Performance comparison of distinct bismuth molybdate single phases for asymmetric supercapacitor applications

Abstract

The enticing features of metal molybdates make them an attractive candidate for energy storage systems. This report describes the synthesis of three distinct single-phase bismuth molybdates (Bi₂Mo_xO_y; α-Bi₂Mo₃O₁₂, β-Bi₂Mo₂O₉, and γ-Bi₂MoO₆) using the gel matrix particle growth method and their application in high-performance asymmetric supercapacitors. The single phase and purity of the synthesized Bi₂Mo_xO_y particles were confirmed by X-ray diffraction (XRD) and further verified by Raman analysis. The UV–visible spectra show the electronic and optical behaviours of the as-synthesized α, β, and γ Bi₂Mo_xO_y. The morphologies of the as-synthesized three different Bi₂Mo_xO_y phases were analysed using scanning electron microscopy (SEM). The particle formation was further investigated by transmission electron microscopy (TEM), and the interplanar spacings of the Bi₂Mo_xO_y phases were in accordance with the planes. The surface area and pore volume of the prepared samples were analysed using Brunauer–Emmett–Teller (BET) analysis. The electrochemical properties of the products were confirmed by various tests, including cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 3 M KOH. Among the three phases, α-Bi₂Mo₃O₁₂ exhibits a huge specific capacitance (Cs) of 714 F g⁻¹ at a current density of 1 A g⁻¹. Furthermore, it displays an admirable cycling stability of 86.55% after 5000 cycles. The chosen α-Bi₂Mo₃O₁₂ electrode possesses an increased energy density of 47.5 W h kg⁻¹ at 1 A g⁻¹ with a capacitive retention rate of 71.90% at 5 A g⁻¹ after 10 000 cycles. A remarkable electrochemical performance of Bi₂Mo₃O₁₂ with an exceptional power density of 750 W kg⁻¹ was observed for the prepared asymmetric device. Bismuth molybdate's notable performance indicates that it can be an active material for energy storage applications.