Improvement Of Photocatalytic Activity Research Articles

Insight into the growth mechanism of AgIn5S8 nanoparticles in a low temperature co-precipitation process and their visible-light-driven photocatalytic activities

AgIn5S8 (AIS) nanoparticles with excellent photocatalytic performance were synthesized by a convenient low temperature co-precipitation process. The growth mechanism of AIS in the reaction system was studied in terms of reaction time, which had obvious effect on the composition, morphology, and photoelectrochemical properties of the resulting samples. During the co-precipitation process, the initially formed Ag2S precipitate gradually transformed to AIS, which was obtained after reacting for 2 h. Although AIS with better crystallization can be obtained by further extending the reaction time to 12 h, the sample S-2 obtained at 2 h showed the best photocatalytic degradation performance towards several organic pollutants, including methyl orange (MO), malachite green (MG), o-nitrophenol (2-NP), p-nitrophenol (4-NP), p-fluorophenol (PFP) and bisphenol A (BPA). In addition, the photocatalytic reduction efficiency of S-2 towards 40 mg/L Cr(VI) reached 98.5% in 80 min. The possible presence of defects in S-2 caused by the phase transition process contribute to the enhancement of photocatalytic performance. Several characterization methods, including UV–vis DRS, photoluminescence (PL), and photoelectrochemical analysis demonstrated that S-2 had the fastest separation efficiency of photoinduced charge carries and the narrowest bandgap among all the synthesized samples, resulting the improvement of photocatalytic activity. A possible visible-right-driven photocatalytic mechanism was proposed in combination with the bandgap (Eg), conduction band (CB) and valence band (VB) position of AgIn5S8. The radical trapping experiments and electron spin resonance (ESR) results revealed that •O2−, h+ and •OH were involved in the photocatalytic process.

Improving natural sunlight photocatalytic efficiency of ZnO nanowires decorated by iron oxide cocatalyst via a simple drop method

In this study, iron oxide cocatalysts were deposited on the surface of ZnO nanostructures by a simple “drop, evaporation, calcination” method. Different deposition concentrations were studied, allowing to extend the photocatalyst absorption spectral range from UV to visible light, improving the photocatalytic efficiency under natural sunlight. An optimal deposition concentration of 0.06% molar percentage of iron against zinc led to improve by 11% the Methyl Orange (MO) photocatalytic degradation after 5 h under natural sunlight. No iron leaching was detected by ICP-MS analysis after the water purification by photocatalysis. By studying the lifetime stability of the optimal sample under a powerful UV light source, no losses of photocatalytic efficiency were recorded after several degradation cycles. Nevertheless, under this powerful light source, photocorrosion damages were observed with two antagonistic effects: (1) no photocorrosion effect for the ZnO regions covered by iron oxide and (2) ZnO photocorrosion and an acceleration of the dissolution of the ZnO nanostructures in uncovered regions. Thus, we assume the electron/hole delocalisation, which is responsible of the photocatalytic activity improvement, is also the reason justifying the ZnO photocorrosion acceleration of uncovered part. The photocorrosion phenomena was observed only under the powerful UV light source, not under natural sunlight.

TiO2/Au/TiO2 plasmonic photocatalyst with enhanced photocatalytic activity and stability under visible-light irradiation

Plasmonic photocatalysis, i.e., photocatalysis with activity under visible-light (vis) irradiation due to plasmonic feature of noble metals (NMs), has been intensively studied as promising method for solar energy conversion. Although various plasmonic photocatalysts have already been investigated, the vis activity is usually low, and thus should be improved for commercial application. Moreover, considering charge carriers’ mechanism, the stability of NMs during long-term irradiation should be also considered. Accordingly, this study has focused on the improvement of photocatalytic activity and stability of gold-modified titania photocatalysts under vis irradiation. Among a few proposed synthesis procedures, modified photodeposition method has resulted in the formation of TiO2/Au/TiO2 composites with high level of photoactivity. Large gold nanoparticles (NPs), formed on large rutile titania particles, are partially covered with fine anatase titania NPs, and thus the interface between titania and gold has been enlarged. Moreover, partial coverage of gold by fine titania NPs hinders gold aggregation, resulting in improved stability of these samples. Action spectrum of 2-propanol oxidation and numerical 3D-FDTD simulations of field distribution have indicated that the enhanced utilization of incident photons is responsible for high activity of TiO2/Au/TiO2 photocatalysts.

