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Mixed phase TiO2 (Degussa P25) exhibits superior photocatalytic performance and stability due to the formation of the hetero-phase junction between anatase and rutile. However, the large bandgap limits its visible light activity. CdS is a photocatalyst with a broad light absorption band up to 550 nm. Constructing a hetero-phase junction will greatly promote the photocatalytic activity of CdS. In this work, the one-step solvothermal method was used to synthesize CdS hetero-phase junction with both hexagonal wurtzite (WZ) and cubic zinc blende (ZB) phases. The ratio of WZ and ZB phases can be tuned by adjusting the solvent ratio and reaction time to construct type I junction and effectively separate the photogenerated electron–hole pair. Under visible-light illumination, the optimal photocatalytic activity of the prepared material reaches 7.96 mmol h−1 g−1, and the quantum efficiency is 36.7% at 420 nm, which is three times higher than that of any single-phase sample (cubic or hexagonal phase) and maintains high photocatalytic stability as well. It is expected that this work will provide a feasible prospect for the practical application of high-efficiency homogeneous junction photocatalysts. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs), as a new zero-dimensional carbon-based nanomaterial with desirable optical properties, exhibit great potential for many application fields. However, the preparation technique of multiple emission CDs with high yield is difficult and complex. Therefore, exploring the large-scale and straightforward synthesis of multicolor CDs from a simple carbon source is necessary. In this work, the solvent-free method prepares a series of multicolor emission CDs from dihydroxybenzoic acid (DHBA). The maximum emission wavelengths are 408, 445, 553, 580, and 610 nm, respectively, covering the visible light region. The 2,4- and 2,6-CDs possess the longer emission wavelength caused by the 2,4-, and 2,6-DHBA easily undergo decarboxylation to form the larger sp2 domain graphitized structure. These CDs incorporated with g-C3N4 can significantly improve the photocatalytic water-splitting hydrogen production rate by extending the visible light absorption and enhancing the charge separation efficiency. The long-wavelength emission CDs can further enhance photocatalytic activity primarily by improving visible light absorption efficiency. [ABSTRACT FROM AUTHOR]

A photocatalyst system is generally comprises a catalyst and cocatalyst to achieve light absorption, electron‐hole separation, and surface reaction. It is a challenge to develop a single photocatalyst having all functions so as to lower the efficiency loss. Herein, the active GaN4 site is integrated into a polymeric carbon nitride (CN) photocatalyst (GCN), which displays an excellent H2 production rate of 9904 μmol h−1 g−1. It is 162 and 3.3 times higher than that of CN with the absence (61 μmol h−1 g−1) and presence (2981 μmol h−1 g−1), respectively, of 1.0 wt % Pt. Under light irradiation the electron is injected and stored at the GaN4 site, where the LUMO locates. The HOMO distributes on the aromatic ring resulting in spatial charge separation. Transient photovoltage discloses the electron‐storage capability of GCN. The negative GaN4 promotes proton adsorption in the excited state. The positive adsorption energy drives H2 desorption from GaN4 after passing the electron to the proton. This work opens up opportunities for exploring a novel catalyst for H2 production. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Cu 3 P/g-C 3 N 4 nanosheets composites catalyst was prepared via chemical deposition and phosphorization. • The Cu 3 P has both promoting charge spatial separation and lowering the overpotential of H 2 production function. • The photogenerated electron is confirm to keep at Cu 3 P site and hole stays at g-C 3 N 4 site. • Z-scheme was proposed to understand the charge transfer route in the catalyst. Abstract Phosphides exhibit relatively low overpotential for electrical hydrogen evolution reaction (HER), thus they have great potential to be used for cocatalyst for photocatalyst. Cu 3 P, as a p-type semiconductor, tends to form a p-n junction with an n-type photocatalyst. Typically, it is treated as a sensitizer to extend the light absorption. However, its function and work mechanism are not fully understood in the catalyst system. In this report, we synthesized g-C 3 N 4 and loaded Cu 3 P nanoparticle on its surface. The photoluminescence (PL) spectra, photocurrent and electrochemical impedance spectra confirm the Cu 3 P greatly enhance the charge separation process. Electrochemical HER results indicate that the composites have lower over-potential for HER. These results confirm the Cu 3 P works as a cocatalyst in the system, not a sensitizer. Further, we tracked the photogenerated electron transfer direction via photodeposition of Pt nanoparticles. The Pt nanoparticles tend to deposit near the Cu 3 P nanoparticles. That illustrates the photogenerated electron will be left on Cu 3 P nanoparticles. On the other hand, the photocatalytic decomposition of Rhodamine B (RhB) illustrates that the holes are left on the g-C 3 N 4 due to both g-C 3 N 4 and Cu 3 P/g-C 3 N 4 have similar decomposition rate, but the Cu 3 P cannot decompose RhB. Based on these, we proposed the photogenerated electron of g-C 3 N 4 recombine with the hole of Cu 3 P, the photogenerated electron of Cu 3 P will be left for HER. That reasonably explain the cocatalyst function of Cu 3 P in the composite catalyst system. [ABSTRACT FROM AUTHOR]