Periodic Pulsed-Potential Electrolysis of Methanol

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This is a test of the hypothesis that periodic, pulsed-potential electrolysis on an unmodified platinum electrode, or in conjunction with surface modification by underpotential-deposited tin or ruthenium, can significantly increase the cycle-averaged power production by lowering the concentration of the poisonous byproduct adsorbed on the electrode. For a small fraction of the cycle, the anode potential is pulsed to a high value at which the surface poison is oxidatively removed; during the remainder of the cycle, the anode potential is at a lower, power-producing polarization. Preliminary results suggest that the average current may be increased by better than two orders of magnitude above that obtainable by using steady- state (DC) control at the same power potential. The effects of pulsed-potential electrolysis in acidic methanol solutions on smooth and carbon-supported platinum, with and without underpotential- deposited tin or ruthenium, are investigated. Conventional current- voltage-time electrochemical measurements, are recorded and surface infrared and X-ray photoelectron spectra are taken. The production rates of formaldehyde and formic acid and the dissolution rate of platinum under the influence of pulsed-potential electrolysis are determined. Methanol-air fuel cells are attractive power sources for many applications, including electric vehicles, remote installations, transportation systems, and emergency backups. Methanol is cheaper, more compact, easier to transport, and much safer to use than hydrogen, which is the principal alternative fuel-cell fuel. Unfortunately, methanol-air fuel cells using a platinum electrocatalyst are self poisoning, severly limiting their efficiency. This work addresses this shortcoming.