Defect and doping synergistic optimization for efficient and durable alkaline seawater hydrogen production

Seawater electrolysis offers a dual benefit of alleviating freshwater scarcity and advancing hydrogen energy technologies. However, its practical implementation is hindered by the complex chemical composition of seawater, particularly the corrosive chloride ions that induce electrode degradation and parasitic chlorine evolution, posing critical challenges to long-term electrolytic stability. To address this issue, we designed an efficient electrocatalyst by introducing vanadium (V) doping and oxygen vacancies (Ov) into nanoflower-structured Co₃O₄ (V-Co₃O₄(Ov)-250) through hydrothermal synthesis and controlled annealing. The Ov configuration modulates electronic structures and facilitates charge transfer, whereas V doping enhances corrosion resistance, increases lattice defects, and generates active sites. This dual modification synergistically improves surface reactivity and conductivity, boosting catalytic performance. V-Co₃O₄(Ov)-250 achieves low overpotentials of 69 mV for the hydrogen evolution reaction (HER) and 158 mV for the oxygen evolution reaction (OER) in alkaline freshwater, and 133 mV (HER) and 228 mV (OER) in alkaline seawater at a current density of 10 mA cm^-2. When assembled into an electrolytic cell, the catalyst requires a low voltage of 1.68 V to drive a current density of 100 mA cm^-2 in an alkaline seawater electrolyzer, while maintaining outstanding stability over 100 h of continuous operation. This performance surpasses that of most non-precious metal-based electrocatalysts for seawater electrolysis. Theoretical analysis elucidates that V doping promotes preferential adsorption of OH^- at the active site and optimizes intermediates' adsorption-desorption equilibrium through its synergy with Ov, consequently lowering the reaction energy barrier and enhancing intrinsic catalytic activity.