Effect of Pt Dissolution on H2O2 Formation based on RRDE Method

Abstract

Potential cycling tests using 42.2 wt% and 19.1 wt% Pt/C catalysts were conducted by the RRDE method to evaluate the changes in the electrochemical surface area (ECSA) and H2O2 formation ability of the catalysts. As the typical operating conditions of a proton exchange membrane fuel cell (PEMFC), square wave potential cycling (0.7–0.9 V) was applied to the catalysts for 150,000 cycles in an O2-saturated 0.1 M HClO4 electrolyte. During the potential cycling test, electrochemical measurements were carried out to characterize the ECSA, oxygen reduction reaction (ORR) activity and H2O2 formation. After 150,000 potential cyclings, while the ECSA of the 42.2 wt% Pt/C dropped by 35 %, the ECSA loss for the 19.1 wt% Pt/C was 55 %. This result implies that the Pt content in the cathode catalyst affects the ECSA loss during the long-term PEMFC operation. Additionally, the H2O2 formation ratio obviously increased with the potential cycling only in the case of the 19.1 wt% Pt/C. In order to verify the H2O2 formation dependence on the ECSA, four types of catalysts, which included different Pt loading amounts (42.2, 28.1, 19.1 and 9.5 wt% Pt/C), were evaluated, and these results explained the relationship between the ECSA decay and H2O2 formation increase in the durability tests.