Enhanced electrochemical performance of α-MnO 2 through Sr 2+ & Cd 2+ Co-doping for advanced energy storage applications

This study presents the synthesis and characterization of Sr2+/Cd2+ co-doped α- MnO2 nanoparticles prepared via a simple chemical co-precipitation method for advanced energy storage applications. XRD analysis confirmed the tetragonal α- MnO2 phase with a reduced crystallite size from 15.8 nm to 7.1 nm, indicating effective dopant incorporation. TEM and SAED revealed a transition from flake-like to rod-shaped morphology, promoting efficient ion transport. XPS spectra verified the coexistence of Mn3+ and Mn4+ oxidation states and the successful substitution of Sr2+ and Cd2+ ions, which introduced lattice strain and oxygen vacancies. VSM results showed weak antiferromagnetic and superparamagnetic behaviour, associated with surface spin interactions and structural distortions. These modifications enhanced electron mobility and ionic conductivity, resulting in a specific capacitance of 614.49 F g−1 at 5 mV s−1 in 3 M KOH, outperforming single-doped MnO2 systems. The synergistic role of Sr2+ and Cd2+ ions, where Sr2+ stabilizes the structure and widens diffusion channels, while Cd2+ creates defect sites that boost charge transfer contributes to superior pseudocapacitive behaviour. The findings establish the Sr2+/Cd2+ co-doped α- MnO2 nanocomposite as a stable, high-performance electrode material suitable for next-generation supercapacitors and hybrid energy storage devices.