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In this work, high quality two-dimension (2D) SnS2 nanoflakes as visible-light responsive photocatalysts were prepared by a facile solvothermal method. And Au/SnS2 composites were fabricated by a rapid microwave-assisted process. The Au/SnS2 heterojunction showed excellent photocatalytic activities in comparison with the bare SnS2. The optimal sample named Au/SnS2-4 can degrade 92.9% MB after 1 h under visible light irradiation. The enhanced photocatalytic activities are due to the LSPR effect of Au NPs and the special structure of SnS2. The theoretical investigations showed that electrons can transfer from the SnS2 to the Au across the interface. Finally, a synergetic photocatalytic mechanism was proposed.

Adjusting the structure of g-C3N4 to significantly enhance its photocatalytic activity has attracted considerable attention. Herein, a novel, sponge-like g-C3N4 with a porous structure is prepared from the annealing of protonated melamine under N2/H2 atmosphere (PH-CN). Compared to bulk g-C3N4 via calcination of melamine under ambient atmosphere (B-CN), PH-CN displays thinner nanosheets and a higher surface area (150.1 m2/g), which is a benefit for shortening the diffusion distance of photoinduced carriers, providing more active sites, and finally favoring the enhancement of the photocatalytic activity. Moreover, it can be clearly observed from the UV-vis spectrum that PH-CN displays better performance for harvesting light compared to B-CN. Additionally, the PH-CN is prepared with a larger band gap of 2.88 eV with the Fermi level and conduction band potential increased and valence band potential decreased, which could promote the water redox reaction. The application experiment results show that the hydrogen evolution rate on PH-CN was nearly 10 times higher than that of B-CN, which was roughly 4104 μmol h−1 g−1. The method shown in this work provides an effective approach to adjust the structure of g-C3N4 with considerable photocatalytic hydrogen evolution activity.

Hexagonal SnS2 nanosheets and Al2O3/SnS2 composites were fabricated via a one-step hydrothermal synthesis method. The investigation indicates that hexagonal SnS2 with diameters of 100–200 nm are well dispersed on the surface of Al2O3. The band gap of SnS2 after coupling with 11 wt%-Al2O3 is reduced by 0.042 eV compared with the pure SnS2. The composite with 11 wt%-Al2O3 shows the highest photocurrent density of 37 μA/cm2 at 0.49 V (vs. Ag/AgCl) under visible light (λ>420 nm), which is approximately 1.2 times that of the pure SnS2 nanosheets. Photoelectrocatalytic measurements demonstrate that an appropriate amount of Al2O3 can enhance the photoelectrocatalytic efficiency of SnS2. The 11 wt%-Al2O3/SnS2 composite (AOSS-11) can degrade 85.9% MB after 3 h under visible light illumination at an applied potential of 0.49 V (vs. Ag/AgCl). The highly effective photoelectrocatalytic activity of the Al2O3/SnS2 composite is attributed to the efficient separation of photoinduced electron-hole pairs based on the defect levels. This work may provide a new design idea for constructing the effective SnS2-based photocatalysts with other defective semiconductors.

Herein, 2D g-C3N4 nanosheets was successfully prepared by two processes: acid treatment and liquid exfoliation. The thickness of the nanosheets was nearly 4.545 nm containing ∼13 C-N layers. The acid treatment process before liquid exfoliation for bulk g-C3N4 could effectively destroy the in-plane periodicity of the aromatic systems and made the bulk easily exfoliated. This work carefully discussed the acid treatment effect for bulk by XRD patterns, nitrogen adsorption-desorption isotherm, FT-IR spectra, and UV–vis–NIR absorption spectra. Moreover, the nanosheets was fabricated and transferred onto FTO substrates by vacuum filtration self-assembled method to carefully investigate their optical, electrical, and photoelectrochemical properties. The thin film filtrated by 2 ml g-C3N4 nanosheets supernatant showed the best photocurrent response nearly 0.5 μA/cm2 and the lowest resistance of charge transfer (Rct) at the interface between FTO and electrolyte. The photocurrent response could be further effectively improved from nearly 0.5 to 1.8 μA/cm2 by the integration of CNTs to promote charge separation and transfer. Thus, the easy, safe, and indirect synthesis of 2D g-C3N4-based nanosheets thin films opens new possibilities for the fabrication of many energy-related devices.

