Greener and facile synthesis of binary zinc oxide/nickel oxide heterojunction nanocomposite for potential solar energy conversion, environmental remediation and energy storage applications

• Eco-friendly green strategy was adopted to prepare ZnO/NiO NC using Syzygium cumini leaf extract. • ZnO/NiO NC photoanode delivered PCE of 2.09 % over DSSC with ZnO photoanode ( ƞ = 1.63 %). • ZnO/NiO NC served as highly efficient photocatalyst for degradation of MB dye achieved ∼99 % efficiency. • ZnO/NiO NC electrode exhibited specific capacitance of 262.50 Fg −1 and cyclic stability by retaining 77.84 % after 5000 GCD cycles. Today's world is prioritized with clean and green energy. Herein, we demonstrate preparation of binary ZnO/NiO NC through a greener manner using extract of Syzygium cumini leaves in view of its multifunctional application potential in DSSC, photocatalysis and energy storage. The optical, structural, phase, composition and morphology of the green synthesized nanomaterials were characterized by appropriate instrumentation techniques. The DSSC constructed using binary ZnO/NiO NC photoanode produced notable PCE of 2.09 % over pristine ZnO NPs (1.63 %). The photocatalytic activity of binary ZnO/NiO NC towards degradation of MB dye attained an efficiency of 99 % when compared to pristine ZnO NPs (88 %). This improvement in the photocatalytic activity could be credited to suppression of charge recombination by enhanced charge separation kinetics. The binary ZnO/NiO NC as working electrode in supercapacitor delivered significant capacitance of 262.50 Fg −1 and good cyclic steadiness of 77.84 %. These findings suggest that the green synthesized ZnO/NiO NC would be a promising material for energy conversion, environmental remediation and energy storage applications.