Enhanced electrocatalysis of oxygen reduction on platinum alloys in proton exchange membrane fuel cells

Enhanced electrocatalysis of the oxygen reduction reaction (ORR) on carbon-supported binary and ternary alloys of Pt in phosphoric acid fuel cells has been reported previously. This investigation focuses on the electrocatalysis of the ORR on some binary alloys of Pt (Pt+Ni, Pt+Cr and Pt+Co) at interfaces with proton exchange membranes (Dow perfluorinated sulfonic acids). Comparison of the results of these studies with those on carbon-supported Pt electrocatalysts (electrodes containing same Pt loading of 0.3 mg/cm2) revealed enhanced activities, lower activation energies and different reaction orders for all the alloys. X-ray powder diffraction showed lattice contractions for the alloys, the predominant phase being Pt3M (LI2) f.c.c. crystalline. X-ray photoelectron spectroscopy studies on the constituent elements of the electrocatalyst showed no chemical energy shifts owing to alloying and/or the presence of oxides on the surface. Lifetime evaluations of proton exchange membrane fuel cells, using both electrochemical as well as scanning electron microscopy/energy-dispersive X-ray analysis techniques, revealed only small amounts of dissolution of the more oxidizable component during the testing periods, which ranged from 400 to 1200 h. Therefore, the enhanced electrocatalysis exhibited by the binary Pt alloys appears to originate primarily as a result of changes in the lattice structure owing to alloying and the unique environment of the supported catalyst in the particle size range 35–75 A.

[1]  B. Cullity,et al.  Elements of X-ray diffraction , 1957 .

[2]  L. Azároff,et al.  Elements of X-ray crystallography , 1968 .

[3]  The Effect of Metallurgical Variables on the Electrocatalytic Properties of PtCr Alloys , 1987 .

[4]  W. B. Pearson,et al.  A handbook of lattice spacings and structures of metals and alloys , 1958 .

[5]  Edson A. Ticianelli,et al.  Dependence of performance of solid polymer electrolyte fuel cells with low platinum loading on morphologic characteristics of the electrodes , 1991 .

[6]  P. Ross,et al.  CO chemisorption on the 61119 and 61009 oriented single crystal surfaces of the alloy CoPt3*1 , 1990 .

[7]  J. Beery,et al.  Oxygen Reduction at Pt0.65Cr0.35, Pt0.2Cr0.8 and Roughened Platinum , 1988 .

[8]  L. Alexander,et al.  X-ray diffraction procedures , 1954 .

[9]  F. d'Heurle,et al.  Interactions Between Cr and Pt Films: New Cr‐Pt Phases , 1978 .

[10]  J. Bockris,et al.  Fuel cells : their electrochemistry , 1969 .

[11]  P. Ross,et al.  The Electrochemical Oxidation of Methanol on Tin-Modified Platinum Single Crystal Surfaces , 2013 .

[12]  S. Gottesfeld,et al.  Combined electrochemical/surface science investigations of Pt/Cr alloy electrodes , 1986 .

[13]  Charles R. Martin,et al.  Electrode kinetics of oxygen reduction at carbon-supported and unsupported platinum microcrystallite/Nafion® interfaces , 1992 .

[14]  P. Ross,et al.  Structure and chemisorptive properties of the Pt3Ti surface , 1986 .

[15]  E. J. Taylor,et al.  Importance of Interatomic Spacing in Catalytic Reduction of Oxygen in Phosphoric Acid , 1983 .