Showing papers on "Photocatalysis published in 2019"

In Situ Irradiated X-Ray Photoelectron Spectroscopy Investigation on a Direct Z-Scheme TiO2 /CdS Composite Film Photocatalyst.

Abstract: Inspired by nature, artificial photosynthesis through the construction of direct Z-scheme photocatalysts is extensively studied for sustainable solar fuel production due to the effectiveness in enhancing photoconversion efficiency. However, there is still a lack of thorough understanding and direct evidence for the direct Z-scheme charge transfer in these photocatalysts. Herein, a recyclable direct Z-scheme composite film composed of titanium dioxide and cadmium sulfide (TiO2 /CdS) is prepared for high-efficiency photocatalytic carbon dioxide (CO2 ) reduction. In situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) confirms the direct Z-scheme charge-carrier migration pathway in the photocatalytic system. Furthermore, density functional theory simulation identifies the intrinsic cause for the formation of the direct Z-scheme heterojunction between the TiO2 and the CdS. Thanks to the significantly enhanced redox abilities of the charge carriers in the direct Z-scheme system, the photocatalytic CO2 reduction performance of the optimized TiO2 /CdS is 3.5, 5.4, and 6.3 times higher than that of CdS, TiO2 , and commercial TiO2 (P25), respectively, in terms of methane production. This work is a valuable guideline in preparation of highly efficient recyclable nanocomposite for photoconversion applications.

Tuning Oxygen Vacancies in Ultrathin TiO2 Nanosheets to Boost Photocatalytic Nitrogen Fixation up to 700 nm

Abstract: Dinitrogen reduction to ammonia using transition metal catalysts is central to both the chemical industry and the Earth's nitrogen cycle. In the Haber-Bosch process, a metallic iron catalyst and high temperatures (400 °C) and pressures (200 atm) are necessary to activate and cleave NN bonds, motivating the search for alternative catalysts that can transform N2 to NH3 under far milder reaction conditions. Here, the successful hydrothermal synthesis of ultrathin TiO2 nanosheets with an abundance of oxygen vacancies and intrinsic compressive strain, achieved through a facile copper-doping strategy, is reported. These defect-rich ultrathin anatase nanosheets exhibit remarkable and stable performance for photocatalytic reduction of N2 to NH3 in water, exhibiting photoactivity up to 700 nm. The oxygen vacancies and strain effect allow strong chemisorption and activation of molecular N2 and water, resulting in unusually high rates of NH3 evolution under visible-light irradiation. Therefore, this study offers a promising and sustainable route for the fixation of atmospheric N2 using solar energy.

Photocatalytic hydrogen production using metal doped TiO2: A review of recent advances

Abstract: Hydrogen (H2) production via photocatalytic water splitting is one of the most promising technologies for clean solar energy conversion to emerge in recent decades. The achievement of energy production from water splitting would mean that we could use water as a fuel for future energy need. Among the various photocatalytic materials, titanium dioxide (TiO2) is the dominant and most widely studied because of its exceptional physico-chemical characteristics. Surface decoration of metal/non-metal on TiO2 nanoparticles is an outstanding technique to revamp its electronic properties and enrich the H2 production efficiency. Metal dopants play a vital role in separation of electron-hole pairs on the TiO2 surface during UV/visible/simulated solar light irradiation. In this paper, the basic principles, photocatalytic-reactor design, kinetics, key findings, and the mechanism of metal-doped TiO2 are comprehensively reviewed. We found that Langmuir-Hinshelwood kinetic model is commonly employed by the researchers to demonstrate the rate of H2 production. Copper (Cu), gold (Au) and platinum (Pt) are the most widely studied dopants for TiO2, owing to their superior work function. The metal dopants can amplify the H2 production efficiency of TiO2 through Schottky barrier formation, surface plasmon resonance (SPR), generation of gap states by interaction with TiO2 VB states. The recent advances and important consequences of 2D materials, perovskites, and other novel photocatalysts for H2 generation have also been reviewed.