Photocatalytic Degradation of Organic Pollutants Using Porous g‐C3N4 Nanosheets Decorated with Gold Nanoparticles

AbstractIn this work, a composite photocatalyst consisted of the porous graphitic carbon nitride (pg‐C3N4) nanosheets decorated with in‐situ grown gold (Au) nanoparticles were prepared. By characterizing and analyzing chemical compositions and structures, and optical and electrical properties of this Au/pg‐C3N4 composite, the excellent photocatalytic performance mainly comes from the following aspects: firstly, pg‐C3N4 synthesized from melamine by high‐temperature calcination with the assistance of ascorbic acid has larger specific surface area and narrower band gap width than common g‐C3N4; secondly, localized surface plasmon resonance (LSPR) effect of Au nanoparticles can enhance light absorption of pg‐C3N4 via near‐field enhancement‐induced excitation; thirdly, the heterojunction formed between Au nanoparticles and pg‐C3N4 nanosheets can promote electron transfer. Consequently, Au/pg‐C3N4 presented the obvious improvement of photocatalytic activity on the degradation of rhodamine B and amaranth under simulated solar irradiation that the kinetic rate constant of degradation reaction can be increased by 3.9 and 5.7 times compared with g‐C3N4, respectively.

Incorporation of Chromophores into Metal–Organic Frameworks for Boosting CO2 Conversion

The exploitation of highly stable and active catalysts for the conversion of CO2 into valuable fuels is desirable but is a great challenge. Herein, we report that the incorporation of chromophores into metal-organic frameworks (MOFs) could afford robust catalysts for efficient CO2 conversion. Specifically, a porous Nd(III) MOF (Nd-TTCA; TTCA3- = triphenylene-2,6,10-tricarboxylate) was constructed by incorporating one-dimensional Nd(CO2)n chains and TTCA3- ligands, which exhibits a very high stability, retaining its framework not only in the air at 300 °C for 2 h but also in boiling aqueous solutions at pH 1-12 for 7 days. More importantly, Nd-TTCA has achieved a 5-fold improvement in photocatalytic activity for reducing CO2 to HCOOH and a 10-fold improvement in catalytic activity for the cycloaddition of CO2 into cyclic carbonate in comparison to those of H3TTCA itself. This work gives a new strategy to design efficient artificial crystalline catalysts for CO2 conversion.

Vacancy-modified g-C3N4 nanosheets via one-step thermal polymerization of thiosemicarbazide precursor for visible-light-driven photocatalytic activity

The graphitic carbon nitride (g-C3N4) with nanosheets structure or carbon vacancies is considered as the promising photocatalysts duo to their fascinating properties. Herein the carbon vacancy modified g-C3N4 nanosheet (TCN-600) was synthesized via one-step thermal polymerization of thiosemicarbazide precursor without auxiliary agent and extra gas protection. The higher calcination temperature and self-generating gas atmosphere (N2H4, CS2 and H2S) during the precursor polymerization impel introduction of carbon vacancies and simultaneous formation of nanosheet structures. The as-prepared TCN-600 exhibits excellent photocatalytic activity for tetracycline (TC) degradation and hydrogen production. TCN-600 shows average hydrogen production rate of 1.86 mmol g−1 h−1, which is 11.6 times higher than that of bulk g-C3N4. Meanwhile, TCN-600 displays high TC degradation efficiency of 83.3% within 90 min. The photodegradation rate of tetracycline by TCN-600 is 5.6 times higher than that by bulk g-C3N4. The significant improvement in photocatalytic activity is mainly attributed to its huge specific surface areas (144.5 m2/g), extended visible-light absorption, negatively shifted conduction band position, longer charge carries lifetime and faster migration of the photo-induced electron-holes. This study provides a new strategy to synthesize g-C3N4 with carbon vacancies and simultaneous nanosheet structure.

