To elucidate the mechanism of NaNO2-promoted Pt dissolution, the weight loss of Pt black-deposited Au quartz resonators was measured in 0.1 mol dm-3 HClO4 containing NaNO2 under potential cycling and constant potential conditions. A continuous weight loss of ca. 50-60 ng cm-2 cycle-1 was detected in the presence of 10 mmol dm-3 NaNO2 during potential cycling above a high potential limit of 1.2 V vs RHE (VRHE) and below a low potential limit (E L) of 0.9 VRHE. A weight loss was observed at constant potentials (0.6-0.8 VRHE) when oxides were initially present; the net weight loss (Δw) magnitude increased as the amount of the initially formed Pt oxide increased. These results indicate that Pt dissolution occurred when Pt oxides were reduced in the presence of NaNO2. The good agreement between the Δw per potential cycle and the Δw at a constant potential (EL of the potential cycling = constant potential) revealed that the formation of Pt oxides in the positive sweep was required for the continuous weight loss under potential cycling. The Δw value increased for higher concentrations of NaNO2 under both conditions. The products of NaNO2 reduction were thought to participate in Pt dissolution.
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