Combinatorial screening for methanol oxidation catalysts in alloys of Pt, Cr, Co and V

Thin film combinatorial sputter-deposited ternary Pt-Cr-V. Pt-Co-Cr, and quaternary Pt-Co-Cr-V catalysts for methanol electro-oxidation in direct methanol fuel cell were studied. Several compositions exhibited better MOR activities than pure Pt based on the peak current density and onset potential of the methanol oxidation reaction measured by voltammetry. Alloying 43% vanadium with pure platinum gave higher electrocatalytic activity evidenced by 5.9 times greater peak current density. Pt30Co40Cr30 outperformed pure Pt by 12x in a ternary Pt-Co-Cr library. Alloying of vanadium into optimum PtCoCr compositions further improved methanoloxidation kinetics. Pt25CO25Cr25V25 showed the highest catalytic activity with a peak methanol oxidation current density that was 17x higher than pure Pt and 1.5 x higher than Pt33Co33Cr33. Atomic absorption studies of dissolved species in the electrolyte showed Co and Cr dissolution at higher rates than V. showing that the chemical ratio of Cr:Co:V in Pt25CO25Cr25V25 changed to 0.738:0.862:1.000 after voltammetry. XPS analysis of Pt25Co25Cr25V25 revealed a Pt-rich PtV binary compositional surface (Pt:V = 89.04%:10.96%) formed after electrochemical testing. The active catalytic performance and good stabilities of catalysts in the PtCoCrV system suggest them as promising alternatives to Pt-Ru for methanol oxidation. (C) 2012 Elsevier B.V. All rights reserved.