Deterioration of Pt Catalyst Under Potential Cycling

Using the rotating ring-disk electrode, Pt consumption has been investigated to clarify the dissolution mechanisms under potential cycling which was the symmetric and asymmetric potential wave. The charge of Pt oxidation was always larger than that of reduction. The difference of the oxidation and reduction charges should be caused by Pt dissolution. Pt dissolved during the oxide formation at anodic sweep for Symmetric rectangular wave , Symmetric triangular wave and Slow anodic triangular wave . The charge transfer number of the anodic dissolution reaction was ca. 4, based on the relationship between the difference of anodic/cathodic charges and the consumption. Therefore, the dissolution reaction would be Pt → Pt4+ + 4e- or chemical dissolution of PtO2 that was electrochemically 4-electron oxidized. For Slow cathodic triangular wave , Pt dissolution during cathodic sweep was also observed. The charge transfer number of the cathodic dissolution reaction was ca. 2. This reaction would be PtO2 + 4H+ + 2e- → Pt2+ + 2H2O.