Toward Enhanced Photocatalytic Oxygen Evolution: Synergetic Utilization of Plasmonic Effect and Schottky Junction via Interfacing Facet Selection

In Situ Fabrication of 2D-2D Bi/BiOBr Ohmic Heterojunction for Enhanced Photocatalytic Nitrogen Fixation

The performance of BiOBr in photocatalytic nitrogen (N2) fixation is suboptimal, attributed to the weak chemisorption and activation of N2 by surface atoms. In our study, we achieved the formation of two-dimensional (2D) bismuth (Bi) on BiOBr nanosheets through in situ annealing in hydrogen atmosphere and successfully constructed a unique 2D-2D Bi/BiOBr ohmic heterojunction using a one-step method. Notably, the Bi/BiOBr heterojunction was utilized for photocatalytic N2 fixation under visible light (λ > 400 nm) in ultrapure water, demonstrating an exceptional N2 fixation rate of 376.16 μmol g-1 h-1. This rate is 7.7 and 4.1 times higher than those of BiOBr and BiOBr-OVs, respectively. The improved photocatalytic efficiency is attributed to the significantly enhanced N2 adsorption capability and more effective separation of photogenerated carriers, both stemming from the distinctive 2D/2D architecture of the Bi/BiOBr heterojunction. This work demonstrates that 2D Bi offers active sites that facilitate photocatalytic N2 fixation and introduces an approach to the design and construction of 2D/2D photocatalysts for applications spanning catalysis, optoelectronics, electronics, and beyond.

Construction of 2D/2D ZnIn2S4/Nb2CTx (MXene) hybrid with hole transport highway and active facet exposure boost photocatalytic hydrogen evolution

In this study, leveraging the tunable surface groups of MXene, the two-dimensional (2D) Nb2CTx with OH terminal (NC) was synthesized. 2D ZnIn2S4 (ZIS) nanosheets were prepared with the aid of sodium citrate, enhancing the exposure ratio of active (110) facet. On this basis, 2D/2D ZnIn2S4/Nb2CTx heterojunctions were fabricated to improve photocatalytic hydrogen evolution reaction (HER) performance. The optimized 6 wt%Nb2CTx/ZnIn2S4-450 (6NC/ZIS-450) photocatalyt exhibits a remarkable HER rate of 3603 μmol g-1h-1, which is 10 times superior to that of the original ZnIn2S4. Its apparent quantum efficiency (AQE) at 380 nm reaches 14.9 %. Meanwhile, even after 5 rounds of HER, the activity of 2D/2D ZnIn2S4/Nb2CTx heterojunction remained at 90 %, far superior to that of pure ZnIn2S4 (34 % and 31 %). Energy band structure analysis and density functional theory (DFT) calculation indicate that Nb2CTx adsorbed with OH exhibit a low work function. By serving as a hole cocatalyst, it effectively boosts the photocatalytic HER rate of ZnIn2S4/Nb2CTx heterojunction and inhibits the photocorrosion of ZnIn2S4. This unique insight, via hole transport highways and increased exposure of active facets, effectively enhances the activity and stability of sulfides photocatalysts.

Solar Light-Driven Molecular Oxygen Activation by BiOCl Nanosheets: Synergy of Coexposed {001}, {110} Facets and Oxygen Vacancies

Single-crystalline BiOCl nanosheets with coexposed {001} and {110} facets, as well as oxygen vacancies, were synthesized using a simple method. These nanosheets have the ability to activate molecular oxygen, producing reactive superoxide radicals (77.8%) and singlet oxygen (22.2%) when exposed to solar light. The BiOCl demonstrated excellent photocatalytic efficiency in producing H2O2 under simulated solar light and in oxidatively hydroxylating phenylboronic acid under blue LED light. Our research highlights the significance of constructing coexposed {001} and {110} facets, as well as oxygen vacancies, in enhancing photocatalytic performance. The BiOCl nanosheets have the capability to produce H2O2 with a solar-to-chemical energy conversion efficiency of 0.11%.

