Intrinsic Photocatalytic Activity Research Articles

Crystal facet/interface anchored Janus activity of BiOBr in driving photocatalytic water splitting

Constructing Janus junctions is expected to provide a novel perspective for analyzing the intrinsic photocatalytic activity of bismuth oxyhalide. Herein, Janus-typed BiOBr(010)/BiOBr(001) homojunction with efficiently photocatalytic H2 evolution has been achieved by a hydrothermal synthesis. The experimental results show that the designed Janus-typed junction can effectively elevate the carrier lifetime, significantly enhance the photocurrent, and prominently reduce the overpotential. The potential difference (0.34 eV) between (010) facet and (001) facet can drive the carrier transport at the interface for Janus junctions. Theoretical calculations indicate that the designed Janus junction has a stable mechanical structure, providing certain support for the long lifetime of the photocatalyst in the photocatalytic process. The carrier distributions in the Janus junction exhibit the typical characteristic distribution. Interestingly, the photo-generated electrons are only localized in BiOBr(001) component, which embodies significantly a role of n-type semiconductor. This essentially activates HER activity (32 µmol/h g−1) of Janus junction. The holes preferentially localize in the BiOBr(010) component of Janus junction. This component undertaking p-type role reduces the free energy of the rate determining step (from OH* to O*) in the oxygen evolution process (0.88 eV). The Janus junction intensively suppresses the carrier recombination probability at the high symmetry point (reciprocal space) in BiOBr. Ab initio molecular dynamics calculations show that the adsorbed water is easy to decompose on the surface of Janus junction. The obtained results of the photocatalytic water splitting further confirm that the designed BiOBr(010)/BiOBr(001) has Janus characteristics, which are consistent with theoretical calculations and tracer tracing results. The diffusion characteristics of hydrogen also evidence that the interaction of the internal electric field in the Janus junction can drive the HER performance. Additionally, these results offer us a unique angle of view to regulate the charge carrier dynamics by the highly oriented facet coupling for the layered semiconductor.

Meso‐ and Microporous Metal–Organic Frameworks for Efficient Photo‐Oxidation of Benzylamine

ABSTRACTThe construction of metal–organic frameworks (MOFs) with desirable structures for high‐performance photocatalysis is attractive but remains challenging. Here, a hierarchically meso‐ and microporous scCu‐MOF‐74 was synthesized in supercritical CO2 (scCO2)/methanol solution. Compared with the conventional microporous Cu‐MOF‐74, the meso‐ and microporous scCu‐MOF‐74 has more exposed and accessible Lewis acid sites derived from the missing‐linker defects. The unique structure endows scCu‐MOF‐74 with superior molecular accessibility, enhanced separation, and transfer efficiency of photogenerated charges. High catalytic activity and reusability can be achieved in photo‐oxidative coupling of amines, reaching a maximum N‐benzylbenzaldimine yield rate of 4.80 mmol g−1 h−1 under mild conditions, that is, air atmosphere and room temperature. This study provides a new idea for improving the intrinsic photocatalytic activities of MOFs.

Light-promoted conversion of aliphatic alcohols to carboxylic acids over Pt-loaded BiVO4 in aqueous solution under ambient conditions

Developing eco-friendly approaches to activate C–H bonds in aliphatic alcohols to obtain valuable aliphatic acids remains a challenge. Here, we report an efficient and sustainable method for the selective oxidation of aliphatic alcohols to aliphatic acids via a rationally designed Pt-loaded BiVO4 (BVO) catalyst with enriched surface oxygen vacancies (OVs), achieving 59.2 % of 1-octanol conversion and 80.6 % of 1-octanoic acid selectivity within 6 h in the dark at room temperature. The production rate of 1-octanoic acid under visible light illumination (580.7 µmol/g/h) is 1.85 times higher than that under dark conditions due to the synergistic photo-thermal effect with selectivity as high as 96.2 %. Further investigations indicate that the abundant surface OVs of BVO accelerated the cleavage of HO-H at the defects, facilitating the conversion of aliphatic alcohol at room temperature in the dark. The intrinsic photocatalytic activity of BVO, combined with the synergistic photothermal effect of surface defects and Pt nanoparticles, further promote the conversion of aliphatic alcohols into aliphatic acids, improving conversion and selectivity under visible light illumination. The broad substrate scope highlights the great promise of this approach for aliphatic acid production via photocatalysis under ambient conditions.

