Bi2O3@TiO2 p-n hetero-junction electrode: A promising approach for improving energy storage performance

A key strategy to boost electrochemical energy storage device efficiency is to develop cost-effective and eco-friendly nano-hetero-junctions with varying potential windows. A novel Bi₂O₃@TiO₂ p-n hetero-junction electrode is synthesized using sequential ionic layer adsorption and reaction (SILAR) chemical approach for obtaining advanced energy storage performance and higher energy density on account of separate working potential windows. Before performing electrochemical energy storage investigations, Bi₂O₃, TiO₂, and Bi₂O₃@TiO₂ p-n hetero-junction electrodes are separately envisaged for confirming various physical and chemical parameters like structures, existing chemical elements, surface morphologies, and electrical conductivities. The as-obtained Bi₂O₃@TiO₂ p-n hetero-junction electrode endows nanoflower-nanoball-type bi-layered surface morphology which shows an ameliorated specific capacitance (SC) of 1942.97 F g⁻¹ and a specific capacity of 1198.18 mA.h.g⁻¹ at a current density of 5 mA cm⁻². Notably, the band gap energy and potential window range of the Bi₂O₃@TiO₂ p-n hetero-junction electrode are reduced to 1.8 eV and extended to 1.7 V, respectively. The symmetrical supercapacitor setup with Bi₂O₃@TiO₂//Bi₂O₃@TiO₂ configuration exhibits a power density as high as 750 W kg⁻¹ at 316.93 Wh kg⁻¹ energy density and a moderate chemical stability with 99.57 % retention even after 10,000 redox cycles. These improvements are associated to; an expanded potential range, a hierarchical porous morphology, and a synergistic effect of the Bi₂O₃ and TiO₂, convincing the importance of the Bi₂O₃@TiO₂ p-n hetero-junction electrode in developing high-performing electrochemical energy storage devices like supercapacitors.