Rich Sulfur Vacancies and Reduced Schottky Barrier Height Synergistically Enable Au/ZnIn2S4 with Enhanced Photocatalytic CO2 Reduction into CO

Constructing the plasmonic metal/semiconductor heterostructure with a suitable Schottky barrier height (SBH) and the sufficiently reliable active sites is of importance to achieve highly efficient and selective photocatalytic CO2 reduction into hydrocarbon fuels. Herein, we report Au/sulfur vacancy-rich ZnIn2S4 (Au/VSR-ZIS) hierarchical photocatalysts, fabricated via in situ photodepositing Au nanoparticles (NPs) onto the nanosheet self-assembled ZnIn2S4 (ZIS) micrometer flowers (MFs) with rich sulfur vacancies (VS). Density functional theory (DFT) calculations confirm that for the Au/VSR-ZIS system, the Au NPs serve as the reaction sites for H2O oxidation, and the VSR-ZIS MFs serve as those for CO2 reduction. The rich VS in the Au/VSR-ZIS hybrid can reduce its SBH so as to boost more hot electrons in the Au NPs across its Schottky barrier and then inject into the conduction band (CB) of the VSR-ZIS MFs. In addition, VS can also act as the electron sink to trap the photogenerated electrons, retarding the recombination of photogenerated carriers. The two merits effectively enhance the photogenerated electron density in the surface of VSR-ZIS MFs, availing CO2 photoreduction. In addition, the introduction of rich VS in the Au/VSR-ZIS hybrid can offer more active sites, benefiting the CO2 adsorption and accelerating the desorption of CO* from the surface of the photocatalyst. Therefore, under visible light illumination with no sacrificial reagent, the optimum photocatalyst (Au/VSR-ZIS-0.4) presents the enhanced and selective CO2 photoreduction into CO (8.15 μmol g-1h-1 and near 100%), which are superior to those of most of ZIS-based and plasmon-based photocatalysts. The photocatalytic activity is about 40.0-fold as high as that of the Vs-poor-ZIS (VSP-ZIS) MFs. This work contributes a viable strategy for designing highly efficient plasmonic photocatalysts by using the synergism of the anion vacancies and the optimized SBH induced by them.

Robust Bi-anchoring carbon dot/BiOCl sheet heterojunction photocatalysts toward superior photocatalytic activity

BiOCl has attracted much attention due to its robust layered structure, excellent photocatalytic activity and nontoxicity. However, its practical application is hindered by its narrowband UV photoresponse and rapid recombination of photocarriers. Herein, zero-dimensional Bi-anchoring carbon quantum dot (Bi-CD)/two-dimensional BiOCl heterojunction (Bi-CD/BiOCl) photocatalysts are designed and synthesized by a facile hydrothermal method. Under 190-1100 nm broadband light irradiation, the optimized Bi-CD/BiOCl sample exhibits a superb rhodamine B (RhB) degradation rate of nearly 100%, which is 2.3 (1.7) times that of pristine BiOCl (CD/BiOCl). Additionally, the optimized sample exhibits an RhB degradation rate of up to 88.1% even under direct outdoor light and robust durability in water solution. Experimental results combined with DFT calculations reveal that the superior photocatalytic activity arises from the synergetic effects of broader light absorption due to the incorporation of CD, extra hot electron excitation by the localized surface plasmon resonance (LSPR) effect of metallic Bi, and enhanced electron transfer across the heterojunction interface as well as the existence of more oxygen vacancy traps in BiOCl. This work gives insights into the structure and photocatalytic properties of Bi-CD/BiOCl and provides a new strategy for the design and fabrication of robust high-performance photocatalysts under wide spectrum light irradiation.

First-Principles Study on Janus-Structured Sc2CX2/Sc2CY2 (X, Y = F, Cl, Br) Heterostructures for Solar Energy Conversion

