Revealing the effect of anion-tuning in bimetallic chalcogenides on electrocatalytic overall water splitting

Enhancing electrocatalytic water splitting performance by modulating the intrinsic electronic structure is of great importance. Here, porous bimetallic oxide and chalcogenide nanosheets grown on carbon paper denoted as NiCo₂X₄/CP (X = O, S, and Se) are prepared to demonstrate how the anion components affect the electronic structures and thereby disclose the correlation between their intermediates interaction and catalytic activities. The experimental characterization and theoretical calculation demonstrate that Se and S substitution can promote the ratio of Co³⁺/Co²⁺ and thereby modulate the electronic structure accompanied with the upshift of d band centers, which not only enhance the inner conductivity but also regulate the interaction between the catalyst surface and intermediates, especially for the adsorption of absorbed H and hydroperoxy intermediates towards respective hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). As a result, a full alkaline electrolyzer using NiCo₂Se₄/CP and NiCo₂S₄/CP as cathode and anode delivers a low voltage of 1.51 V at 10 mA·cm^-2, which is comparable even superior to most transition metal-based electrolyzers.