Design of cation (Mo) substituted transition metal dichalcogenide (NiSe2): NiMoSe2 electrode for high-performance asymmetric supercapacitors

High electrochemical activity and good stability in electrode materials are crucial to enhance supercapacitor performance. Cation-substituted bi-metal selenides have substantially higher electrochemical activity and capacity than mono-metal selenides. Cation substitution is a potential strategy to modify the structural and electrochemical properties of metal selenides. Here, the cation-substituted ternary nickel molybdenum selenide (NiMoSe2) nanoparticles were prepared using the facile solvothermal method, and utilised as pseudocapacitive electrodes for hybrid supercapacitors. The novel attempt of molybedum (Mo) substitution in the NiSe2 lattice, showed improved electrochemical performance owing to its enhanced charge transfer kinetics and ionic diffusion. The excellent faradic redox properties of the developed electrodes exhibit excellent pseudocapacitive behaviour in a potential window of 0.0 and 0.75 V. In a typical three-electrode system, the fabricated electrodes exhibit a specific capacitance of 480 Fg- 1 at the current density of 5 Ag-1, which is greater than that of monometal selenide - NiSe2 nanoparticles. The optimum NiMoSe2 electrode retains 99.4 % of the initial specific capacitance over 5000 cycles at 5 Ag- 1. Additionally, the fabricated asymmetric supercapacitor device (ASC) showed an energy density of 44.04 Whkg- 1 at 2.1 kWh power density with exceptional device stability of 87.4 % retention after 15,000 cycles, demonstrating its exceptional performance and stability. Thus, this work demonstrates that metal selinides are promising supercapacitor electrode materials and the potential of cation substitution as a performance-improving strategy.