Cl-Doped Cu2O Nanocube as an Efficient Oxygen Evolution Catalyst for Seawater Electrolysis

Abstract Electrolytic water splitting is a critical technology for sustainable hydrogen production, yet its reliance on freshwater resources exacerbates global scarcity. Seawater electrolysis offers a promising alternative, but it faces challenges due to competitive chlorine evolution reactions (ClER) induced by high chloride ion (Cl–) concentrations. Herein, we report the synthesis of chlorine-doped cuprous oxide (Cu2O-Cl) nanocubes as a robust, nonprecious oxygen evolution reaction (OER) catalyst for seawater electrolysis. By strategically incorporating Cl into the Cu2O lattice, we achieve a +0.30 V upward shift in the valence-band maximum, enabling thermodynamically favorable OER activity while suppressing ClER. The Cu2O-Cl catalyst exhibits superior performance in both an alkaline electrolyte and simulated seawater, delivering a low overpotential of 386 mV at 10 mA cm–2, a small Tafel slope of 204.7 mV dec–1, and remarkable stability over 40 h of continuous operation. Enhanced hydrophilicity, accelerated charge transfer, and optimized reaction kinetics are attributed to Cl doping, as confirmed by electrochemical measurements and theoretical calculations. This work introduces an electronic structure-modulated catalyst that addresses intrinsic limitations of Cu2O, paving the way for scalable, durable seawater electrolysis systems.