Electrodeposition of nickel selenides thin films for high-performance hybrid supercapacitor

Numerous studies have investigated energy storage devices, such as supercapacitors (SCs) and their corresponding active material electrodes, in response to the increased demand for renewable energy sources. Cyclic voltammetry (CV) was applied to synthesize nickel selenides (NiSe) through the discontinuity of deposition, resulting in distinguished morphology with more electrochemical active sites compared with the constant potential process of potentiostatic (Ps) method. The effect of cycle number (deposition period) of the CV method on morphology and, hence, the corresponding electrochemical performance were also studied. The sponge-like structure of NiSe with few aggregates was obtained at 17 cycles (almost 30 min of deposition). It has a high capacity value of 751 C g−1 at 1 A g−1 with good rate capability in a three-electrode apparatus. When a hybrid supercapacitor (HSC) was assembled using sponge-like NiSe as a positive electrode and activated carbon (AC) as a negative electrode, it showed a remarkable stability of 99 % after 9000 cycles at 8 A g−1 and 42.2 Wh kg−1 specific energy at a specific power of 958.3 W kg−1 at 1 A g−1, which is higher than previous electrodeposited NiSe used in SC applications. This study provides compelling evidence supporting the potential of NiSe as a promising electrode material in supercapacitors.