A facile and effective hydrothermal method for the fabrication of the Ag 3 PO 4 -graphene (Ag 3 PO 4 -GR) visible light photocatalyst has been developed to improve the photocatalytic performance and stability of Ag 3 PO 4 , and also to reduce the high cost of Ag 3 PO 4 for practical uses. The size and morphology of Ag 3 PO 4 particles could be tailored by the electrostatically driven assembly of Ag + on graphene oxide (GO) sheets and by the controlled growth of Ag 3 PO 4 particles on the GO surface. The generation of Ag 3 PO 4 and the transformation of GO to GR can be achieved simultaneously in the hydrothermal process. The improved photocatalytic activity of Ag 3 PO 4 -GR composites under visible light irradiation is attributed to high-surface-area GR sheets, enhanced absorption of organic dyes, and more efficient separation of photogenerated electron−hole pairs. The transfer of photogenerated electrons from the surface of Ag 3 PO 4 to GR sheets also reduces the possibility of decomposing Ag + to metallic Ag, suggesting an improved stability of recyclable Ag 3 PO 4 -GR composite photocatalyst. Moreover, with the advances in the large-scale production of high-quality GO, the use of GO as the starting material can also reduce the cost for the synthesis of Ag 3 PO 4 -based photocatalysts without weakening their photocatalytic activities.

Cadmium Sulfide (CdS) nanostructures have been widely applied for solar driven H2 generations due to its suitable band gap and band edge energetics. For an efficient photoreduction reaction, hole scavenging from CdS needs to compete favorably with many recombination processes. Extensive spectroscopic studies show evidence for hole trapping in CdS nanostructures, which naturally leads the concern of extracting trapped holes from CdS in photocatalytic reactions. Here, we report a study of hole transfer dynamics from colloidal CdS nanorods (NRs) to adsorbed hole acceptor, phenothiazine (PTZ), using transient absorption spectroscopy. We show that >99% of the holes were trapped (with a time constant of 0.73 ps) in free CdS NRs to form a photoinduced transient absorption (PA) feature. In the presence of PTZ, we observed the decay of the PA feature and corresponding formation of oxidized PTZ(+) radicals, providing direct spectroscopic evidence for trapped hole transfer from CdS. The trapped holes were extracted by PTZ in 3.8 ± 1.7 ns (half-life) to form long-lived charge separated states (CdS(-)-PTZ(+)) with a half lifetime of 310 ± 50 ns. This hole transfer time is significantly faster than the slow conduction band electron-trapped hole recombination (half lifetime of 67 ± 1 ns) in free CdS NRs, leading to an extraction efficiency of 94.7 ± 9.0%. Our results show that despite rapid hole trapping in CdS NRs, efficient extraction of trapped holes by electron donors and slow recombination of the resulting charge-separated states can still be achieved to enable efficient photoreduction using CdS nanocrystals.

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Z-scheme heterojunction photocatalysts have received considerable attention for solar energy conversion and environmental purification due to their spatially separated reduction and oxidation sites, effective separation and transportation of photo-excited charge carriers and strong redox ability. With their wide visible-light responsive range and high photocatalytic activity, metal sulphide is an important material in developing photocatalysts. This review summarizes and highlights recent research progress in sulphide-based direct Z-scheme photocatalysts, followed by analysis on the limitations over all-solid-state Z-scheme photocatalyst. Furthermore, the applications and characterization methods of sulphidebased direct Z-scheme photocatalyst are summarized. Finally, the challenges and perspectives of sulphide-based Z-scheme photocatalyst are discussed.[a] T.

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Solar-driven water oxidation is the key step for overall water splitting that efficiently harvests and converts solar energy into fuels; the development of a highly efficient photocatalyst that can mediate water oxidation has become an appealing challenge. Herein, we report a facile two-step process to decorate silver phosphate (Ag3PO4) particles on different types of graphitic carbon nitrides (g-C3N4) as composite photocatalysts for water oxidation. For all the Ag3PO4/g-C3N4 materials, an in situ Z-scheme is created by the generation of Ag nanoparticles which act as a cross-linking bridge between Ag3PO4 and g-C3N4 in the composite, resulting in better charge separation and higher catalytic performance. A detailed analysis emphasizes the importance of the g-C3N4 on the chemical, photophysical, and catalytic properties of the composite materials. Our results show that the alteration of the morphology dominates the performance of the composite materials.

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