Interfacial Carbonate‐Mediated Activation of Pre‐Catalysts for Water Electrolysis

ABSTRACT Pre‐catalyst reconstruction fundamentally governs the local structure and solid–liquid interface of the derived phase, significantly influencing water electrolysis performance. However, fully unlocking the intrinsic potential of pre‐catalysts remain a persistent bottleneck, as conventional electrolytes cannot functionalize the interface during reconstruction. Herein, we propose an interfacial carbonate‐dominated activation strategy to simultaneously tune the derived NiOOH structure and its interface, enabling efficient oxygen evolution reaction (OER). Using Ca‐Ni 3 S 2 as the model pre‐catalyst and K 2 CO 3 to replace KOH as the reconstruction electrolyte, the carbonate‐dominated interface kinetically and thermodynamically impedes the transformation of Ni 3 S 2 into NiOOH, enabling surface‐confined reconstruction at elevated potential that preserves the interior Ni 3 S 2 while forming the functionalized NiOOH phase on the surface. This functionalized surface, induced by the retained CO 3 2− from reconstruction, optimizes the electron distribution, interface water framework, and establishes a stable buffer layer, facilitating water oxidation and suppressing NiOOH deactivation. Resultantly, the reconstructed catalyst (Ca‐Ni 3 S 2 ‐RC) shows an overpotential of only 261 mV at 100 mA cm −2 , a remarkable reduction of 198 mV compared to its KOH‐reconstructed counterpart. Integrated into an alkaline water electrolyzer (AWE), Ca‐Ni 3 S 2 ‐RC presents a competitive energy consumption of 4.21 kWh m −3 H 2 to deliver 4000 A m −2 over 900 h, highlighting its promise for industrial applicability.