Methanol oxidation on Pt/Ru, Pt/Ni, and Pt/Ru/Ni anode electrocatalysts at different temperatures for DMFCs

Pt/Ru (1:1), Pt/Ni (1:1), and Pt/Ru/Ni (5:4:1) electrocatalysts for use in direct methanol fuel cells (DMFCs) were synthesized by reduction with NaBH4 combined with freeze-drying and their activity as a methanol oxidation catalyst was examined at different temperatures. The onset potential of Pt/Ru/Ni (5:4:1) was lower than that of Pt/Ru (1:1) and current density of Pt/Ru/Ni (5:4:1) was larger than that of Pt/Ru (1:1). In addition, Pt/Ru/Ni (5:4:1) had a larger turnover number and a smaller activation energy for methanol oxidation than Pt/Ru (1:1). Polarization and power density data in a liquid-feed DMFC unit cell test were in good agreement with the voltammetry and chronoamperometry data, for which Pt/Ru/Ni (5:4:1) showed a higher catalytic activity than Pt/Ru (1:1). The role of Ni from the standpoint of the oxidation states of Ni and the modification of the electronic structure of Pt by X-ray photoelectron spectroscopy is discussed. (C) 2003 The Electrochemical Society.