Nanostructured TiO2 photocatalyst modified with Cu for improved imidacloprid degradation

We investigated the role of Cu(II) ions, their local atomic structure and chemical state in the Cu-modified immobilized nanostructured TiO2 photocatalysts used for imidacloprid degradation under UV/VIS-radiation. Catalyst samples were prepared via electrochemical anodization and modified with different Cu concentrations (0.2–1 M). The catalysts’ structure and morphology were characterized by X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy, UV–VIS-NIR spectroscopy, Photoluminescence spectroscopy and X-ray absorption spectroscopy: extended X-ray absorption fine structure and X-ray absorption near edge structure. The EXAFS results indicate formation of Ti–O–Cu connections, suggesting that the Cu(II) cations are attached to TiO2 surface which contributes to the photocatalytic activity improvement, i.e. Cu(II) ions are free electron traps that reduce high recombination rate of photo generated charge carriers. The results here demonstrate the role of Cu(II) cations on photocatalytic activity of the Cu@TiO2 photocatalyst.

Hierarchical Z-scheme Bi2S3/CdS heterojunction: Controllable morphology and excellent photocatalytic antibacterial

The hierarchical nanostructure can significantly increase photocatalytic centers and enhance light harvesting. In this study, a series of hierarchical Z-scheme Bi2S3/CdS heterojunctions with solvent-dependent morphologies are synthesized by a solvothermal method. The Bi2S3/CdS nanostructures synthesized in ethylene glycol (BC-EG) and N, N-dimethylformamide (BC-DMF) are assembled by Bi2S3 nanowires and CdS nanoparticles. Notably, the photocatalytic efficiency of BC-DMF for the antibacterial of E.coli and S.aureus is 100.00 % and 93.85%, respectively. The improvement of photocatalytic activity by BC-DMF is mainly ascribed to the increased photocatalytic active centers, enhanced photo-induced carriers separation and transfer between Bi2S3 and CdS as a Z-scheme heterojunction and the relatively suitable Bi2S3/CdS ratio. This study can provide an insight into constructing Z-scheme hierarchical photocatalysts for antibacterial.

Self-cleaning photocatalytic MXene composite membrane for synergistically enhanced water treatment: Oil/water separation and dyes removal

Membrane separation has been widely used for water treatment, but the accumulation of pollutants on membrane surface is still inevitable during practical applications. Photocatalytic technology is an effective and environmentally friendly method for the degradation of pollutants. Here, we reported a simple method to prepare novel two-dimensional (2D) Bi2O2CO3@MXene photocatalytic composite membranes as well as their multi-functional abilities for water treatment. The experimental results exhibited that the composite membrane has ultrahigh water flux after incorporation of N-doped Bi2O2CO3 nanoparticles (815.3 L·m−2·h−1). In addition, the rejection ratio for three different types of oil/water emulsions was all over 99 %, and excellent dyes removals were obtained by membrane separation, adsorption and photodegradation abilities, which were approximately 99.9 % (Congo red), 98 % (Trypan blue) and 98.4 % (Rhodamine B), respectively. Most importantly, the composite membrane maintained a stable permeability and selectivity after five consecutive cycles with visible light irradiation. Density functional theory (DFT) calculation and Finite Element Method (FEM) analysis were carried out to reveal the mechanisms for the improvement of photocatalytic activity and membrane permeability, respectively.

Fabrication of a novel Ag3PO4/WO3·H2O composite with enhanced visible light photocatalytic performance for the degradation of methylene blue and oxytetracycline

A novel Ag3PO4/WO3·H2O composite was prepared by loading Ag3PO4 on WO3·H2O substrate via a two-step hydrothermal method and characterized by various analytical techniques. The photocatalytic performance was evaluated by the degradation of methylene blue (MB) and oxytetracycline (OTC) under visible light irradiation. Within 30 min, 98.9 % MB can be degraded by the Ag3PO4/WO3·H2O composite with a molar ratio of 3:1 (3Ag/1W), which is higher than that of individual Ag3PO4 and WO3·H2O. The 3Ag/1W photocatalyst also exhibits improved photocatalytic activity for OTC degradation than pure WO3·H2O and Ag3PO4. The improvement of photocatalytic activity would be mainly ascribed to the highly efficient separation of photo-induced electron-hole pairs due to matched band structure, as confirmed by photoluminescence spectra (PL) and photocurrent responses test. According to the experimental results of radical trapping and electron spin resonance (ESR), a possible photocatalytic mechanism of the Ag3PO4/WO3·H2O composite was proposed.

