Influence of Perovskite Catalysts and Carbon Graphitization on Carbon Oxidation under Oxygen Evolution Reaction Conditions: A DEMS Study

Perovskite oxide based composites with conductive carbonaceous materials have garnered significant attention for their high oxygen evolution reaction (OER) activity in alkaline media. While extensive research has focused on the rational design of transition metal oxides, such as perovskites, the role of carbon additives has received comparatively less attention despite their thermodynamic instability under OER conditions. This study investigated the OER and corrosion behavior of composite catalysts by employing LaCoO 3 (LCO) and Sr 2 Co 0.8 Fe 0.2 O 3 Cl (SCFOC) catalysts with different OER mechanisms and activities, and carbonaceous materials with different graphitization degrees. We applied the online differential electrochemical mass spectroscopy (DEMS) for the quantification of the CO 2 evolution current hidden in the overall oxidation current at the OER potential. The LCO composite with amorphous carbon exhibited a substantial CO 2 evolution when compared with the graphitized carbon, indicating that the apparent OER currents include contributions from carbon oxidative corrosion. On the other hand, the noticeable CO 2 evolution current of the SCFOC composite was almost independent of the graphitization degree of the carbon, suggesting overestimation of its OER activity. These findings highlight the importance of selecting appropriate conductive carbon materials and optimizing the catalyst compositions for precise determination of the OER activities from a methodological viewpoint, while balancing the performance and durability from a practical viewpoint.