Biomass-derived porous carbon-supported MnWO4/CeVO4 nanocomposites: Influence of solvent and natural surfactant on morphology and electrochemical hydrogen storage performance

Abstract

This work introduces a new and green way to the hydrothermal synthesis of MnWO₄/CeVO₄ nanocomposites (NCs) in the presence of Ginseng extract as a natural surfactant. The nanocomposites were evaluated as novel candidates for electrochemical hydrogen storage using charge-discharge chronopotentiometry technique. Three different molar ratios of monoclinic MnWO₄ phase to tetragonal CeVO₄ phase (1:1, 2:1, and 4:1) were studied, among which the 4:1 composition showed superior storage capacity (672 mAhg⁻¹ at current of 1 mA after 15 cycles). The influence of different solvents such as ethanol and ethylene glycol on the morphology and performance was also examined. The sample synthesized in ethanol medium displayed a porous morphology and delivered a higher hydrogen storage capacity (845 mAhg⁻¹ at current of 1 mA after 15 cycles) compared to those prepared in other solvents. To enhance performance, the optimized MnWO₄/CeVO₄ nanostructures were further composited with biomass-derived porous carbon (PC) synthesized using green source of jujuba powder. The ternary composite containing 70 wt% porous carbon with BET surface area of 15.89 m²g⁻¹ exhibited the highest capacity, reaching up to 1100 mAhg⁻¹ at current of 1 mA after 15 cycles. All samples characterized in terms of phase purity, crystallite structure, chemical bonding, morphology, and surface area using XRD, FT-IR, EDS, SEM, TEM and BET-BJH analyses. These findings suggest that structure control through natural surfactants and solvent selection, coupled with carbon incorporation, can significantly boost hydrogen storage efficiency in transition metal-based nanocomposites.