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The different surface functional groups of carbon quantum dots (CQDs) affect their optical property, especially the up-conversion photoluminescence (UCPL) property. In this study, the CQDs/BiVO4 composite photocatalyst was synthesized by a simple hydrothermal process. The prepared photocatalysts were comprehensively characterized. The photocatalytic activity of CQDs/BiVO4 was tested by degrading rhodamine B (RhB). The photocatalytic removal rate of RhB with BiVO4 was largely enhanced by incorporation of CQDs. The enhanced photocatalytic performance was mainly attributed to the broadened response spectra generated by the UCPL of CQDs. Furthermore, loading CQDs had improved the separation efficiency of photogenerated carriers, resulting in the photocatalytic performance increasement of CQDs/BiVO4. The content of surface graphitic nitrogen and oxygen-containing groups on CQDs could adjust its UCPL wavelength and intensity, and ultimately adjust photocatalytic ability of composite photocatalysts. More surface graphitic nitrogen and oxygen-containing groups on CQDs could benefit the photocatalytic ability of CQDs/BiVO4. Free radical scavenging experiments determined that the holes (h+) and hydroxyl radicals (·OH) played a crucial role in the photodegradation process.

Novel Bi@BiOBr–Bi2MoO6 ternary heterostructure photocatalysts were successfully prepared by a facile two-step solvothermal strategy, which presents a uniform spherical structure with around 200 nm. The composition, morphology and light-harvesting properties of Bi@BiOBr–Bi2MoO6 were characterized by XRD, XPS, SEM, TEM and DRS. As expected, the as-prepared heterojunction exhibits extraordinary photocatalytic activity for nitrogen fixation in water without any sacrificial agent. The results reveal that the optimized Bi@BOB–BMO-2 sample has an excellent NH4+ yield rate of 167.2 μmol g−1 h−1, which is 2.5 and 2.1 times higher than that of pure Bi2MoO6 and Bi@BiOBr. The effect of an electron scavenger on the rate of NH4+ production and the stability of Bi@BOB–BMO-2 was also investigated, and the results were desirable. This study provides a promising strategy to design superior simulated solar-light driven heterojunction photocatalysts with distinguished nitrogen fixation performance under mild conditions.

A series of niobium-doped BiOBr (Nb-BiOBr) were successfully synthesized via hydrothermal method. Moreover, the morphology structure and optical property of BiOBr and Nb-BiOBr samples were determined using various characterization techniques including SEM, TEM, EDS, BET, XRD, XPS and DRS, etc. The photocatalytic performance of Nb-BiOBr was deeply investigated with the rhodamine B and ofloxacin degradation under visible-light irradiation as model reaction. The results showed that Nb-BiOBr samples depicted the outstanding photocatalytic performance, especially for the 1.25Nb-BiOBr. Moreover, its reaction kinetic constant was ca. 6.4 times higher than that of undoped BiOBr. The observed photocatalytic performance could be attributed to the strong light absorption, enhanced separation efficiency of charge carriers as well as high specific surface area. Meanwhile, 1.25Nb-BiOBr demonstrated stability in RhB degradation, thereby facilitating the water treatment application.

Solar-driven reduction of dinitrogen (N2) to ammonia (NH3) is still challenging due to the highly stable N-N triple bond. Herein, orthorhombic phase H-Bi5O7I microspheres with abundant oxygen vacancies (OVs) were successfully prepared via a simple calcination and hydrogen reduction strategy. Based on the combined bismuth-rich strategy and the introduction of OVs in H-Bi5O7I, a remarkable photocatalytic nitrogen fixation performance was achieved under visible light irradiation in the absence of any organic scavengers or noble-metal cocatalysts. H-Bi5O7I exhibits an NH4+ generation rate of 162.48 μmol g-1 h-1, which is 2.0 and 7.4 times higher than that of Bi5O7I and BiOI. It is because H-Bi5O7I with abundant OVs has a more proper band gap, better electron capturing ability and more effective separation and transfer rate for the photogenerated charge carriers. This study may provide a new direction and useful insight for the design of defect assisted N2 fixation photocatalysts.

Photocatalysis is a promising technology for removing contaminant in water. However, the rapid recombination of photogenerated charge carriers limits the performance of photocatalysis in water treatment. Here, a novel light response B/W-TiO2 homojunction catalyst based on the black TiO2 (B-TiO2) and TiO2 (W-TiO2) was successfully synthesized by a facile hydrothermal method. The mass ratio of B-TiO2 to W-TiO2 was tuned to study its effect on homojunction formation and photocatalytic performance. Beneficial from the band difference between B-TiO2 and W-TiO2, the conduction band (CB) electrons of W-TiO2 can migrate to the CB of B-TiO2 and the valence band (VB) holes of B-TiO2 transfer to the VB of W-TiO2, hence effectively promoting the separation of photogenerated charge carriers. The formation of homojunction can dramatically improve the photocatalytic ability of B/W-TiO2; the kinetic constant of rhodamine B degradation of B/W-TiO2 with optimal mass ratio is nearly 3.9 and 5.2 times higher than that of B-TiO2 and W-TiO2, respectively. Moreover, the superoxide radical (O 2 ·− ) and hydroxyl radicals (·OH) species play a crucial role in the photodegradation process. The enhancement of photocatalytic activity is attributed to the construction of B/W-TiO2 homojunction, which is beneficial to improve the separation efficiency of photogenerated electron–holes.