Remarkable improvement in photocatalytic activity of g-C3N4 for NO oxidation through surface hydroxylation

The nitrogen oxide emissions originating from combustion pose significant risks to the environment. Photocatalysis is considered an efficient and environmentally friendly strategy to alleviate this problem. Graphitic carbon nitride (g-C3N4) is regarded as one of the most promising organic photocatalytic materials for environmental purification. However, its small specific surface area, weak adsorption and high recombination rate of charge carriers result in low intrinsic photocatalytic activity. To overcome these obstacles, a hydrothermal treatment of dicyandiamide-derived g-C3N4 (DCN) at different temperatures (140–200 °C) was employed to enhance the photocatalytic activity for NO oxidation. The experimental results demonstrated a significant improvement in the photocatalytic oxidation removal rate of NO after a hydrothermal treatment. The optimal photocatalyst, DCN-180, treated at 180 °C, demonstrated the highest NO removal efficiency (65.0 %), which is twice the value of pristine DCN (32.5 %). Additionally, the formation of the toxic intermediate NO2 was effectively suppressed during the reaction. Photoelectrochemical tests revealed that DCN-180 exhibited higher photocurrent density and smaller impedance radius compared to the untreated g-C3N4 sample. Moreover, density functional theory (DFT) calculations confirmed that the DCN-180 sample showed a stronger ability to adsorb O2 and NO. The enhanced photocatalytic NO oxidation performance of DCN-180 has been primarily attributed to its enlarged specific surface area (from 10.7 to 35.5 m2 g−1), local polarization effect, reduced interfacial charge transfer resistance, and improved adsorption abilities for NO and O2 molecules. This study provides valuable insights for designing and preparing highly efficient g-C3N4 based photocatalysts through surface modification for photocatalytic NO purification.

Precise structure-tailoring of multicomponent nanocatalysts enabled by continuous flow-controlled flash nanoprecipitation technique

Nanostructured catalysts with diverse compositions offer an exciting prospect for various catalytic applications. The precise control of nanostructures allows to tune the physicochemical properties of nanocatalysts and improve their performance. However, most preparative methods rely on conventional batch systems, which require tedious procedures and cause low productivity. Herein, we reported a novel engineered flash nanoprecipitation (FNP) technique to synthesize well-structured nanocatalysts in a continuous-flow procedure with intelligent operation and high productivity, in which a series of multicomponent bismuth oxyhalides (BiOClxBr1-x) were demonstrated as the model catalysts. This method was established on the uninterrupted continuous synthesis of BiOClxBr1-x with precisely controlled microstructure by simply altering the flow rate ratio of precursor fluids in the reactor. The computational fluid dynamics (CFD) simulation showed that the automized flow setup could achieve the accurate control over the intensified fluid mixing. Significantly, a volcano relationship between the halogen compositions and catalytic activities toward photodegradation of tetracycline (TC) was observed, which indicated that the structural changes enabled band structure-dependent regulation. The FNP-processed BiOCl0.75Br0.25 possessed a balanced redox ability and light absorption, thus located at the peak of volcano with a five-fold enhancement of intrinsic photocatalytic activity. Overall, this work provides a promising prospect of continuous-flow technique in the engineered manufacturing of the advanced nanomaterials, offering fine-tuning of the nanostructures of materials with low cost and high productivity.