Direct Z-scheme ZnO/CdS hierarchical photocatalyst for enhanced photocatalytic H2-production activity

Abstract: Herein, ZnO/CdS hierarchical composite was prepared through a hydrothermal and chemical bath deposition (CBD) process. Its photocatalytic H2-production performance was tested. Mass ratio of CdS acted a pivotal part in light absorption and photocatalytic properties. Noticeably, promoted photocatalytic H2-production activity of 4134 μmol g−1 h-1 was achieved by the sample with optimal CdS content. Significantly, the photoluminescence (PL) detection of hydroxyl radicals, as well as the in-situ XPS measurements was selected to verify the direct Z-scheme charge migration mechanism. This mechanism endowed the composite with strong capability for hydrogen evolution and elucidated the improved photocatalytic performance. The improvement of photocatalytic activity was due to hierarchical structure, extended visible light response and direct Z-scheme mechanism. This work will give an innovative vision in constructing direct Z-scheme photocatalytic system with great photocatalytic H2-production activity.

Synergy of Dopants and Defects in Graphitic Carbon Nitride with Exceptionally Modulated Band Structures for Efficient Photocatalytic Oxygen Evolution.

Abstract: Electronic structure greatly determines the band structures and the charge carrier transport properties of semiconducting photocatalysts and consequently their photocatalytic activities. Here, by simply calcining the mixture of graphitic carbon nitride (g-C3 N4 ) and sodium borohydride in an inert atmosphere, boron dopants and nitrogen defects are simultaneously introduced into g-C3 N4 . The resultant boron-doped and nitrogen-deficient g-C3 N4 exhibits excellent activity for photocatalytic oxygen evolution, with highest oxygen evolution rate reaching 561.2 µmol h-1 g-1 , much higher than previously reported g-C3 N4 . It is well evidenced that with conduction and valence band positions substantially and continuously tuned by the simultaneous introduction of boron dopants and nitrogen defects into g-C3 N4 , the band structures are exceptionally modulated for both effective optical absorption in visible light and much increased driving force for water oxidation. Moreover, the engineered electronic structure creates abundant unsaturated sites and induces strong interlayer C-N interaction, leading to efficient electron excitation and accelerated charge transport. In the present work, a facile approach is successfully demonstrated to engineer the electronic structures and the band structures of g-C3 N4 with simultaneous introduction of dopants and defects for high-performance photocatalytic oxygen evolution, which can provide informative principles for the design of efficient photocatalysis systems for solar energy conversion.

Liquid exfoliation of g-C3N4 nanosheets to construct 2D-2D MoS2/g-C3N4 photocatalyst for enhanced photocatalytic H2 production activity

Abstract: Although graphitic carbon nitride (g-C3N4) is an attractive photocatalyst for solar H2 generation, the preparation of g-C3N4 nanosheets via a “green” and simple method as well as the construction of highly-efficient g-C3N4-based photocatalysts are still challenges. In this study, g-C3N4 nanosheets prepared by a simple probe sonication assisted liquid exfoliation method were used to construct 2D-2D MoS2/g-C3N4 photocatalyst for photocatalytic H2 production. The 2D-2D MoS2/g-C3N4 photocatalyst containing 0.75% MoS2 showed the highest H2 evolution rate of 1155 μmol·h−1·g−1 with an apparent quantum yield of 6.8% at 420 nm monochromatic light, which is much higher than that of the optimized 0D-2D Pt/g-C3N4 photocatalyst. The high photocatalytic H2 production activity of 2D-2D MoS2/g-C3N4 photocatalyst can be attributed to the large surface area and the formed 2D interfaces between MoS2 and g-C3N4 nanosheets. As demonstrated by photoluminescence quenching and time-resolved fluorescence decay studies, the 2D interfaces can accelerate the photoinduced charge transfer, resulting in the high photocatalytic H2 production performance. This study provides a new strategy in developing highly-efficient g-C3N4-based photocatalysts for H2 production via using 2D nanojunction as a bridge to promote the photoinduced charge separation and transfer.