Facile synthesis of a novel AgIO3/BiVO4 photocatalyst with two-step charge separation to enhance visible-light-driven photocatalytic performance for carbamazepine degradation

Rapid recombination of photo-generated electron-hole in photocatalyst limits the improvement in photocatalytic activity. A novel visible-light-driven AgIO3/BiVO4 photocatalyst with two-step charge separation enhancing photocatalytic activity was fabricated. The composite with optimum molar ratio of 40% AgIO3 to BiVO4 has a narrow band gap of 2.28 eV, which is smaller than that of BiVO4 (2.41 eV). The composite presented 99.38% degradation efficiency of rhodamine B in 40 min under visible light irradiation, which is higher than 1% and 9% degradation efficiencies by BiVO4 and AgIO3, respectively. In addition, a 97.86% degradation efficiency of carbamazepine was achieved in 60 min. Thus, the significant enhancement of photocatalytic activity depended on the two-step charge separation in AgIO3/BiVO4. The first step was the spatial pre-separation among different crystal facets in decahedral BiVO4. Photo-generated electrons accumulated on {010} facets. Moreover, photo-generated holes on {110} facets facilitated the production of •OH radicals. The second separation was achieved by the type Ⅱ heterojunction structure of AgIO3/BiVO4. Photo-generated electrons in conduction band were transferred from BiVO4 {010} facets to AgIO3, and holes in valence band accumulated on BiVO4 {110} facets. This work provides an effective method to further decrease electron-hole recombination in photocatalysts and promote their environmental application in contaminated water purification.

Synthesis of Ag3PO4/SnO2 composite photocatalyst for improvements in photocatalytic activity under visible light

Ag3PO4/SnO2 composites with various molar ratios of SnO2 were synthesized by a simple in situ precipitation method. All the obtained samples were structurally, optically, and morphologically characterized by various techniques, such as X-ray diffraction, Rietveld refinement, micro-Raman, Fourier transform infrared, UV–Vis diffuse reflectance, and photoluminescence spectroscopies. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were also utilized, wherein the Ag3PO4 microparticles were in contact with the SnO2 nanoparticles and microrods. The interaction between the two phases was confirmed based on the improvement in the photocatalytic performance for the degradation of an aqueous solution of Rhodamine B dye when exposed to visible light irradiation (>400 nm). The photocatalytic performance increased significantly in the composites with 5%–15% SnO2, followed by a slight decrease in the composite with 20% SnO2. The rate of reaction of the composite with 15% SnO2 was approximately 3.0 times higher than that of pure Ag3PO4. From the experimental results, a possible photocatalytic mechanism for the pure Ag3PO4 and the composite with 15% SnO2 was proposed, showing that the superoxide radicals contributed significantly to the improvement of the photocatalytic activity of the composite. In addition, the photocatalytic mechanism observed in the composites was associated with the formation of a possible p-n junction between Ag3PO4 and SnO2.

In-situ carbon-coated TiO2 boosting the visible-light photocatalytic hydrogen evolution

A straightforward hydrolysis–carbonization strategy for synthesizing carbon-coated TiO2 photocatalyst is developed. During the calcination process, boric acid functions as a template to maintain the size of TiO2 nanoparticles, expose more active surfaces, and further improve photocatalytic activity. And butyl alcohol generated from the hydrolysis of butyl titanate is carbonized and covered on the surface of TiO2 nanoparticles, forming in-situ carbon-coated TiO2 photocatalyst. Under the irradiation of Xenon lamp, the catalyst TiO2-500-W shows excellent photocatalytic hydrogen evolution ability (434.91 μmol h−1 g−1) and recycling stability. The band gap of carbon-coated TiO2-500-W is 2.82 eV so that it can even promote the hydrogen evolution under visible-light irradiation. Experiments and DFT calculations reveal that the presence of carbon sheet on TiO2 can reduce the band gap, generate valence band tail, and decrease the work-function, which facilitate the improvement of photocatalytic activity for H2 evolution.