Flower-like Bi that deposited BiOBr with oxygen vacancies (OVs) has been successfully fabricated via a simple solvothermal method followed by an easy hydrogenated treatment. The characterization results show that three-dimensional (3D) H-1.0Bi@BiOBr microspheres with the diameter about 1.2–1.5 μm were self-assembled by countless two-dimensional (2D) interlaced BiOBr nanosheets. Bi-deposited and oxygen vacancies endowed the H-1.0Bi@BiOBr samples with a dramatically enhanced photocatalytic performance for the degradation of organic pollutants (Rhodamine B and Ofloxacin) and the solar-energy nitrogen fixation. It disclosed that the photocatalytic performance order of the photocatalyst was H200-1.0Bi@BiOBr > H250-1.0Bi@BiOBr > H150-1.0Bi@BiOBr > 1.0Bi@BiOBr > 2.0Bi@BiOBr > 0.5Bi@BiOBr > BiOBr. Particularly, the enhanced photocatalytic activity was ascribed to higher BET specific area, enhanced visible-light absorption, effective photoinduced charge separation and suitable amounts of oxygen vacancies. The H-1.0Bi@BiOBr samples also showed good photochemical stability under repeated visible-light irradiation. This work could shed light on exploring high-photocatalytic-property materials and stimulating the development of OVs-Bi@BiOBr photocatalysts, which had great potential for the solar-energy conversion, environmental purification and organic pollution treatment in water.

The graphene (Gr)/PI (pyromellitic dianhydride (PMDA) modified g-C3N4) heterojunction was fabricated by a handy sonochemical method. After adding PMDA in the forming process of g-C3N4, the conduction position of obtained catalyst was lowered to −0.59 eV (closer to the Fermi level of Gr), which is beneficial for constructing high-efficient heterojunction with less energy loss. The photocatalytic efficiency of Gr/PI for Rodamine B (RhB) degradation was greatly enhanced compared with Gr/g-C3N4. The k of RhB removal on Gr/PI was 1.60 times as that of Gr/g-C3N4. The excellent photocatalytic ability of Gr/PI was mainly attributed to the effective separation of photogenerated electron-holes.

The rapid recombination of photoinduced electron-holes and the low utilization of solar energy have become two disadvantages limiting the performance of current photocatalysts. In this work, a novel composite photocatalyst, in which the carbon quantum dots (CQDs) were supported on the NH2-MIL-125 (a kind of metal-organic frameworks (MOFs)), was designed and constructed. The CQDs could not only serve as electron-acceptors for promoting the photoinduced charge separation in NH2-MIL-125, but also act as the spectrum converter (convert near-infrared light into visible light) to realize the enhanced light absorption by NH2-MIL-125. The NH2-MIL-125 supported CQDs (CQDs/NH2-MIL-125) displayed significantly enhanced photocatalytic activity compared with NH2-MIL-125 for Rhodamine B (RhB) degradation, regardless of the light source varied from the full-spectrum, visible light or even near-infrared light. Moreover, the photocatalytic efficiency of CQDs/NH2-MIL-125 was influenced by the CQDs content, and the composite with 1% CQDs loading exhibited the best performance. The excellent photocatalytic performance of CQDs/NH2-MIL-125 is attributed to the enhanced photoinduced charge separation and improved utilization efficiency of light energy. This work is expected to provide an attractive strategy for constructing high-efficiency photocatalyts towards environmental remediation.

Photocatalysis has been regarded as a sustainable and efficient technology for removing refractory pollutants in water. However, the performance of photocatalysis is usually limited by the fast recombination of photoinduced electron–holes and the narrow range of spectrum absorption. In this work, the visible-light-sensitive BiVO4 quantum tube (q-BiVO4) was decorated with the carbon quantum dots (CQDs) possessing unique upconversion fluorescence function for enhanced photocatalytic degradation of organic pollutants. Under visible light (λ > 420 nm) and even near-infrared light (λ > 700 nm) irradiation, the CQDs/q-BiVO4 composite displayed significantly enhanced performance compared with q-BiVO4 alone for the degradation of phenol and rhodamine B (RhB). The CQDs/q-BiVO4 with 2% CQDs loading exhibited the best performance, whose kinetic constants for phenol and RhB degradation were 3.0 and 2.4 times higher than that on q-BiVO4. The outstanding photocatalytic performance of CQDs/q-BiVO4 was ascribed to the quantum-sized BiVO4 and the dual function of CQDs, which not only served as the electron acceptor to separate the photoinduced electron–holes in q-BiVO4, but also improved the light absorption of q-BiVO4 through converting the near-infrared light into visible light. This work provides new insight into designing high-efficiency photocatalyst for enhanced environmental remediation.

Photocatalysis is intensely employed to remove refractory organic pollutants in water but suffers from low efficiency due to the rapid recombination of photogenerated electrons and holes. Here, car...

Hydrothermal carbonation carbon (HTCC) is emerging as a promising alternative for photocatalytic removal of contaminants from water. However, the catalytic activity of HTCC is limited by its poor charge transfer ability, and its photocatalytic mechanism remains unclear. Herein, a unique photosensitization-like mechanism was firstly found on Fe modified HTCC (Fe-HTCC) derived from glucose for effective removal of organic pollutants. Under visible light illumination, the organic pollutant coordinated with Fe-HTCC enabled electrons transfer from its highest occupied molecular orbital (HOMO) to conduction band (CB) of Fe-HTCC, which not only oxidized pollutant itself, but also generated oxygen-centered radical for reducing O2 into O2•- towards pollutant removal. The degradation kinetic constant of sulfamethoxazole (SMX) over Fe-HTCC was about 1024.4 and 20.5 times higher than that of HTCC and g-C3N4, respectively. The enhanced performance of Fe-HTCC was originated from dual role of Fe modification: one is to boost the electron-deficient C sites which prefer to coordinate with amino or hydroxyl of pollutants; the other is to enhance the linkage of discrete polyfuran chains in Fe-HTCC for effective electron transfer from pollutant to Fe-HTCC. This work provides new insight into the synthesis and mechanism of HTCC-based high-efficiency photocatalyst for water decontamination.

