1015840 = 25and 25mol resp) CeO

2catalysts were examined by TEM

Figure 1 reveals two different (big and small) size distribu-tions one was lt20 nm and the other was lt5 nm The largerand smaller particles could be attributed to bulk CeO

2and

doped metal nanoparticles which could be further clearlyidentified by energy dispersive X-ray spectroscopy and highresolution transmissionmicroscopyThe smaller metal parti-cles could be active sites for the catalytic reactions The AgAu doped sample showed much higher aggregation and theaggregation was found to be in the order of AgAu gtAuNi simAuPd gt NiPd

Material characterization and CO oxidation were focusedonly for Ag and Au doped and codoped CeO

2NPs Figure 2

presents the powder XRD patterns of undoped CeO2and

Au and Ag doped and codoped (05 41 2525 14 and50mol resp) CeO

2catalysts For undoped Ce oxide

several major peaks (red filled circles) were observed at 2120579 =285∘ 330∘ 474∘ 563∘ 590∘ and 693∘ which were assignedto the (111) (200) (220) (311) (222) and (400) planes of thecubic (Fm-3m) structure (JCPDS 034-0394) of CeO

2 respec-

tively [11 12] The major peak at 2120579 = 285∘ showed no criticaldifference in peak position for all the samples This meansthat the crystal lattice of the CeO

2support was not critically

affected by metal-doping On the other hand the broadnessof the peak was somewhat different indicating a differencein particle size The particle sizes of the undoped 5molAg 41mol of AgAu 2525mol of AgAu 14mol ofAgAu and 5mol of Au doped CeO

2were calculated

(using the peak at 2120579 = 285∘) using Scherrerrsquos equation tobe 130 140 124 80 100 and 86 nm respectively For themetal doped samples new peaks (green filled circles) were


Ag 25 Au 25 25mol





Cou

nt ra

te (a

rb u

nit)

(111

)(200

)

(111

)

(002

)(220

)

(311

)(222

)

(022

)

(400

)

= 5 0

4 1

25 25

1 4

= 0 5

CeO2

2120579 (degree)70605040302010

Ag Au

Ag Au

Ag Au (mol)Doped





Abso

rban

ce (a

rb u

nit)

CeO2Ag = 5mol

Au = 5mol



4mol 1mol

Doped Ag Au


2and





2


2 the color of the










Tran

smitt

ance

(arb

uni

t)

CeO2

Ag = 5mol

Au = 5mol


Doped Ag Au

1mol 4mol

25 mol 25 mol

4mol 1mol



H2

cons

umpt

ion

(arb

uni

t)

CeO2

Au = 5mol

H2-TPR

100800600400200

Temperature (∘C)

1mol 4mol

25 mol 25 mol

4mol 1mol

Doped Ag Au

Ag = 5mol





2



2 The





2 The peak


2









2and Au and Ag


















2


2(g)









2-O2treated samples











3COOCH





1st run

CeO2

Ag = 5molAu = 5mol

Temperature (∘C)700600500400300200100

00

20

40

60

80

100CO

conv

ersio

n (

)



(a)

2nd run

Temperature (∘C)700600500400300200100

00

20

40

60

80

100

CO co

nver

sion

()

CeO2



(b)

1st run2nd run

Au=

5mol

14m

ol

25

25m

ol

41m

ol

Ag

=5m

ol

0

minus50

minus100

minus150

T10

(MC

eO2)

minusT

10(b

are)

(c)

Au = 5 mol

14 mol

2525 mol

41 mol

Ag = 5mol

T10

(2nd

)minusT

10

minus100

minus50

0

50

100

(1st)

(d)


bf C

O o

xaf

CO

ox

(e)










Wavelength (nm)


350300250

Doped Ag AuAb

sorb

ance

(arb

uni

t)

10

05

00

15

00

01

02

03

04

Abso

rban

ce (a

rb u

nit)

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)





25 mol 25 mol

4 mol 1 mol

O

O

O

(a)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Ni Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(b)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Pd Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(c)

O

O

O

Au = 5mol


at 80∘C


Wavelength (nm)

350300250

Doped Ni Pd

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)



4 mol 1 mol

(d)







2cata-







2NPs the






3CH2O (ad) +H (ad) (1)



(2)