Bimetallic Ag-Zn-BTC/GO composite as highly efficient photocatalyst in the photocatalytic degradation of reactive yellow 145 dye in water

Agx-Zn100−x-BTC/GO composites (BTC: benzene-1,3,5-tricarboxylic, GO: graphene oxide) with different Ag/Zn molar ratios were synthesized using microwave-assisted hydrothermal treatment. The Agx-Zn100−x-BTC/GO exhibited excellent photocatalytic performance in the reactive yellow 145 dye (RY-145) degradation under irradiation of visible light with nearly 100% of RY-145 removal after 35 min, as compared to Zn-BTC/GO and Ag-BTC/GO. Reactive oxygen species scavenging assays have shown that the holes (h+) and superoxide radical anion (O2−•) play a primary role in RY-145 degradation. Based on the band structure of materials, the Z-scheme photocatalytic mechanism was suggested. The effect of catalyst dosage, pH and dye concentration on the efficiency of photocatalytic activity of bimetallic Ag50-Zn50-BTC/GO was also investigated. The improvement in photocatalytic activity of bimetallic Ag50-Zn50-BTC/GO could be given by the synergism of (i) absorption of visible light confirmed by UV-Vis diffuse reflectance spectra; (ii) the increased lifetime as evidenced by photoluminescence spectra and transient photocurrent response; (iii) the increased oxygen vacancy defects as confirmed by X-ray photoelectron spectroscopy results. The degradation pathway of RY-145 dye was also predicted based on liquid chromatography-mass spectrometer analysis. The removed chemical oxygen demand, biological oxygen demand, total organic carbon outcomes indicated the high mineralization ability for RY-145 degradation over Ag50-Zn50-BTC/GO.

Effect of HCl treatment on physico-chemical properties and photocatalytic performance of Fe–TiO2 nanotubes for hexavalent chromium reduction and dye degradation under visible light

In this study, we prepared Fe2O3/TNT composite (Fe-TNT) foil by combining anodization with the hydrothermal method. Photocatalytic reaction was restricted by a cluster of iron particles accumulated on the foil surface and the photocatalytic reaction sites reduces. Herein, using XPS determined that these iron particles are composed of iron oxide. An acid treatment, hydrochloric acid (HCl) was used to successfully remove the surface accumulation of iron oxide particles on the photocatalyst. Using cleaned Fe-TNT foil, the photocatalytic activity of 5 mg/L Congo red (CR) and hexavalent chromium reduction was significantly increased under visible irradiation. In addition, the influence of different aspects such as pH, the concentration of Fe, and the effect of different acid treatment time was evaluated. Removing the surface accumulated iron oxide and adjusting the pH in acidic medium, 73% hexavalent chromium reduction achieved within 180 min. The reusability was also explored by monotonous CR degradation. The CR degradation using Fe0.25-TNT was lessened from 78% in the first cycle to 71% in the 3rd cycle. It was also confirmed experimentally that photocatalytic activity improvement of HCl treated Fe-TNT was not due to alternation in nanotube structure.

An Interface Optimization Strategy for g-C3N4-Based S-Scheme Heterojunction Photocatalysts.

Graphitic carbon nitride (CN) has attracted much attention in photocatalytic fields due to its unique electronic band structure. However, the rapid recombination of photogenerated carriers severely inhibits its catalytic activity. The heterojunction structure has been widely confirmed to significantly improve the photocatalytic activity of CN through the formed interface structure. However, researchers often give attention to the band matching and conductivity of the cocatalyst, while the importance of the interface as a migration channel for photogenerated carriers is often overlooked. In this work, we adopt the strategy of morphology engineering to regulate the morphology of the CN photoactive component so as to achieve the interface optimization of the traditional heterojunction structure. The photocatalytic degradation experiment of rhodamine B shows that compared with the traditional CeO2@CN heterojunction structure, the photocatalytic activity of the interface-optimized CeO2/CN is increased by more than 20%. The following points could be used to explain the improvement of photocatalytic activity: (I) the formed S-scheme heterojunction structure, which inhibits the recombination of useful electrons and holes but expedites the recombination of relatively useless electrons and holes, (II) the increased interface area, which provides more carrier migration channels, and (III) the reduced interface contact resistance, which facilitates the separation and migration of photogenerated carriers. Furthermore, the interface optimization of the traditional Al2O3@CN and Fe2O3@CN heterojunction structures also achieved consistent results. This shows that the strategy in this work is a universal method for interface optimization, which provides potential alternative for further improving the catalytic activity of other heterojunction composites.

