Molybdenum-Promoted Surface Reconstruction in Polymorphic Cobalt for Initiating Rapid Oxygen Evolution

It has been well recognized that the surface reconstruction of electrocatalysts at the initial stage in the form of phase transitions, defect migrations, valence regulations, etc., plays a critical role in generating real, surface active catalytic centers and achieving steady surface reactions. It is also expected that a low activation energy barrier for initiating surface reconstruction is crucial for rapid and stable electrochemical catalysis. Despite this, the surface reconstruction kinetics and their effects on catalytic reactions have been rarely investigated. Herein, using phase modulated polymorphic cobalt-based catalysts with tailorable nitrogen-metal bonds through a cationic molybdenum-substitution strategy, real-time X-ray photoelectron spectroscopy (XPS) structural monitoring of the surface chemical state evolution during the catalytic reaction is performed to track the initial surface reconstruction kinetics during the alkaline oxygen evolution reaction (OER). It is concluded that the molybdenum-modulated cobalt-based nanocatalyst can be tuned with favorable initial surface reconstruction and stabilized active centers to reach optimized OER catalysis, accompanied by a low onset overpotential of only 210 mV and a favorable overpotential at 10 mA cm–2 of 290 mV, outperforming the commercial, noble-metallic RuO2 catalyst. This study thus provides new conceptual insights into rationally regulating the initial surface reconstruction kinetics for high-performance electrocatalysis reactions.