CH3CH2O (ad) ndashM


(3)


3COO (ad) +H (ad)

997888rarr CH3COOH

(4)


997888rarr CH3COOCH

2CH3+H2O

(5)


3COOCH

2CH3 (6)



2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)






3COOH (acetic



3CHO in (6)




3CH(OH)OC

2H5(hemi-


3COOCH







2H5OHrarrC

2H5OC2H5



3CHOrarr CH

3COCH

3





4 Conclusion


2






Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

nanoclusters and









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Ag 25 Au 25 25mol





Cou

nt ra

te (a

rb u

nit)

(111

)(200

)

(111

)

(002

)(220

)

(311

)(222

)

(022

)

(400

)

= 5 0

4 1

25 25

1 4

= 0 5

CeO2

2120579 (degree)70605040302010

Ag Au

Ag Au

Ag Au (mol)Doped





Abso

rban

ce (a

rb u

nit)

CeO2Ag = 5mol

Au = 5mol



4mol 1mol

Doped Ag Au


2and





2


2 the color of the










Tran

smitt

ance

(arb

uni

t)

CeO2

Ag = 5mol

Au = 5mol


Doped Ag Au

1mol 4mol

25 mol 25 mol

4mol 1mol



H2

cons

umpt

ion

(arb

uni

t)

CeO2

Au = 5mol

H2-TPR

100800600400200

Temperature (∘C)

1mol 4mol

25 mol 25 mol

4mol 1mol

Doped Ag Au

Ag = 5mol





2



2 The





2 The peak


2









2and Au and Ag


















2


2(g)









2-O2treated samples











3COOCH





1st run

CeO2

Ag = 5molAu = 5mol

Temperature (∘C)700600500400300200100

00

20

40

60

80

100CO

conv

ersio

n (

)



(a)

2nd run

Temperature (∘C)700600500400300200100

00

20

40

60

80

100

CO co

nver

sion

()

CeO2



(b)

1st run2nd run

Au=

5mol

14m

ol

25

25m

ol

41m

ol

Ag

=5m

ol

0

minus50

minus100

minus150

T10

(MC

eO2)

minusT

10(b

are)

(c)

Au = 5 mol

14 mol

2525 mol

41 mol

Ag = 5mol

T10

(2nd

)minusT

10

minus100

minus50

0

50

100

(1st)

(d)


bf C

O o

xaf

CO

ox

(e)










Wavelength (nm)


350300250

Doped Ag AuAb

sorb

ance

(arb

uni

t)

10

05

00

15

00

01

02

03

04

Abso

rban

ce (a

rb u

nit)

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)





25 mol 25 mol

4 mol 1 mol

O

O

O

(a)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Ni Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(b)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Pd Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(c)

O

O

O

Au = 5mol


at 80∘C


Wavelength (nm)

350300250

Doped Ni Pd

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)



4 mol 1 mol

(d)







2cata-







2NPs the






3CH2O (ad) +H (ad) (1)



(2)

CH3CH2O (ad) ndashM


(3)


3COO (ad) +H (ad)

997888rarr CH3COOH

(4)


997888rarr CH3COOCH

2CH3+H2O

(5)


3COOCH

2CH3 (6)



2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)






3COOH (acetic



3CHO in (6)




3CH(OH)OC

2H5(hemi-


3COOCH







2H5OHrarrC

2H5OC2H5



3CHOrarr CH

3COCH

3





4 Conclusion


2






Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

nanoclusters and









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Abso

rban

ce (a

rb u

nit)

CeO2Ag = 5mol

Au = 5mol



4mol 1mol

Doped Ag Au


2and





2


2 the color of the










Tran

smitt

ance

(arb

uni

t)

CeO2

Ag = 5mol

Au = 5mol


Doped Ag Au

1mol 4mol

25 mol 25 mol

4mol 1mol



H2

cons

umpt

ion

(arb

uni

t)

CeO2

Au = 5mol

H2-TPR

100800600400200

Temperature (∘C)

1mol 4mol

25 mol 25 mol

4mol 1mol

Doped Ag Au

Ag = 5mol





2



2 The





2 The peak


2









2and Au and Ag


















2


2(g)









