Consumption rate of Pt under potential cycling

The consumption rate of Pt in sulfuric acid under potential cycling has been investigated in 1 mol dm(-3) H2SO4 at 40 degrees C as a basic study to understand the consumption rate of the electrocatalyst of polymer electrolyte fuel cells. With a higher potential limit, EH was 1.5 V vs reversible hydrogen electrode ( RHE ), the consumption rate was a few ng cm(-2) cycle(-1) for rectangular and symmetric triangular waves, and the consumption rate increased with the EH up to 1.8 V vs RHE. Among the triangular waves between 0.5 to 1.8 V vs RHE, the consumption rate of symmetric waves and fast cathodic asymmetric triangular waves were a few ng cm(-2) cycle(-1). However, the slow cathodic triangular wave, which were 20 V s(-1) anodic and 0.5 V s(-1) cathodic, showed 24 ng cm(-2) cycle(-1) consumption rate. The ratio in the difference of charge to the consumption showed that the electron transfer number was about 2 for the slow cathodic triangular wave, and that of the electron transfer number was about 4 for the symmetric waves and the fast cathodic triangular waves. Therefore, PtO2 + 4H(+) + 2e(-). Pt2+ + 2H(2)O that follows the Pt oxidation, Pt + 2H(2)O. PtO2 + 4H(+) + 4e(-) would occur under the enhanced condition, and Pt. Pt4+ + 4e(-) would occur under symmetric conditions. (c) 2006 The Electrochemical Society.