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Applied Catalysis A: General 470 (2014) 89– 96

Contents lists available at ScienceDirect

Applied Catalysis A: General

j ourna l h om epage: www.elsev ier .com/ locate /apcata

acile synthesis of highly catalytic activity Ni–Co–Pd–P compositeor reduction of the p-Nitrophenol

ing Yanga,∗, An-Dong Xua, Jun Xiab, Jie Hea,∗∗, Hong-Long Xinga, Xiao-Mei Zhanga,hu-Yang Weia, Ning-Ning Wanga

College of Chemical Engineering, Anhui University of Science and Technology, NO.168, Shungeng Road Huainan, Anhui 232001, PR ChinaHuainan Police Station, Huainan, Anhui 232001, PR China

r t i c l e i n f o

rticle history:eceived 27 July 2013eceived in revised form 20 October 2013ccepted 23 October 2013vailable online 29 October 2013

eywords:atalytic activity

a b s t r a c t

A simple hydrothermal method was developed for the one-step synthesis of an urchin-likeNi@Ni3P@CoP2@P composite. p-Nitrophenol can be completely reduced to p-Aminophenol using theas-synthesized composites as catalysts, and the reaction was monitored by UV–vis spectroscopy. Fur-ther research implied that the presence of Co greatly improves the catalytic ability of the composites forthe reduction of p-Nitrophenol . Palladium (Pd) nanoparticles (NPs) were subsequently loaded into the

i–Co–Pd–P compositeseduction-Nitrophenol

Ni–Co–P composites to obtain better catalytic effects. Aside from excellent catalytic ability for reducingp-Nitrophenol, the strong magnetism of the as-prepared Ni–Co–Pd–P composites allowed the facile col-lection of the catalysts from the reaction system. After using the as-synthesized Ni–Co–Pd–P compoundsseven times every 15 min, recyclability was estimated by monitoring the formation of p-Aminophenolusing the catalysts via UV–vis spectroscopy. The as-synthesized Ni–Co–Pd–P composites presented good

llent r

catalytic ability and exce

. Introduction

As a type of arene, nitrophenol is highly toxic and can invadehe body through the respiratory system, digestive system, andkin. Nitrophenol has major adverse effects on the blood, liver, andentral nervous system. Concerns over the ability of nitrophenolo transform hemoglobin into methemoglobin, which can causeypoxia, have also been raised. The presence of nitrophenol in bod-

es of water can reduce their self-purification ability [1]. Aside fromeing an important intermediate in the preparation of several anal-esic and antipyretic drugs, such as paracetamol, acetanilide, andhenacetin [2], p-Aminophenol has also been applied as a photo-raph developer, corrosion inhibitor, anti-corrosion lubricant, andair-dyeing agent [3].

p-Nitrophenol is mainly formed from the catalytic/lectrochemical reduction of nitrobenzene [4]. Thus, exploitationf an excellent catalyst for the catalytic reduction of p-Nitrophenol

nto p-Aminophenol is an important task [5–7]. Some metal com-osites have been studied widely for the catalytic hydrogenation ofitrophenol [8,9]. However, heterogeneous noble metal catalysts,

∗ Corresponding author. Tel.: +86 183 65209852; fax: +86 554 6668520.∗∗ Corresponding author. Tel.: +86 183 65209852; fax: +86 554 6668520.

E-mail addresses: pyang8066@163.com (P. Yang), jhe@aust.edu.cn (J. He).

926-860X/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.apcata.2013.10.043

ecyclability for the reduction of p-Nitrophenol .© 2013 Elsevier B.V. All rights reserved.

which are traditionally applied in the hydrogenation of arenes,usually require extreme reaction conditions [10–12]. Today, thecatalytic research for hydrogenation of arene is still in its infancy,and the development of highly effective catalysts that can promotethe reduction of arenes under mild conditions remains a significantchallenge for researchers.

Interest in constructuring metallic micro/nano catalysts withdifferent architectures, such as polymers [13], dendrimers [14],micelles [15], and mesoporous materials [16,17], within aspecific reaction space has recently increased [18,19]. Surface-functionalization of micro/nano materials allows their fabricationinto catalyst supporters [20], sensors [21], and drug-delivery mate-rials [22]. Considering their economic benefits, some non-metallicmaterials, such as carbon and phosphorus (P), have been usedas substituents for constructing multifunctional micro/nano cat-alysts [11,23,24]. The resultant catalysts not only feature thecombined properties of their individual constituents but also shownew properties and capabilities due to synergy istic interactionsbetween components [25]. Developing composite materials is anurgent requirement from the viewpoint of sustainable chem-istry and green synthesis in material chemistry [26]. Among

the different surface modification strategies recently developedfor multifunctional micro/nano catalysts, the synthesis of micro-structures with increased catalytic effects has received the mostattention.

