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 incorporati...