Research on Ni-Co bimetallic-based composite materials and their electrocatalytic oxygen evolution performance

A series of Ni-Co bimetallic oxides were synthesized via a microwave-assisted hydrothermal method. The phase structure, morphological features, valence states, and defects of the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The results reveal the regulatory mechanism of Ni-Co bimetallic synergy on the formation of oxygen vacancies (Ov). When the molar ratio of Ni to Co was 1∶3, the obtained NiCo3Ox exhibited the best OER performance, delivering an overpotential of only 393 mV at a current density of 50 mA/cm2, along with a low Tafel slope (172.3 mV/dec) and catalytic stability exceeding 24 h. This superior activity is attributed to the synergistic redox interplay between Co2+/Co3+ and Ni2+/Ni3+, as further verified by in situ Raman spectroscopy, which confirmed that *OOH intermediate adsorption promoted reaction kinetics and that Ov mediated rapid electron transfer. Density functional theory (DFT) calculations further demonstrated that electronic coupling at the bimetallic interface enhanced the material’s conductivity. This study provides a new strategy for designing efficient OER catalysts based on oxygen-vacancy regulation.