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0 P. Yang et al. / Applied Cata

Microstructural composites of transition-metal phosphidesave recently received great attention in the field of catalysis dueo their low cost and high catalytic ability [27]. However, high tem-eratures and toxic P sources (e.g., trictylphosphine) are often used

n the synthesis of some transition-metal phosphide nanocrys-als, such as FeP, Fe2P, Ni2P, Co2P, and MnP [20,28,29]. Effortso investigate the impact of processing conditions on productionields during the preparation of transition-metal phosphides com-osites are well underway [24,30–32]. Aside from its low cost,

ts ability to impart ferromagnetic behavior to another materials an important advantage of nickel (Ni) [33]. Magnetic catalysts

ay be easily collected from various reaction systems by magneticeparation, thereby allowing the reuse of the catalyst and mini-ization of noble metal loss in the catalyst, when the recycling

xperiment has been completed. Aside from its advantages of highatalytic rate and strong magnetism, the porous urchin-like Ni–Picrostructures were synthesized through a simple water and N,N-

imethylformamide solvothermal route, and this microstructurean rapidly remove heavy metal ions from water [28].

Considering its excellent catalytic ability and wide availability,obalt (Co) is quickly becoming a popular material for the synthesisf novel catalysts [34]. Some noble metals, such as gold, palladiumPd), platinum (Pt), and Rh, among others, may be partly replacedy Co without loss of the catalytic ability of the whole material35]. Many Co-containing catalysts, such as Pt–Co and Mo–Co, haveecently been exploited [36,37]. These reports indicate that com-osite microstructural materials containing Ni and Co may offerxcellent opportunities for developing highly effective catalystshat can reduce noble metal usage while retaining or even enhanc-ng catalytic properties [38,39].

Using a method reported earlier [28] for the synthesis of Ni–Picrostructural materials with slight modifications, an urchin-likeaterial containing Ni, Co, and P was prepared in this study via

simple one-step hydrothermal method, and the structure of itas identified as Ni@Ni3P@CoP2@P through the characterization

f X-ray diffractometer (XRD). To achieve high catalytic activity, Pdons absorbed by the urchin-like materials were reduced into Pdanoparticles (NPs) in the presence of NaBH4. The catalyst showedtronger catalytic ability for reducing p-Nitrophenol than catalystsontaining Ni, Co, or P alone. The multifunctional materials con-aining Ni, Co, P, and Pd were filled into a micro/nano reactor andpplied in the hydrogenation of p-Nitrophenol . A novel catalyst

as developed for the hydrogenation of p-Nitrophenol . Improved

atalytic activity for the reduction of p-Nitrophenol and easy sepa-ation of the as-prepared Ni–Co–Pd–P composites from the reactionixture were simultaneously achieved.

Scheme 1. Schematic illustration of the synthesis of Ni–Co–Pd–P comp

: General 470 (2014) 89– 96

2. Experimental

2.1. Chemicals

All reagents were of analytical grade and used as receivedwithout further purification. CoCl2·6H2O, sodium hypophosphite(NaH2PO3·H2O), N,N-dimethylformamide (DMF), and NaBH4, NiCl2(Guoyao Chemicals Co., Shanghai, China) were purchased for prepa-ration of Ni–Co–P nanocomposites. PdCl2 (guoyao Chemicals Co.,Shanghai, China) was used to synthesize and load Pd nanoparti-cles in Ni–Co–P composites. p-Nitrophenol (Guoyao Chemicals Co.,Shanghai, China) was used to evaluate the catalytic ability of theas-prepared Ni–Co–Pd–P composites.

2.2. Synthesis of the urchin-like Ni–P composites

The urchin-like Ni–Co–P composite was prepared accordingto the method Mi and co-workers [28] has reported with littlemodification. The brief description is as follows: after dissolvingand mixing 2 mmol NiCl2, 2 mmol CoCl2, and 1 mmol Na2PO2 with20 mL water, 20 mL N,N-dimethylformamide (DMF) were addedinto the mixture under stirring. The mixture was transferred intothe Teflon-lined autoclave reaction for 16 h at 160 ◦C. The obtainedproducts were collected through a magnet and washed with waterand ethanol for several times.

