Phase-controllable synthesis of nickel selenide nanostructures decorated on carbon nanotubes as efficient binder-free cathodes for hybrid supercapacitors

In this work, we employed a facile pulse-reversal (PR) electrodeposition route to successfully synthesize nickel selenide nanostructures directly decorated on carbon nanotubes (CNTs) by adjusting different pulse-reversal potentials. The study systematically investigated the effects of PR potential on the morphology and composition of nickel selenides on CNTs. The experimental results suggested that regulating the PR potential could effectively manage the formation of nickel selenide nanostructures on the backbones of CNTs. By decreasing the PR potential from 0.2 to -0.2 V, the composition of nickel selenide nanostructures changed from NiSe2 to Ni0.85Se. The CNTs@NiSe2 electrode outperformed the others with a specific capacity of 125.4 mAh g-1 at 2 A g-1 and an impressive capacity retention of 81.2 % at 16 A g-1. The assembled hybrid supercapacitor using CNTs@NiSe2 as the cathode achieved exceptional performance with a high specific capacity of 42 mAh g-1 at 1 A g-1 and a maximum energy density of 33.6 Wh kg-1 at 800 W kg-1. This work presents an efficient approach that can be widely employed to fabricate one-dimensional carbon material-supported transition metal selenide nanostructures for practical applications in the next generation of energy storage and conversion.