This study investigates the photodegradation of the organic dye rhodamine B by Ag-nanoparticle-containing BiVO4 catalysts under different irradiation conditions. The catalysts consist of Ag nanoparticles deposited on oxygen-vacancy-containing BiVO4. The morphology of the BiVO4 is olive shaped, and it has a uniform size distribution. The BiVO4 possesses a high oxygen vacancy density, and the resulting Ag nanoparticle-BiVO4 catalyst exhibits higher photocatalytic activity than BiVO4. The RhB degradation by the Ag nanoparticle-BiVO4 catalyst is 99% after 100 min of simulated solar irradiation. BiVO4 containing oxygen vacancies as a rationally designed support extends the catalyst response into the near-infrared region, and facilitates the trapping and transfer of plasmonic hot electrons. The enhanced photocatalytic efficiency is attributed to charge transfer from the BiVO4 to Ag nanoparticles, and surface plasmon resonance of the Ag nanoparticles. These insights into electron-hole separation and charge transfer may arouse interest in solar-driven wastewater treatment and water splitting.

Photocatalysis has been regarded as an attractive strategy for the elimination of contaminants, but its performance is usually limited by the fast recombination of photogenerated electron–holes. A heterojunction photocatalyst could achieve the effective separation of electron–holes. However, the electrons migrate to the less negative band while holes move to the less positive band, leading to a weakened redox ability. Z-scheme photocatalysis is a feasible way to realize the efficient separation of photogenerated electron–holes without sacrificing the reductive ability of electrons and oxidative ability of holes. In this work, a new Z-scheme photocatalyst, composed of g-C3N4 (photocatalyst I), FeWO4 (photocatalyst II) and RGO (electron mediator), was fabricated through a facile hydrothermal and mixing method. The effect of contact ways (the electron mediator firstly combined with photocatalyst I or with photocatalyst II) on the Z-scheme photocatalytic performance was investigated. The photocatalytic removal rate of rhodamine B (RhB) was largely enhanced by the construction of a Z-scheme photocatalyst, compared with the g-C3N4/FeWO4 composite without RGO. The contact ways could affect the photocatalytic ability of a Z-scheme photocatalyst. The enhanced photocatalytic performance was attributed to the Z-scheme induced efficient separation of photogenerated charge carriers. Furthermore, remaining holes (on the VB of FeWO4) or remaining electrons (on the CB of g-C3N4) with powerful oxidation or reduction ability would promote the photocatalytic degradation of RhB.

We present a facile approach to preparing a BiOCl1−xBrx@AgBr heterostructure using a two-step solvothermal method. Multiple characterisation techniques have been employed to investigate its morphology, structure, optical and electronic properties and photocatalytic performance. The photocatalytic activity of the BiOCl1−xBrx@AgBr heterostructure was sufficiently evaluated by adopting Reactive Blue KN-R as the target organic pollutant under visible light irradiation. The as-prepared BiOCl1−xBrx@AgBr exhibited much higher photocatalytic activity than BiOCl1−xBrx and BiOCl, which was ascribed to the movement of photogenerated electrons from AgBr to BiOCl1−xBrx, resulting in effective charge separation and transfer. Moreover, the modification of BiOCl1−xBrx with AgBr broadened the light absorption range, making the composite suitable for visible light excitation. The excellent photocatalytic performance provides potential opportunities to utilize BiOCl1−xBrx@AgBr for environmental purification and organic pollution treatment of water.

The cotton cellulose nanofibers framework of Z-Scheme ZnO/Ag3PO4 heterojunction has been successfully fabricated by a simple route of the electrospun-hydrothermal method. The photocatalytic activity of the as-prepared cotton cellulose nanofibers framework of Z-Scheme ZnO/Ag3PO4 heterojunction exhibits significant enhancement after the Ag3PO4 being introduced by the degradation of methylene blue (MB) under visible light irradiation. Furthermore, the high dispersibility of the CCNFs, high visible light absorption and photon-generated carriers separation of Z-Scheme ZnO/Ag3PO4 heterostructure are considered as the main reasons for the enhancement.

The polydopamine (PDA) coating α-S hydrophilic composites (SD) were fabricated by a self-assembly process for enhanced α-S photocatalytic performance under visible light. The XRD patterns analysis indicated that we had successfully prepared the orthorhombic α-S. The SEM, FT-IR and TGA showed that PDA had been successfully coated on α-S. The photocatalytic ability was illustrated by the DRS and FL. Moreover, the measurement of the water contact angle of SD and the corresponding original α-S (SA) showed the hydrophilicity of α-S had been improved. The photocatalytic ability of SD and SA was evaluated by photocatalytic decomposition of Methylene blue (MB) solution. The MB elimination rate with SD in the photocatalytic process was 2.46 times as great as that with SA under visible light. The enhanced photocatalytic ability could be attributed to the improved hydrophilicty of α-S.