Two-dimensional van der Waals heterostructures have good application prospects in solar energy conversion due to their excellent optoelectronic performance. In this work, the electronic structures of Sc2CF2/Sc2CCl2, Sc2CF2/Sc2CBr2, and Sc2CCl2/Sc2CBr2 heterostructures, as well as their properties in photocatalysis and photovoltaics, have been comprehensively studied using the first-principles method. Firstly, both of the three thermodynamically and dynamically stable heterostructures are found to have type-II band alignment with band gap values of 0.58 eV, 0.78 eV, and 1.35 eV. Meanwhile, the photogenerated carriers in Sc2CF2/Sc2CCl2 and Sc2CF2/Sc2CBr2 heterostructures are predicated to follow the direct Z-scheme path, enabling their abilities for water splitting. As for the Sc2CCl2/Sc2CBr2 heterostructure, its photovoltaic conversion efficiency is estimated to be 20.78%. Significantly, the light absorption coefficients of Sc2CF2/Sc2CCl2, Sc2CF2/Sc2CBr2, and Sc2CCl2/Sc2CBr2 heterostructures are enhanced more than those of the corresponding monolayers. Moreover, biaxial strains have been observed to considerably tune the aforementioned properties of heterostructures. All the theoretical results presented in this work demonstrate the application potential of Sc2CX2/Sc2CY2 (X, Y = F, Cl, Br) heterostructures in photocatalysis and photovoltaics.

Copper-decorated strategy based on defect-rich NH2-MIL-125(Ti) boosts efficient photocatalytic degradation of methyl mercaptan under sunlight

Photocatalysis has received significant attention as a technology that can solve environmental problems. Metal-organic frameworks are currently being used as novel photocatalysts but are still limited by the rapid recombination of photogenerated carriers, low photogenerated electron migration efficiency and poor solar light utilization rate. In this work, a novel photocatalyst was successfully constructed by introducing Cu species into thermal activated mixed-ligand NH2-MIL-125 (Ti) via defect engineering strategy. The constructed defect structure not only provided 3D-interconnected gas transfer channels, but also offered suitable space to accommodate introduced Cu species. For the most effective photocatalyst 0.2Cu/80%NH2-MIL-125 (300 °C) with optimized Cu content, the photocatalytic degradation rate of CH3SH achieved 4.65 times higher than that of pristine NH2-MIL-125 under visible light (λ > 420 nm). At the same time, it showed great degradation efficiency under natural sunlight, 100 ppm CH3SH was completely removed within 25 min in full solar light illumination. The improved catalytic efficiency is mainly due to the synergistic effect of the integrated Schottky junction and rich-defective NH2-MIL-125, which improved the bandgap and band position, and thus facilitated the separation and transfer of the photo-generated carriers. This work provided a facile way to integrate Schottky junctions and rich-defective MOFs with high stability. Due to its excellent degradation performance under sunlight, it also offered a prospective strategy for rational design of high-efficiency catalysts applied in environmental technologies.

Gradient oxygen doping triggered a microscale built-in electric field in CdIn2S4 for photoelectrochemical water splitting

Construction of a built-in electric field has been identified as an attractive improvement strategy for photoelectrochemical (PEC) water splitting by facilitating the carrier extraction from the inside to the surface. However, the promotion effect of the electric field is still restrained by the confined built-in area. Herein, we construct a microscale built-in electric field via gradient oxygen doping. The octahedral configuration of the synthesized CdIn2S4 (CIS) provides a structural basis, which enables the subsequent oxygen doping to reach a depth of ∼100 nm. Accordingly, the oxygen-doped CIS (OCIS) photoanode exhibits a microscale built-in electric field with band bending. Excellent PEC catalytic activity with a photocurrent density of 3.69 mA cm-2 at 1.23 V vs. RHE is achieved by OCIS, which is 3.1 times higher than that of CIS. Combining the results of thorough characterization and theoretical calculations, accelerating migration and separation of charge carriers have been determined as the reasons for the improvement. Meanwhile, the recombination risk at the doping centers has also been reduced to the minimum via optimal experiments. This work provides a new-generation idea for constructing a built-in electric field from the view point of bulky configuration towards PEC water splitting.

Surface and interface engineering of BiOCl nanomaterials and their photocatalytic applications

BiOCl materials have received much attention because of their unique optical and electrical properties. Still, their unsatisfactory catalytic performance has been troubling researchers, limiting the application of BiOCl-based photocatalysts. Therefore, many researchers have studied the adjustment of BiOCl-based materials to enhance photocatalytic efficiency. This review focuses on surface and interface engineering strategies for boosting the photocatalytic performance of BiOCl-based nanomaterials, including forming oxygen vacancy defects, constructing metal/BiOCl, and the fabrication of semiconductor/BiOCl nanocomposites. The photocatalytic applications of the above composites are also concluded in photodegradation of aqueous pollutants, photocatalytic NO removal, photo-induced H2 production, and CO2 reduction. Special emphasis has been given to the modification methods of BiOCl and photocatalytic mechanisms to provide a more detailed understanding for researchers in the fields of energy conversion and materials sciences.

