Influence of pH on optical and electrochemical performance of BiPO4 electrode material for energy storage applications

Abstract

Bismuth phosphate nanostructures were fabricated by a simple microwave approach under an optimum atmosphere at different pH values (3, 5, 7, 9, and 11) without the aid of any surfactants and studied the optical and electrochemical energy storage behaviour of BiPO4 nanostructures. XRD study revealed hexagonal phase structure of BiPO4 nanostructures devoid of any contamination peak. FTIR and Raman spectra as well authenticate the hexagonal structure of all the developed samples. The FESEM investigation revealed the formation of non-uniform cube-like crystals, with the size allocation estimated to be in the range of 45–69 nm, which is consistent with the XRD findings. An extensive reduction in optical band energy (Eg) is ascertained by raising the pH values (3–11). In a three-electrode mechanism with 4 M KOH as an electrolyte, CV, GCD, and EIS addressed the electrochemical behaviour of the as-developed samples. The Faradic battery's oxidation-reduction efficiency is illustrated by the CV and GCD curves. The BiPO4 electrode synthesized at pH 7 as a battery-like activity shows excellent electrochemical evolution with a large specific capacity (∼328 Cg-1), perfect cycle life (∼89.0% at 5 Ag-1 over 900 cycles), respectively. According to the EIS analysis, the electrode prepared with pH 7 values has dominant capacitive behaviour due to a double layer capacitor formed at the interfacial between the electrode surface and the electrolyte. Therefore, such promising findings help the significant perspective of an electrode in enhancing energy storage appliances with superior efficiency for energy storage applications.