We have designed and manufactured In2S3 nanotubes containing sulfur vacancies as effective and stable photocatalysts for nitrogen fixation and ammonia production. In the preparation process of In2S3, a self-templated strategy was used to obtain the nanotubes. The sulfur vacancies were then manufactured by calcination under a nitrogen atmosphere. The existence of sulfur vacancies enhances the light absorption and promotes the separation and migration of the photoinduced charge carriers. In addition, sulfur vacancies can serve as the active sites to achieve strong N2 adsorption and activation. Thus the obtained samples show enhanced photocatalytic performance with a high NH3 generation rate (52.49 μmol h−1 g−1) and excellent stability under UV-vis light.

The conversion of atmospheric nitrogen (N2) to ammonia (NH3) under mild conditions is quite challenging due to high stability of the triple covalent bond. Here we report that Bi-decorated BiOBr microspheres with plentiful oxygen vacancies (OVs) were successfully fabricated by one-step solvothermal strategy and used as effective photocatalysts for nitrogen fixation. The metallic Bi was reduced in-situ by glycerol and deposited on the surface of BiOBr microspheres. The synchronously generated OVs can serve as the activation center for nitrogen. Compared to pure BiOBr, Bi@BiOBr hetero-structured microspheres have higher specific surface area, superior visible-light utilization, more effective separation of photoexcited charge carriers, thus exhibiting more pronounced visible light photocatalytic N2 fixation performance. Specifically, the N2 reduction rate of the Bi@BiOBr-2 is 1350 μmol g−1 h−1, which is 11.8 times higher than pure BiOBr (114 μmol g−1 h−1). This study provides a simple and low energy consumption method for effective and stable photocatalytic N2 fixation.

g-C3N4 modified with Li doping and Ag deposition has been successfully prepared via a facile and cost-effective method. The composite presents the excellent photocatalytic performance for the degradation of Rhodamine B. The introduction of Li and Ag could effectively increase the absorbance in the visible light region, inhibit the recombination of photogenerated electron–hole pairs and improve the generation of reactive oxidation species. The synergetic effect between the Li doping and Ag deposition gives birth to the enhancement of photocatalytic activity of g-C3N4.

Herein, we demonstrated for the first time the fabrication of a novel nanosheet-assembled Bi2MoO6 micronbox via a simple one-step method. In particular, this new Bi2MoO6 framework structure with ultra-large surface area can endow the sample with strong light harvesting ability and abundant surface active sites and it exhibits remarkably enhanced photocatalytic activity toward organic dye degradation and nitrogen fixation under solar-light irradiation, far exceeding that of conventional Bi2MoO6 with a different structure.

Heterojunction or homojunction construction has been demonstrated to be an effective method to boost photocarrier separation and transfer, leading to a greatly enhanced photocatalytic activity. However, the photocatalytic performance of conventional heterojunction or homojunction photocatalysts usually faces some challenges, such as low surface area, insufficient active sites, and poor interface contact area. In this research, for the first time, a novel graphitic carbon nitride/graphitic carbon nitride (g-C3N4/g-C3N4) metal-free homojunction was successfully synthesized by calcining the supramolecular precursor self-assembly formed between hydrothermal melamine and dicyandiamide. The novel g-C3N4/g-C3N4 metal-free homojunction features a nanomesh morphology with a high specific surface area, which is not detected in the other g-C3N4/g-C3N4 composites. In addition, the in situ formation of the homojunction creates abundant interface contact, which improves the charge transfer ability. As expect, the as-prepared sample exhibited significantly enhanced visible light activity for rhodamine B degradation compared to the use of g-C3N4 alone and was 4.3 times as active as conventional g-C3N4/g-C3N4 composites. The results presented in this paper demonstrate that the novel supramolecular pre-organization route is valuable for the creation of a g-C3N4 isotype homojunction with a large specific surface area and abundant interface contact. The feasibility of developing different supramolecular precursors for efficient C3N4 photocatalysis using simple hydrothermal melamine and other nitrogen-rich precursors is proposed.

Efficient coupling between solar energy and active oxygen-related radicals plays a very important role in promoting photocatalytic oxidation processes; however, the poor solar energy harvesting, serious carrier recombination and especially sluggish interfacial reaction kinetics always make this process very inefficient. Here we report for the first time that the synergy mechanism between surface oxygen defects and graphene nanodots over the TiO2 photocatalyst boosts the solar-to-chemical energy conversion and hence enables the ultra-efficient photocatalytic decomposition of volatile organic compounds (VOCs). As a proof of concept, the surface oxygen defect incorporation not only can effectively suppress surface charge recombination, but also can promote the chemisorption of oxygen and hence enables robust H2O2 evolution over the TiO2 photocatalyst through visible–near-infrared illumination. The graphene nanodots (GDs), which were originally synthesized via an electrochemical tailoring method and possess excellent peroxidase activity can substitute Fe3+ to trigger robust solid–gas interfacial Fenton-like reaction (the rigorous reaction environment of the classic Fenton reaction greatly limits its implementation under ordinary air conditions). In addition, the excellent photophysical properties of GDs also can act as a sensitizer to further optimize the light harvesting performance of the resultant hybrid from the UV to NIR region. As a surprising achievement, the robust interfacial Fenton-like reaction, broader optical window and efficient charge separation endow the hybrid catalyst with ultra-efficient energy coupling between photons, excitons and oxygen-related radicals, and hence enable excellent photocatalytic oxidation activity for the decomposition of various VOCs.

