High‐Entropy Metal Phosphide for Efficient Hydrogen Conversion Reactions

High‐entropy metal phosphides (HEMPs) with complex compositions have garnered significant attention in catalysis. However, the cost‐effective synthesis of single‐phase HEMPs with high activity and stability remains a critical challenge, limiting their practical applications. Herein, we propose an innovative, versatile, and cost‐effective thermal treatment strategy based on cation‐bonded phosphate resin to synthesize single‐phase HEMP nanoparticles anchored on porous carbon substrates (Co 0.62 Fe 0.20 Ni 0.14 Cu 0.23 Mn 0.38 P/C). This catalyst demonstrates high performance for both the hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). It achieves a current density of 1.71 mA cm −2 at 0.1 V vs. reversible hydrogen electrode (RHE) for HOR in 0.1 m KOH and supports water electrolysis at 100 mA cm −2 with a low voltage of 1.66 V. Systematic characterizations and density functional theory (DFT) calculations reveal that Mn incorporation optimizes the electronic structure, accelerates electron transfer between metal sites, lowers hydrogen adsorption free energy, and enriches active sites, significantly enhancing catalytic performance. These results set a new benchmark for sustainable hydrogen energy. This study not only introduces a scalable synthesis route for HEMPs but also provides critical insights into designing next‐generation electrocatalysts for efficient and stable hydrogen‐related applications.