Indirect
Z-scheme assembly of graphene-bridged 2D ZnV2O6/pCN nanosheets composite has been fabricated by one-step
solvothermal process and tested for photoinduced CO2 conversion
under visible-light irradiations. The highest CH3OH production
of 3488 μmol g-cat–1 was obtained over ZnV2O6/RGO/g-C3N4 composite,
1.02 and 1.25 times higher comparing to ZnV2O6/RGO and ZnV2O6/g-C3N4 samples, respectively. This enhanced efficiency can be ascribed
to well-designed ternary heterojunction with hierarchical structure
and efficient charges separation by RGO. More importantly, CH3OH yield was further improved by introducing RGO/pCN as an
electron sink, which led to a 1.07 times higher yield than using only
RGO. This reveals that ternary 2D ZnV2O6/RGO/pCN
nanostructure has higher visible-light absorption, improved charge
separation, and enhanced photocatalytic efficiency due to RGO/pCN
as multiple mediators. The stability of composite catalyst also prevailed
for 32 h for continuous CH3OH production. Therefore, structured
Z-scheme composite with multiple electron mediators enables efficient
CO2 conversion under visible-light irradiation.
Fabrication
of two-dimensional (2D) titanium carbide (Ti3C2) MXene nanosheets with a unique morphology coupled
with a 2D g-C3N4/TiO2 heterojunction
for hydrogen-rich syngas production during photocatalytic bireforming
of methane (PBRM) under visible light has been investigated. The delaminated
Ti3C2 layered nanosheets in the TiO2/g-C3N4/Ti3C2 heterojunction
promoted charge-carrier separation efficiency by decreasing the traveling
distance to reach the surface and increased the visible light absorption.
The highest CO and H2 production of 48.38 and 83.2 μmol
g–1 was achieved over g-C3N4/TiO2/Ti3C2, which is 5.17- and
9.85-fold higher compared to TiO2, respectively. The enhanced
photoactivity can be attributed to the extension of visible light
absorption, accelerated migration rates of the charge carrier, intimate
contact, decreased traveling distance of excited electrons, and strong
adsorption of reactants. In view of adsorption competition among the
reactants, an optimized CO2/CH4 molar feed ratio
of 1.0 promoted H2-rich syngas production. The apparent
quantum yield (AQY) reached as high as 0.408 and 0.698% for CO and
H2 production during the BRM process under visible light.
The stability analysis further confirms high stability and durability
of the composite catalyst in multiple cycles because of the presence
of MXene sheets. This work provides new pathways to construct a low-cost
and noble metal-free structured composite for stimulating photocatalytic
BRM under visible light, which can be employed in solar energy applications.
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