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Graphical abstract Highlights • The α-Fe 2 O 3 nanoclusters were encapsulated in the pores of UiO-66. • The α-Fe 2 O 3 @UiO-66 exhibited an improved photodegradation rate of MB. • The photocatalytic activity was improved due to the confining effect. Abstract α-Fe 2 O 3 is narrow bandgap photocatalyst that is widely used for organic-pollutant photodegradation and photoelectrochemical conversion. However, α-Fe 2 O 3 with short mean-free path exhibits low photocatalytic activity due to the high recombination rate of photoexcited carriers. Accordingly, the importance of controlling particle size to reduce the recombination rate of α-Fe 2 O 3 is increasingly being recognized. In this study, UiO-66 with various pore diameters was employed to confine α-Fe 2 O 3 growth. The α-Fe 2 O 3 nanoclusters were encapsulated inside the UiO-66 cage through simple adsorption and thermal conversion. The structure and state of α-Fe 2 O 3 @UiO-66 were studied by SEM, TEM and XPS analyses. Results showed that α-Fe 2 O 3 @UiO-66 had significantly improved photodegradation efficiency for methylene blue under visible-light irradiation due to the confining effect on α-Fe 2 O 3 nanoclusters and the synergistic effect between UiO-66 and α-Fe 2 O 3. [ABSTRACT FROM AUTHOR]

Noble-metal-free semiconductor materials are widely used for photocatalytic hydrogen generation because of their low cost. ZnO-based heterostructures with synergistic effects exhibit an effective photocatalytic activity. In this work, NiO@Ni-ZnO/reduced graphene oxide (rGO)/CdS heterostructures are synthesized by a multi-step method. rGO nanosheets and CdS nanoparticles were introduced into the heterostructures via a redox reaction and light-assisted growth, respectively. A novel Ni-induced electrochemical growth method was developed to prepare ZnO rods from Zn powder. NiO@Ni-ZnO/rGO/CdS heterostructures with a wide visible-light absorption range exhibited highly photocatalytic hydrogen generation rates under UV–vis and visible light irradiation. The enhanced photocatalytic activity is attributed to the Ni nanoparticles that act as cocatalysts for capturing photoexcited electrons and the improved synergistic effect between ZnO and CdS due to the rGO nanosheets acting as photoexcited carrier transport channels. [ABSTRACT FROM AUTHOR]

