Vanadium-regulated medium-entropy hydroxide catalysts for enhanced activity and corrosion resistance in seawater splitting

Abstract

Hydrogen production via seawater electrolysis holds significant promise for large-scale hydrogen generation. However, developing highly active anode catalysts with excellent oxygen evolution selectivity and robust resistance to chloride ion corrosion remains an unresolved hurdle. This study presents a novel vanadium-doped medium-entropy hydroxide (V-MEH) catalyst, fabricated via a straightforward hydrothermal approach without noble metals. Its electrochemical efficiency was systematically assessed for hydrogen generation in seawater electrolytes. The V-MEH catalyst demonstrated outstanding hydrogen evolution performance, requiring only extra 228 mV to reach 10 mA cm⁻². The reaction kinetics were further confirmed by the observed Tafel slope of 36.64 mV dec⁻¹, indicating highly efficient charge transfer. Under seawater conditions, the V-MEH variant maintained high performance, with overpotentials as low as 231, 267 and 271 mV at progressively higher current densities (10, 100 and 250 mA cm⁻²). Additionally, it exhibited exceptional stability, sustaining 224 mA cm⁻² for 100 hours. Benefiting from the entropy effect, V-MEH enhances OH⁻ adsorption while suppressing Cl⁻ adsorption, thereby achieving high selectivity in seawater and improving corrosion resistance. This medium-entropy electrocatalyst demonstrates exceptional OER performance in alkaline seawater environments, positioning itself as the most effective metal-based system developed to date and representing a major advancement toward practical seawater electrolysis.