Electroreduction of nitrous oxide on platinum and palladium: Toward selective catalysts for methanol–nitrous oxide mixed-reactant fuel cells

Abstract

The kinetics of N2O electroreduction in the absence and presence of methanol was studied between 295 and 333K on polycrystalline Pt and Pd electrodes in 0.1M NaOH. In the absence of methanol the reduction of N2O on Pd is more facile than on Pt as shown by the approximately four times lower apparent activation energy and lower Tafel slope (Pt: 0.111±0.019Vdec−1, Pd: 0.084±0.007Vdec−1 at 295K). Two different electroreduction mechanisms are proposed for Pt and Pd with and without participation of underpotential deposited hydrogen, respectively. The selectivity of Pt and Pd electrodes toward both N2O electroreduction and methanol (0.5 and 1M) oxidation at 295K was also investigated. Pt based electrocatalysts are promising candidates for the anode of a mixed reactant CH3OH–N2O fuel cell due to inhibition of N2O reduction by chemisorbed methanol. Pd on the other hand is a selective cathode electrocatalyst since N2O reduction takes place fairly actively in the presence of 1M methanol, while methanol oxidation is inhibited.