Facile assembled biochar-based nanocomposite with improved graphitization for efficient photocatalytic activity driven by visible light

Abstract: The preparation processes of efficient photocatalyst containing defect regulation and heterostructure construction are usually complicated and difficult to control at present, besides, the catalyst agglomeration in solution further limits their application. There is an urgent need for designing a potentially cheap, efficient, sustainable and easy-prepared nanocomposite to improve photocatalytic performance. In present study, the facile synthesized porous graphitic carbon with microtubular structure, high graphitization degree and abundant porosity demonstrates an outstanding advantage of excellent conductivity and facilitated mass transport. Such porous graphite biochar (PGBC) self-assembled with g-MoS2 nanosheets is observed by the optimized band gap, enhanced visible light harvesting, accelerated charge transfer and efficient photo-generated carrier’s separation. Considering the favorable specific surface area and pore distribution of PGBC for avoiding nanosheet agglomeration, the as-prepared composites display quite high efficiency for tetracycline hydrochloride (TC) removal based on the synergistic action of the desirable absorption and photocatalytic capability. Mechanism exploration indicates that surface adsorption is mainly dominated by electrostatic interaction, hydrogen bonding, π-π stacking and pore-filling, and hole (h+) and hydroxyl radical (·OH) are the predominant active species responsible for TC degradation. Furthermore, the nanocomposites possess advisable stability performance for TC removal in contaminated river water, further providing an underlying insight for establishing high-efficient and easy-prepared photocatalysts in practical contaminated water remediation.

Photocatalytic Activity Improvement and Application of UV-TiO2 Photocatalysis in Textile Wastewater Treatment: A Review

Abstract: Treatment of textile wastewater using titanium dioxide (TiO2) photocatalysis has been started from the last decade and reached attention to the researchers because of its versatile application. The variety of applications of TiO2 as a photocatalyst has been taken place because of low operating temperature, biologically inert nature, low energy consumption, water insolubility, ease availability and photoactivity, less toxicity, high chemical stability, suitable flat band potential, narrow band gap and environmentally benign. The successful and efficient application of photocatalysis depends on quality of photocatalyst, nature of pollutants, and source of light, which should be in close contact with each other. The TiO2 photocatalyst is used for the effluent treatment of textile wastewater in the presence of ultraviolet (UV) irradiation. Heterogeneous UV-TiO2 photocatalysis is capable to remove organic pollutants from textile wastewater, which has been widely studied and the technology also being commercialized in many developing countries in the world. This review focuses on the mechanism of UV-TiO2 photocatalysis, modification of TiO2 photocatalyst, and application of doping and co-doping in order to improve the photocatalytic activity in wastewater treatment. In addition, the review conveys comprehensive and fundamental assessments of the photocatalytic activity for the removal of organic dyes and phenolic compounds from textile wastewater.

Ti3C2 Mxene/porous g-C3N4 interfacial Schottky junction for boosting spatial charge separation in photocatalytic H2O2 production

Abstract: The development of efficient photocatalysts for the production of hydrogen peroxide (H2O2) is a promising strategy to realize solar-to-chemical energy conversion. Graphitic carbon nitride (g-C3N4) presents giant potential for photocatalytic H2O2 production, but the sluggish charge separation depresses its photocatalytic performance. Herein, an interfacial Schottky junction composed of Ti3C2 nanosheets and porous g-C3N4 nanosheets (TC/pCN) is constructed by a facile electrostatic self-assembly route to significantly boost the spatial charge separation to promote the activation of molecular oxygen for H2O2 production. As the optimal sample, TC/pCN-2 possesses the highest H2O2 production rate (2.20 μmol L−1 min−1) under visible light irradiation (λ > 420 nm), which is about 2.1 times than that of the porous g-C3N4. The results of superoxide radical detection and rotating disk electrode measurement suggest that the two-step single-electron reduction of oxygen is the predominant reaction step during this photocatalytic H2O2 production process. The enhanced photocatalytic performance is ascribed to the formation of Schottky junction and subsequent built-in electric field at their interface, which accelerate the spatial charge separation and restrain the charge recombination. This work provides an in-depth understanding of the mechanism of photocatalytic H2O2 production, and gives ideas for the design of highly active materials for photocatalytic H2O2 production.

