Regulating Reconstruction Activity of Cobalt Electrode for Optimized Water Oxidation

Elucidating and regulating dynamic catalyst reconstruction are crucial for various electrocatalytic reactions. Here, we applied model fittings with operando characterizations to quantify the reconstruction activity (i.e., ability to reconstruct) of layered Co(OH)₂ toward the oxygen evolution reaction (OER). By modulating the intercalation species into Co(OH)₂, we governed distinct reconstruction thermodynamics and kinetics, with diverse mass changes and heterogeneous Co oxidation during the OER. We further established a volcano-type relationship between reconstruction activity and OER activity and identified that a moderate reconstruction activity, achieved by dual-anion intercalation, favored a high OER activity. This might result from its proper basal spacing that regulated the coupled ion (de)intercalation–electron transfer for reconstruction, leading to optimal Co for binding OER intermediates. The optimally reconstructed Co(OH)_1.26Cl_0.08(CO₃)_0.33·0.84 H₂O delivered 1 A cm^–2 at 1.78 V for anion-exchange membrane water electrolysis. This work laid the foundation for modulating reconstruction activities to benefit electrocatalysis.