Cobalt–Nickel Vanadate Nanonest Colonies Deposited Carbon Fabric as a Bifunctional Electrode for Li-Ion Batteries and Oxygen-Evolution Reactions

Transition metal vanadates (TMVs) have attracted significant attention in various research fields owing to their advantageous features. Furthermore, synthesizing TMVs directly on current collectors at the nanoscale is a promising strategy for achieving better performance. Herein, cobalt–nickel vanadate (CoV2O6–Ni2V2O7, CNV) was directly grown on carbon fabric using a facile one-step hydrothermal method. In particular, the CNV sample prepared for 3 h (CNV-3) exhibited a benefit-enriched nanonest-colony morphology in which abundant nanowires (diameter: 10 nm) were intertwined, providing sufficient space for electrolyte diffusion. All the CNV electrodes exhibited good cycling performance in the lithium-ion battery study. Especially, the CNV-3 electrode retained higher discharge and charge capacities of 616 and 610 mAh g−1, respectively at the 100th cycle than the other two electrodes owing to several morphologic features. The electrocatalytic activity of all the CNV samples for the oxygen-evolution reaction (OER) was also explored in an alkaline electrolyte. Among these CNV catalysts, the CNV-3 displayed excellent OER performance and required an overpotential of only 270 mV to drive a current density of 10 mA cm−2. The Tafel slope of this catalyst was also found to be low (129 mV dec−1). Moreover, the catalyst exhibited excellent durability in a 24 h stability test. These results indicate that the metal vanadates with favorable nanostructures are highly suitable for both energy storage and water-splitting applications.