Highly Efficient and Stable ITO-Free Organic Solar Cells Based on Squaraine N-Doped Quaternary Bulk Heterojunction

Simultaneously achieving high efficiency and robust device stability remains a significant challenge for organic solar cells (OSCs). Solving this challenge is highly dependent on the film morphology of the bulk heterojunction (BHJ) photoactive blends; however, there is a lack of rational control strategy. Herein, it is shown that the molecular crystallinity and nanomorphology of nonfullerene-based BHJ can be effectively controlled by a squaraine-based doping strategy, leading to an increase in device efficiency from 17.26% to 18.5% when doping 2 wt% squaraine into the PBDB-TF:BTP-eC9:PC71 BM ternary BHJ. The efficiency is further improved to 19.11% (certified 19.06%) using an indium-tin-oxide-free column-patterned microcavity (CPM) architecture. Combined with interfacial modification, CPM quaternary OSC excitingly shows an extrapolated lifetime of ≈23 years based on accelerated aging test, with the mechanism behind enhanced stability well studied. Furthermore, a flexible OSC module with a high and stable efficiency of 15.2% and an overall area of 5 cm2 is successfully fabricated, exhibiting a high average output power for wearable electronics. This work demonstrates that OSCs with new design of BHJ and device architecture are highly promising to be practical relevance with excellent performance and stability.

Research status and prospect of nano silver (Ag)-modified photocatalytic materials for degradation of organic pollutants

Nano silver (Ag) was metallic Ag monomers with particle size to the nanoscale. Photocatalyst was a kind of semiconductor material with photocatalytic function. Loading precious metal Ag onto semiconductor surfaces by microwave, laser-induced, solvent-thermal and hydrothermal methods could capture photogenerated electrons, reduced the compounding rate of holes and photogenerated electrons during the photocatalytic process, thereby improving the electron transfer efficiency of photocatalysis and enhancing the absorption of visible light by silver nanoparticles through the plasma resonance effect. The highly reactive free radicals produced by photocatalysts were used in the organic degradation process to degrade organic matter into inorganic matter and was a faster, more efficient and less polluting method of pollutant degradation, which has attracted a lot of attention from researchers. This review discussed the modification of various types of photocatalysts by nano Ag through different methods. The photocatalytic degradation of dyes, antibiotics and persistent organic pollutants by different modified composites was also analyzed. This review covered the several ways and means in which nano Ag has modified diverse photocatalytic materials as well as the photocatalytic degradation of dyes, antibiotics and persistent organic pollutants. This review identified the drawbacks of the existing nano Ag-modified photocatalytic materials, including their low yield and lack of recyclability, and it also offered suggestions for potential future directions for their improvement. The purpose of this review was to further research on the technology of nano Ag-modified photocatalytic materials and to encourage the creation of new modified photocatalytic nanomaterials for the treatment of organic pollutant degradation.

Piezo-photocatalysis for efficient charge separation to promote CO2 photoreduction in nanoclusters

The substantial emissions of CO2 greenhouse gases have resulted in severe environmental problems, and research on the implementation of semiconductor materials to minimize CO2 is currently a highly discussed subject. Effective separation of interface charges is a major challenge for efficient piezo-photocatalytic systems. Meanwhile, the ultrasmall-sized metal nanoclusters can shorten the distance of electron transport. Herein, we synthesized Au25(p-MBA)18 nanoclusters (Au25 NCs) modified red graphitic carbon nitride (RCN) nanocatalysts with highly exposed Au active sites by in-situ seed growth method. The loading of Au25 NCs on the RCN surface provides more active sites and creates a long-range ordered electric field. It allows for the direct utilization of the piezoelectric field to separate photogenerated carriers during photo-piezoelectric excitation. Based on the above advantages, the rate of CO2 reduction to CO over Au25 NCs/RCN (111.95 μmol g-1 h-1) was more than triple compared to that of pristine RCN. This paper has positive implication for further application of metal clusters loaded semiconductor for piezo-photocatalytic CO2 reduction.