2.3. Synthesis of the urchin-like Ni–Co–P composites

The method for synthesis of the urchin-like Ni–Co–P compos-ite is similar to prepare Ni–P composites. Briefly, mixing 1 mmolNaH2PO2·H2O, 2 mmol CoCl2·6H2O and 2 mmol NiCl2·6H2O in20 mL H2O, then the clear solution was obtained after diluting theabove solution with 20 mL DMF under stirring. At last, the mixturewas transferred into a Teflon-lined autoclave and reacted for 16 h at160 ◦C. Then, the product was collected with a magnet and wash-ing with deionized water to remove the unreacted reagents andimpurities.

2.4. Synthesis of Ni–Co–Pd–P composite

25 mg the synthesized Ni–Co–P composites were first mixed

with 1 ml of PdCl2 (2.8 mM) for a night. After collecting and washingthe product several times with a magnet, 5 mL NaBH4 (7.9 M) wasdropped into the as-prepared catalyst solution quickly to reducePd2+ absorbed in composite into Pd NPs. In the end, the products

osites and their catalytic ability for reduction of p-Nitrophenol .

P. Yang et al. / Applied Catalysis A: General 470 (2014) 89– 96 91

Fig. 1. The SEM of Ni–P (a), Ni–Co–P (b), the TEM image of Ni–Co–P composites (c) and their EDS (d), the TEM (e) and HRTEM image of Ni–Co–Pd–P (f).

b) in the as-synthesized Ni–Co–P composites.

ww

2w

ict(bpadywcm

Fig. 2. The XRF peak of Ni, Co (a) and P (

ere collected by a magnet and washing three times with deionizedater.

.5. Catalysis of reducing of p-Nitrophenol into p-aminphenolith as-synthesized Ni–Co–Pd–P composite

Referring to the reported method [4], the catalytic abil-ty of Ni–P, Ni–Co–P, and Ni–Co–Pd–P were evaluated throughatalytic reduction of p-Nitrophenol under the same condi-ions. Typically, the newly prepared 0.264 M sodium borohydride30 mL) and 2.5 mM p-Nitrophenol (20 mL) were mixed in aeaker. After keeping the mixture at 45 ◦C for 10 min, 25 mg as-repared Ni–Co–Pd–P composites were added into the beaker,nd 0.5 mL of the solution was extracted with a magnet andiluted to 5 mL with DIW for further UV–vis absorption anal-

sis at certain intervals. At last, 0.5 mL of the final solutionas extracted at 15 min for UV–vis absorption analysis, and the

atalyst was re-collected with a magnet for recycling experi-ent. In the process of reduction p-Nitrophenol, a magnet was

Fig. 3. The XRD of Ni–P (curve a), Ni–Co–P (curve b) and Ni–Co–Pd–P (curve c)composites.

92 P. Yang et al. / Applied Catalysis A: General 470 (2014) 89– 96

F XPS spN the Nc

psv

wp

TT

ig. 4. (a) XPS survey spectra of the as-synthesized Ni–Co–P composites, (b) fitted

i 2p region for Ni–Co–P composites, (d) fitted XPS spectra of the P 2p region foromposites.

laced under the bottom of the beaker, making it possible toeparate the mixture quickly from the beaker at fixed time inter-als.

The recyclability of the as-synthesized Ni–Co–Pd–P compositeas evaluated by running the catalyst 7 times in the reduction of

-Nitrophenol .

able 1he elemental species and valence of Ni, Co, P, Pd and their pencentange on the surface o

Element state Raw area(eV) Atomic sensitivit

Co2+ 104052 4.5

Co3+ 36993Ni2+ 76598 5.4Ni3+ 34817P5+ 8931 0.25Pd 1795 2.0

ectra of the Co 2p region for the Ni–Co–P composites, (c) fitted XPS spectra of thei–Co–P composites, (e) fitted XPS spectra of the Pd 2p region for the Ni–Co–Pd–P

2.6. Characterization of the synthesized Ni–Co–P andNi–Co–Pd–P composite

The Ni–P and Ni–Co–P composites were characterized by ascanning electron microscope (JEOL JSM-6700F). A transmissionelectron microscope (TEM, JEOL-2010) was used to record the

f composites.

