Vanadium-Modulated Mo/Ni-Based Multi-Heterostructures Finely Tailoring D-Band Centers for Electrocatalytic Water Splitting

Abstract

Finely tailoring of d-band centers (ɛd) of various metals is expected to balance the absorption/desorption of multiple intermediates for water electrolysis, but challenging. Herein, a porous ultrathin nanosheet consisting of V-doped multi-heterostructured Ni-Mo interstitial compound (V-MoN/NixNy) is designed as a bifunctional electrocatalyst for hydrogen/oxygen evolution reaction (HER/OER). V-substituted Mo-based polyoxometalates were assembled with Ni(OH)2 to target multi-interface coupled Ni-Mo heterojunctions and precise V-doping. Theoretical calculations validate the synergistic effect of V doping and heterostructure results in electron accumulation on the V-MoN side, induces the upward shift of ɛd (Mo), thus strengthening the adsorption of H2O, while generating a new active site (V) for *OH adsorption, and a nearby N site for H* adsorption, which is beneficial to HER. Meanwhile, electron-deficient Ni3N has appropriate absorption of various key intermediates (OH*, O* and OOH*), and the elaborate customizing of the ɛd (Ni) effectively promotes the transition of O* to OOH*, thereby facilitating OER. Resultantly, V-MoN/NixNy manifests excellent activity, which only requires overpotentials of 193/460 mV at a large current density of 400 mA cm−2 for HER/OER, significantly outperforming commercial Pt/C (306 mV) and RuO2 (512 mV). The assembled electrolyzer takes only 1.50 V@10 mA cm−2 for overall water splitting with good durability. This study underscores the superiority of finely customizing d-band centers in triggering multi-site synergism.

Keywords: Heteroatom Doping, Heterostructure, Electronic Structure Modulation, Metal Nitrides, hydrogen evolution reaction, Oxygen Evolution Reaction