BiOCl nanosheets (BiOCl NSs) were synthesized by hydrolyzing a hierarchical flowerlike molecular precursor (Bi(n)(Tu)(x)Cl(3n), Tu = thiourea). High photoactivity of {001} facets of BiOCl NSs was observed, and the mechanism was discussed.

Ag/AgX/BiOX (X = Cl, Br) three-component visible-light-driven (VLD) photocatalysts were synthesized by a low-temperature chemical bath method and characterized by X-ray diffraction patterns, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and UV−vis diffuse reflectance spectra. The Ag/ AgX/BiOX composites showed enhanced VLD photocatalytic activity for the degradation of rhodamine B, which was much higher than Ag/AgX and BiOX. The photocatalytic mechanisms were analyzed by active species trapping and superoxide radical quantification experiments. It revealed that metallic Ag played a different role for Ag/AgX/BiOX VLD photocatalysts, surface plasmon resonance for Ag/AgCl/BiOCl, and the Z-scheme bridge for Ag/AgBr/BiOBr.

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Photocatalysis technology, using semiconductor nano-materials to decompose toxic pollutants under solar light irradiation, displays great prospects for environmental protection. This review gives an overview of the applications of BiOX (X = Cl, Br and I) photocatalysts for efficient photocatalytic degradation (PCD) removal of pollutants in water/air, such as volatile organic compounds (VOCs), organic molecule pollutants, polymer pollutants and biological substances. In addition, the hybridization, facet effects and photocatalytic mechanisms of BiOX are highlighted to offer guidelines for designing highly-active BiOX visible-light-driven (VLD) photocatalysts. Furthermore, the research trends and future prospects of BiOX photocatalysts are also briefly summarized. It may lead to feasible green and efficient photocatalytic reaction systems using BiOX as the photocatalyst. Nano impactIn the area of environmental remediation, photocatalytic technology using nano-photocatalysts is one of the most important parts. In the past ten years, BiOX (X = Cl, Br and I) 2D nanosheets and 3D hierarchical structures with 2D nanoflakes have offered potential for efficient photocatalytic degradation (PCD) removal of pollutants in air, water and biological contaminants. Based on the layer structure characterized as [Bi 2 O 2 ] slabs interleaved by double slabs of halogen atoms, BiOX 2D crystals show open crystalline structures and indirect optical transitions. So, they display very high photocatalytic activity for environmental remediation. On the other hand, the thickness and exposed facets of BiOX 2D crystals also affect their photocatalytic performance and mechanism.

Two kinds of graphitic carbon nitride (g-C 3 N 4 ) were synthesized through a pyrolysis process of urea or melamine. It is found that the obtained g-C 3 N 4 , as photocatalysts, can reduce CO 2 to organic fuels under visible light, and exhibit different photoactivity and selectivity on the formation of CH 3 OH and C 2 H 5 OH. The product derived from the urea (denoted as u-g-C 3 N 4 ) shows a mesoporous flake-like structure with a larger surface area and higher photoactivity for the CO 2 reduction than the non-porous flaky product obtained from melamine (denoted as m-g-C 3 N 4 ). Moreover, using u-g-C 3 N 4 as a photocatalyst can result in the formation of a mixture containing CH 3 OH and C 2 H 5 OH, while m-g-C 3 N 4 only leads to the selective formation of C 2 H 5 OH. The present interesting findings could shed light on the design of efficient, eco-friendly and convenient photocatalysts and the tuning of their photoreactivity in the field of sustainable light-to-energy conversion.

Black BiOCl with oxygen vacancies was prepared by UV light irradiation with Ar blowing. The as-prepared black BiOCl sample showed 20 times higher visible light photocatalytic activity than white BiOCl for RhB degradation. The trapping experiment showed that the superoxide radical (O(2)(•-)) and holes (h(+)) were the main active species in aqueous solution under visible light irradiation.

Prompt recombination of photogenerated electrons and holes in bulk and on the surface of photocatalysts harshly impedes the photocatalytic efficiency. However, the simultaneous manipulation of photocharges in the two locations is challenging. Herein, the synchronous promotion of bulk and surface separation of photoinduced charges for prominent CO2 photoreduction by coupling macroscopic spontaneous polarization and surface oxygen vacancies (OVs) of BiOIO3 single crystals is reported. The oriented growth of BiOIO3 single‐crystal nanostrips along the [001] direction, ensuing substantial well‐aligned IO3 polar units, renders a large enhancement for the macroscopic polarization electric field, which is capable of driving the rapid separation and migration of charges from bulk to surface. Meanwhile the introduction of surface OVs establishes a local electric field for charge migration to catalytic sites on the surface of BiOIO3 nanostrips. Highly polarized BiOIO3 nanostrips with ample OVs demonstrate outstanding CO2 reduction activity for CO production with a rate of 17.33 µmol g−1 h−1 (approximately ten times enhancement) without any sacrificial agents or cocatalysts, being one of the best CO2 reduction photocatalysts in the gas–solid system reported so far. This work provides an integrated solution to governing charge movement behavior on the basis of collaborative polarization from bulk and surface.

Thin layer fabrication and crystal facet engineering favor the prompt charge transfer from bulk to the surface of a material and spatial charge separation among different facets, tremendously benefitting photocatalytic activity. However, the thickness and surface facet composition are considered as two entwined characteristics of layered materials with well-defined and tunable shapes, which possess great promise to achieve the simultaneous manipulation of charge transfer and spatial separation. Herein, it is demonstrated that one solution for the aforementioned issue by controllably regulating the surface {010}/{100} facet junctions of a layered thickness-tunable bismuth-based material, BiOIO 3 . The attenuation in thickness of BiOIO 3 nanoplates shortens the diffusion pathway of charge carriers, and more importantly the tuning of nanolayer thickness renders the ratio variation of the top {010} facet to the lateral {100}facet, which dominates the spatial separation of photogenerated electrons and holes. As a result, the highest CO evolution rate from CO 2 reduction over BiOIO 3 nanoplates with the optimal thickness and ratio of exposed facets reaches 5.42 µmol g −1 h −1 , over 300% that of the bulk counterpart (1.77 µmol g −1 h −1 ). This work paves a new way for governing charge movement behaviors on the basis of the synergistic engineering of layer structure and exposing facets.