Defect-engineered Y3 +-doped α-MnO2 /ZnO nanocomposite for enhanced electrochemical energy storage performance

A Y 3+ -doped α-MnO 2 /ZnO nanocomposite was synthesised using a chemical precipitation method to enhance electrochemical energy storage performance. X-ray diffraction analysis confirmed the coexistence of tetragonal α-MnO 2 and hexagonal ZnO phases, with a reduced crystallite size of 13.54 nm attributed to Y 3+ -induced lattice distortion. X-ray photoelectron spectroscopy identified mixed Mn 3+ /Mn 4+ oxidation states together with defect-related oxygen species, indicating the formation of oxygen vacancies that contribute to improved electrical conductivity and redox activity. Transmission electron microscopy revealed a well-defined heterostructure with uniformly distributed nanoparticles (8–15 nm), promoting efficient electrode–electrolyte interaction. Electrochemical performance, evaluated in a three-electrode system, demonstrated that the Y 3+ -doped α-MnO 2 /ZnO nanocomposite outperforms both ZnO and Y-doped α-MnO 2 electrodes. Cyclic voltammetry yielded a specific capacitance of 952.91 F g −1 at 10 mV s −1 , while galvanostatic charge–discharge analysis produced a maximum capacitance of 1005.8 F g −1 . The electrode maintained approximately 80% of its capacitance at higher scan rates, reflecting strong rate capability. Electrochemical impedance spectroscopy indicated reduced charge-transfer resistance and improved ion diffusion kinetics. The enhanced electrochemical performance results from the combined effects of Y 3+ -induced defect engineering, oxygen vacancy formation, and efficient charge transport across the α-MnO 2 /ZnO heterointerface. These findings indicate that rare-earth doping, together with heterostructure design, offers an effective approach for developing high-performance electrode materials for supercapacitor applications.