Chemical bonding and facet modulating of p-n heterojunction enable vectorial charge transfer for enhanced photocatalysis

Heterojunctions have been proved to be the promising photocatalysts for hazardous contaminants removal, but the inferior interfacial contact, low carrier mobility and random carrier diffusion seriously hamper the photoactivity improvement of the conventional heterojunctions. Herein, SO chemically bonded p-n oriented heterostructure is fabricated via selectively anchoring of p-type Ag2S nanoparticles on the lateral facet of n-type Bi4TaO8Cl nanosheet. Such a p-n heterojunction engineering on specific facet of Bi4TaO8Cl semiconductor derives ingenious double internal electric field (IEF), which not only effectively creates the spatially separated oxidation and reduction sites, but also delivers the powerful driving forces for impactful spatial directed photocarrier transfer along the cascade path. Additionally, our experimental and theoretical analyses jointly signify that the interfacial SO bond could serve as an efficient atomic-level interfacial channel, which is conducive to encouraging the vectorial charge separation and migration kinetic. As a result, the Ag2S/Bi4TaO8Cl oriented heterojunction exhibits significantly enhanced visible light driven photocatalytic redox ability for tetracycline oxidation and hexavalent chromium reduction than those of single component and the traditional random/mixed heterojunctions. This study could provide a deeper insight into the synergistic effects of multi-IEF modulation and interfacial chemical bond bridging on optimizing the photogenerated carrier behaviors.

Water effect on the band edges of anatase TiO2 surfaces: A theoretical study on charge migration across surface heterojunctions and facet-dependent photoactivity

The charge migration mechanism across the surface heterojunction constructed on an anatase TiO2 nanocrystal is still under debate. To solve this longstanding question, we present a systematic study of the band edges (vs. standard hydrogen electrode, SHE) of aqueous TiO2 interfaces with anatase (101), (100) and (001) surfaces, using a combination of density functional theory-based molecular dynamics (DFTMD) and efficient computational SHE (cSHE) methods. Our calculations show that the conduction band minimum (CBM) of the (101) surface is lower than that of (001) and (100) surfaces, which is thermodynamically favorable for electrons migrating to the (101) surface through the surface heterojunction, while the hole preferentially accumulates on the (100) surface due to its highest valence band minimum (VBM). In addition, we qualitatively explore the facet-dependent photocatalytic activity of anatase TiO2. Due to the possession of both the beneficial atomic structure (with 100% undercoordinated Ti5c atoms at the surface) and electronic structure (more strongly oxidizing holes in the VBM and efficient electron-hole spatial separation separation), the (001) surface exhibits the most efficient photocatalytic performance for water oxidation. Furthermore, it is confirmed that the use of simplified theoretical models neglecting the detailed atomic structures of water at the aqueous interface is inadequate to predict the band alignment of semiconductors relative to water redox potentials, so that it may result in substantial errors in evaluating the photocatalytic performance of materials to be used for water splitting.

Improved Plasmonic Hot-Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad-Spectrum Photocatalytic H2 Evolution

Rationally designing broad-spectrum photocatalysts to harvest whole visible-light region photons and enhance solar energy conversion is a "holy grail" for researchers, but is still a challenging issue. Herein, based on the common polymeric carbon nitride (PCN), a hybrid co-catalysts system comprising plasmonic Au nanoparticles (NPs) and atomically dispersed Pt single atoms (PtSAs) with different functions was constructed to address this challenge. For the dual co-catalysts decorated PCN (PtSAs-Au2.5/PCN), the PCN is photoexcited to generate electrons under UV and short-wavelength visible light, and the synergetic Au NPs and PtSAs not only accelerate charge separation and transfer though Schottky junctions and metal-support bond but also act as the co-catalysts for H2 evolution. Furthermore, the Au NPs absorb long-wavelength visible light owing to its localized surface plasmon resonance, and the adjacent PtSAs trap the plasmonic hot-electrons for H2 evolution via direct electron transfer effect. Consequently, the PtSAs-Au2.5/PCN exhibits excellent broad-spectrum photocatalytic H2 evolution activity with the H2 evolution rate of 8.8 mmol g-1 h-1 at 420 nm and 264 μmol g-1 h-1 at 550 nm, much higher than that of Au2.5/PCN and PtSAs-PCN, respectively. This work provides a new strategy to design broad-spectrum photocatalysts for energy conversion reaction.