Encapsulating Perovskite Quantum Dots in Iron-Based Metal-Organic Frameworks (MOFs) for Efficient Photocatalytic CO 2 Reduction

Abstract: Improving the stability of lead halide perovskite quantum dots (QDs) in a system containing water is the key for their practical application in artificial photosynthesis. Herein, we encapsulate low-cost CH3 NH3 PbI3 (MAPbI3 ) perovskite QDs in the pores of earth-abundant Fe-porphyrin based metal organic framework (MOF) PCN-221(Fex ) by a sequential deposition route, to construct a series of composite photocatalysts of MAPbI3 @PCN-221(Fex ) (x=0-1). Protected by the MOF the composite photocatalysts exhibit much improved stability in reaction systems containing water. The close contact of QDs to the Fe catalytic site in the MOF, allows the photogenerated electrons in the QDs to transfer rapidly the Fe catalytic sites to enhance the photocatalytic activity for CO2 reduction. Using water as an electron source, MAPbI3 @PCN-221(Fe0.2 ) exhibits a record-high total yield of 1559 μmol g-1 for photocatalytic CO2 reduction to CO (34 %) and CH4 (66 %), 38 times higher than that of PCN-221(Fe0.2 ) in the absence of perovskite QDs.

Z‐Scheme 2D/2D Heterojunction of Black Phosphorus/Monolayer Bi2WO6 Nanosheets with Enhanced Photocatalytic Activities

Abstract: Black phosphorus (BP), a star-shaped two-dimensional material, has attracted considerable attention owing to its unique chemical and physical properties. BP shows great potential in photocatalysis area because of its excellent optical properties; however, its applications in this field have been limited to date. Now, a Z-scheme heterojunction of 2D/2D BP/monolayer Bi2 WO6 (MBWO) is fabricated by a simple and effective method. The BP/MBWO heterojunction exhibits enhanced photocatalytic performance in photocatalytic water splitting to produce H2 and NO removal to purify air; the highest H2 evolution rate of BP/MBWO is 21042 μmol g-1 , is 9.15 times that of pristine MBWO and the NO removal ratio was as high as 67 %. A Z-scheme photocatalytic mechanism is proposed based on monitoring of . O2 - , . OH, NO2 , and NO3 - species in the reaction. This work broadens applications of BP and highlights its promise in the treatment of environmental pollution and renewable energy issues.

Designed Synthesis of a 2D Porphyrin-Based sp 2 Carbon-Conjugated Covalent Organic Framework for Heterogeneous Photocatalysis.

Abstract: The construction of stable covalent organic frameworks (COFs) for various applications is highly desirable. Herein, we report the synthesis of a novel two-dimensional (2D) porphyrin-based sp2 carbon-conjugated COF (Por-sp2 c-COF), which adopts an eclipsed AA stacking structure with a Brunauer-Emmett-Teller surface area of 689 m2 g-1 . Owing to the C=C linkages, Por-sp2 c-COF shows a high chemical stability under various conditions, even under harsh conditions such as 9 m HCl and 9 m NaOH solutions. Interestingly, Por-sp2 c-COF can be used as a metal-free heterogeneous photocatalyst for the visible-light-induced aerobic oxidation of amines to imines. More importantly, in comparison to imine-linked Por-COF, the inherent structure of Por-sp2 c-COF equips it with several advantages as a photocatalyst, including reusability and high photocatalytic performance. This clearly demonstrates that sp2 carbon-linked 2D COFs can provide an interesting platform for heterogeneous photocatalysis.