2-O2treated samples











3COOCH





1st run

CeO2

Ag = 5molAu = 5mol

Temperature (∘C)700600500400300200100

00

20

40

60

80

100CO

conv

ersio

n (

)



(a)

2nd run

Temperature (∘C)700600500400300200100

00

20

40

60

80

100

CO co

nver

sion

()

CeO2



(b)

1st run2nd run

Au=

5mol

14m

ol

25

25m

ol

41m

ol

Ag

=5m

ol

0

minus50

minus100

minus150

T10

(MC

eO2)

minusT

10(b

are)

(c)

Au = 5 mol

14 mol

2525 mol

41 mol

Ag = 5mol

T10

(2nd

)minusT

10

minus100

minus50

0

50

100

(1st)

(d)


bf C

O o

xaf

CO

ox

(e)










Wavelength (nm)


350300250

Doped Ag AuAb

sorb

ance

(arb

uni

t)

10

05

00

15

00

01

02

03

04

Abso

rban

ce (a

rb u

nit)

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)





25 mol 25 mol

4 mol 1 mol

O

O

O

(a)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Ni Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(b)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Pd Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(c)

O

O

O

Au = 5mol


at 80∘C


Wavelength (nm)

350300250

Doped Ni Pd

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)



4 mol 1 mol

(d)







2cata-







2NPs the






3CH2O (ad) +H (ad) (1)



(2)

CH3CH2O (ad) ndashM


(3)


3COO (ad) +H (ad)

997888rarr CH3COOH

(4)


997888rarr CH3COOCH

2CH3+H2O

(5)


3COOCH

2CH3 (6)



2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)






3COOH (acetic



3CHO in (6)




3CH(OH)OC

2H5(hemi-


3COOCH







2H5OHrarrC

2H5OC2H5



3CHOrarr CH

3COCH

3





4 Conclusion


2






Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

nanoclusters and









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




2 The peak


2









2and Au and Ag


















2


2(g)









2-O2treated samples











3COOCH





1st run

CeO2

Ag = 5molAu = 5mol

Temperature (∘C)700600500400300200100

00

20

40

60

80

100CO

conv

ersio

n (

)



(a)

2nd run

Temperature (∘C)700600500400300200100

00

20

40

60

80

100

CO co

nver

sion

()

CeO2



(b)

1st run2nd run

Au=

5mol

14m

ol

25

25m

ol

41m

ol

Ag

=5m

ol

0

minus50

minus100

minus150

T10

(MC

eO2)

minusT

10(b

are)

(c)

Au = 5 mol

14 mol

2525 mol

41 mol

Ag = 5mol

T10

(2nd

)minusT

10

minus100

minus50

0

50

100

(1st)

(d)


bf C

O o

xaf

CO

ox

(e)










Wavelength (nm)


350300250

Doped Ag AuAb

sorb

ance

(arb

uni

t)

10

05

00

15

00

01

02

03

04

Abso

rban

ce (a

rb u

nit)

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)





25 mol 25 mol

4 mol 1 mol

O

O

O

(a)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Ni Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(b)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Pd Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(c)

O

O

O

Au = 5mol


at 80∘C


Wavelength (nm)

350300250

Doped Ni Pd

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)



4 mol 1 mol

(d)







2cata-







2NPs the






3CH2O (ad) +H (ad) (1)



(2)

CH3CH2O (ad) ndashM


(3)


3COO (ad) +H (ad)

997888rarr CH3COOH

(4)


997888rarr CH3COOCH

2CH3+H2O

(5)


3COOCH

2CH3 (6)



2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)






3COOH (acetic



3CHO in (6)




3CH(OH)OC

2H5(hemi-


3COOCH







2H5OHrarrC

2H5OC2H5



3CHOrarr CH

3COCH

3





4 Conclusion


2






Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

nanoclusters and









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


1st run

CeO2

Ag = 5molAu = 5mol

Temperature (∘C)700600500400300200100

00

20

40

60

80

100CO

conv

ersio

n (

)



(a)

2nd run

Temperature (∘C)700600500400300200100

00

20

40

60

80

100

CO co

nver

sion

()

CeO2



(b)

1st run2nd run

Au=

5mol

14m

ol

25

25m

ol

41m

ol

Ag

=5m

ol

0

minus50

minus100

minus150

T10

(MC

eO2)

minusT

10(b

are)