• Tunable products were realized by changing the feeding ratio of NCQDs/NaBiO 3 ·2H 2 O during the hydrothermal process. • NCQDs act as one active component or carbon source dependant on the feeding ratio of NCQDs/NaBiO 3 ·2H 2 O. • Both NCQDs/Bi 2 O 4 and Bi 2 O 4 /Bi 2 O 2 CO 3 heterostructures exhibit enhanced photocatalytic removal efficiency for MO and BPA, compared with Bi 2 O 4. • Bi 2 O 4 /Bi 2 O 2 CO 3 is more effective in promoting the catalytic activity of Bi 2 O 4 than NCQDs/Bi 2 O 4. Regulating the composition and proportion of heterojunctions is critical to improve their photocatalytic properties. Many bismuth-based oxides are readily converted from one oxide to another under certain conditions, which supplies a simple strategy for the in-situ construction of bismuth-based oxides heterostructures with controllable composition and proportion. Herein, a series of tunable products from NCQDs/Bi 2 O 4 composite (NCQDs: nitrogen-doped carbon quantum dots) to Bi 2 O 4 /Bi 2 O 2 CO 3 heterojunction to pure Bi 2 O 2 CO 3 were obtained just by adjusting the NCQDs/NaBiO 3 ·2H 2 O precursors' feeding ratio during the hydrothermal process, in which NCQDs act as an active component or carbon source dependant on the feeding ratio. Both NCQDs/Bi 2 O 4 and Bi 2 O 4 /Bi 2 O 2 CO 3 heterostructures exhibit enhanced photocatalytic efficiency for removing methyl orange (MO) and bisphenol A (BPA) under simulated sunlight, compared with Bi 2 O 4 alone. Nevertheless, the latter is more effective in promoting the catalytic activity of Bi 2 O 4 than the former. The reaction rate constant k of the optimal NCQDs/Bi 2 O 4 hybrid is only 1.6 and 2.37 times higher than that of single Bi 2 O 4 , whereas the k of the optimal Bi 2 O 4 /Bi 2 O 2 CO 3 heterojunction is about 2.93 and 3.07 times higher than that of single Bi 2 O 4 for the degradation of MO and BPA, respectively. The much higher photoinduced charges' separation efficiency, verified by the transient photocurrent response and EIS results, should be the main reason the Bi 2 O 4 /Bi 2 O 2 CO 3 heterojunction possesses superior photocatalytic activity to the NCQDs/Bi 2 O 4 heterostructure. Hole (h+) and superoxide radical (•O 2 −) are determined to be the primary and secondary important active species for the photodegradation reaction, respectively. This work supplies a convenient strategy to modulate the composition and proportion of the hydrothermal reaction products and their photocatalytic properties through changing the precursors' feeding ratio of NCQDs/NaBiO 3 ·2H 2 O. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] TiO 2 /Au@rGO(reduced graphene oxide) ternary hybrids were successfully fabricated via a simple two-step method, namely photodepositing of Au nanoparticles (NPs) on large TiO 2 particles first and then coating rGO sheets onto the surface of Au/TiO 2 binary hybrids. The major beneficial structural feature of TiO 2 /Au@rGO hybrids lies in the existence of mutual interfacial area among all of the three components. This outstanding feature enlarges the contact area and improves the separation efficiency of photoexcited charge carriers between components, and thus allowing the efficient realization of fascinating plasmonic effect of Au NPs in photocatalysis. Enabled by this unique structure design, the photocatalytic activity of TiO 2 /Au@rGO hybrids for the degradation of methyl orange was dramatically higher than those of pure TiO 2 , Au/TiO 2 and TiO 2 /@rGO hybrids, under both UV and simulated solar light. The enhancement of photocatalytic activity of TiO 2 /Au@rGO hybrids could be attributed to the synergistic effect between Au NPs, TiO 2 and rGO, and the existence of multi-channel electron transfer paths. This work represents a step toward the rational design of semiconductor-noble metal-graphene hybrids structures for broad-spectrum photocatalysis. [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen evolution over semiconductors is an efficient method for solar-energy conversion. Heterostructural photocatalysts with separated photoexcited carriers exhibit efficient photocatalytic hydrogen evolution without co-catalysts. In this study, heterostructures comprising of Cd 1-x Zn x S and Zn 1-y Cd y S phases were prepared through the replacement and sulfuration process at high temperature using Zn powders as the precursor. Highly crystalline Cd 1-x Zn x S-Zn 1-y Cd y S heterostructures without noble metal co-catalysts present a stable and highly effective photocatalytic hydrogen evolution rate under both UV–visible and visible-light irradiations due to the synergistic effects of Cd 1-x Zn x S and Zn 1-y Cd y S. [ABSTRACT FROM AUTHOR]

Hexagonal prism-like ZnO crystals dominated with polar facets were synthesized using a hydrothermal method. The Gold (Au) nanoparticles were selectively photodeposited on the polar surfaces of faceted ZnO crystals as a result of anisotropic photocatalytic activities of the polar and nonpolar facets. The size of Au nanoparticles uniformly dispersed on the polar facets increased with increasing Au-loading amount. These Au-loaded ZnO crystals showed an additional visible light absorption band from 400 nm to 800 nm. The 0.1 wt% Au-loaded ZnO crystals with visible light absorption peak at approximately 690 nm exhibited the highest photocatalytic activity under visible light irradiation. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) nanosheets are introduced to ZnS–CdS heterostructures to improve photocatalytic hydrogen generation. ZnS and CdS nanoparticles are formed on the surface of GO nanosheets via a light irradiation-assisted method. Here, GO construct a carrier transport channel between ZnS and CdS to enhance cooperative effects. The ZnS–CdS/GO heterostructures exhibit high photocatalytic hydrogen generation rates under either UV–visible or visible light irradiation. After loading of Pt nanoparticles as co-catalysts, the photocatalytic hydrogen generation rate of the proposed heterostructures is significantly improved to as high as 1.68 mmol h −1 under UV–visible light irradiation. [ABSTRACT FROM AUTHOR]

S@rGO(reduced graphene oxide) composites were synthesized by a facile electrostatic attraction in the presence of cetyltriethylammnonium bromide (CTAB). Scanning electron microscopy images show that sulfur particles were wrapped by a thin layer of rGO. The rGO nanocoating enhanced the absorption of visible light, facilitated the separation of photogenerated charges, promoted the adsorption of dye moleculars, and provided the perfect chemical protection to inner sulfur particles. As a result, the rGO nanocoating improved the photocatalytic activity and photostability of the sulfur photocatalyst for the degradation of methylene blue under simulated solar light irradiation. Our results might open up a promising way to develop stable and highly efficient sulfur-based photocatalyst. [ABSTRACT FROM AUTHOR]