In this work, Er-doped BiOBr hollow microspheres wrapped with graphene nanosheets, which acted as a photocatalyst with excellent photocatalytic activity and stability, have been successfully synthesized through a simple two-step hydrothermal method. The related properties of the as-prepared photocatalyst were analyzed and a possible reaction mechanism was proposed. Incorporating the rare-earth element Er into the BiOBr crystal lattice can greatly expand the optical window, maybe owing to the reduced energy band gap by the impurity energy level introduced below the conduction band and indirect utilization of long-wavelength visible light caused by the up-conversion performance. The wrapping with surface graphene nanosheets can efficiently promote charge separation and transmission over the hybrid photocatalyst. The synergistic effect between efficient solar energy harvesting and charge separation gives rise to a remarkable improvement of photocatalytic activity for RhB degradation under simulated sunlight irradiation. In addition, the as-prepared photocatalyst possesses excellent photocatalytic stability, mainly due to the robust coordination interaction between the graphene and the (001) facets of the BiOBr subunits. The rational design of this highly active and stable photocatalyst provides a promising approach for future applications.

The presence of surface oxygen vacancies over oxide semiconductors plays a versatile role in the development of light-driven organic degradation and energy production. Simultaneously, the role of defect sites successfully forms an ideal model for the photocatalytic responsiveness over BiVO4-OV in the NIR region.

The Ag@AgCl modified K 2 Ta 2 O 6 composites are prepared via a simple route of precipitation-photoreduction method. The results of XRD, SEM and TEM indicate that K 2 Ta 2 O 6 is well combined with Ag@AgCl. By degradation of Rhodamine B under natural light, the composites exhibit a significant enhancement in photocatalysis. Furthermore the heterojunction and the remarkable visible light absorption from Ag@AgCl are considered as the main reasons of the enhancement.

The cotton cellulose nanofibers(CCNFs)/ZnO/CuS nanocomposites have been successfully fabricated by the electrospun-hydrothermal method and successive ionic layer adsorption. The results of XRD, SEM and TEM indicate that the CuS are successfully combined with the ZnO. The photocatalytic activity of the CCNFs/ZnO/CuS nanocomposites is investigated by the degradation of methylene blue under visible light irradiation, and it is demonstrated to be significantly enhanced after the CuS is introduced. Furthermore, the direct interfacial charge transfer of the ZnO/CuS is considered as the main reason for the enhancement.

Constructing highly efficient metal-free material towards peroxymonosulfate (PMS) activation under photocatalytic assistance is a promising strategy for water decontamination. Herein, N vacancy modified g-C3N4 nanotube (VCN) was prepared to build a novel photo-assisted PMS activation system (PPAS), in which the unique electronic structure created by N vacancy could favor the PMS activation on VCN under visible-light irradiation. The role of N vacancy in PPAS was firstly studied through tuning its content in VCN. The results showed that the N vacancy greatly improved PMS activation on VCN PPAS towards organic pollutants removal. The VCN PPAS with moderate N vacancy modification performed best, whose kinetic constant for Rhodamine B degradation was 9.6 and 2.6 times higher than that of VCN/PMS system and pristine g-C3N4 PPAS, respectively. Moreover, the VCN PPAS performed well in wide pH range (3-12) and real water background. Selective removal of different organic pollutants was found on VCN PPAS, owing to the different interaction between pollutant and the catalyst surface with surface-bound radicals. The O2- and OH were major oxidants for pollutant removal in VCN PPAS, which were produced on dual active sites of VCN via two pathways: The N vacancy enhanced PMS adsorption and trapped photogenerated electrons for PMS reduction into OH, while the electron-deficient C atoms created by N loss promoted the PMS oxidation into O2-.

BiOI nanosheets have been successfully deposited on the porous Bi2O3 nanorobs via a one-pot precipitation method. The physicochemical features of the as-prepared materials were characterized in detail by a series of techniques, and the results revealed that BiOI nanosheets were evenly distributed on the porous Bi2O3 nanorobs. Because of higher photogenerated electron-hole pairs separation efficiency and the larger specific surface area compared to the pristine Bi2O3 and BiOI, the 50%Bi2O3/BiOI composite exhibited significantly enhanced photocatalytic activity for Cr(VI) reduction under visible light irradiation, and the reduction rate constant was 0.02002 min-1, which was about 27.4 and 2.6 times higher than that of pure Bi2O3 (0.00073 min-1) and BiOI (0.00769 min-1), respectively. Moreover, the 50%Bi2O3/BiOI composite also possessed the excellent photochemical stability and recyclability, thereby facilitating its wastewater treatment application.

Photocatalysis is outstanding for contaminants removal. However, the rapid recombination of photoinduced electron-holes generally restricts its photocatalytic performance. Herein, a novel oxygen vacancies (OVs) modified TiO2 (TiO2−x)/Ti3C2 (A-TOTC) photocatalyst was synthesized, in which TiO2−x nanoparticles were in situ grown on Ti3C2 (MXenes) to construct schottky junction for improving the separation efficiency of photogenerated charge carriers. Different annealing duration was applied to control the content of OVs in TiO2 for investigating its role on the photocatalytic performance of A-TOTC. The introduction of OVs dramatically improve the photocatalytic ability of A-TOTC, and the kinetic constant of bisphenol A (BPA) degradation of A-TOTC with optimal oxygen vacancy content was nearly 5.1 and 4.0 times higher than that of TiO2/Ti3C2 and TiO2−x, respectively. The hydroxyl radicals ( OH) and superoxide radical ( O2−) were the main active substances. The enhanced photocatalytic activity of A-TOTC arises from the decreased of schottky barrier caused by OVs.

