Epitaxial growth-engineered CoS@CoSe2 heterojunction for enhanced oxygen evolution reaction

Single metal chalcogenide catalysts still face challenges of insufficient catalytic active sites and slow catalytic reaction kinetics for oxygen evolution reactions (OER). Herein, a novel CoS@CoSe 2 heterojunction composite catalyst was constructed through heterojunction interface engineering strategy. The single-crystal CoSe 2 nanorods were successfully epitaxially grown on the surface of amorphous CoS nanoblocks by a two-step hydrothermal cascade in-situ growth technique. Benefiting from the interface coupling and synergistic effect of the CoS@CoSe 2 heterojunction, the designed electrocatalyst exhibited outstanding catalytic activity for OER, attaining a current density of 10 mA cm −2 with a low overpotential of only 115 mV, surpassing other reported chalcogenide electrocatalysts. Density functional theory (DFT) calculations revealed that the work function difference between CoS and CoSe 2 induces directional redistribution of charges at the heterojunction interface, rendering the CoSe 2 surface electron-deficient, thereby significantly optimising OH⁻ adsorption energy. Simultaneously, the heterojunction structure significantly enhances the total density of states around the Fermi level while also improving the d -band center of metallic active sites. These modifications promote more favorable adsorption of reaction intermediates, effectively reduce the energy barrier for the OER, accelerate reaction kinetics, and ultimately improve the overall catalytic performance. This study presents a promising strategy for the rational design and development of high-performance catalytic materials.