Oxygen Evolution Reaction by Ni‐Hexacyanoferrates Nanocubes Integrated with Trigonal Selenium: Effect, Properties and Performances

Abstract Oxygen evolution reaction (OER) is a key step affecting the large‐scale hydrogen fuel production from water splitting due to its slow kinetics. Despite numerous OER electrocatalysts, there is still a need for cheap, robust, and efficient catalysts. Here, a new facile protocol aimed at synthesizing composite nanostructures is described in which the characteristics of Prussian Blue Analogues (PBAs), namely nickel hexacyanoferrate (Ni‐HCF), and trigonal selenium ( t‐ Se) are merged. A novel surface‐structure modulation strategy is proposed that allows the PBA Ni‐HCF to develop a new morphology while integrating t‐ Se. Increasing selenization rates influence the shape, size, composition, and electronic and functional properties of the materials with a cube‐to‐sphere transition at high t‐ Se content. The catalyst with the second highest t‐ Se content exhibits an overpotential of 180 mV, achieving a current density of 10 mA cm −2 in 1 m KOH with a Tafel slope of 59.9 mV dec −1 . This performance, attributable to the synergistic effect of PBA‐based nanomaterial and trigonal selenium, rivals the best results described in the literature. The study suggests a simplified route for developing effective OER electrodes using economically affordable and abundant materials like Ni, Fe, and Se in Ni‐HCF/ t‐ Se, potentially replacing expensive Ru‐ and Ir‐based commercial catalysts.