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

Abstract

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, K<inf>2</inf>H<inf>5</inf>[NiV<inf>14</inf>O<inf>40</inf>](NiV<inf>14</inf>), 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-NiV<inf>14</inf>, 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-NiV<inf>14</inf> 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 NiV<inf>14</inf> composition were studied in acidic aqueous electrolyte (0.5 M H<inf>2</inf>SO<inf>4</inf>) solution. We observed that the 15 wt.% of AC-NiV<inf>14</inf> hybrid electrode showed remarkable specific energy value (~63.2 Wh kg?1) compared with pristine AC and NiV<inf>14</inf> electrodes, separately. Besides, the asymmetric layout (AC//AC-NiV<inf>14</inf>) 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-NiV<inf>14</inf>//NiV<inf>14</inf> 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. © 2021 Elsevier Ltd