Engineering the Lattice and Electronic Configurations of N-Rich-CoMoCN by Mo Doping and N Enrichment for Enhanced Water Splitting

Abstract

Developing efficient, low-cost electrocatalysts for overall water splitting (OWS) is critical for advancing hydrogen energy technologies. Here, we fabricate Mo-incorporated N-rich-CoMoCN electrocatalyst from ZIF-67 (CoCN material), ammonium molybdate, and melamine precursors. This catalyst, featuring the predominant Co/Co₆Mo₆C₂ heterojunction and abundant surface-layered architecture, collectively provides an ideal microenvironment for catalytic reactions and facilitates charge transfer. In alkaline media, it exhibits outstanding bifunctional activity, delivering overpotentials of only 107 and 256 mV for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, at a current density of 10 mA cm⁻², far surpassing the performance of CoCN and CoMoCN. Notably, the N-rich-CoMoCN-based electrolyzer requires only 1.52 V to achieve 10 mA cm⁻² in a two-electrode system with 1.0 M KOH. The comprehensive structural and electrochemical characterizations reveal that the incorporation of Mo and N modulates the catalyst's morphology as well as lattice and electronic configurations, resulting in the strong electronic interaction between Co, Mo, and N, thereby accelerating the intrinsic reaction kinetics. Density functional theory (DFT) calculation further uncovers that N enrichment can effectively modulate the electronic state distribution of Co and Mo, thereby promoting interfacial charge rearrangement and regulating the d-band center of the catalyst. The synergistic effect between heterostructure construction and N enrichment optimizes the electronic structure and surface energy of the N-rich-CoMoCN catalyst, which facilitates charge transfer, ultimately leading to enhanced electrocatalytic activity in OWS performance. This work highlights an efficient strategy for designing high-performance bifunctional catalysts from MOF-derived heterostructures for sustainable hydrogen production.