y factors (ASF) Molar percentage Co2+/Co3+/Ni2+/Ni3+/P5+/Pd

25.8: 9.2: 15.8: 7.2: 39.8: 1

P. Yang et al. / Applied Catalysis A: General 470 (2014) 89– 96 93

F mposs P: 25

trrmrcmeUSc

3

3c

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ig. 5. (a) The catalytic reduction effect of the as-synthesized urchin-like Ni–P coynthesized urchin-like Ni–Co–P composites at several interval and (d) 15 min (Ni–

ransmission electron microscope (TEM) and energy dispersive X-ay spectroscopy (EDS), respectively. A Japanese Rigaku DMax-gAotation anode X-ray diffractometer (XRD) equipped with graphiteonochromatized Cu Ka radiation was used to measure the X-

ay powder diffraction (PXRD) patterns of the as-synthesizedomposites. X-ray photoelectron spectroscopy (XPS) analysis waseasured on electron spectrometer (ESCALAB 250, thermo-VG Sci-

ntific). The UV–visible spectra were studied with a ShimadzuV-2550 spectrophotometer. The X-ray fluorescence (XRF-1800,HIMADZU) was used to measure the content of Ni, Co, and P in theomposites.

. Results and discussion

.1. The structure and component of the as-synthesizedomposite

Scheme 1 describes the preparation of the urchin-like mate-ials containing Ni, Co, and P according to a previously reportedethod under mild hydrothermal conditions. The scanning elec-

ron microscopy (SEM) image shown in Fig. 1 illustrates that aimilar urchin-like pattern to that of the Ni–P composites (Fig. 1a)s the as-synthesized Ni–Co–P composites were prepared, whichndicates that the Ni–Co–P composites possess great absorptionapacity for metal ions. The transmission electron microscopyTEM) image shown in Fig. 1c further confirms the SEM results, andhe urchin-like microspheres can be clearly seen. An abundance of

anoscalar prominences resembling urchins form the porous struc-ure of the microspheres. As such, we can conclude that dopingith Co does not change the pattern of the as-synthesized product.

hen Pd NPs were loaded onto the product through reducing the

ites at several interval and (b) 15 min, (c) the catalytic reduction effect of the as-mg; Ni–Co–P: 25 mg, p-Nitrophenol: 0.05 mmol, NaBH4: 0.792 mmol, T: 45 ◦C).

Pd ions absorbed onto the surface of Ni–Co–P composites. X-rayspectroscopy (EDS) analysis (Fig. 1d) of the product also impliedthe formation of Ni–Co–P microstructures, and the characteristicpeaks of Ni, Co, and P can be readily observed in the figure. Pd NPswere loaded into the product by reducing the Pd ions absorbed onthe surface of the Ni–Co–P composites. As shown in Fig. 1e and f,the TEM and HRTEM show that the Pd NPs with the size of about6–7 nm were formed on the surface of as-synthesized composites.Furthermore, the composition and contents of the as-synthesizedNi–Co–P composites were analyzed with XRF. Fig. 2 shows thecharacteristic peaks of Ni, Co (Fig. 2a), and P (Fig. 2b), and the per-centages of Ni, Co, and P are 52.65%: 33.65%: 13.70% from their pureintensity.

X-ray diffraction (XRD) patterns of the products were obtainedto identify the phases of the as-prepared urchin-like products. Thecrystallization nature of the as-prepared Ni–P and Ni–Co–P com-posites can be observed in Fig. 3. Curve a shows that the two strongdiffraction peaks centered at 44.6 and 51.8◦ can be ascribed to the(1 1 1) and (2 0 0) phases of the composites and indicate the pres-ence of the fcc Ni phase (JCPDS 87-0712). Diffraction peaks at 13.9,28.3, and 33.1◦, which respectively correspond to the (1 1 0), (2 2 0),and (3 1 0) reflections of tetragonal Ni3P (JCPDS 74-1384), may alsobe observed. These results indicate that Ni@Ni3P microstructurescan be formed via a hydrothermal method.

When Co was doped into the urchin-like composites (Fig. 3b,curve b), the intensity of the diffraction peaks increased obviouslyand new diffraction peaks at 19.7, 32.3, 37.5, and 58.3◦, which can

be ascribed to the (200) phase of Ni3P as well as the (020), (121), and(131) phases of CoP2 (JCPDS 77-0263), respectively, were observed.Other diffraction peaks can be ascribed to P (JCPDS 75-0577). There-fore, Co can be doped into the Ni-P composite via the hydrothermal