Ultrathin Metal-Organic Framework Nanosheets with Ultrahigh Loading of Single Pt Atoms for Efficient Visible-Light-Driven Photocatalytic H 2 Evolution

Abstract: A surfactant-stabilized coordination strategy is used to make two-dimensional (2D) single-atom catalysts (SACs) with an ultrahigh Pt loading of 12.0 wt %, by assembly of pre-formed single Pt atom coordinated porphyrin precursors into free-standing metal-organic framework (MOF) nanosheets with an ultrathin thickness of 2.4±0.9 nm. This is the first example of 2D MOF-based SACs. Remarkably, the 2D SACs exhibit a record-high photocatalytic H2 evolution rate of 11 320 μmol g-1 h-1 via water splitting under visible light irradiation (λ>420 nm) compared with those of reported MOF-based photocatalysts. Moreover, the MOF nanosheets can be readily drop-casted onto solid substrates, forming thin films while still retaining their photocatalytic activity, which is highly desirable for practical solar H2 production.

In-situ Fe-doped g-C3N4 heterogeneous catalyst via photocatalysis-Fenton reaction with enriched photocatalytic performance for removal of complex wastewater

Abstract: In this work, an in-situ Fe-doped g-C3N4 catalyst was synthesized by thermal shrinkage polymerization. A heterogeneous photocatalysis-Fenton system was formed with the addition of H2O2 under visible irradiation and exhibited excellent and recyclable removal performance for refractory contaminants such as: phenol, bisphenol A, 2, 4-dichlorophenol and coking wastewater, which was due to the formation of σ-π bonds via Fe and N element in the triazine ring skeleton of Fe-g-C3N4. The electrons generated can be quickly transferred to Fe3+ to form Fe2+ under the interaction of the chemical bond. The efficiency of photoelectron separation was accelerated, and OH radicals were quickly generated with the reaction between Fe2+ and H2O2. Specifically, the recycling of Fe can be achieved in the heterogeneous system, which avoids the problems for the recycling and secondary pollution of Fe ions in homogeneous Fenton reaction. Parameters such as Fe doping amount, hydrogen peroxide concentration, pH value, catalyst concentration, and complex wastewater (coking wastewater) were optimized. The degradation of coking wastewater were also performed, and the chemical oxygen demand (COD) and total organic carbon (TOC) values for 300 ml coking wastewater could be reduced from 64.6 and 25.3 mg/L to 22.8 and 12.3 mg/L in 60 min, respectively. These results demonstrate photocatalysis-Fenton reaction with Fe-g-C3N4 catalyst is promising for environmental remediation.

The enhancement of photocatalytic hydrogen production via Ti3+ self-doping black TiO2/g-C3N4 hollow core-shell nano-heterojunction

Abstract: The Ti3+ self-doping B-TiO2/g-C3N4 hollow core-shell nano-heterojunction is synthesized via the continuous hydrothermal deposition and sculpture-reduction processes. The results of SEM, XRD, TEM, XPS and FT-IR imply that the B-TiO2/g-C3N4 hollow core-shell nanospheres have been prepared successfully. The photocatalytic activity of the B-TiO2/g-C3N4 nano-heterojunctions remarkably exhibits an enhancement of 18 times and 65 times than that of normal TiO2 and g-C3N4, respectively. Further, the photocatalytic process and the mechanism of the photocatalytic hydrogen production enhancement have been studied, which could be ascribed to the Ov-Ti3+ in the B-TiO2 and interface nano-heterojunction, that have been proved by the transient photocurrent, PL, EIS and Mott-Schottky plots.