The purpose of this paper is to develop hierarchically N-doped (BiO)2CO3/Bi2S3 heterostructures with highly exposed {001} facets. l-cysteine was used as both the capping agent and soft template to assemble hierarchically (BiO)2CO3 architectures with highly exposed {001} facets through a facile hydrothermal process. Rose-like (BiO)2CO3 architectures could be easily obtained by tuning the l-cysteine concentration. Introducing l-cysteine can inhibit the growth in [001] orientation and subsequently cause the preferential growth in [110] or [11̅0] orientation, which can significantly enhance the percentage of exposed {001} facets in (BiO)2CO3. Results showed that the introduction of l-cysteine successfully realizes N doping and construction of (BiO)2CO3/Bi2S3 heterostructures, which narrows band gap, significantly enhances the optical absorption and reduces the recombination of photogenerated electrons and holes. The as-obtained hierarchically N-doped (BiO)2CO3/Bi2S3 photocatalysts show superior photocatalytic activity and excellent stability for degradation of reactive brilliant blue (KN-R) under sunlight irradiation. Keywords: N-doping, Bi2S3/(BiO)2CO3 heterostructure, {001} facets exposure, Hierarchically architecture

Herein, using a simple one-step method, a Bi2MoO6-based photocatalyst with novel ultrathin nanohollow structure and simultaneous sub-10 nm Bi nanoparticles and sub-1 nm graphitic nitrogen-doped carbon nanodot (NCD) modification were successfully obtained. The coordination impact of the novel structure, SPR effect of Bi nanoparticles, up-conversion performance of graphitic NCDs and cooperative electronic capture properties of Bi metal and NCDs make the hybrid simultaneously exhibit fast charge separation and broad spectrum photocatalytic activity under UV, visible and near-infrared irradiation, leading to excellent photooxidation and photoreduction performance.

Herein, a Bi2MoO6 mesoporous hollow framework composed of atomically-thin nanosheets was fabricated for the first time using a one-step solvothermal route. The novel mesoporous hollow structure and ultrathin subunits simultaneously endow the as-prepared catalyst with robust light harvesting ability, excellent charge separation efficiency and abundant surface active sites, leading to improved photocatalytic performance for water oxidation.

Bi2MoO6 is an outstanding semiconductor photocatalyst and has been extensively studied; the construction of ordered mesoporous Bi2MoO6, however, remains a great challenge. Herein, for the first time, ordered mesoporous Bi2MoO6 crystals were synthesized employing a novel vacuum-assisted nanocasting method. More interestingly, this nanocasting method creatively utilized the amorphous complex as a precursor instead of metal salt ions, by which a new kind of single phase Bi2MoO6 (M-Bi2MoO6) could be successfully prepared. The as-prepared M-Bi2MoO6 exhibited much enhanced photocatalytic activity, which is about 5 times higher than that of conventional Bi2MoO6 for the photodegradation of RhB, BPA, CBZ or the photocatalytic reduction of Cr(VI). More importantly, in this paper, through some quantitative results, the mechanism of the photocatalytic activity enhancement of ordered mesoporous Bi2MoO6 was thoroughly investigated. Compared to conventional Bi2MoO6, the nanometer-sized, ordered mesoporous structure can make the as-prepared M-Bi2MoO6 possess excellent light harvesting ability, higher charge separation efficiency and larger catalysis activity areas, which are beneficial for photocatalytic oxidation and reduction. In summary, this work not only constructed a new kind of ordered mesoporous nanomaterial and provided a new vacuum-assisted nanocasting method, but also offered scientific insights into the photo-electron conversion property and carrier transport mechanism.

Over the past few years, the direct assembly of co-catalyst/modification materials into mesoporous photocatalysts has been considered a great challenge. Additionally, for photooxidation, the simultaneous achievement of fast charge separation, broad spectrum photocatalytic activity and higher carrier utilization efficiency (generating more active oxidizing groups) is quite necessary but has never been studied. To this end, for the first time, using sub-3 nm GQDs as co-catalyst, we have successfully achieved uniform modification for a mesoporous photocatalyst (mesoporous Bi2MoO6) using a novel electrostatic self-assembly method. The sub-3 nm GQDs, which were prepared from graphene nanosheets by a modified chemical oxide method, exhibit many unique physical and chemical properties, such as small size, electronic capture, up-conversion, and in particular, peroxidase-like activity. After the GQDs were modified, the resulting mesoporous hybrid photocatalyst (GQDs–BM) exhibited excellent charge separation efficiency and broad spectrum photocatalytic activity from UV to NIR light. More importantly, we found that a certain amount of H2O2 was produced through a photoreduction effect during the photocatalytic process. Unfavorably, for bare Bi2MoO6, the continuously-accumulating H2O2 could not efficiently convert into ·OH by a one-photoelectron reduction, which results in the indirect waste of photo-excited electrons. However, the chemical co-catalysis of GQDs could make this process (H2O2 → ·OH) more quick and efficient and moreover, did not need any additional photoelectrons, which means the effective enhancement of the utilization efficiency of photo-excited electrons (generating more ·OH). Additionally, for the as-prepared GQDs–BM, a sharp increase in photo-degradation activity for different target pollutants, such as BPA, MB, TC, CIP and phenol further confirmed that the simultaneous physical and chemical co-catalysis of GQDs can efficiently enhance the photocatalytic activity of mesoporous Bi2MoO6.

