Oxidation of hydrogen peroxide on gold rinc electrode in acid medium
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Answer:
Explanation:
It is shown that the cathodic reduction processes of oxygen and hydrogen peroxide on gold electrodes in 0·5 M H2SO4 at 25°C interfere with each other, and that a stationary concentration of hydrogen peroxide (4 × 10-3 M at -0·1 V (nhe)) is attained in solution. Below this concentration, oxygen reduces to hydrogen peroxide (two-electron process); above it, oxygen reduces to water (four-electron process). In the latter case an initial block of the gold surface occurs, giving rise to a maximum current peak, attributable to the temporary occurrence of both reactions. Anodic oxidation of hydrogen peroxide begins to occur at + 1·0 V (nhe) at which potential absorbed oxide begins to form on gold, so that an indirect mechanism, involving hydrogen peroxide and adsorbed oxide, is proposed. In the presence of bulk gold oxide at potentials higher than + 1·4 V (nhe) the anodic oxidation of hydrogen peroxide is hindered, as the reactivity of bulk gold oxide is lower than the reactivity of adsorbed oxide.