Wet-chemical engineering of Ag-BiVO4/Bi2S3 heterostructured nanocomposite on graphitic carbon nitride (g-C3N4) sheets for high performance supercapacitor application

Abstract

Graphitic carbon nitride (g-C3N4), a structural analogue of graphite has opened a new arena in energy storage. The N-rich g-C3N4 sheets similar to N-doped carbon materials provide large number of defect sites for increased diffusion and adsorption of electrolyte ions. High N-content in g-C3N4 is most suitable to escalate metal‑carbon binding energy which stabilizes the pseudo-active transition metal oxides/chalcogenides over carbon support to realize high capacitive performance. In this study, we have impregnated binary Ag-BiVO4/Bi2S3 heterostructures on g-C3N4 sheets through wet-chemical approach, as novel electrode material for supercapacitor application. As prepared Ag-BiVO4/Bi2S3@g-C3N4 composite (ABVBS@g-C3N4) along with Ag-BiVO4/Bi2S3 (ABVBS), Ag-BiVO4 (ABV), and Bi2S3 (BS) were systematically characterized by different techniques i.e., XRD, FTIR, FESEM, EDS, and BET analysis. When applied for electrochemical tests, among all the analyzed electrodes ternary composite ABVBS@g-C3N4 exhibited highest electrochemical activity with a specific capacitance value of 872 F/g (@5 mV/s) and 815.4 F/g (@1 A/g), and 91.5 % capacitance retention up to 5000 GCD cycles. The initial coulombic efficiency of ABVBS@g-C3N4 was noteworthy (99.42 %) due to very low internal resistance. Moreover, it was analyzed that ternary composite ABVBS@g-C3N4 has lower equivalent series resistance (RES) as 6.73 Ω and charge transfer resistance value as 7.73 Ω, in comparison to other electrodes. This excellent electrochemical performance of ABVBS@g-C3N4 is attributed to combined contributions from ABVBS and g-C3N4 in terms of multiple redox states, increased wettability of electrode, and high structural and chemical stability. Considering the results, our study proposes feasible strategy to generate hybrid electrode materials with optimized properties to serve as energy storage material for next generation supercapacitors.