Activated carbon- supported Vanado-nickelate (IV) based hybrid materials for energy application

The rapid development of supercapacitor (SC) technology leads to increased demand for nanofabrication of novel and effective electroactive hybrid materials for next-generation energy storage devices. Herein, nickel tetradecavanadate, K₂H₅[NiV₁₄O₄₀](NiV₁₄), is doped into porous activated carbon (AC), for the first time, in different wt.% in order to investigate the homogeneous loading of the inorganic metal-oxide component on the AC matrix. The resulting complex, AC-NiV₁₄, is found to have possessed an enhanced electrochemical characteristic (for both symmetric and asymmetric SC cell), which operates at a significantly higher potential of 1.2 V. The combination of the double-layer capacitance (EDLC) and the redox-active polyoxometalate cluster leads to an intrinsic increase in specific capacitance (capacity) (from 45.3 Fg⁻¹ (54.4 Cg⁻¹) for AC to 316 Fg⁻¹ (379.2 Cg⁻¹) for 15 wt.% AC-NiV₁₄ at a current density of 1 Ag⁻¹). It was also observed that there is an increase of 20% in the operating voltage compared to conventional AC supercapacitors with acidic aqueous electrolytes. Firstly, symmetric supercapacitor's electrochemical performances of various wt.% of NiV₁₄ composition were studied in acidic aqueous electrolyte (0.5 M H₂SO₄) solution. We observed that the 15 wt.% of AC-NiV₁₄ hybrid electrode showed remarkable specific energy value (~63.2 Wh kg⁻¹) compared with pristine AC and NiV₁₄ electrodes, separately. Besides, the asymmetric layout (AC//AC-NiV₁₄) increased the potential window up to 1.5 V and enhanced the specific energy and power values (90.1 Whkg⁻¹ and 2400 Wkg⁻¹, respectively), with 98% coulombic efficiency. Meanwhile, the AC-NiV₁₄//NiV₁₄ asymmetric cell possesses a specific capacitance (capacity) of 375 Fg⁻¹ (450 Cg⁻¹) with a maximum power of 3140 Wkg⁻¹ at the high current density of 2 Ag⁻¹.