This study highlights the recent trends in the structural, textural and morphological variations of g-C3N4 for visible-light-induced hydrogen evolution.
Herein, a novel Cu-MoO3/g-C3N4 hybrid nanocomposite was successfully synthesized by a two-step strategy of one-pot pyrolysis followed by the impregnation method. The structure, phase, morphology and electronic environment of MoO3, g-C3N4 and Cu in the composite were determined by various characterization methods. The oxygen vacancies of MoO3 were ascertained by UV-DRS, Raman, and XPS analysis. The formation of the heterostructure was characterised by electrochemical measurements. The photocatalytic performance of the composite was investigated by the water reduction reaction and the reduction of an important inorganic pollutant, Cr(vi). In the presence of Cu NPs, the H2 evolution of the MoO3/g-C3N4 hybrid was found to be 652 μmol h-1 with an apparent energy conversion efficiency of 13.46%, and up to 95% of Cr(vi) was reduced using citric acid as a hole scavenger. The remarkably enhanced photocatalytic performance was attributed to the combined effect of the double Z-scheme mechanism and defective MoO3. The in situ formation process of the MoO3/g-C3N4 hybrid followed a direct Z-scheme charge transfer by generating a great number of defects at the solid-solid interface, similar to that of a conductor, and offered low electrical resistance, whereas loading of Cu NPs built up an indirect Z-scheme charge transfer to establish the double Z-scheme charge transfer mechanism. This hybrid material produces a photocurrent density of 12.1 mA cm-2, in good agreement with the photocatalytic activity. This study highlights the facilitation effect of MoO3 due to oxygen vacancies and charge transfer through the double Z-scheme mechanism to open up a new window in the field of 2D nanostructured photocatalytic materials.
Herein,
we have designed nonstoichiometric WO3, coupled
with ZnCr layered double hydroxide (LDH) nanosheeet through Ag nanoparticle
as the solid-state electron mediator to form WO3–X/Ag/ZnCr LDH Z-scheme photocatalyst. The presence
of oxygen defect levels in as-synthesized materials was confirmed
by Raman, X-ray photoelectron spectroscopy (XPS), and photoluminescence
(PL) analyses. The photocatalytic performance of the catalysts was
investigated by the tetracycline degradation and H2 energy
production under visible light irradiation. The WO3–X/Ag/ZnCr LDH ternary heterostructure exhibits superior
activity toward tetracycline degradation and hydrogen evolution. The
excellent photocatalytic performance of the catalyst was attributed
to the synergistic effects among three species (WO3–X, Ag, and ZnCr LDH) and the enhanced separation efficiency
of photoinduced charge carriers through the Z-scheme WO3–X/Ag/ZnCr LDH system. In addition, the created oxygen
deficiency on WO3–X could improve
the photocatalytic behavior of ZnCr LDH in heterostructure by delaying
the recombination efficiency of photoexcited electron–hole
pairs. Furthermore, the higher affinity of tetracycline at the oxygen
defect levels of the photocatalyst supports the high rate of tetracycline
degradation. The enhanced photocatlytic activity of the catalysts
was further supported by PL spectra and photoelectrochemical studies
(electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry
(LSV) plot). The present research opens up a new strategy for designing
highly efficient visible light-induced Z-scheme-based photocatalysts
with high population of active sites for energy and environmental
applications in a sustainable manner.
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