Direct Evaluation of O₂-Reduction-Based H₂O₂ Generation at Pt/C-Containing Powder Microelectrode Using Scanning Electrochemical Microscopy

Abstract

The percentage of H2O2 during oxygen reduction reaction (ORR) at practical powder electrocatalysts have been evaluated using a scanning electrochemical microscopy (SECM). We employed a porous microelectrode which contains the electrocatalysts of Pt/C, Pt-Co/C, and Pt-Ru/C as the oxygen reduction electrode of the SECM. And the Pt microelectrode was used as the H2O2 detector. First, the H2O2 generation amount at Pt/Cs has been measured by changing the Pt loading amount. A higher Pt loading Pt/C possesses a higher ORR activity and generates a larger amount of H2O2. However, the percentage of H2O2 generated with respect to the ORR is the same irrespective of the Pt loading amount. Next, H2O2 generations have been drastically suppressed at the Pt-Co/C and Pt-Ru/C in the potential ranges of practical fuel cell cathode and anode, respectively. This explains that the used Pt-Co/C is effective when used as a cathode; and, the anode Pt-Ru/C enables to reduce the H2O2 generation even if O2 crossleak occurred in the practical PEFC.