Phospholipid membrane-protected photoelectrochemical chip: A specific test-to-treat platform for bacteria secreting pore-forming toxins with phosphatidylcholine receptor

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a frequent cause of purulent skin and soft tissue infections. In this study, a test-to-treat chip was developed as an integrated platform for the highly sensitive detection and treatment of MRSA infections. By integrating arginine (Arg) ligand-doped FeMOFs onto TiO2 nanotube arrays (TNT), the resulting Arg-FeMOF-TNT chips exhibited excellent photoelectrochemical (PEC) activity under visible-light irradiation. As phosphatidylcholine (PC) specific pore-forming toxins (PC-PFTs) secreted by MRSA can specifically generate small holes in the phospholipid membrane (PM), the PM covered Arg-FeMOF-TNT photoactive surface can be re-exposed to the electrolyte in the presence of PC-PFTs and then reacted with electron donors in the electrolyte. On the basis of switch-on PEC signals, a detection limit as low as 6 CFU mL−1 was achieved for MRSA. Furthermore, benefitting from its intrinsic photocatalytic activity, the Fenton-like catalytic activity of FeMOFs, and the loaded Arg on the chip, abundant reactive oxygen species (ROSs) and nitric oxide (NO, arginine decomposition product) were generated in the bacterial microenvironment, resulting in the effective sterilization of MRSA. Importantly, the PM modification endow the chip to process good biosafety and remarkable antibacterial specificity towards MRSA. Animal experiment results further demonstrated that the chip can rapidly kill MRSA in wounds and promote wound healing under 532-nm-laser irradiation. This all-in-one chip offers a new method for the diagnosing bacteria and also provides new insight into the design of test-to-treat platforms for PC-PFTs bacteria.

Polyoxometalate-based hybrid materials with electronic interaction boosting photocatalytic H2 evolution coupled with alcohol oxidation

Efficient separation of the mixed H2 and O2 products is a crucial step in the photocatalytic overall water splitting process, often hindered by the slow kinetics of the O2-producing half-reaction. One effective approach is to employ organic substrates that can capture the holes, thereby enhancing the overall reaction rate and yielding valuable alcohol oxidation products in parallel. Enhance electronic structure advantages through electrostatic interactions and intermolecular hydrogen bonding, thereby facilitating accelerated electron transfer and boosting the intrinsic photocatalytic activity. This is the first study that demonstrates the successful implementation of Ru oxo cluster-based hybrid materials with electronic interaction and intermolecular hydrogen bonding, NaH[Ru(bpy)3][Ru8(CO3)4(CO)16Cl4]·EtOH·5H2O. The triethanolamine sacrificial reaction system has a remarkable 15-fold increase in H2 evolution, alongside concurrent H2 production coupled with 1-(4-chlorophenyl)ethanol oxidation reactions (with a selectivity of 99 %). This observed enhancement is three times higher (HER = 1.60 mmol⋅g−1⋅h−1) than a discrete catalyst NaH2(TPA)[Ru8(CO3)4(CO)16Cl4]·EtOH·5H2O (HER = 0.48 mmol⋅g−1⋅h−1). Activity contrast experiments were conducted to gain insights into the photocatalytic reaction pathways, enabling the proposal of potential mechanisms that further elucidate the process. This research presents a significant expansion in the realm of designing and developing novel multifunctional artificial photocatalysts based on polyoxometalate (POMs) with enhanced electronic interactions. These advancements open up exciting possibilities for diverse economic and ecological photoredox applications.

Effects of synthesis temperatures on the photocatalytic activities of bismuth oxides for phenol and water oxidation under visible light

Bismuth oxides with different crystal structures possess distinct photocatalytic properties. Herein, BiO2−x and Bi4O7 were prepared by a hydrothermal process done at varied synthesis temperatures (Ts), where BiO2−x was obtained at Ts = 25–180 °C and Bi4O7 was resulted at Ts = 200–220 °C. The samples (BiO-Ts) possessed increased crystallinity and decreased visible light absorption with the increment of Ts. They showed certain activities for phenol oxidation due to the oxygen species generated by tiny room light in the dark, which were much weaker than those under visible light irradiation, and all the reaction rates decreased with the increment of Ts. For water oxidation on a photoanode, BiO2−x and Bi4O7 showed an increased and decreased activity with Ts increasing, which agrees with the corresponding charge separation efficiencies. BiO2−x possesses an improved intrinsic photocatalytic activity with increased crystallinity, but its apparent activity is determined by the organics adsorbed thereon.

