Abstract: As a low- and zero-carbon energy source, hydrogen energy is an important part of the future national energy system. The development of an efficient and inexpensive alkaline hydrogen evolution reaction (HER) electrocatalyst is of great significance for the large-scale preparation and utilization of hydrogen energy. In this paper, the MoO₃/Ni-NiO/Nb₂CT_x was prepared by one-step co-electrodeposition method to loaded MoO₃/Ni-NiO heterostructure on two-dimensional Nb₂CT_x MXene, and the obtained MoO₃/Ni-NiO/Nb₂CT_x exhibited excellent HER performance. The XRD, SEM and TEM were conducted to analyze the surface morphology and structure of the catalysts. Results demonstrate that the MoO₃/Ni-NiO heterostructure were successfully electrodeposited on the surface of Nb₂CT_x MXene nanosheets. The results of HER tests in 1.0 mol/L KOH electrolyte show that the MoO₃/Ni-NiO/Nb₂CT_x at current densities of 10 and 100 mA·cm⁻² has small overpotentials of 8 and 201 mV, respectively, and Tafel plot is 51 mV·dec⁻¹. The MoO₃/Ni-NiO/Nb₂CT_x also has good catalytic stability with almost no detectable activity decay after 20 h HER test at current densities of 10 and 50 mA·cm⁻², respectively. Besides, the operando electrochemical impedance spectroscopy measurements were used to estimate electrocatalytic HER kinetics of different catalysts at overpotential from 0 to 220 mV (vs reversible hydrogen electrode (RHE)), which indicating the MoO₃/Ni-NiO/Nb₂CT_x can effectively promote hydrolysis dissociation process and active hydrogen adsorption process, thus improving HER activity.