Highly uniform and well dispersed CaF2 hollow spheres codoped with rare-earth (RE) ions Ce3+ and Yb3+ were synthesized by a facile and effective hydrothermal approach based on Ostwald ripening mechanism. The chosen phosphors were added in the SiO2 sols so as to get the anti-reflection (AR) coatings with wavelength conversion property, further to availably enhance the photovoltaic performance of solar cells. The ultraviolet (UV) light excitation induced the transition from 5D to 4F energy levels of Ce3+ with two emission bands centering at 317 nm and 336 nm. Through an efficient energy transfer process, the intense characteristic near-infrared (NIR) emission of Yb3+ peaking at 965 nm and 1026 nm attributed to the transition of 2F5/2 to 2F7/2, which is just matched the spectral response of Si band gap. In addition, all of the AR coating films containing phosphors showed an incredible transmittance performance in visible and NIR region as well as a preferable photo-electricity response. CaF2:Ce3+–Yb3+ AR coating film could effectively improve the photoelectric conversion efficiency by 0.16%, 0.50% and 1.20% compared to CaF2:Ce3+ AR coating film, SiO2 AR coating film and pure glass respectively. This work may promote a new platform and wider application of the wavelength conversion materials for silicon solar cells.

In this article, we report a facile solvothermal route, via using green and nontoxic absolute ethyl alcohol as the solvent and surfactant. Hydrazine hydrate is a reductant. A thin flake-like InSe nanocrystals successfully synthesized by a two-step solvothermal-annealing process. In addition, we have optimized the experimental conditions, included solvothermal time, annealing temperature and annealing time to explore the change in photoelectric response and analyzes the reason of enhancement of photocurrent densities from mechanism of photocurrent generation in detail. The InSe powders have shown a high absorption coefficient in the visible range (λ > 420 nm). By optimizing preparation conditions, the as-synthesized film of 180 °C, 12 h–250 °C, 2 h shows the highest photocurrent density of 15.9 µA cm−2 at 0.5 V (versus SCE) under visible light. Photocurrent densities of thin film samples increased by approximately 2.8 times that of unoptimized nanosheets. It was shown that InSe nanosheets have superior photoelectric response characteristics under visible light illumination.

In this paper, anatase TiO2 nanotube (NT) film photoelectrodes are successfully fabricated by a simple and effective hydrothermal method. Subsequently, an aqueous-phase processing technique is adopted to construct highly dispersed ZnSe quantum dots (QDs) on Au/TiO2 NT films prepared by microwave-assisted chemical reduction, which formed composite ZnSe/Au/TiO2 NT film systems (ZATs) with excellent performance in photoelectrocatalytic (PEC) applications. The morphology and performance of as-obtained ZATs were investigated based on various characterizations. The investigation revealed that as-obtained ZATs not only greatly extend spatial separation of charges and restrain the recombination rate of photogenerated electron–hole pairs, but also improve the efficiency to use visible light and display a wide and strong absorption in the visible light region ranging from 400 nm to 800 nm. Moreover, we observe a larger fluorescence quenching of ZATs compared with that of pure TiO2 NT films and binary composites. Experimental results indicate that the photocurrent densities of pure TiO2, 0.8 Au/TiO2, 60 min ZnSe/TiO2, and ZATs are 0.020 mA cm−2, 0.032 mA cm−2, 0.037 mA cm−2 and 0.070 mA cm−2, respectively, which is approximately 2–3.5 times higher than that of pure TiO2 NT films and binary compound photoelectrodes. Additionally, experimental results suggest that the as-prepared ZATs photoelectrode has exhibited considerable stability and significantly increased PEC activity for the degradation of methylene blue (MB) in distilled water under 100 mW cm−2 xenon lamp irradiation. The degradation efficiency on MB of 45 min ZnSe/0.8 Au/TiO2 NT films approaches 91%; however, the counterpart of TiO2 NT films is less than 10%. Eventually, the mechanism for the improvement of the PEC performance of ZATs is discussed to point out that ZATs display prominent charges transport performance, and a stepwise band alignment structure is built up in its photoelectrode, which indicates that charge separation and migration across the interfaces should favor vectorial electron transfer according to the scheme of ZnSe → TiO2 → Au → Ti substrates.