Chapter 3: Strontium-Doped Manganese Sulfide Nanostructures: Synthesis, Characterization, and Advanced Energy Storage Applications

The growing global energy crisis and the environmental impacts of fossil fuel reliance have driven a shift toward sustainable energy storage systems. Transition metal sulfides have become strong candidates for next-generation pseudocapacitors because of their excellent electrical conductivity and mechanical stability compared to oxides. This chapter explores the synthesis and electrochemical improvement of Strontium (Sr)-doped Manganese Sulfide (MnS) nanostructures. Using a scalable and eco-friendly hydrothermal method, we produced a series of Sr-doped MnS samples with different dopant levels (0%, 1%, 3%, 5%, and 7%). Structural analysis with X-ray Diffraction (XRD) confirmed a stable cubic phase, with an increase in crystallite size from 20.86 nm to 22.16 nm after doping, due to lattice expansion from the larger ionic radius of Sr²⁺. Morphological inspection showed spherical nanostructures that become more prominent as Sr content rises. Optical tests showed a gradual decrease in the bandgap from 4.11 eV to 3.96 eV, indicating improved electronic mobility. Notably, the 7% Sr-doped MnS electrode achieved a high specific capacitance of 1487 F/g at a scan rate of 5 mV/s, nearly doubling the performance of undoped MnS. ling the performance of pristine MnS. These findings emphasize the transformative potential of Sr-doping in customizing the electronic and electrochemical characteristics of MnS for advanced energy storage devices.