| Autor: |
Sowmya S; Department of Applied Chemistry, Karunya Institute of Technology and Sciences, Coimbatore 641114, Tamilnadu, India., Vijaikanth V; Department of Applied Chemistry, Karunya Institute of Technology and Sciences, Coimbatore 641114, Tamilnadu, India. |
| Abstrakt: |
Due to environmental contamination and the depletion of energy supplies, it is very important to develop low-cost, high-performance, multifunctional electrocatalysts for energy conversion and storage systems. Herein, we report the development of cost-effective modified electrodes containing g-C 3 N 4 /chlorocobaloxime composites (C1-C4) and their electrocatalytic behavior toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), followed by their energy-storage applications. A series of chlorocobaloximes {ClCo(dpgH) 2 B} with diphenylglyoxime (dpgH) and neutral bases (B) containing a carboxylic acid moiety (isonicotinic acid, pyridine-3,5-dicarboxylic acid, indole-2-carboxylic acid, and p-aminobenzoic acid) have been synthesized and characterized by spectroscopic techniques. The nanocomposites of g-C 3 N 4 /chlorocobaloximes are prepared and characterized by Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), particle size distribution analysis (PSA), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray analysis (EDAX) techniques. The composite coatings exhibit enhanced HER performance at lower overpotential and with a lower Tafel slope. When the water-splitting reactions are studied using 0.5 M H 2 SO 4 and 0.5 M KOH as electrolytic solutions, the composite g-C 3 N 4 /C2 containing pyridine-3,5-dicarboxylic acid as a neutral base shows excellent HER activity with a lower overpotential of 173 mV at -10 mA cm -2 and OER activity with a lower overpotential of 303 mV. The HER reaction takes place through the Volmer-Heyrovský mechanism, where the desorption step is the rate-determining step. Among the synthesized nanocomposites, the nanocomposite g-C 3 N 4 /C2 shows higher efficiency toward both HER and OER reactions, with a lower Tafel slope of 55 mV dec -1 for HER and 114 mV dec -1 for OER than the other nanocomposites. The overall water-splitting studies of the composite g-C 3 N 4 /C2 in 0.5 M KOH indicate that the evolution of hydrogen and oxygen occurs constantly up to 120 h. The supercapacitance applications studied using cyclic voltammetry and charge-discharge studies indicate that the nanocomposite g-C 3 N 4 /C1 shows a good specific capacitance of 236 F g -1 at 0.5 A g -1 compared to others. The increased electrochemical performance of the synthesized nanocomposites is due to the incorporation of electron-withdrawing carboxylic-acid-functionalized neutral bases present in cobaloximes, which increases electron mobility. The incorporation of a cobaloxime complex into a g-C 3 N 4 nanosheet enhances the electrocatalytic behavior of the nanosheet, and its performance can further be fine-tuned by systematic variation in the structure of cobaloxime by changing the halide ion, dioxime, the neutral base ligand, or the substituent.
Competing Interests: The authors declare no competing financial interest.
(© 2023 The Authors. Published by American Chemical Society.) |
