3D Ordered Macroporous Superstructures of High Entropy Hydroxide with Strong Orbital Coupling Enhancing Water/Seawater Oxidation

Abstract The water splitting performance is strongly influenced by intrinsic properties of the catalyst and the accessibility of the active center. Herein, high‐entropy hydroxides (HEH) with 3D ordered macroporous (3DOM) structure are prepared by chemical etching method with rational design. The 3DOM structure can maximize the exposure of the active sites and also facilitates bubble transport. As demonstrated by finite element analysis, the 3DOM structure modifies the spatial curvature of the catalyst, resulting in the enrichment of OH ⁻ . Moreover, the strong orbital coupling of transition metals significantly regulates the electronic structure of the catalyst, selectively adsorbs OH ⁻ at Fe sites, and inhibits the adsorption of Cl ⁻ . Thanks to these characteristics, 3DOM‐HEH‐300 shows the best oxygen evolution reaction (OER) performance in 1 m KOH (182 mV@100 mA cm ⁻² , 211 mV@500 mA cm ⁻² ), and stables operation of more than 400 h. Besides, in natural seawater, it also exhibits the best catalytic activity (245 mV@100 mA cm ⁻² , 278 mV@500 mA cm ⁻² ), which is better than similar catalysts without 3DOM structure. This work verifies the great synergistic effect of high entropy and mass transfer on the performance of OER, which also provides a new idea for constructing high‐performance electrodes.