Quantitative evaluation of trace ritonavir in serum by versatile SERS substrate based on silver-decorated hollow reduced graphene oxide/zinc oxide nanotubes

Because of its fascinating molecular fingerprint identification ability and high sensitivity, surface-enhanced Raman scattering (SERS) shows an attractive application prospect in the clinical monitoring of blood drug concentration and efficacy judgment. In this study, a quantitative SERS-based detection of ritonavir in serum sample was conducted by developing silver (Ag)-decorated zinc oxide (ZnO)@reduced graphene oxide (rGO) nanotubes. Taking advantage of the efficient light absorption and molecular enrichment capabilities of hollow rGO-modified ZnO nanotubes with high specific surface area, an extremely low limit of detection (LOD) value of 466.7 pg/mL was achieved for ritonavir owing to the synchronous electromagnetic and chemical enhancement after the participation of Ag islands. Such a detection was carried out in a recyclable mode based on the intrinsic photocatalytic activity of ZnO, which was ascribed to the Ag and rGO-mediated effective separation of photo-induced electron-hole pairs. A practical SERS-based monitoring of ritonavir was finally facilitated in serum, demonstrating high recovery rates varied from 82.1% to 89.7%. Such a novel metal-semiconductor SERS sensor with ideal biocompatibility and sensitivity is promising in drug diagnostics.

Biochar-derived flower-like Co-Mo2C spheres/g-C3N4 photocatalyst: Engineering morphology configuration and electronic structure tuning

As a class of highly recalcitrant water contaminants, pharmaceuticals and personal care products (PPCPs) have raised considerable concerns. Here, we develop a biochar-derived flower-like Co-Mo2C sphere/g-C3N4 (CMCN) heterostructure photocatalyst for typical PPCPs degradation. The flower-like Co-Mo2C nanostructure is derived from biochar, an inexpensive and ubiquitous plant byproduct. The open-up nanoflake structure with sharp edges can induce the fast charge collection and separation. DFT calculations and experimental characterizations are conducted to fundamentally understand the enhanced intrinsic photocatalytic activity of the as-prepared CMCN photocatalysts, especially the role of Co atoms. The delocalized charge density of CMCN could be rational tailored via the increasing density of state and the difference in work functions between g-C3N4 and Co-Mo2C. The electron density of Mo 3d in CMCN is increased through integrating it with Co atoms, which possess numerous delocalized electrons. Compared with the Mo2C/g-C3N4 (MCN) bulk, the CMCN catalyst displays superior photocatalytic activity for the typical PPCPs degradation, mainly arising from the multifaceted open-up surfaces of Co-Mo2C nanoflower, the higher density of electron and more efficient charge transfer ability, as well as the prolonged life time of photogenerated charge carriers. This work provides a cheap and mild route for synthesizing Co-doped Mo2C nanoflower catalyst and expands the scope of constructing high active g-C3N4 based heterostructure.

Mechanistic Understanding of Alkali‐Metal‐Ion Effect on Defect State in SrTiO3 During the Defect Engineering for Boosting Solar Water Splitting

