The Nature of the Catalytic Peak for Oxygen Reduction in Alkaline Electrolyte on the Au(100) Surface

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Abstract
We have studied the phenomenology of the catalytic peak for oxygen reduction on the Au(100) surface using cyclic potential voltammetry. In the potential region of this catalytic peak, oxygen is reduced via the overall four‐electron process to hydroxide with a half‐wave potential significantly positive to that of the Au(111), Au(110), and polycrystallite gold surfaces. We have studied the effect of sweep rate, sweep direction, and potential limits on the formation and definition of the catalytic peak. Our data indicate that an “oxidized Au(100)” surface is uniquely catalytic and selective for the overall four‐electron reduction of oxygen to hydroxide. However, the oxygen reduction activity of the “reduced Au(100)” surface is analogous to that of the Au(111) surface. The reduced Au(100) surface promotes the two‐electron reduction of oxygen to peroxide ion, and the half‐wave potential for oxygen reduction is more negative. We conclude that a potential‐induced kinetically limited process is operative during oxygen reduction on oxidized and reduced Au(100) surfaces. Processes consistent with our conclusion are: (i) potential‐induced surface reconstruction between a catalytic and noncatalytic surface and (ii) potential‐induced formation and destruction of a catalytic oxide or hydroxide. Additionally, trace level ionic species other than hydroxide ion could account for the behavior of the oxidized and reduced Au(100) surfaces.

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