Balancing high entropy complexity and defects for efficient green hydrogen production

Abstract Producing green hydrogen through water electrolysis is central to a sustainable energy future, yet its scalability is limited by sluggish half reactions, especially the oxygen evolution reaction (OER) on the anode. While both increasing configurational entropy and introducing defects are well-established strategies to enhance the activity of transition metal–based catalysts, these factors are not simply additive but instead exhibit a coupled and nontrivial relationship that governs catalytic performance. Herein, we use pentanary FeAlNiCoZn high-entropy layered double hydroxides (HE-LDHs) as a tunable model system to decouple these two design variables. By selectively leaching Zn, we create cation vacancies while gradually reducing configurational entropy, thereby tuning the material along a well-defined entropy–defect axis. This reveals a volcano-shaped relationship between OER activity and the balance of defects and entropy, with peak performance at an optimal intermediate state. Guided by this insight, we propose an “etching-and-fill” strategy, inserting Mn that is the active site of oxygen evolution cluster in photosystem II into defect-engineered LDH framework to restore the beneficial high configurational entropy. The resulting catalyst lowers the overpotential by 81 mV at 10 mA/cm 2 , decreases the operating potential by over 20% at 100 mA/cm 2 , and sustains stable electrolysis for 450 h without obvious degradation, enabling more efficient hydrogen generation. Our work establishes a clear entropy–defect–performance relationship and demonstrates that the coordinated modulation of entropy and defects provides a powerful and generalizable paradigm for the rational design of advanced multicomponent electrocatalysts for green hydrogen and beyond.