Unveiling the Role of Nickel Precursors Driven Engineering of Ni-MoS2 for Enhanced Supercapacitor Energy Storage

This study reports the strategic doping of nickel (Ni) onto molybdenum disulfide (MoS2) to enhance its electrochemical performance for supercapacitor applications. Ni was introduced from three different precursors, nickel chloride (NiCl2), nickel hydroxide (Ni(OH)2), and nickel nitrate (Ni(NO3)2) via a facile hydrothermal method, enabling uniform atomic dispersion and effective precursor mixing at elevated temperatures. A comprehensive understanding of the resulting Ni–MoS2 nanostructures was achieved through systematic physicochemical and electrochemical characterization. All these characterizations revealed significant improvement in the Ni-MoS2 nanostructures compared to pristine MoS2. Structural analysis indicates that Ni atoms either substitute Mo sites or intercalate between MoS2 layers, resulting in solid solutions or defect structures rather than forming separate NiO phases. Using nickel chloride and nickel hydroxide precursors produced purely Ni-doped MoS2, whereas nickel nitrate led to partial NiO formation. In all cases, the incorporation of Ni or NiO enhanced conductivity, facilitated charge transfer, and increased the density of electrochemically active sites, thereby supporting non-faradaic capacitance behavior. Notably, MoS2 derived from NiCl2 achieved a specific capacitance of 686.4 mF/cm2 at 10 mV/s and 1185 mF/cm2 at 2 mA/cm2, along with an energy density of 69.5 mWh/cm2 and a maximum power density of 3250 mW/cm2 at 10 mA/cm2. These findings underscore the superior performance of Ni–MoS2 and highlight precursor-dependent tuning as a promising route for next-generation supercapacitors.