Electronic structure and quantum capacitance analysis of transition metal doped cobalt diselenide for supercapacitors

Abstract

The accelerating degradation of conventional fossil fuels and ever-growing consumption of energy have prompted the search for renewable energy sources. Renewable energy storage necessitates immediate attention toward the development of efficient storage technologies, such as supercapacitors. Among the various transition metal diselenides, CoSe2 is widely known for its improved supercapacitor applications. The present work uses density functional theory for quantum capacitance (CQ) and surface charge analysis of transition metal doped (Fe, Cu) CoSe2. Doping enhances the structural stability and increases the number of electronic states near the Fermi level. Fe-doping has a more prominent effect than Cu-doping, resulting in more redox active sites as compared to Cu-doping due to the lower redox potential of Fe. The optimized Co0.5Fe0.5Se2 material exhibits maximum a CQ of ∼1154 μF/cm2 compared to CoSe2 (906 μF/cm2) at −0.6 V. The CQ shows a higher value at negative potential, suggesting that pristine CoSe2 and Co0.5Fe0.5Se2 are suitable cathode materials for asymmetric supercapacitors. Surface charge analysis also suggests the asymmetric nature of CoSe2 and Co0.5Fe0.5Se2. In addition, the mechanical strength of CoSe2 and Co0.5Fe0.5Se2 was analyzed. The higher bulk modulus of Co0.5Fe0.5Se2 suggests its higher mechanical strength. All of our results suggest that doping a suitable transition metal can significantly boost the performance of supercapacitors.