Graphene quantum dots assisted CuCo2S4/MWCNT nanoflakes as superior bifunctional electrocatalysts for dye-sensitized solar cell and supercapacitor applications

In this investigation, Graphene Quantum Dot (GQD) and MWCNT embedded Copper Cobalt Sulfide (CCS) composites for energy conversion and energy storage performance have been investigated. The hydrothermally synthesized bare CCS and their composites with MWCNT and GQD have been characterized for XRD, SEM, TEM, and XPS to investigate the crystalline nature, shape, and chemical content of the synthesized composites. The electrochemical properties of CCS, CCS/MWCNT and CCS/MWCNT/GQD composites have been analyzed using cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). The CV spectrum results demonstrate that the GQD embedded CCS/MWCNT composite has a lower peak-to-peak potential separation (EPP) and a higher peak current density (JPC) than CCS and CCS/MWNCT composites, indicating significant electrochemical activity and electrical conductivity. The estimated power conversion efficiency (PCE) of the CCS, CCS/MWCNT, and CCS/MWCNT/GQD composites have been determined in the following order: CCS/MWCNT/GQD (4.15%) > CCS/MWCNT (3.09%)> CCS (1.91%). In addition, the prepared CCS, CCS/MWCNT and CCS/MWCNT/GQD composites are used as a working electrode to investigate energy storage performance. Among the CCS-based composites, the GQD enriched CCS/MWCNT electrode exhibits the maximum effective specific capacity (402 C g−1) with 70% capacitive retention after 1200 charge-discharge cycles. As a result, we led to the realization that the GQD-supported CCS microstructure is an acceptable electrode material for integrated energy conversion and storage gadgets.