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Herein, we prepare MoS₂ and Cu-MoS₂ catalysts using the solvothermal method, a widely accepted technique for electrocatalytic overall water-splitting applications. TEM and SEM images, standard tools in materials science, provide a clear view of the morphology of Cu-MoS₂. HRTEM analysis, a high-resolution imaging technique, confirms the lattice spacing, lattice plane, and crystal structure of Cu-MoS₂. HAADF and corresponding color mapping and advanced imaging techniques reveal the existence of the Cu-doping, Mo, and S elements in Cu-MoS₂. Notably, Cu plays a crucial role in improving the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of the Cu-MoS₂ catalyst as compared with the MoS₂ catalyst. In addition, the Cu-MoS₂ catalyst demonstrates significantly lower overpotential (167.7 mV and 290 mV) and Tafel slopes (121.5 mV dec⁻¹ and 101.5 mV dec⁻¹), standing at −10 mA cm⁻² and 10 mA cm⁻² for HER and OER, respectively, compared to the MoS₂ catalyst. Additionally, the Cu-MoS₂ catalyst displays outstanding stability for 12 h at −10 mA cm⁻² of HER and 12 h at 10 mA cm⁻² of OER using chronopotentiaometry. Interestingly, the Cu-MoS₂‖Cu-MoS₂ cell displays a lower cell potential of 1.69 V compared with the MoS₂‖MoS₂ cell of 1.81 V during overall water splitting. Moreover, the Cu-MoS₂‖Cu-MoS₂ cell shows excellent stability when using chronopotentiaometry for 18 h at 10 mA cm⁻².