A direct Z-scheme g-C3N4/SnS2 photocatalyst with superior visible-light CO2 reduction performance

摘要

udud - SnS quantum dots anchored in situ on g-CN by a simple one-step hydrothermal method.udud - The internal electric field between g-CN and SnS was confirmed.udud - Internal-electric-field-induced direct Z-scheme g-CN/SnS charge transfer for enhanced photocatalytic CO reduction.udud - In situ FTIR analysis further proved the suggested photocatalytic mechanism.ududududPhotocatalytic reduction of CO to solar fuels is an ideal approach to simultaneously solve the global warming and energy crisis issues. Constructing a direct Z-scheme heterojunction is an effective way to overcome the drawbacks of single-component or conventional heterogeneous photocatalysts for photocatalytic CO reduction. Here, a novel type of direct Z-scheme g-CN/SnS heterojunction was constructed by depositing SnS quantum dots onto the g-CN surface in situ via a simple one-step hydrothermal method. -Cysteine not only acted as the sulfur source, but also grafted ammine groups onto g-CN in the hydrothermal process, which greatly enhanced the CO uptake of the composite. XPS analysis and density functional theory (DFT) calculation show that electron transfer occurred from g-CN to SnS, resulting in the formation of interfacial internal electric fields (IEF) between the two semiconductors at equilibrium. As a result, Z-scheme charge transfer took place under photoexcitation, with the electrons in SnS combining with the holes in g-CN, which improved the extraction and utilization of photoinduced electron in g-CN. The g-CN/SnS hybrid shows superior photocatalytic CO reduction as compared with individual g-CN and SnS, which should be attributed to the IEF-induced direct Z-scheme as well as improved CO adsorption capacity. In situ FTIR spectra illustrate that HCOOH appeared as an intermediate during the CO conversion, which can only be generated by g-CN according to the energy level of the photoinduced electrons, further confirming the Z-scheme configuration for the g-CN/SnS system.