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Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels
Lisa McElwee-WhiteUniversity of Florida
Start Date = 1 January 2004Planned Completion = 31 December 2007
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Research Goals and Objectives
Objective: Synthesize heterobimetallic complexes and evaluate them as catalysts for methanol electrooxidation as a model for direct utilization of hydrocarbons in fuel cells
Crucial Questions:• Can the function of bulk Pt/Ru alloy be reproduced in a
simple complex using much less precious metal?• Can simple complexes immobilized on anodes serve as
electrocatalysts for fuel cells?• Can cheaper, more readily available, more active first row
transition metals be used in catalysts?
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Relevance to Current State-of-the-Art
• For direct utilization of hydrocarbon fuels in fuel cells, state of the art is DMFC with Pt/Ru surface serving as anode catalyst
Relevance to NASA
• Future direct use of hydrocarbon fuels in fuel cells will require new catalysts and understanding of the reactions involved
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Budget, Schedule and DeliverablesBudget • $ 40,000 for the grant period 10/1/05 to 3/31/07
Deliverables• 1st Quarter: oxidation data from previously prepared Fe/Pt, Fe/Pd and
Fe/Au catalysts and comparison to Ru/Pt, Ru/Pd, Ru/Au analogues
• 2nd Quarter: modified carbon paste electrodes with neutral catalysts• 3rd Quarter: bulk electrolysis data from modified carbon paste
electrodes• 4th Quarter: new Ru/Pt, Ru/Pd, Ru/Au, Fe/Pt, Fe/Pd and Fe/Au
catalysts with charged ligands• 5th Quarter: modified Nafion electrodes with charged catalysts• 6th Quarter: bulk electrolysis data from modified Nafion electrodes
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Anticipated Technology End Use
• Results on single molecule catalysts and use of more active first row transition metals could be generally relevant to direct utilization of hydrocarbons in fuel cells
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Accomplishments and ResultsMethanol as a model for more complex hydrocarbon fuels
– Complex oxidation mechanism
– Requires activation of C-H bonds
CH3OH - 2 e-
CH2O + 2 H+
CH2O- 2 e- CO + 2 H+
HCOOH - 2 e-
CO2 + 2 H+
CO + H2O - 2 e-
CO2 + 2 H+
CH2O + H2O- 2 e- HCOOH + 2 H+
CH2O + 2 CH3OH CH2(OCH3)2 + H2O
HCOOH + CH3OH HCO2CH3 + H2O
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Accomplishments and ResultsSynthesis of Charged Catalysts for Modified Electrodes
Ru I
PPh2Ph2PPh3P
NHMe2I-
RuI
PPh2Ph2PPh3P
NHMe2I-
Pd
Cl
Cl
RuI
PPh2Ph2PPh3P
NHMe2I-
Pt
Cl
Cl
Pd(COD)Cl2
Pt(COD)Cl2
• Positive charge facilitates incorporation into Nafion for preparation of modified electrodes
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Accomplishments and ResultsSynthesis of First and Second Row Metal Catalysts for Comparison
FeI
Ph2POC
PPh2
FeI
OCOC Pt
I
I
Pt(COD)I2Fe
I
Ph2POC
PPh2
RuI
Ph2POC
PPh2
RuI
OCOC Pt
I
I
Pt(COD)I2Ru
I
Ph2POC
PPh2
dppm
dppm
• Catalytic behavior of 1st row metal (Fe) can be compared to 2nd row (Ru)
