Bioinspired Bi₂O₃-ZrO₂ nanocomposite heterojunction as energy storage material and high-performance electrocatalyst for water oxidation

Phyto-mediated nanocomposite materials possess significant potential in morphological control as well as in electrocatalytic activity, which is the main reason for steered interest in the design of new materials for their applications in water splitting. In this work, nanocomposites of Bi₂O₃-ZrO₂ have been prepared by using Amaranthus viridis L. (AVL)–based aqueous extract as a reducing agent. The synthesized nanomaterial’s composition and charge storage properties have been examined in detail. A crystalline structure for the synthesized Bi₂O₃-ZrO₂-based nanocomposite has been elucidated by XRD analysis, while analysis through FTIR, UV, and SEM along with EDX also confirmed the successful biogenic synthesis of the desired nanocomposite. The synthesized biocomposite material is further applied on the nickel foam to be utilized in supercapacitor applications as a working electrode. Results manifest an exceptional specific capacitance value of 283.9 F/g at 2 mV/s by the AVL-Bi₂O₃-ZrO₂ electrode. The columbic efficiency of the electrode was determined to be 99% even after 5000 GCD cycles. The synthesized Bi₂O₃-ZrO₂ nanocomposite is considered to be an efficient electrocatalyst with a comparatively lower band gap of 2.7 eV. This lower bandgap further manifests its potential role in environmental remediation processes through photocatalysis. Additionally, the Bi₂O₃-ZrO₂ composite has also been tested for cyclic stability through chronoamperometry showing reasonable stability. The Ragone plot has been used to determine the power density and energy density as 12 WhKg⁻¹ and 3 KWKg⁻¹ manifesting the higher capacitive behavior of nanocomposite. The synthesized bio-based nanocomposite has a good potential as an electrocatalyst for water splitting having highest productivity of the electrode up to 16.5 h as displayed by hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). To the best of our knowledge, this study represents the first account on the green synthesis of Bi₂O₃-ZrO₂ nanocomposites, wherein Amaranthus viridis L. (AVL) serves as the eco-friendly source, in combination with Bi₂O₃, which has reduced toxicity, and ZrO₂, renowned for its exceptional stability. Our investigation further highlights the importance of synthesis of materials through phytoextract-assisted route for utilization in overall water splitting and energy storage applications.