Hierarchical TiO 2 hollow spheres partially wrapped with reduced graphene oxide were synthesized through a facile three-step wet chemistry process. This method involves preparation of amine-modified TiO 2 hollow spheres, assembly of amine-modified TiO 2 hollow spheres and graphene oxide via peptide bond (–CONH–) formation, and final hydrothermal reduction of graphene oxide. The prepared hybrid composites could be used as photocatalysts to reduce 4-nitroaniline with excellent photocatalytic performance. This property is attributed to the efficient nanostructures of the composites, which result in obvious improvements in interfacial charge separation and transfer efficiency, reactant adsorptivity, and light harvesting. This study provides guidance for future designs of new graphene-based composites with enhanced photocatalytic reduction performance.

The ZnO/CdS nanocomposites have been successfully synthesized on the electrospun cotton cellulose nanofibers (CCNFs). ZnO nanorods (70–80 nm in diameter and 1 μm in length) are uniformly grown on the CCNFs by a simple hydrothermal method firstly and then different amount of CdS nanoparticles (20–30 nm in diameter) are loaded on the ZnO nanorods by the chemical bath deposition method. The visible light photocatalytic activity of ZnO/CdS nanocomposites is investigated by degradation of Rhodamine B under visible light irradiation, and it demonstrates that the photocatalytic performance of this composites is significantly enhanced compared with that of pure ZnO. Furthermore, the relatively narrow band gap and novel nanostructure of the composites are considered as the main reasons of this enhancement.

Herein, a simple one-pot solvothermal strategy was put forward to obtain metal Bi-decorated BiOBr composites (Bi/BiOBr) with abundant oxygen vacancies. The metal Bi (Bi0) can be deposited into the BiOBr surface via reduction of glycerol solvent in solvothermal process. Precipitation of Bi on surface of BiOBr turned the morphologies of BiOBr from regular flower-like hierarchical architectures to scattered sheets with increase of Bi content, enhanced photoabsorption of BiOBr in whole light region. Interestingly, deposition of metallic Bi (Bi0) on the BiOBr surface could lead to formation of abundant surface oxygen vacancies. As-synthesized Bi/BiOBr composites showed better photocatalytic activity for phenol degradation under sunlight irradiation, as compared with that of BiOBr reference. The enhancement of photocatalytic activities for Bi/BiOBr composites can be attributed to the existence of Bi/BiOBr hetero-structure and abundant oxygen vacancies (as active electron trap), which causing efficient separation of electron–hole pairs in Bi/BiOBr composites.

Visible-light-active α-sulfur spheres with hierarchical nanostructures were fabricated by simple solution-phase synthesis with PVP as the template for enhanced photocatalytic ability. The α-sulfur hierarchical spheres with an ultrahigh specific surface area can controllable synthesized by changing the addition quantity of PVP. The obtained products are systematically studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis absorption spectroscopy (DRS), Fluorescence (FL) and Brunauer-Emmett-Teller (BET). The photocatalytic activity of the as-prepared samples is evaluated by photocatalytic degradation of Rhodamine B (RhB) aqueous solution under visible light illumination. The results indicate that the morphology, specific surface area, photo absorbance ability, the separation efficiency of photogenerated carriers and the reactant adsorption performance can be controlled by varying the addition quantity of PVP. When 200 mg PVP is added, α-sulfur hierarchical spheres with uniform particle size about 1 μm and ultrahigh specific surface area of 67.1 m2/g is obtained, and its photocatalytic activity reaches a maximum value, which can be attributed to the combined effects of photo absorbance ability, the separation efficiency of photogenerated carriers and the reactant adsorption performance.

In this study, the sulfurized (BiO)2CO3 heterostructures were synthesized using a facile liquid-phase sulfurization strategy and characterized by XRD, SEM, FT-IR, XPS, UV–Vis DRS and PL techniques. It is found that sulfurization shifts slightly XRD diffraction peaks toward to lower Bragg angle, enhances significantly the optical absorption and reduces the recombination of photogenerated electrons and holes. Based on the experimental results, it is considered that novel Bi2S3/(BiO)2CO3 heterostructures with S doping (oxygen atoms substituted by sulfur) were successfully constructed. The as-obtained photocatalysts showed excellent photocatalytic activity for degradation of reactive brilliant blue (KN-R), as compared with that of pure (BiO)2CO3 under sunlight irradiation. The enhanced photocatalytic performance may be ascribed to the role of Bi2S3/(BiO)2CO3 heterostructure and S doping, which causes high absorption efficiency of light and efficient separation of photoinduced carriers in sulfurized (BiO)2CO3.

In this paper, the Ni-decorated ZnO photocatalysts with magnetic separable characteristics were prepared by a simple replacing-hydrothermal process for the first time. The as-synthesized composites were characterized by powder x-ray diffraction, UV–visible diffuse reflectance spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscopy, and so on. It is found that the introduction of Ni (as Ni0 and Ni2+ forms) turned the morphologies of ZnO photocatalysts, enhanced photoabsorption in a visible light region, and increased amount of surface adsorbed oxygen. The photodegradation test of anthraquinone dye (reactive brilliant blue KN-R) indicated that the Ni-decorated ZnO photocatalysts have better activities as compared to the ZnO reference. The enhancement of photocatalytic activity of Ni-decorated ZnO photocatalysts can be attributed to the existence of Ni2+ doping, Ni0/ZnO heterostructure, and abundant-adsorbed oxygen (as the electronic scavenges), which caused efficient separation of electron–hole pairs in Ni-decorated ZnO photocatalysts. Furthermore, the introduction of metallic Ni also endued ZnO with good magnetic recoverability. The re-collected experiments by external magnetic field indicated that Ni-decorated ZnO as a magnetically recoverable photocatalyst is acceptable.

