The influence of oxygen atmosphere on platinum (Pt) dissolution under potentiodynamic conditions was investigated in 1.0 mol dm<sup>-3</sup> HClO <inf>4</inf> at 80 °C over the range 0.0.0.7MPa of oxygen partial pressure (pO2). The rate of Pt dissolution depended concavely on pO2 with the minimum at 0.091 MPa. When pO2 was below 0.091 MPa, the oxygen atmosphere suppressed the platinum dissolution from an oxide-deprived Pt surface owing to an increase in the coverage of passive oxides, resulting in a decrease in the rate of Pt dissolution with increasing values of pO2. For pO2 ≥ 0.091 MPa, the current of oxygen reduction reaction (ORR) increases with pO2. This further participated in an increase in the rate of Pt dissolution, probably through the cathodic dissolution of higher-order oxides formed as intermediates in ORR.
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