Electrocatalytic mechanism and kinetics of SOMs oxidation on ordered PtPb and PtBi intermetallic compounds: DEMS and FTIRS study

Abstract

The electrocatalytic activities and mechanisms of PtPb and PtBi ordered intermetallic phases towards formic acid, formaldehyde and methanol oxidation have been studied by DEMS and FTIRS, and the results compared to those for a pure polycrystalline platinum electrode. While PtPb exhibits an enhanced electrocatalytic activity for the oxidation of all three organic molecules when compared to a Pt electrode, PtBi exhibits an enhanced catalytic activity towards formic acid and formaldehyde oxidation, but not methanol. FTIRS data indicate that adsorbed CO does not form on PtPb or PtBi intermetallic compounds during the oxidation of formic acid, formaldehyde and methanol, and therefore their oxidation on both PtPb and PtBi intermetallic compounds proceeds via a non-CO_ads pathway. Quantitative DEMS measurements indicate that only CO₂ was detected as a final product during formic acid oxidation on Pt, PtPb and PtBi electrodes. At a smooth polycrystalline platinum electrode, the oxidation of formaldehyde and methanol produces mainly intermediates (formaldehyde and formic acid), while CO₂ is a minor product. In contrast, CO₂ is the major product for formaldehyde and methanol oxidation at a PtPb electrode. The high current efficiency of CO₂ formation for methanol and formaldehyde oxidation at a PtPb electrode can be ascribed to the complete dehydrogenation of formaldehyde and formic acid due to electronic effects. The low onset potential, high current density and high CO₂ yield make PtPb one of the most promising electrocatalysts for fuel cell applications using small organic molecules as fuels.