Cobalt Vanadate Nanostructures on Graphitic Carbon Nitride for Energy Conversion and Storage Applications

This study presents a dual functionalization strategy to develop high-performance bifunctional electrocatalysts based on cobalt vanadate, specifically Co 2 V 2 O 7 and Co 3 V 2 O 8, and their nanocomposite with graphitic carbon nitride (Co 3 V 2 O 8 /GCN) for electrochemical water splitting (EWS) and supercapacitors (SCs) applications. The structural, chemical, and surface morphological analyses reveal that Co 2 V 2 O 7, Co 3 V 2 O 8, and their nanocomposite exhibit a unique nanosphere-on-nanosheet structure that enhances their electrocatalytic performance. Further, the observed morphology allows easy electrolyte access, resulting in low overpotentials of 133 mV at 50 mA/cm 2 for the Oxygen Evolution Reaction (OER) and 112 mV at 50 mA/cm 2 for the Hydrogen Evolution Reaction (HER), respectively. The optimized electrocatalysts achieve a potential of 1.51 V at 100 mA/cm 2 to split water into oxygen and hydrogen. Additionally, the nanocomposite materials exhibit superior charge storage capabilities, with a high specific capacitance ( C s ) of 1487 F/g at 5 mA/cm 2 . In addition to this, a hybrid solid-state supercapacitor device (HSSD) was constructed, delivering a better energy density ( E d ) of 41.69 Wh/kg and power density ( P d ) of 3.75 kW/kg at 5 mA/cm 2 . Further, the device exhibited excellent electrochemical stability of 82.70% of its capacity over 10,000 charge–discharge cycles at 11 mA/cm 2, with a Coulombic efficiency of 79.89%, respectively. Therefore, the prepared new material of cobalt vanadate with carbon-based graphitic nitrite nanocomposite shows promising results in the field of energy conversion and storage.