Fabrication of direct Z-scheme Cu2O@V-CN (octa) heterojunction with exposed (111) lattice planes and nitrogen-rich vacancies for rapid sterilization

The Z-scheme heterojunction has demonstrated significant potential for promoting photogenerated carrier separation. However, the rational design of all-solid Z-scheme heterojunctions catalysts and the controversies about carrier transfer path of direct Z-scheme heterojunctions catalysts face various challenges. Herein, a novel heterojunction, Cu₂O@V-CN (octa), was fabricated using V-CN (carbon nitride with nitrogen-rich vacancies) in-situ electrostatic self-wrapping Cu₂O octahedra. Density functional theory (DFT) calculations revealed that the separation of carriers across the Cu₂O@V-CN (octa) heterointerface was directly mapped to the Z-scheme mechanism compared to Cu₂O/V-CN (sphere). This is because the Cu₂O octahedra expose more highly active (111) lattice planes with more terminal Cu atoms and V-CN with abundant nitrogen vacancies to form delocalized electronic structures like electronic reservoirs. This facilitates the wrapping of Cu₂O octahedra by V-CN and protects their stability via tighter interfacial contact, thus enhancing the tunneling of carriers for rapid photocatalytic sterilization. These findings provide novel approaches for designing high-efficiency Cu₂O-based photocatalytic antifoulants for practical applications.

Exploiting the LSPR effect for an enhanced photocatalytic hydrogen evolution reaction

Incorporation of plasmonic metals is one of the most widely adopted strategies for improving the photocatalytic hydrogen evolution reaction (HER) activity of semiconductor photocatalysts. This article summarizes recent advances in the development of plasmonic metal-semiconductor photocatalysts and four localized surface plasmon resonance (LSPR) driven mechanisms by which plasmonic metal nanoparticles can contribute to enhancement of HER activity. In addition, principles for maximizing the contribution of these LSPR driven mechanisms are highlighted to provide insights for future design of plasmonic metal-semiconductor photocatalysts with enhanced HER activity.

Design of the Synergistic Rectifying Interfaces in Mott-Schottky Catalysts

The functions of interfacial synergy in heterojunction catalysts are diverse and powerful, providing a route to solve many difficulties in energy conversion and organic synthesis. Among heterojunction-based catalysts, the Mott-Schottky catalysts composed of a metal-semiconductor heterojunction with predictable and designable interfacial synergy are rising stars of next-generation catalysts. We review the concept of Mott-Schottky catalysts and discuss their applications in various realms of catalysis. In particular, the design of a Mott-Schottky catalyst provides a feasible strategy to boost energy conversion and chemical synthesis processes, even allowing realization of novel catalytic functions such as enhanced redox activity, Lewis acid-base pairs, and electron donor-acceptor couples for dealing with the current problems in catalysis for energy conversion and storage. This review focuses on the synthesis, assembly, and characterization of Schottky heterojunctions for photocatalysis, electrocatalysis, and organic synthesis. The proposed design principles, including the importance of constructing stable and clean interfaces, tuning work function differences, and preparing exposable interfacial structures for designing electronic interfaces, will provide a reference for the development of all heterojunction-type catalysts, electrodes, energy conversion/storage devices, and even super absorbers, which are currently topics of interest in fields such as electrocatalysis, fuel cells, CO₂ reduction, and wastewater treatment.

Plasmonic Metal Mediated Charge Transfer in Stacked Core-Shell Semiconductor Heterojunction for Significantly Enhanced CO2 Photoreduction

