Hydrothermal reaction time-dependent morphology and electrochemical performance of BaMoO4 for asymmetric...

The escalating global energy crisis necessitates the development of sustainable and high-performance energy storage systems. In the present work, the barium molybdate (BaMoO4, BMO) nanoparticles were prepared using a hydrothermal process for different reaction times (5, 10, 15, and 20 h) and the formation process and its effect on the electrochemical behaviour were systematically studied. The structural and vibrational analyses showed that the pure tetragonal phase BMO-15 with an average crystallite size value of 17.05 nm. The characteristic Ba-O and Mo-O bonding was confirmed by Fourier-transform infrared (FTIR) spectroscopy, and the high-resolution transmission electron microscopy (HRTEM) confirmed the presence of uniformly distributed spherical nanoparticles. The time-dependent samples were analysed using field-emission scanning electron microscopy (FESEM), which revealed a systematic change in the morphology, from the initial nuclei, to the well-developed crystalline nanoparticles with the reaction time, thereby giving an insight into the growth mechanism. The optimized BMO-15 electrode showed superior specific capacitance of 531 F g-1 at the current density of 1 A g-1 with retaining 90% capacity after 10,000 charge-discharge cycles at 6 A g-1, which revealed its cycling stability. Moreover, the fabricated asymmetric supercapacitor device (BMO-15//AC) exhibited a remarkable energy density of 33.05 Wh kg-1 and power density of 1399 W kg-1, and it maintained 72% of its initial capacitance after 5000 charge-discharge cycles. The electrochemical performance is explained by the structural stability of the tetragonal BMO-15 framework, the high redox activity of the active sites of Mo and the synergistic effect of the BMO-15 and activated carbon electrodes. Based on these results, BMO-15 nanoparticles are shown to be a promising material for the next generation of high-performance supercapacitors which can be considered as a sustainable material.