94 P. Yang et al. / Applied Catalysis A: General 470 (2014) 89– 96

Fig. 6. (a) Photographic illustration of the reduction of p-Nitrophenol by NaBH4 under catalysis of the as-synthesized Ni–Co–Pd–P composites, (b) the UV–vis absorptionspectra of the reduction of p-Nitrophenol by NaBH4 in the presence of as-synthesized catalyst at several intervals, (c) the reusability of the as-synthesized catalyst forr catalyb mol,

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ciaXsTbaBatab

eduction of 4-nitrophenol by NaBH4, (d) the cycle capalicity of the as-synthesized

etween Ln (Ct/C0) and reaction time (t) (Ni–Co–Pd–P: 25 mg, p-Nitrophenol: 0.05 m

ethod, and the presence of Co increases the crystallization degreef the whole composite. The urchin-like products can be identi-ed as Ni@Ni3P@CoP2@P. However, Fig. 3 (curve c) shows that theeaks of the Ni–Co–P composites do not change compared to Fig. 3,urve b. This may be because of the few number and little sizef Pd NPs which cannot change the crystallization of the wholeomposites.

X-ray photoelectron spectroscopy (XPS) was used to furtherharacterize the as-prepared Ni–Co–P and Ni–Co–Pd–P compos-tes. Fig. 4 shows the XPS survey spectra of the products as wells the high-resolution spectra of Ni, Co, and P. Furthermore, thePS curves of Co, Ni, and P have been fitted to analyze elementalpecies and valence modes of them accurately in the composite.wo different valences of Co were observed. Fig. 4b shows theinding energies of Co 2p at 786.85 and 803.5 eV, which can bettributed to the Co2p3/2 and Co 2p1/2 peaks, respectively, of Co2+.inding energies of 787.6 and 804.8 eV correspond to the Co2p3/2

nd Co 2p1/2 peaks, respectively, of Co3+ (Fig. 4b). In the same way,he binding energies of Ni 2p are 855.5 and 873.5 eV, which can bettributed to Ni 2p3/2 and Ni 2p1/2 peaks, respectively, of Ni 2+;inding energies of 861.3 and 880.0 eV can be attributed to the

st for reduction of p-Nitrophenol by NaBH4 at several intervals, (e) the relationship NaBH4: 0.792 mmol, T: 45 ◦C).

Ni 2p3/2 and Ni 2p1/2 peaks, respectively, of Ni 3+ (Fig. 4c). Thus,two different valences of Ni were found in the as-synthesized com-posites. P 2p has a noticeable binding energy of 133.6 eV (Fig. 4d),which corresponds to the P2p3/2peak of high-valence P. Wang et al.have reported that the higher phosphorus regions were supposedto be increased via extraction of P dissolved in nickel grains, whichin turn gave rise to precipitation of the hard inter-metallic Ni3P,and CoP2 phase [40]. As shown in Fig. 4e, after loading of the PdNPs into the Ni–Co–P composites, the binding energies of Ni, Co,and P did not change. New binding energies found at 335.5 and340.1 eV can be ascribed to the Pd 3d5/2 and Pd 3d3/2 peaks, respec-tively, of Pd (Fig. 4e). The elemental species and their valences in theas-synthesized Ni–Co–Pd–P composites are summarized in Table 1.

3.2. Catalytic reduction of p-Nitrophenol

Because of their unique catalytic, magnetic, magneto-caloric,

and semiconducting properties, transition-metal phosphides haveattracted extensive research interest in recent years [41].These phosphides have been applied as a new class of highlyactive hydroprocessing catalysts for hydrodesulfurization and

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P. Yang et al. / Applied Cata

ydrodenitrogenation to replace general catalysts [42]. The hydro-enation of p-Nitrophenol was carried out to evaluate the catalyticbility of the as-synthesized urchin-like composite materials. Totudy the influence of Co and Pd on the reduction of p-Nitrophenol,hree different component urchin-like composites containing Ni–P,i–Co–P, and Ni–Co–Pd–P were prepared, respectively. UV–visbsorption spectra were obtained to illustrate the reduction pro-ess of p-Nitrophenol .

Fig. 5a shows that p-Nitrophenol has a noticeable absorptioneak at about 400 nm. However, when the as-synthesized Ni–Pomposites were mixed with a mixed solution of p-Nitrophenolnd NaBH4, the peak at 400 nm decreased as the reaction timencreased. A new peak at about 295 nm appeared and graduallyncreased in intensity with time, which indicates the transforma-ion of p-Nitrophenol into p-Aminophenol under the catalysis of thes-synthesized Ni–P composites. However, the reaction rate grad-ally slowed after 30 s. Fig. 5b shows that the as-prepared Ni–Pomposites could not completely catalyze the hydrogenation of-Nitrophenol into p-Aminophenol within 15 min. When Co wasoped into the Ni–P composite (Fig. 5c), the catalytic ability ofhe composite increased rapidly and p-Nitrophenol could be com-letely reduced into p-Aminophenol within 15 min (Fig. 5d). Thus,o plays an important role in the reduction of p-Nitrophenol .

