Cation-boosted CoMoSe2@Ti3C2 hybrid electrode framework for high-performance asymmetric supercapacitors†

The increasing global energy demands, rapid consumption of fossil fuels, and rising environmental crisis are all crucial challenges requiring immediate attention. Maximizing supercapacitor performance necessitates superior electrochemical performance and outstanding stability in the electrode materials. Altering the structural and electrochemical characteristics of transition metal selenides by substituting cations and subsequently hybridizing them with MXenes is a potential strategy for designing efficient supercapacitors. Herein, facile solvothermal technique was employed to synthesize cation-substituted CoMoSe₂ nanoparticles, which were subsequently hybridized with Ti₃C₂ before being employed as a supercapacitor electrode. This novel attempt to substitute molybdenum (Mo) in the CoSe₂ lattice and the subsequent hybridization resulted in a supercapacitor electrode that exhibited enhanced electrochemical properties owing to its improved charge transfer kinetics, multivalences, and enhanced active sites. The outstanding faradaic redox characteristics of the fabricated electrodes show remarkable pseudocapacitive behaviour within a potential range between −0.2 and 0.45 V. The developed electrodes in a standard three-electrode setup show a specific capacitance of 520 F g⁻¹ at a current density of 1 A g⁻¹, which is greater than that of pure CoMoSe₂ and mono-metal selenide CoSe₂. Over 5000 cycles at 5 A g⁻¹, the optimal CoMoSe₂@Ti₃C₂ electrode maintains 97.43% of its initial specific capacitance. Furthermore, the designed asymmetric supercapacitor device (ASC) exhibited exceptional performance and stability with an energy density of 73.7 W h kg⁻¹ at 740 W kg⁻¹ power density and 93.3% retention after 15 000 cycles. This work thus demonstrates that metal selenides are a suitable material for supercapacitors. Furthermore, the cation substitution and MXene hybridization could potentially be employed as performance-enhancing strategies.