Combinatorial screening of thin film electrocatalysts for a direct methanol fuel cell anode

The Pt-Ru-W and Pt-Ru-Co ternary alloy systems were investigated for use as anode catalysts in direct methanol fuel cells. Plasma sputtering through shadow masks was used to deposit discrete composition combinatorial libraries. Post-deposition annealing promoted multilayer homogenization, with interdiffusion of the layers confirmed by X-ray diffraction. The short term methanol oxidation activities of the different compositions were compared in parallel by cyclic voltammetry with a multichannel electrochemical cell. It was found that the optimum composition changed from initial to final tests. Initially Pt25Ru0W75 and Pt17Ru17Co66 outperformed the best binary Pt-Ru catalyst by 3× and 20×, respectively. Cycling the potential at 60 °C was found to change the performance of some compositions. The performance of Pt-Ru binary catalysts were improved by this conditioning and the optimum ternary compositions shifted to Pt44Ru12W44 and Pt12Ru50Co38. The optimum Pt-Ru-W composition had a peak methanol oxidation current density that was 1.5× more than the best Pt-Ru binary composition. The peak methanol oxidation current density of the best Pt-Ru-Co composition was 2.5× more than the best Pt/Ru binary composition and had a substantially lower onset potential.