Activated CuNi@Ni Core@shell structures via oxygen and nitrogen dual coordination assembled on 3D CNTs-graphene hybrid for high-performance water splitting

Herein, a unique nanohybrid, in which CuNi@Ni core@shell nanoparticles were dual-coordinated with oxygen and nitrogen heteroatoms (CuNi@Ni(ON) NPs) and uniformly assembled on 3D porous carbon nanotubes-graphene (CNTs-Gr), was well-designed via an effective synthesis process. The CuNi@Ni(ON)/CNTs-Gr material with tunable electronic properties and conductivity displayed favorite adsorption energies towards reactants, thus manifesting its remarkable bifunctional activities for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) operating in 1.0 M KOH. To achieve current responses of 10 and 100 mA cm⁻², small overpotential values of 42.1 and 410 mV were needed for HER and OER, respectively. An electrolyzer employing CuNi@Ni(ON)/CNTs-Gr electrodes delivered an exciting cell voltage of 1.51 V at 10 mA cm⁻² and good stability over 25 h operation, surpassing performance of a commercial Pt/C//RuO₂-based system. These achievements suggested the CuNi@Ni(ON)/CNTs-Gr is one of the most effective nonprecious catalysts for high-performance production of green hydrogen gas via water splitting.