(c)

Au = 5 mol

14 mol

2525 mol

41 mol

Ag = 5mol

T10

(2nd

)minusT

10

minus100

minus50

0

50

100

(1st)

(d)


bf C

O o

xaf

CO

ox

(e)










Wavelength (nm)


350300250

Doped Ag AuAb

sorb

ance

(arb

uni

t)

10

05

00

15

00

01

02

03

04

Abso

rban

ce (a

rb u

nit)

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)





25 mol 25 mol

4 mol 1 mol

O

O

O

(a)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Ni Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(b)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Pd Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(c)

O

O

O

Au = 5mol


at 80∘C


Wavelength (nm)

350300250

Doped Ni Pd

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)



4 mol 1 mol

(d)







2cata-







2NPs the






3CH2O (ad) +H (ad) (1)



(2)

CH3CH2O (ad) ndashM


(3)


3COO (ad) +H (ad)

997888rarr CH3COOH

(4)


997888rarr CH3COOCH

2CH3+H2O

(5)


3COOCH

2CH3 (6)



2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)






3COOH (acetic



3CHO in (6)




3CH(OH)OC

2H5(hemi-


3COOCH







2H5OHrarrC

2H5OC2H5



3CHOrarr CH

3COCH

3





4 Conclusion


2






Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

nanoclusters and









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




Wavelength (nm)


350300250

Doped Ag AuAb

sorb

ance

(arb

uni

t)

10

05

00

15

00

01

02

03

04

Abso

rban

ce (a

rb u

nit)

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)





25 mol 25 mol

4 mol 1 mol

O

O

O

(a)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Ni Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(b)

O

O

O

Au = 5mol


at 80∘C

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)


Wavelength (nm)

350300250

Doped Pd Au

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15



(c)

O

O

O

Au = 5mol


at 80∘C


Wavelength (nm)

350300250

Doped Ni Pd

Rxn in 24 hrs

Abso

rban

ce (a

rb u

nit)

10

05

00

15

0

1

2

3

4

5

Abso

rban

ce (a

rb u

nit)



4 mol 1 mol

(d)







2cata-







2NPs the






3CH2O (ad) +H (ad) (1)



(2)

CH3CH2O (ad) ndashM


(3)


3COO (ad) +H (ad)

997888rarr CH3COOH

(4)


997888rarr CH3COOCH

2CH3+H2O

(5)


3COOCH

2CH3 (6)



2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)






3COOH (acetic



3CHO in (6)




3CH(OH)OC

2H5(hemi-


3COOCH







2H5OHrarrC

2H5OC2H5



3CHOrarr CH

3COCH

3





4 Conclusion


2






Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

nanoclusters and









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





2NPs the






3CH2O (ad) +H (ad) (1)



(2)

CH3CH2O (ad) ndashM


(3)


3COO (ad) +H (ad)

997888rarr CH3COOH

(4)


997888rarr CH3COOCH

2CH3+H2O

(5)


3COOCH

2CH3 (6)



2H5 (hemiacetal)

997888rarr CH3COOCH

2CH3(major) +H

2

(7)






3COOH (acetic



3CHO in (6)




3CH(OH)OC

2H5(hemi-


3COOCH







2H5OHrarrC

2H5OC2H5



3CHOrarr CH

3COCH

3





4 Conclusion


2






Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

nanoclusters and









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





Tightly capped

OOH

O

O

O

lowast

lowast

O

OH

OHO

OO

Abso

rban

ce

10

05

00

Diethyl ether 50


Acetone sim1


Ethyl acetate 01


(a)


O

O

Mass (amu)1009080706050M

ass s

igna

l (au

)


50 60

Mass (amu)70 80 90 100M

ass s

igna

l (au

)

Afterreaction

01234

UV-VisO

O

Mass (amu)1009080706050M

ass s

igna

l (au

)

Abso

rban

ce


(b)




2





3CHO)






3CH2O(ad)-MrarrCH









Competing Interests


Acknowledgments


References


25(SR)18

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2

















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Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of









2support and the











2nanofibers for the





2-


2

















2hybrid







2


















2(111) facet



2rdquo ACS















2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





2semiconductor






2catalyst






3O4-CeO













Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Research Article Liquid-Phase Ethanol Oxidation and...

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