Synergistic effect of artificial enzyme and 2D nano-structured Bi2WO6 for eco-friendly and efficient biomimetic photocatalysis

Abstract: Highly-efficient and eco-friendly materials and technologies are urgently needed to meet the requirements of nowadays green development. Photocatalysis with using solar energy and enzymatic catalysis with eco-friendly nature are effective alternatives to address the problem. Notably, beneficial use of the synergistic effect of artificial enzyme and advanced photocatalyst has attracted wide attention. This work presents a biomimetic photocatalytic material, two-dimensional (2D) biomimetic hemin-bismuth tungstate (HBWO). Stable HBWO composites formed by immobilization of monomeric hemin on 2D bismuth tungstate layer, exhibit high photocatalytic performance, better than that of pure 2D bismuth tungstate and unsupported hemin. HBWO shows layered structure with the interlayer spacing at ˜0.35 nm. In the photocatalytic process, hemin can not only act as an electron shuttle, also play an important role in oxygen transfer. Additionally, the synthesized HBWO composites exhibit nice binding affinities and high photocatalytic activity in tetracycline degradation. It is anticipated that beneficial use of synergistic effect of artificial enzyme and photocatalyst via HBWO composites can be a promising eco-friendly and efficient solution for addressing the environmental crisis.

Fabrication of Bi2MoO6/ZnO hierarchical heterostructures with enhanced visible-light photocatalytic activity

Abstract: The construction of heterostructures is regarded as an excellent strategy to achieve efficient charge separation and improved photocatalytic activity. Herein, a series of Bi2MoO6/ZnO hierarchical heterostructured photocatalysts were synthesized by a solvothermal method. The morphology of Bi2MoO6 grown on the surface of ZnO nanorods could be controlled by adjusting the experimental conditions. The synthesized samples were characterized by various analytical techniques and their photocatalytic performance was evaluated by photocatalytic reduction of Cr(VI) under visible-light irradiation. Compared with those of pure Bi2MoO6 and ZnO, the Bi2MoO6/ZnO composites showed higher photocatalytic activity towards the reduction of Cr(VI). The enhanced photocatalytic activity was mainly attributed to the formation of a heterojunction between Bi2MoO6 and ZnO, which effectively facilitated the separation and transfer of electrons and holes. In addition, the Bi2MoO6/ZnO photocatalysts maintained good stability after three cycles of Cr(VI) photoreduction. A possible photocatalytic mechanism of the as-synthesized composites was proposed.

Half-unit-cell ZnIn2S4 monolayer with sulfur vacancies for photocatalytic hydrogen evolution

Abstract: Two-dimensional (2D) photocatalytic materials have attracted extensive attention due to the unique properties different from those of their bulk. 2D ZnIn2S4 nanosheets with the intrinsic bilayer in one-unit-cell with interlayer force generally perform better than that of the bulk in photocatalytic hydrogen evolution. Here, we for the first time demonstrate that the half-unit-cell ZnIn2S4 monolayer possesses an excellent photocatalytic performance compared with the one-unit-cell bilayer owing to its increased carrier lifetime. Meanwhile, sulfur vacancies are introduced in the half-unit-cell ZnIn2S4 monolayer to trap the photo-generated electrons and further prolong the carrier lifetime. First-principle calculations reveal that sulfur vacancies in the ZnIn2S4 monolayer induce more charge carriers at the valence band maximum to participate in the photocatalytic activity. As expected, the photocatalytic hydrogen production rate of the monolayer ZnIn2S4 with sulfur vacancies is up to 13.478 mmol/g/h under the visible light irradiation, which is much higher than the available values reported of ZnIn2S4 so far. These findings provide a new strategy for optimization of 2D photocatalysts to enhance photocatalytic hydrogen evolution.