Sustainable one-step synthesis of nanostructured potassium poly(heptazine imide) for highly boosted photocatalytic hydrogen evolution

Regulating bulk polymeric carbon nitride (PCN) into nanostructured PCN (NPCN) has long been proved effective to improve its photocatalytic activity, which is applicable to crystalline carbon nitride: potassium poly (heptazine imide) (K-PHI). Currently, simplifying the synthesis of nanostructured K-PHI (NK-PHI) is challenging and has drawn widespread attention. This work demonstrated the one-step concise and sustainable synthesis of NK-PHI by a steam-assisted method. The NK-PHI exhibited a highly boosted visible-light photocatalytic hydrogen evolution activity, which is 38.4, 4.4 and 3.4 times to that of PCN, NPCN and K-PHI. The improvement of photocatalytic activity mainly benefitted from increased active sites and highly facilitated photoinduced charges transfer and separation. Moreover, the sustainability of this approach was proved by recycling the structure-directing agents (KCl) and steam source (Mg(OH)2) to repeatedly synthesize high-quality NK-PHI.

Constructing CdSe QDs modified porous g-C3N4 heterostructures for visible light photocatalytic hydrogen production

Constructing heterostructures with narrow-band-gap semiconductors is a promising strategy to extend light absorption range of graphitic carbon nitride (g-C3N4) and simultaneously promote charge separation for its photocatalytic activity improvement. However, its highly localized electronic states of g-C3N4 hinder photo-carrier migration through bulk towards heterostructure interfaces, resulting in low charge carrier separation efficiency of solid bulk g-C3N4-based heterostructures. Herein, porous g-C3N4 (PCN) material with greatly shortened migration distance of photo-carriers from bulk to surface was used as an effective substrate to host CdSe quantum dots to construct type II heterostructure of CdSe/PCN for photocatalytic hydrogen production. The homogeneous modification of the CdSe quantum dots throughout the whole bulk of PCN together with proper band alignments between CdSe and PCN enables the effective separation of photo-generated charge carriers in the heterostructure. Consequently, the CdSe/PCN heterostructure photocatalyst gives the greatly enhanced photocatalytic hydrogen production activity of 192.3 μmol h−1, which is 4.4 and 8.1 times that of CdSe and PCN, respectively. This work provides a feasible strategy to construct carbon nitride-based heterostructure photocatalysts for boosting visible light driven water splitting performance.

Plasmon-driven engineering in bimetallic CuCo combined with reduced graphene oxide for photocatalytic overall water splitting

Light-induced water splitting by artificial photocatalysis is one of the cornerstones to produce sustainable energy. Plasmonic photocatalyst exhibits considerable photoactivities under a wide range of the solar spectrum and therefore designing sophisticated plasmonic photocatalyst is important to realize high efficient solar conversion. Here, we fabricate CuCo/reduced graphene oxide junctions tailored for photocatalytic water splitting without a sacrificial agent. The CuCo bimetal converts the energy of sunlight into surface plasmon resonance oscillations and transfer the plasmonic energy to electron-hole pair via Landau damping. Electron in the CuCo bimetal will spontaneously transfer to reduced graphene oxide, which greatly improve the separation efficiency of electron-hole pair as compared to the CuCo bimetal alone. Compared to the pure Cu, the CuCo bimetal unveils an expected enhancement of photocatalytic activity due to the synergistic interaction in the bimetallic material. Taken together, our studies offer experimental validation of water splitting of plasmonic photocatalyst and demonstrate an improvement of photocatalytic activity of pure Cu after alloying with Co and modification with reduced graphene oxide.

Synthesis and visible-light photocatalytic activity of brookite/BiOBr

Brookite TiO2 was synthesized and BiOBr was supported on the surface of brookite TiO2 by a hydrothermal method. X-ray diffraction and X-ray photoelectron spectroscopy analyses of the composites confirmed the formation of brookite TiO2/BiOBr. Transmission electron microscopy results confirmed the as-prepared composites were nano-sized. The optimum loading amount of BiOBr was 30%. The photocatalytic results show that the degradation efficiency of rhodamine B by titanite TiO2/BiOBr (30%) under visible-light irradiation for 2 h is close to 100%. •O2– and h+ are the main active species during the photocatalytic process. The improvement of photocatalytic activity might be because the formation of p–n hetero-junction enhanced the separation efficiency of photogenerated electron–hole pairs. The photocurrent density of the brookite/BiOBr (30%) was about 2 times higher than that of pure brookite.