Z-scheme Heterostructure Photocatalysts Research Articles

All-solid-state artificial Z-scheme porous g-C3N4/Sn2S3-DETA heterostructure photocatalyst with enhanced performance in photocatalytic CO2 reduction

Nowadays, the increasing CO2 emissions have attracted widespread attentions and it is necessary to reduce CO2 emissions to solve the global warming problem. So photocatalytic reduction of CO2 into chemical fuels is a promising strategy. Here, a Z-scheme porous g-C3N4/Sn2S3-diethylenetriamine (Pg-C3N4/Sn2S3-DETA) composite without an electron intermediary is designed. Photocatalytic performance of the as-fabricated samples is investigated on the basis of photocatalytic CO2 reduction (PCR) to form CH4 and CH3OH. We find that the Z-scheme heterostructure photocatalysts show a higher PCR performance than Pg-C3N4 and Sn2S3-DETA. An optimized Pg-C3N4/Sn2S3-DETA heterostructure sample displays high CH4 production rate of 4.84 μmol h−1 g−1 and CH3OH-production rate of 1.35 μmol h−1 g−1 with 5% Pg-C3N4 content. The superior PCR performance could be ascribed to the special structure of a direct Z-scheme Pg-C3N4/Sn2S3-DETA photocatalyst, which is beneficial to efficient separation of electron-hole pairs. Density functional theory (DFT) calculation further confirms the presence of direct Z-scheme mechanism. This Z-scheme heterostructure photocatalyst with superior performance may inaugurate the perspective on a new promising hierarchy of materials on CO2 photoreduction.

Pt@Cu2O/WO3 composite photocatalyst for enhanced photocatalytic water oxidation performance

In this study, Pt@Cu2O/WO3 composite photocatalyst was constructed via coupling Cu2O onto the edged (200) and (020) facets of square-like WO3 nanoplates and followed by photodeposition of Pt onto Cu2O. The remarkably enhanced photocatalytic water oxidation activity over such assembled Pt@Cu2O/WO3 composite photocatalyst was observed. The superior photocatalytic performance can be attributed to intrinsic nature of charge separation between different facets of square-like WO3, highly efficient WO3-to-Cu2O electron transfer occurring at the intimate contact interface between WO3 and Cu2O, and Pt as reduction cocatalyst. This work will provide new deep insights into the design of crystal-based Z-scheme heterostructure photocatalysts by facet-preferentially coupling one semiconductor with another.

Construction of urchin-like ZnIn2S4-Au-TiO2 heterostructure with enhanced activity for photocatalytic hydrogen evolution

The ternary ZnIn2S4-Au-TiO2 Z-scheme heterostructure photocatalysts has been fabricated by selecting effectiveness Au NPs as a solid electron mediator, via a chemical-deposition process for water splitting under simulated solar light irradiation. The designed photocatalysts exhibit high surface area and wide light absorption range, which significantly enhance photocatalytic efficiency. At an optimal ratio of 24 wt% Au NPs and 60 wt% ZnIn2S4, the obtained ZnIn2S4-Au-TiO2 photocatalysts achieve the highest H2 production with the rate of 186.3 μmol g−1 h−1, and the O2 production rate is reached to 66.3 μmol g−1 h−1. It showed that the ZnIn2S4-Au-TiO2 composite structures exhibit significantly better photocatalytic activity than ZnIn2S4-TiO2 and Au-ZnIn2S4-TiO2 structure. Such an excellent performance should be attributed to the Au NPs in the Z-scheme system structure which favor to enhance the transfer rate of the photogenerated electrons and holes and remain strong redox ability of the photocatalysts. It is worth pointing out that the unique Z-scheme ZnIn2S4-Au-TiO2 heterostructure shows great solar activity toward water splitting into renewable hydrocarbon fuel.

Novel AgCl/Ag/AgFeO2 Z-scheme heterostructure photocatalyst with enhanced photocatalytic and stability under visible light

A new AgCl/Ag/AgFeO2 composite was synthesized for the first time via a simple precipitation method. The very detailed characterizations were enforced in photocatalytic activity and stability. The photocatalytic performance was studied by the degradation of the rhodamine B (RhB, a cationic dye) under visible irradiation. The as-prepared AgCl/Ag/AgFeO2 photocatalyst exhibited excellent photocatalytic activity and stability under the visible light region compared to pure AgCl and AgFeO2. About 97.47% of RhB can be removed in 60min by the optimized AgCl/Ag/AgFeO2 composite, which was ∼2.26 and ∼10.83 times as fast as that pure AgCl and pure AgFeO2. After three cycles visible light irradiation experiments found that degradation rate of RhB reached 76.35%, which was still higher than pure AgCl and AgFeO2. The obviously enhanced photocatalytic activity of AgCl/Ag/AgFeO2 composites can be attributed to the efficient separation of electron-hole pairs of the Z-scheme heterostructure between AgCl, Ag and AgFeO2. In this study, we also found the superoxide radicals (O2−) was considered to be the dominant active radical in the degradation of dye.