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Accomplishments and ResultsRu and Fe heterobimetallic complexes
RuI
Ph2POC
PPh2
Pt
I
I
RuI
Ph2POC
PPh2
Pd
I
I
FeI
Ph2POC
PPh2
Pt
I
I
FeI
Ph2POC
PPh2
Pd
I
I
RuI
Ph2POC
PPh2
Au
I
FeI
Ph2POC
PPh2
Au
I
FeI
Ph2POC
PPh2
RuI
Ph2POC
PPh2
υco= 1958 cm-1
υco= 1947 cm-1
υco= 1980 cm-1
υco= 1992 cm-1
υco= 1939 cm-1
υco= 1949 cm-1
υco= 1972 cm-1
υco= 1984 cm-1
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Accomplishments and Results
Cyclic Voltammetry
RuI
Ph2POC
PPh2
Pt
I
I
E vs. NHE (V)
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
I (µA
)
-100
0
100
200
300
400
500
600
5 mM catalyst50 µL MeOH5 µL H2O 1.160 V
1.962 V1.843 V
RuI
Ph2POC
PPh2
Pd
I
I
E vs. NHE (V)
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
I (µA
)
-50
0
50
100
150
200
250
300
350
5 mM catalyst50 µL MeOH5 µL H2O
1.134 V
1.582 V
2.036 V
1.432 V
FeI
Ph2POC
PPh2
Pd
I
I
Pd(II/IV)Fe(II/III)
Fe(III/IV)
Ru(II/III)
Ru(III/IV)
Pd(II/IV)
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Charge (C)
0 20 40 60 80 100 120 140
Pro
duct
evo
lutio
n (µ
mol
)0
10
20
30
40
DMM from Ru/Pd DMM from Ru/Pd-PPh3
Charge (C)
0 20 40 60 80 100 120 140
Pro
duct
evo
lutio
n (µ
mol
)
0
20
40
60
80
100
DMM from Ru/PtMF from Ru/PtDMM from (Ru/Pt + PPh3)MF from (Ru/Pt + PPh3)
Accomplishments and ResultsBulk Electrolysis: Product Evolution for Electrooxidation of Methanol by
Ru/Pt and Ru/Pd Heterobimetallic Complexes
RuI
Ph2POC
PPh2
Pt
I
IRu
I
Ph2POC
PPh2
Pd
I
I
DMM = CH2(OCH3)22 e- oxidation
MF = HCO2CH34 e- oxidation
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Charge (C)
0 20 40 60 80 100 120 140
Pro
duct
evo
lutio
n (µ
mol
)
0
10
20
30
40
DMM from Ru/Pd DMM from Ru/Pd-PPh3
Accomplishments and ResultsBulk Electrolysis: Product Evolution for Electrooxidation of Methanol by
Ru/Pd and Fe/Pd Heterobimetallic Complexes
Charge (C)
0 20 40 60 80 100 120
Pro
duct
evo
lutio
n (µ
mol
)
20
30
40
50
60
70
80
DMM from Fe/PdDMM from Fe/Pd-PPh3
RuI
Ph2POC
PPh2
Pd
I
I
DMM = CH2(OCH3)22 e- oxidation
MF = HCO2CH34 e- oxidation
FeI
Ph2POC
PPh2
Pd
I
I
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Accomplishments and ResultsSummary
• Heterobimetallic Ru/Pt, Ru/Pd, Ru/Au, Fe/Pt, Fe/Pd and Fe/Au complexes have been synthesized
• Cationic Ru/Pt and Ru/Pd complexes have been prepared for incorporation into Nafion films for fabrication of modified electrodes
• These heterobimetallic complexes have been demonstrated to be catalysts for the electrochemical oxidation of methanol
• Fe/Pt and Fe/Pd binuclear complexes are more active catalysts than their Ru/Pt and Ru/Pd analogues
Florida Universities Hydrogen Review 2005Florida Solar Energy Center November 1-4, 2005
Bimetallic Catalysts for the Electro-oxidation of Hydrocarbon Fuels – McElwee-White – University of Florida
Future Plans
• Fabricate carbon paste electrodes modified with neutral catalysts
• Fabricate modified electrodes using Nafion films impregnated with cationic catalysts
• Test modified electrodes for electrooxidation of methanol
• Continue synthesis of catalysts bearing first row metals– additional Fe/Pt, Fe/Pd, Ru/Ni, Fe/Ni complexes designed
• Evaluate performance of new catalysts for electrooxidation of methanol as a model for hydrocarbon systems