Facet-dependent active sites of a single Cu 2 O particle photocatalyst for CO 2 reduction to methanol

Abstract: Atomic-level understanding of the active sites and transformation mechanisms under realistic working conditions is a prerequisite for rational design of high-performance photocatalysts. Here, by using correlated scanning fluorescence X-ray microscopy and environmental transmission electron microscopy at atmospheric pressure, in operando, we directly observe that the (110) facet of a single Cu2O photocatalyst particle is photocatalytically active for CO2 reduction to methanol while the (100) facet is inert. The oxidation state of the active sites changes from Cu(i) towards Cu(ii) due to CO2 and H2O co-adsorption and changes back to Cu(i) after CO2 conversion under visible light illumination. The Cu2O photocatalyst oxidizes water as it reduces CO2. Concomitantly, the crystal lattice expands due to CO2 adsorption then reverts after CO2 conversion. The internal quantum yield for unassisted wireless photocatalytic reduction of CO2 to methanol using Cu2O crystals is ~72%. Photocatalytic reduction of CO2 to methanol offers a promising route to storage of solar energy in the form of chemical fuels. Here, Wu et al. use in operando microscopy to identify the active facets for CO2 reduction on Cu2O and exploit this to obtain high conversion efficiency and selectivity to methanol.

Tailoring the Grain Boundary Chemistry of Polymeric Carbon Nitride for Enhanced Solar Hydrogen Production and CO2 Reduction

Abstract: Photocatalytic water splitting is a promising and clean way to mimic plant photosynthesis in a sustainable manner. Improvements of the quantum efficiency and optical absorption in the relevant range are necessary steps to approach practicality. Herein, we reported that these issues can be readily addressed when 5-aminotetrazole, a monomer with high nitrogen content, is used for the synthesis of carbon nitride. The molten salt mixture NaCl/KCl is used as a high-temperature solvent to tailor the grain boundary structure and chemistry. Visible light quantum efficiency for H2 production of 0.65 could be obtained in the presence of K2 HPO4 as a double layer modifier. This value is very high, considering that this number depends on light to charge couple conversion, charge localization, as well as a successful oxidation and reduction reaction.

Direct Z‐Scheme Hetero‐phase Junction of Black/Red Phosphorus for Photocatalytic Water Splitting

Abstract: Black phosphorus (BP) has recently drawn attention in photocatalysis for its optical properties. However, limited by the rapid recombination of photogenerated carriers, the use of BP for photocatalytic water splitting still remains a huge challenge. Herein, we prepare a black/red phosphorus (BP/RP) hetero-phase junction photocatalyst by a wet-chemistry method to promote the interfacial charge separation and thus achieve Z-scheme photocatalytic water splitting without using sacrificial agents. The Z-scheme mechanism was confirmed by time-resolved transient absorption spectroscopy. This work provides a novel insight into the interface design of hetero-phase junction with atomic precision.

Defect-Tailoring Mediated Electron-Hole Separation in Single-Unit-Cell Bi 3 O 4 Br Nanosheets for Boosting Photocatalytic Hydrogen Evolution and Nitrogen Fixation.

Abstract: Solar photocatalysis is a potential solution to satisfying energy demand and its resulting environmental impact. However, the low electron-hole separation efficiency in semiconductors has slowed the development of this technology. The effect of defects on electron-hole separation is not always clear. A model atomically thin structure of single-unit-cell Bi3 O4 Br nanosheets with surface defects is proposed to boost photocatalytic efficiency by simultaneously promoting bulk- and surface-charge separation. Defect-rich single-unit-cell Bi3 O4 Br displays 4.9 and 30.9 times enhanced photocatalytic hydrogen evolution and nitrogen fixation activity, respectively, than bulk Bi3 O4 Br. After the preparation of single-unit-cell structure, the bismuth defects are controlled to tune the oxygen defects. Benefiting from the unique single-unit-cell architecture and defects, the local atomic arrangement and electronic structure are tuned so as to greatly increase the charge separation efficiency and subsequently boost photocatalytic activity. This strategy provides an accessible pathway for next-generation photocatalysts.