The controllable synthesis of strongly coupled TiO 2 /graphene composites has been a long-standing challenge for developing advanced photocatalysts. Here, we report a facile water-phase protocol for synthesis of TiO 2 –graphene composites using GO aqueous suspension and TiO 2 aqueous nanosols as precursors. By controlling the ratio of GO to TiO 2 , both high-/low-dense TiO 2 nanoparticles across graphene and graphene–TiO 2 –graphene sandwich structured composites are successfully achieved through electrostatic attraction between negatively charged GO nanosheets and positively charged TiO 2 nanosols . The TiO 2 –graphene composites show an enhanced photocatalytic activity for the degradation of methylene blue (MB) under UV light. Interestingly, the sandwich structured TiO 2 –graphene composite exhibits the best photocatalytic activity and the highest photocurrent density, which is 12.2 and 35.46 times as that of pure TiO 2 , respectively. The outstanding photocatalytic activity of sandwich structured composite is likely due to the following two reasons, two-channel electron conduction path between TiO 2 and graphene, as well as the better adsorption capability of MB molecule. [ABSTRACT FROM AUTHOR]

Highlights: [•] High crystallinity of TiO2 with exposed {001} facets was prepared by an alcohothermal approach through inclusion of water. [•] Water played an important role in conducting the size, shape, crystallinity, microstructure and photocatalytic activity of TiO2. [•] High crystallinity of TiO2 could retard the recombination and promote the separation of electron–hole pairs. [Copyright &y& Elsevier]

[Display omitted] • Single-crystal ordered networks of Ta 2 O 5 was constructed by micro-terminal regulation. • Single-crystal ordered networks reduce carrier recombination rate at grain boundaries. • The SCON-Ta 2 O 5 exhibits a considerably improved photocatalytic H 2 evolution activity. The ordered macroporous structure of photocatalytic semiconductors can enable smooth mass transfer, high hydrogen release efficiency and multiple reaction site interfaces. Remote electronic communications and structural continuity are necessary to achieve these goals. The single-crystal ordered network structures are ideal candidates to meet the above requirements. However, fabricating such continuous single-crystal structures is very challenging due to the rapid formation of grain boundaries. In this study, highly ordered poly(methyl methacrylate) (PMMA) was chosen as hosts to build a nanoreactor. A micro-terminal was developed in nanoreactors to generate the suitable growth environment for single-crystal ordered networks of Ta 2 O 5 (SCON-Ta 2 O 5). By regulation of the nanoreactor space, the effect of mass transfer channel and carrier migration distance on the photocatalytic performance of SCON-Ta 2 O 5 was systematically investigated. A substantially improved photocatalytic hydrogen performance was realized on SCON-Ta 2 O 5. Thus, SCON-Ta 2 O 5 has a great potential in other applications and this general synthetic strategy could extend the possibility of macroporous single-crystal growth to other functional semiconductors. [ABSTRACT FROM AUTHOR]

• Hydroxyl imprinting sites are constructed by meso-erythritol on the BiOBr. • The BiOBr nanosheets can rapidly degrade phenol and high concentration RhB. • A more positive valence band was obtained to improve the oxidation ability. BiOBr is a promising photocatalytic semiconductor material for pollutant treatment, but its photocatalytic application is limited due to its poor photo-oxidation capability. Hydroxyl radicals (OH) play a key role in surface photochemical reaction. Thus, improving the response of semiconductor catalysts to hydroxyl is a key problem to be solved through a suitable surface atomic regulation strategy. In this study, we selected a meso-erythritol (ME) containing a number of hydroxyl groups to regulate the surface of BiOBr nanosheets. The ME-regulated BiOBr sheets showed a more positive valence band and a much improved oxidation capability than the unregulated ones. The ME-regulated BiOBr nanosheets also had a positive response to OH in the photocatalytic process. The BiOBr nanosheets rapidly degraded phenol and RhB at a high concentration (0.4 mmol L−1). This strategy of surface atom regulation by using sugars provided a reliable means of obtaining highly effective photocatalytic materials. [ABSTRACT FROM AUTHOR]

Review: 106 refs. [ABSTRACT FROM AUTHOR]