Enhanced dye-sensitized solar cell performance and electrochemical capacitive behavior of bi-functional ZnO/NiO/Co3O4 ternary nanocomposite prepared by chemical co-precipitation method

Increasing prerequisites for sustainable energy storage and conversion technologies have necessitated the exploration of advanced materials with improved properties. Here, we present the synthesis and characterization of ZnO nanoparticles (NPs), ZnO/NiO, ZnO/Co₃O₄ and ZnO/NiO/Co₃O₄ NCs as promising bi-functional materials for dye-sensitized solar cell (DSSC) and electrochemical energy storage applications. A facile chemical co-precipitation approach was followed to synthesize pure ZnO NPs, ZnO/NiO, ZnO/Co₃O₄ and ZnO/NiO/Co₃O₄ NCs. The structural and morphological analyses revealed the successful integration of ZnO, NiO, and Co₃O₄ NPs and also the formation of well-defined core-shell and homogenous nanocomposite structures. The XRD and HRTEM analyses confirmed the crystalline nature and nanoscale morphology of synthesized materials, respectively. The photovoltaic performance of DSSC fabricated using ternary ZnO/NiO/Co₃O₄ NC photoanode showed optimum dye-loading and best solar to electrical energy conversion efficiency with J_sc of 11.29 mA cm⁻² and ƞ of 4.66%, which was considerably higher than the DSSC fabricated using pure ZnO NPs photoanode (ƞ = 2.01%). The increment in photocurrent density (J_sc) could be ascribed to the perfect band alignment of NiO and Co₃O₄ NPs in the ternary NC. Further, the ZnO/NiO/Co₃O₄ NC photoanode integrated DSSC disclosed 97% retainment in energy conversion efficiency even after 10 days of operation. The electrochemical performance of supercapacitor fabricated using ternary ZnO/NiO/Co₃O₄ NC showed high specific capacitance of 534.7 Fg⁻¹ at 1 Ag⁻¹ with favourable rate ability (∼52% at 16 Ag⁻¹), good cyclic stability (91.07%) and low internal resistance. Moreover, the ZnO/NiO/Co₃O₄ NC at a current density of 2 Ag⁻¹ exhibited a significantly high capacitance value of 463.1 Fg⁻¹, which was 1.93, 1.58 and 1.22 times greater than ZnO NPs, ZnO/Co₃O₄ NC and ZnO/NiO NC, respectively.