The core–shell heterojunctions of ultra-thin C3N4 nanosheet enwrapping spherical α-S composites (α-S@C3N4) were fabricated via a self-assembly process by electrostatic force to realize enhanced photocatalytic ability under visible light. The photocatalytic ability can be adjusted by tuning the amount of the ultra-thin C3N4 nanosheet. The α-S@C3N4 composite with 35% composition of C3N4 nanosheet has the highest photocatalytic ability. The degradation rate of Rhodamine B (RhB) with α-S@C3N4 (35% C3N4) is 6.72 times faster compared to α-S as photocatalyst. This increase could be attributed to the efficient photogenerated holes and electrons separation by the heterojunction, which has excellent charge transfer ability arising from the ultra-thin C3N4 nanosheet. The stability of the α-S is also largely improved by the heterojunction construction.

Magnetic Fe3O4@SiO2/Bi2SiO5composites with a novel hierarchical nanostructure were synthesized by sol-gel and hydrothermal methods and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). It was found that the introduction of Fe3O4@SiO2could turn the morphology of Bi2SiO5from close-grained slab to hollow hierarchical architecture with fabric-structure. The Fe3O4@SiO2/Bi2SiO5composite showed enhanced photodegradation efficiency for the degradation of reactive brilliant red dye (X-3B) in aqueous solution under simulated sunlight irradiation, as compared with that of commercial P25. In addition, the Fe3O4@SiO2/Bi2SiO5composite exhibited good magnetic recoverability and excellent photocatalytic stability (no obvious activity loss after recycling tests).

Multilayered TiO2@SnO2 hollow nanostructures have been successfully synthesized via a simple approach employing the template-assisted and hydrothermal methods. The results showed that the molar ratio of Ti(SO4)2 to SnSO4 played important roles in the composition and morphology of the nanostructures. The as-prepared TiO2@SnO2 hollow nanostructures exhibited excellent photocatalytic activity when used as photocatalysts for the degradation of organic dyes. The mesoporous structure could facilitate the diffusion of dye molecules. In addition, the multilayered hollow nanostructure allows multiple reflections of incident light, making efficient utilization of light energy. Moreover, the coupling TiO2 with SnO2 could also effectively improve the charge separation efficiency.

The synthesis of a novel In2O3/In2S3 microsphere heterostructures is conducted through a well-designed two-step hydrothermal method. These composites are first applied for efficient fixation of N2 to NH3 under mild conditions without any organic scavengers and precious-metal cocatalysts. Here the In2S3 flakes are in situ generated and uniformly assembled on In2O3 microsphere. The phase structures, morphologies and oxygen vacancies of the samples are systematically characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse-reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL), Raman, electron spin resonance (ESR) spectroscopy and photoelectrochemistry. Meanwhile, the investigation of photocatalytic performance can confirm that the nitrogen fixation rate of In2O3/In2S3 (III) heterostructure is 40.04 μmol g−1 h−1, which is about 4.7 and 6.0 times higher than that of pure In2O3 and In2S3, respectively.

A bilayer TiO2 photonic crystal (PC)/porous BiVO4 was constructed by using liquid-phase deposition (LPD) and spin coating method for the enhancement of visible-light-driven photocatalytic ability by the improvement of light absorbance. Crystal form, morphology, film thickness, and light absorption performance were investigated. The photocatalytic activity of the bilayer TiO2 PC/porous BiVO4 film was evaluated by the degradation of MB and was compared with that of porous BiVO4 film. The effect of the film thickness of the porous BiVO4 on its photocatalytic ability was determined. It was found that the film thickness significantly affected the light absorption, and therefore its photocatalytic ability. The bilayer film with 1.03 μm of thickness of porous BiVO4 film exhibited the highest photocatalytic performance. The photocatalytic ability of porous BiVO4 was enhanced by combination with a TiO2 PC layer as the back reflector. This increase could be attributed to the intensified light absorbance produced by reflection from the TiO2 PC layer. The effects of porous structure and the application of photoelectrocatalytic process on the photocatalytic performance were also discussed.

Herein, Ni doped ZnO-TiO2composites were prepared by facile sol-gel approach and were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The results indicated that the Ni ions can be incorporated into the lattice of TiO2structure and replace Ti. The introduction of Ni expanded light absorption of TiO2to visible region, increased amount of surface hydroxyl groups and physically adsorbed oxygen (as the electronic scavenges), and then enhanced separation rate of photogenerated carriers. The photodegradation test of reactive brilliant blue (KN-R) under simulated solar light indicated that Ni doped ZnO-TiO2composites have better photocatalytic activities, as compared to those of TiO2and ZnO-TiO2.

Ordered mesoporous Bi2WO6was fabricated by nanocasting technique using SBA-15 as the template. The effect of the dosage of SBA-15 on the formation of the ordered structure and the photocatalytic ability of mesoporous Bi2WO6was discussed. It was confirmed that the ordered mesoporous structure was obtained as the dosage of SBA-15 was 0.3 g. It was found that, compared to Bi2WO6, the RhB degradation rate with ordered mesoporous Bi2WO6was enhanced under visible light (λ>400 nm) by the photocatalytic measurements. The enhanced photocatalytic performance of ordered mesoporous Bi2WO6was attributed to its particular ordered mesoporous structure which could increase the light-harvesting efficiency, reduce the recombination of the photogenerated charge carriers, and promote the surface reaction.