AbstractDecreasing the Ti3+ defect concentration in SrTiO3 is recognized as the focus of seeking a perfect photocatalytic activity. However, the defect‐engineered SrTiO3 by doping different low‐valence metal ions have no similarly good activity in overall water spitting, of which the reason has not been determined. Here, Na+, K+, and Cs are deliberately doped in SrTiO3 to obtain a close low‐level concentration of Ti3+ defect for comparison. An interesting phenomenon is found that the K‐doped SrTiO3 has a higher Ti3+ concentration than others but with a better intrinsic photocatalytic activity. The analysis of band structure and charge‐carriers behavior indicates the formation of a deep‐state defect in Na or Cs‐doped SrTiO3, leading to a decrease in photocatalytic activity. With the density functional theory calculation and synchrotron radiation characterization, the differences in A‐site‐metal ionic polarization are found to localize some defect charge, accompanied by uneven structural relaxation. As a result, the deep‐state defect can form in the area containing some group of atoms around the higher‐polarization metal ions, limiting the activity. This study further complements the important effect of doping ions on defect state in addition to the Ti3+ defect concentration in theory, for designing defect engineering in SrTiO3.

Plasmon-Mediated Oxidase-like Activity on Ag@ZnS Heterostructured Hollow Nanowires for Rapid Visual Detection of Nitrite.

Rational design of fast and sensitive determination of nitrite (NO2-) from a complicated actual sample overtakes a crucial role in constructing a high-efficiency sensing platform. Herein, a visual NO2- sensing platform with outstanding selectivity, sensitivity, and stability based on a surface plasmon resonance (SPR)-enhanced oxidase-like activity has been proposed. Benefiting from the intrinsic photocatalytic activity and limited light penetration of ZnS, the oxidase-like activity based on ZnS decorated on Ag nanowires (Ag@ZnS) is determined. It is demonstrated that the electrons are generated efficiently on the surface of ZnS and then transferred into the hot electrons of Ag with the help of localized SPR excitation, thus greatly oxidating the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to produce dark blue oxidized TMB (oxTMB). When nitrite is added into the reaction system, the oxTMB will selectively react with NO2- to generate diazotized oxTMB, leading to a visual color change from dark blue to light green and subsequently to dark yellow. Owing to the specific recognition between nitrite and oxTMB, the recovery of catalytic activity induced an enhanced colorimetric test with a wider linear range for NO2- determination, an ultralow detection limit of 0.1 μM, excellent selectivity, and practicability for application in real samples. This plasmon-enhanced oxidase-like activity not only provides a smart approach to realize a colorimetric assay with high sensitivity and simplicity but also modulates oxidase-like activities.

Plasmon-Mediated Peroxidase-like Activity on an Asymmetric Nanotube Architecture for Rapid Visual Detection of Bacteria.

Rapid and sensitive detection of bacteria from a complex real media remains a challenge. Herein, we report a visual bacterial sensing assay with excellent specificity, anti-interference ability, and sensitivity based on a surface plasmon resonance (SPR)-enhanced peroxidase (POD) mimetic. The POD mimetic based on Pt nanoparticles (NPs) asymmetrically decorated on Au/TiO2 magnetic nanotubes (Au/Pt/MTNTs) is designed by combining the intrinsic photocatalytic activity of TiO2 and the limited transport depth of light. It is revealed that the localized surface plasmon resonance (LSPR) effect of the asymmetric nanotubes is more effective in facilitating the generation of hot electrons, which are subsequently transferred to Pt and MTNTs, thus greatly promoting the catalytic performance. Using Staphylococcus aureus (S.aureus) as a model of Gram-positive bacteria, the dependence of the colorimetric reaction on the active sites of the POD mimetic is used for the sensing of target bacteria. Owing to the specific recognition between S.aureus and peptide, the fluorescein isothiocyanate (FITC) labeled peptide probes are captured by S.aureus and removed from the Au/Pt/MTNTs, leading to the recovery of POD-like activity and fluorescence emission of S.aureus. Particularly, benefiting from the Au-SPR effect and the magnetic feature of the Au/Pt/MTNTs, the recovery of catalytic activity induced an improved colorimetric assay with a wider linear response for S.aureus qualification and a detection limit of four cells, as well as satisfactory selectivity and feasibility for application in real samples. The plasmon-enhanced POD activity would provide a simple-yet-effective approach to achieve a colorimetric bioassay with high efficiency and sensitivity. This asymmetric design can also be utilized to engineer nanozymes in colorimetric assays for the specific detection of biotoxins, biomarkers, and cancer cells.

