Ultrastable Bifunctional Electrocatalyst Based on High-Entropy Layered Hydroxide/Sulfide Heterostructure Enabled by Cerium Modulation for Water/Seawater Splitting

Developing efficient, durable electrocatalysts for sustainable hydrogen production via water/seawater electrolysis remains a critical challenge due to the sluggish kinetics of oxygen evolution reactions (OER) and material degradation in corrosive environments. Herein, a cerium ion-modulated high-entropy layered hydroxide/sulfide heterostructure composite (HELH/HEMS-6h) is synthesized through a two-step hydrothermal strategy integrating lattice distortion, defect engineering, and hierarchical architecture. The optimized catalyst exhibits exceptional bifunctional activity, achieving low overpotential of 239 mV (OER) and 71 mV (HER) at 10 mA cm –2 in alkaline seawater media, alongside requiring only 1.55 V to drive overall water splitting at 10 mA cm –2 respectively. Structural and electronic analyses reveal that cerium doping induces valence modulation and charge redistribution. In addition, the epitaxial growth of sulfide nanoflakes on hydroxide cores enhances the exposure of active sites, charge transfer efficiency, and chloride resistance via sulfate-mediated anion repulsion. Remarkably, HELH/HEMS-6h demonstrates robust stability in simulated and natural seawater electrolytes, attributed to entropy-driven phase stabilization and interfacial electronic synergy. This work provides a scalable approach to designing high-entropy electrocatalysts for practical hydrogen generation in diverse environments, advancing the viability of seawater electrolysis for sustainable energy systems.