As shown in Fig. 6a, the yellow solution of mixed p-Nitrophenolnd NaBH4 became colorless after immersion of the as-preparedrchin-like Ni–Co–Pd–P composites into the beaker for 50 s. More

nterestingly, higher reduction rates were observed with Pd NPshan with Ni–P and Ni–Co–P composites under the same conditionsFig. 6b). The catalyst could also be collected with a magnet due tohe strong magnetism of the as-synthesized material.

The recyclability of the as-synthesized Ni–Co–Pd–P compositesas evaluated by testing their catalytic performance after the com-osites had been run seven times every 15 min. As shown in Fig. 6c,he catalysts obtained after running for seven times exhibited cat-lytic efficiencies similar to those of the original products for theeduction of p-Nitrophenol . However, the reaction rate observedfter the seventh run was slower than that found after the first runFig. 6d). Nevertheless, a linear relationship (R2 > 0.98) between LnCt/Co) and reaction time (t) was observed (Fig. 6e), thereby con-rming the pseudo-first-order kinetics of the reduction reaction.inetic constant of 7.9 × 10−3 s−1 was obtained for the first cat-lytic cycles. A comparison to the obtained k values, such as Ag NPs43], Ni NPs [44], and alloy contains of Fe(II) [45,46], the synthe-ized catalyst has higher catalytic proprieties for the reduction of-Nitrophenol .

.3. The possible mechanism

As previously reported for other metal catalysts [47], a disper-ion process of BH4

− and p-Nitrophenol from aqueous solutiono the surface of the catalyst were involved for discussing theossible mechanism of catalytic reduction of p-Nitrophenol usinghe urchin-like composites, Ni, Co, and Pd in the compositesould adjust the electron transfer from BH4

− to p-Nitrophenol .he enhanced catalytic proprieties of the as-synthesized urchin-ike Ni–Co–P–Pd composites may be explained in several ways.irst, the urchin-like microstructure obtained in the presence of

enhances the absorption proprieties of the composites towardd ions and p-Nitrophenol . Obviously, direct contact between theeactants and the catalyst is essential in the electron transfer pro-ess. Second, the catalytic performance of Co is better than thatf pure Ni. [48] Thus, Ni–Co–P composites could support better

atalytic proprieties better than Ni–P composites because of accel-rated electron transmission from Ni to Co when p-Nitrophenols absorbed into the surface of the Ni–Co–P composites. Finally,d NPs have good catalytic properties for the hydrogenation of

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: General 470 (2014) 89– 96 95

arenes. After loading of the Pd NPs into the surface of the urchin-like composites, electron transfer from BH4

− to p-Nitrophenolmay be enhanced because of synergistic effects between Ni, Co,and Pd. Electron transfer may promote the quick formation of p-Aminophenol in the presence of Ni–Co–Pd–P composites.

4. Conclusion

In summary, urchin-like Ni@Ni3P@CoP2@P composites withhigh catalytic ability for reducing p-Nitrophenol were synthesizedthrough a simple hydrothermal method. Pd NPs can be loaded intothe urchin-like composites via a facile method. Because of the syn-ergistic actions of Ni, Co, Pd, and P, the as-prepared material couldcatalytically reduce p-Nitrophenol into p-Aminophenol within 50 s.Furthermore, the as-synthesized Ni–Co–Pd–P composites could becollected easily from the reaction system because of their strongmagnetism. The current research contributes significantly towardthe development of highly active nano-catalysts.

Acknowledgements

This work is supported by the Research Fund for the DoctoralProgram of Anhui University of Science and Technology “Synthesis,investigation and application of the multifunctional nanocom-posites”, the Outstanding Young Talent Project of High Schoolof Anhui Province “Construction and investigation of graphenebased composites as electrode materials for energy storage”, theKey Young Found of Anhui University of Science and Technology“Construction and application of magnetic fluorescent compositeas nano-probe”, the National Natural Science Foundation of China(Grants 21271008, E030703), and the Key Fund Project of AnhuiProvincial Department of Education (Grants KJ2011A091).

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