Surface and Defect Engineering Coupling of Halide Double Perovskite Cs2NaBiCl6 for Efficient CO2 Photoreduction

AbstractNon‐toxic halide double perovskite materials have many advantages of lead halide perovskite. Whereas, they usually exhibit poor stability and very low intrinsic photocatalytic CO2 reduction activity due to the insufficient separation of photogenerated charges and the lack of active sites. In this work, stable chlorine‐deficient 3D hierarchical Cs2NaBiCl6 porous microspheres assembled by highly crystalline nanoflakes were prepared by a simple grinding method. An unprecedented CO yield of 30.22 µmol g−1 h−1 was achieved in the gas‐solid photocatalytic reduction of CO2 without sacrificial agents, which is the highest value among lead‐free halide perovskite photocatalysts. Experimental results and density‐functional theory calculations show that the chlorine vacancy plays the triple role of suppressing photogenerated electron‐holes recombination, enhancing CO2 adsorption, and significantly reducing the free energy barrier for the key intermediate COOH* generation. In comparison with the pristine Cs2NaBiCl6, coupling of surface and defect engineering of the hierarchical sample brings 12.34 times enhancement of CO2 photoreduction activity. This work proposes a simple method to synthesize a chlorine‐vacancy rich 3D hierarchical lead‐free halide perovskite and offers a new design idea to substantially enhance the photocatalytic activity, opening a door for the prospective contribution of these materials to carbon neutralization.

Enhanced photocatalytic degradation of tetracycline hydrochloride over Au-doped BiOBr nanosheets under visible light irradiation.

Bismuth(III) oxybromide (BiOBr) is a typical photocatalyst with a unique layered structure. However, the response of BiOBr to visible light is not strong enough for practical application. Moreover, the charge separation efficiency of BiOBr still needs to be improved. In this study, series of Au-doped BiOBr photocatalysts was prepared through a facile one-step hydrothermal method. The as-prepared Au0.3-BiOBr nanosheets exhibited an excellent electrochemical performance. The charge separation efficiency of Au0.3-BiOBr nanosheets was enhanced by 18.5 times compared with that of BiOBr. The intrinsic photocatalytic activity of Au0.3-BiOBr nanosheets in the degradation of tetracycline hydrochloride was approximately twice higher than that of BiOBr under visible light irradiation. In addition, three pathways were identified for the photocatalytic degradation and mineralization of tetracycline hydrochloride, which involve four reactions: hydroxylation, demethylation, ring opening and mineralization. Accordingly, this study proposes a feasible and effective Au-doped BiOBr photocatalyst, and describes a promising strategy for the design and synthesis of high-performance photocatalysts.

Visible-Light-Driven Ag-Doped BiOBr Nanoplates with an Enhanced Photocatalytic Performance for the Degradation of Bisphenol A.

Based on the low utilization rate of visible light and the high-charge carriers-recombination efficiency of bismuth oxybromide (BiOBr), in this work, noble metal Ag was used to modify BiOBr, and Ag-doped BiOBr nanoplates (Ag-BiOBr) were obtained through a one-step hydrothermal method. Compared with BiOBr, the absorption edge of Ag-BiOBr showed a redshift from 453 nm to 510 nm, and the absorption efficiency of visible light was, obviously, improved. Bisphenol A (BPA) was chosen as the target pollutant, to evaluate the photocatalytic performance of the samples. Ag0.1-BiOBr showed the highest degradation efficiency. The intrinsic photocatalytic activity of Ag0.1-BiOBr, under visible light, was approximately twice as high as that of BiOBr. In this way, a new visible-light-driven photocatalyst was proposed, to fight against organic pollution, which provides a promising strategy for water and wastewater treatment.

