Unveiling the Bifunctional
Photo/Electrocatalytic
Activity of In Situ Grown CdSe QDs on g‑C3N4 Nanosheet Z‑Scheme Heterostructures for Efficient
Hydrogen Generation
posted on 2024-01-02, 13:05authored byAmir Mehtab, Tokeer Ahmad
The successive ionic layer adsorption and reaction (SILAR)
method
was used to deposit several CdSe quantum dots (QDs) on the surface
of g-C3N4 nanosheets. In comparison to the single
moiety of g-C3N4, as-prepared heterostructures
displayed an improved bifunctional photo- and electrocatalytic activity
for oxygen (OER) and hydrogen evolution reactions (HER). Significantly,
the 30 SILAR cycles optimized CdSe QDs/g-C3N4 heterostructure exhibited high performances and stabilities for
the OER and HER reaction in alkaline conditions. The as-prepared heterostructure
catalyst also exhibited an efficient photocatalytic activity toward
the H2 evolution reaction and produced 4306 μmol
of H2 gas with 23.8% of apparent quantum yield in the presence
of triethanolamine as a sacrificial agent. Photoluminescence spectroscopy,
electron paramagnetic resonance, and impedance spectroscopy suggest
that the synergy between g-C3N4 nanosheets and
CdSe QDs leads to higher catalytic activities, as indicated by the
low overpotentials of 147 and 218 mV to obtain a 10 mA cm–2 current density for the HER and OER reactions, respectively. Furthermore,
in situ Fourier transform infrared spectroscopy, liquid chromatography–mass
spectroscopy, and high-performance liquid chromatography were conducted
to determine the photochemical intermediate products to confirm the
successful oxidation of TEOA by capturing holes. The outcome is in
accordance with the fact that the photogenerated electrons are transferred
from the conduction band (CB) of g-C3N4 nanosheets
to the valence band (VB) of CdSe QDs in a Z-scheme manner.