Stabilizing Water Dissociation Sites via Ethylenediamine Coordination for Industrial-Current-Density Alkaline...

Incorporating water dissociation sites into electrocatalysts significantly boosts the catalytic activity for the alkaline hydrogen evolution reaction (HER), yet the reconfiguration of these sites under industrial-level current densities-an issue that has received limited prior attention-severely impairs catalytic stability. Herein, we construct a highly active and ultra-stable hybrid electrocatalyst composed of metallic nickel and a hydroxy(ethylenediamine)nickel(II) complex (Ni[(OH)₂en_x]/Ni) via a scalable cathodic alkalization strategy. The interface-coupled Ni[(OH)₂en_x] complex, featuring high oxophilicity and enhanced thermodynamical stability against reduction, not only accelerates the water-dissociation step but also renders long-term catalytic durability. The resulting hybrid catalyst delivers a low overpotential of 35.2 mV at 10 mA cm^-2 and a small Tafel slope of 43.68 mV dec^-1, outperforming the benchmark Ni(OH)₂/Ni and Ni(OH)₂/Pt catalysts. When integrated into an anion-exchange membrane water electrolyzer, the electrode delivers 500 mA cm^-2 for 3000 h in 1.0 M KOH at 25°C. This work demonstrates the great potential of coordination complexes as robust active sites for Volmer step, a concept that can be extended to other electrocatalytic reactions involving water dissociation.