Synthesis of different manganese tungstate nanostructures for enhanced charge-storage applications: theoretical support for experimental findings

Abstract

Manganese tungstate (MnWO₄) has been widely studied over the past few years due to its outstanding magnetic, catalytic, and sensing features. However, the electrochemical properties of the morphology tuned MnWO₄ nanoform is less explored in the literature. Herein, we report the synthesis of MnWO₄ nanostructures of different aspect ratios by subtle tuning of the reaction temperature and reaction time. An immediate utility of the size-controlled nanostructures is their use as the electrode material for supercapacitors. The impact of various reaction parameters, namely the growth time and processing temperature, over the MnWO₄ nanorods size was studied by different characterization techniques, such as X-ray diffraction, field emission scanning electron microscopy, and Raman spectroscopy. It was shown that all the samples showed considerably good charge-storage properties with the highest values of specific capacitance being 455.07 and 239.07 F g⁻¹ at 2 mV s⁻¹ and 1 A g⁻¹, respectively. The corresponding sample further showed an appreciable capacitance retention of ∼94% even after 10 000 long charge–discharge cycles, indicating a high electrochemical stability of the electrode. Theoretical analysis using density functional theory predicted that the presence of electronic states near Fermi level and the enhanced quantum capacitance were the prime reasons behind the excellent charge-storage performance of the as-synthesized MnWO₄.