Strategic design of mixed-phase nickel sulfide decorated rGO sheets for high-performance dual functionality in DSSC and supercapacitor electrodes

The growing need for large-scale energy storage demands the creation of multifunctional electrode materials. This paper describes the production and manufacture of mixed-phase nickel sulfide composites containing rGO for use as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) and supercapacitor electrodes. XRD, SEM, XPS, and TEM were used to investigate the composites' structural, morphological, and optical features. The use of CEs in DSSC required the exploration of NiS/rGO composite CEs. The DSSC based on NiS/rGO20 attained a fill factor (FF) of 0.72 and a photoconversion efficiency of 7.95%, outperforming the pure NiS-based DSSC, which had an FF of 0.63 and a power conversion efficiency of 5.45%. In supercapacitor applications, the NiS/rGO20 electrode had a Cs of 801 F g⁻¹ at a scan rate of 5 mV s⁻¹, which was much higher than the pristine NiS electrode's capacitance of 545 F g⁻¹ under the same circumstances. In supercapacitor assessments, the NiS/rGO20 electrode displayed a specific capacitance of 1015 F g⁻¹ at a current density of 2 A g⁻¹, showing a 24% boost over the pure NiS electrode. The asymmetric supercapacitor containing NiS/rGO20 and activated carbon attained an energy density of 43.8 Wh kg⁻¹ at a power density of 1999 W kg⁻¹, with 91% capacitance retention after 5000 cycles. The results show that NiS/rGO20 is a very efficient material for converting and storing energy purposes.