Computation-Aided Discovery and Synthesis of 2D PrOBr Photocatalyst

Developing photocatalysts is essential for converting solar energy into chemical fuels. Herein, we report the discovery and synthesis of praseodymium oxyhide (PrOBr), a two-dimensional (2D) rare-earth material, as an efficient photocatalyst. By performing high-throughput screening over popular computational 2D materials databases, we have identified 2D PrOBr as a promising photocatalyst with potentially good stability and activity. 2D PrOBr was successfully synthesized via the exfoliation of bulk PrOBr powders. The intrinsic photocatalytic activities of this 2D material were further validated. The measured hydrogen evolution rate of water splitting and the methane production rate of carbon dioxide reduction are 60.28 μmol·h–1·g–1 and 0.862 μmol·h–1·g–1, which are about 3–6 times and 7 times higher than that of the typical 2D photocatalysts (e.g., 2D C3N4 and BiOCl), respectively.

Controlled synthesis and structural modulation to boost intrinsic photocatalytic activity of BiVO4

A feasible solution-processed surface modification is presented to boost the intrinsic photoactivity of BiVO4via hydrothermal, solvothermal and solid-state reactions, enabling as a promising photocatalyst for degradation of dye pollutants in water.

Intrinsic photocatalytic water oxidation activity of Mn-doped ferroelectric BiFeO3

The development of stable and efficient visible light-absorbing oxide-based semiconductor photocatalysts is a desirable task for solar water splitting applications. Recently, we proposed that the low photocurrent density in film-based BiFeO3 (BFO) is due to charge recombination at the interface of the domain walls, which could be largely reduced in particulate photocatalyst systems. To demonstrate this hypothesis, in this work we synthesized particulate BFO and Mn-doped BiFeO3 (Mn-BFO) by the sol-gel method. Photocatalytic water oxidation tests showed that pure BFO had an intrinsic photocatalytic oxygen evolution reaction (OER) activity of 70 μmol h-1 g-1, while BFO-2, with an optimum amount of Mn doping (0.05%), showed an OER activity of 255 μmol h-1 g-1 under visible light (λ ≥ 420 nm) irradiation. The bandgap of Mn-doped BFO could be reduced from 2.1 to 1.36 eV by varying the amount of Mn doping. Density functional theory (DFT) calculations suggested that surface Fe (rather than Mn) species serve as the active sites for water oxidation, because the overpotential for water oxidation on Fe species after Mn doping is 0.51 V, which is the lowest value measured for the different Fe and Mn species examined in this study. The improved photocatalytic water oxidation activity of Mn-BFO is ascribed to the synergistic effect of the bandgap narrowing, which increases the absorption of visible light, reduces the activation energy of water oxidation, and inhibits the recombination of photogenerated charges. This work demonstrates that Mn doping is an effective strategy to enhance the intrinsic photocatalytic water oxidation activity of particulate ferroelectric BFO photocatalysts.

Novel S-doped BiOBr nanosheets for the enhanced photocatalytic degradation of bisphenol A under visible light irradiation

Bisphenol A (BPA), a typical endocrine disrupting chemical, is widespread in aqueous environment and cannot be efficiently treated by traditional water treatment technologies. Bismuth oxybromide (BiOBr) is a promising photocatalyst with a special layered structure. However, its band gap (2.8 eV) is not narrow enough for the efficient harvesting of visible light, severely restricting its practical use. Given that the band gap of Bi2S3 is only 1.3 eV, S-doping modification could be used to tailor the band structure of BiOBr. Here, series of S-doped BiOBr nanosheets was prepared through a facile hydrothermal procedure. The as-prepared S0.2-BiOBr nanosheets showed a narrower band gap of 2.33 eV. The intrinsic photocatalytic activity of S0.2-BiOBr sample for the degradation of BPA was 2.78 times higher than that of BiOBr under visible light degradation. Moreover, the mechanism of BPA degradation over the S-doped BiOBr under visible light irradiation was elucidated based on the experimental results and density functional theoretical calculations. Overall, a feasible and effective doping method was proposed to improve the utilization efficiency of visible light.