Catalytic reduction of CO2 to CO has been considered promising for converting the greenhouse gas into chemical intermediates. Compared to other catalytic methods, photocatalytic CO2 reduction, which uses solar energy as the energy input, has attracted significant attention because it is a clean and inexhaustible resource. Therefore, using high-performance photocatalysts for effective CO2 reduction under mild reaction conditions is an active research hotspot. However, several current photocatalysts suffer from low solar energy conversion efficiency due to the extensive charge recombination and few active sites, leading to low CO2 reduction efficiency. Generally, constructing an S-scheme heterojunction can not only promote charge separation but also help maintain strong redox ability. Therefore, the S-scheme heterojunction is expected to help in achieving high conversion activity and CO2 reduction efficiency. Here, 2D tetragonal BiOBr0.5Cl0.5 nanosheets and hexagonal WO3 nanorods were prepared using a simple hydrothermal synthesis method, and the 2D/1D BiOBr0.5Cl0.5 nanosheets/WO3 nanorods (BiOBr0.5Cl0.5/WO3) S-scheme heterojunction with near infrared (NIR) light (> 780 nm) response were prepared via the electrostatic self-assembly method for the photocatalytic CO2 reduction. Following characterization and analysis, including diffuse reflectance spectra (DRS), Mott-Schottky plots, transient photocurrent response, time-resolution photoluminescence spectrum (TRPL), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and electron spin resonance (ESR) measurements, it can be demonstrated that an S-scheme carrier transfer route was formed between the 2D BiOBr0.5Cl0.5 nanosheets and 1D WO3 nanorods. Driven by the internal electric field, which was formed between the two semiconductors, electron migration was boosted, thus inhibiting the recombination of photogenerated carriers, while the stronger redox ability was maintained, thus providing good reduction efficiency over BiOBr0.5Cl0.5/WO3 composite in CO2 reduction. In addition, the 2D/1D nanosheet/nanorod structure allowed for enhanced interface contact with abundant active sites, which favored charge separation and increased photocatalytic activity. Furthermore, the amount of WO3 nanorods added during the preparation of the composites was altered, which led to the optimal amount of 5% (w, mass fraction) for the photocatalytic CO2 reduction. As a result, the BiOBr0.5Cl0.5/WO3 composite exhibited superior photocatalytic reduction performance with a CO yield of 16.68 μmol•g −1 •h −1 in the presence of any precious metal cocatalyst or sacrificial agent, which was 1.7 and 9.8 times that of pure BiOBr0.5Cl0.5 and WO3, respectively. In addition, the BiOBr0.5Cl0.5/WO3 composite provided continuously increased CO yields with excellent selectivity under full-spectrum light irradiation, suggesting good photocatalytic stability. This work describes a novel idea for the construction of 2D/1D S-scheme heterojunction photocatalysts for efficient CO2 reduction.

Transition-metal phosphides and sulfides are considered as promising cocatalysts for the photocatalytic hydrogen evolution reaction (HER), and the cocatalytic effect can be improved by directed heterostructure engineering. In this study, a novel lattice-matched CoP/CoS 2 heterostructure having a nanosheet morphology was developed as an HER cocatalyst and integrated in situ onto graphitic carbon nitride (g-C 3 N 4 ) nanosheets via a successive phosphorization and vulcanization route. First-principles density functional theory calculations evidenced that the construction of the lattice-matched CoP/CoS 2 heterostructure resulted in the redistribution of interface electrons, enhanced metallic characteristics, and improved H* adsorption. As a result of these effects, the CoP/CoS 2 heterostructure cocatalyst formed a 2D/2D Schottky junction with the g-C 3 N 4 nanosheets, thus promoting photoelectron transfer to CoP/CoS 2 and realizing fast charge-carrier separation and good HER activity. As expected, the CoP/CoS 2 heterostructure exhibited excellent cocatalytic activity, and the optimal loading of the cocatalyst on g-C 3 N 4 enhanced its HER activity to 3.78 mmol g −1 h −1 . This work furnishes a new perspective for the development of highly active noble-metal-free cocatalysts via heterostructure engineering for water splitting applications.

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A Zero-dimensional/two-dimensional (0D/2D) tungsten trioxide/graphitic carbon nitride (WO 3 /g-C 3 N 4 ) Z-scheme hybrid was prepared by employing a simple calcination process. Then, the photocatalytic property of the WO 3 /g-C 3 N 4 hybrids was assessed through their efficiency in the degradation of toxic industrial dye pollutant, Rhodamine B (RhB) and phenol under visible light irradiation. From the results and analysis, the 1 % WO 3 /g-C 3 N 4 composite with a larger Brunauer-Emmett-Teller (BET) surface area of 41.14 m 2 g À 1 compared to the pristine g-C 3 N 4 (25.25 m 2 g À 1 ) presented the uppermost improvement in the photocatalytic performance contrasted to both WO 3 and g-C 3 N 4 . It achieved the degradation of RhB and phenol with an efficiency of 96 % in 15 min and 98.5 % in 30 min, respectively. X-ray photoelectron spectroscopy (XPS) results confirmed the existence of the internal electric field. The enhanced activity was attributed to the homogeneous distribution of the WO 3 nanoparticles on the g-C 3 N 4 nanosheets with intimate interface and matched band gap structure which favored the construction of the Z-scheme hybrid, therefore boosting the electronhole separation efficiency and maintaining the strong redox capability for photocatalytic degradation.

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