Graphene-guided growth of rare earth-doped Bi2Mo2O9 nano self-assembly for enhanced asymmetric supercapacitor device performance

Abstract

Nanoparticle self-assembly optimizes super-capacitive behaviour with sustainable life and ascertains the most optimal active material for electrodes. A nano self-assembly consisting of rare earth (RE = Ce and Gd)-doped Bi₂Mo₂O₉ (Bi_2−xRE_xMo₂O₉) and reduced graphene oxide (rGO)-modified Bi_2−xRE_xMo₂O₉ (GM-Bi_2−xRE_xMo₂O₉; RE = Ce and Gd) was synthesized using a gel combustion method. The phase formation of the as-synthesized nano self-assembly was confirmed using X-ray diffraction. Raman spectroscopy and XPS analysis confirmed the optical properties and chemical composition of the prepared materials. The morphology of the synthesized nano self-assemblies and their effect on the rare earth doping and rGO modification were explored using SEM and TEM. Brunauer–Emmett–Teller analysis confirmed the surface area and pore volume. Through CV, GCD, and EIS analysis, the electrochemical performance of the nano self-assembly was examined. GM-Bi_2−xRE_xMo₂O₉ (RE = Ce and Gd) exhibited high specific capacitance in a three-electrode configuration along with feasible cyclic stability. The fabricated asymmetric supercapacitor device of GM-Bi_1.9Ce_0.1Mo₂O₉ and GM-Bi_1.9Gd_0.1Mo₂O₉ exhibited an extraordinary energy density of 58.96 W h kg⁻¹ and 56.67 W h kg⁻¹, respectively, with an equivalent power density of 750 W kg⁻¹. However, GM-Bi_1.9Gd_0.1Mo₂O₉ exhibited a higher cyclic stability of 86.55%, with the fabricated GM-Bi_1.9Ce_0.1Mo₂O₉ asymmetric device providing a superior super-capacitive performance. We improved the electrochemical performance of bismuth molybdate by rare earth doping and rGO modification, and it can potentially be a desirable electrode material.