Non-Pt Anode Catalysts for Alkaline Direct Alcohol Fuel Cells

Pd- and Au-based binary catalysts have been tested as non-Pt anode catalysts for alkaline direct alcohol fuel cells toward the electrooxidation of methanol, ethanol, and ethylene glycol. The activity of Pd for alcohol oxidation is very low in acid but relatively high in alkaline, in which an onset potential can be observed around 0.4 V (vs RHE). After incorporation of Ru, the onset potential shifts negatively ca. 0.15 V. It is notable that Pd-Ru is extremely active for ethanol oxidation, and the current density is four times that on Pt-Ru within 0.3–0.4 V. Whereas Au is inert in acid for the electrooxidation of alcohol, but it is somewhat active in alkaline. An anodic current of alcohol oxidation can be observed in alkaline at potentials positive than 0.6 V (vs RHE). Au-Ru exhibits higher activity than Au at relatively positive potentials, but it does not cause a negative shift in the onset potential, which may imply that the dissociative adsorption of alcohol molecules on the Au surface is the rate-determining step at relatively negative potentials.