Construction of core-shell semiconductor heterojunctions and plasmonic metal/semiconductor heterostructures represents two promising routes to improved light harvesting and promoted charge separation, but their photocatalytic activities are respectively limited by sluggish consumption of charge carriers confined in the cores, and contradictory migration directions of plasmon-induced hot electrons and semiconductor-generated electrons. Herein, a semiconductor/metal/semiconductor stacked core-shell design is demonstrated to overcome these limitations and significantly boost the photoactivity in CO₂  reduction. In this smart design, sandwiched Au serves as a "stone", which "kills two birds" by inducing localized surface plasmon resonance for hot electron generation and mediating unidirectional transmission of conduction band electrons and hot electrons from TiO₂  core to MoS₂  shell. Meanwhile, upward band bending of TiO₂  drives core-to-shell migration of holes through TiO₂ -MoS₂  interface. The co-existence of TiO₂  → Au → MoS₂  electron flow and TiO₂  → MoS₂  hole flow contributes to spatial charge separation on different locations of MoS₂  outer layer for overall redox reactions. Additionally, reduction potential of photoelectrons participating in the CO₂  reduction is elaborately adjusted by tuning the thickness of MoS₂  shell, and thus the product selectivity is delicately regulated. This work provides fresh hints for rationally controlling the charge transfer pathways toward high-efficiency CO₂  photoreduction.

High-Throughput Strategies for the Design, Discovery, and Analysis of Bismuth-Based Photocatalysts

Bismuth-based nanostructures (BBNs) have attracted extensive research attention due to their tremendous development in the fields of photocatalysis and electro-catalysis. BBNs are considered potential photocatalysts because of their easily tuned electronic properties by changing their chemical composition, surface morphology, crystal structure, and band energies. However, their photocatalytic performance is not satisfactory yet, which limits their use in practical applications. To date, the charge carrier behavior of surface-engineered bismuth-based nanostructured photocatalysts has been under study to harness abundant solar energy for pollutant degradation and water splitting. Therefore, in this review, photocatalytic concepts and surface engineering for improving charge transport and the separation of available photocatalysts are first introduced. Afterward, the different strategies mainly implemented for the improvement of the photocatalytic activity are considered, including different synthetic approaches, the engineering of nanostructures, the influence of phase structure, and the active species produced from heterojunctions. Photocatalytic enhancement via the surface plasmon resonance effect is also examined and the photocatalytic performance of the bismuth-based photocatalytic mechanism is elucidated and discussed in detail, considering the different semiconductor junctions. Based on recent reports, current challenges and future directions for designing and developing bismuth-based nanostructured photocatalysts for enhanced photoactivity and stability are summarized.

Facet synergy dominant Z-scheme transition in BiOCl with enhanced 1O2 generation

BiOCl powders with different morphology were obtained through self-assembling. Their photocatalytic performance was tested through degradation of organic dye and mechanism of photocatalytic for obtained samples were investigated. Relevant characterization demonstrated that facet synergy was a main reason of photocatalytic performance promotion due to changed facet exposure and proportion under self-assembling. Theory and experimental analysis manifested that synergistic facet stimulated Z scheme transition in samples with lower (001) facet proportion, which provided favorable condition of ¹O₂ generation and simultaneously generated prominent charge separation. This work unveiled the facet synergy dominant photocatalytic performance improvement in self-assembling system of BiOCl and verified decisive role of facet proportion in constructing Z-scheme facet junction, which also prompted possibility of improving ¹O₂ generation through facet engineering under self-assembling.

An overview on recent progress in photocatalytic air purification: Metal-based and metal-free photocatalysis

Air pollution is becoming a distinctly growing concern and the most pressing universal problem as a result of increased energy consumption, with the multiplication of the human population and industrial enterprises, resulting in the generation of hazardous pollutants. Among these, carbon monoxide, nitrogen oxides, Volatile organic compounds, Semi volatile organic compounds, and other inorganic gases not only have an adverse impact on human health both outdoors and indoors, but have also substantially altered the global climate, resulting in several calamities around the world. Thus, the purification of air is a crucial matter to deal with. Photocatalytic oxidation is one of the most recent and promising technologies, and it has been the subject of numerous studies over the past two decades. Hence, the photocatalyst is the most reassuring aspirant due to its adequate bandgap and exquisite stability. The process of photocatalysis has provided many benefits to the atmosphere by removing pollutants. In this review, our work focuses on four main themes. Firstly, we briefly elaborated on the general mechanism of air pollutant degradation, followed by an overview of the typical TiO₂ photocatalyst, which is the most researched photocatalyst for photocatalytic destruction of gaseous VOCs. The influence of operating parameters influencing the process of photocatalytic oxidation (such as mass transfer, light source and intensity, pollutant concentration, and relative humidity) was then summarized. Afterwards, the progress and drawbacks of some typical photoreactors (including monolithic reactors, microreactors, optical fiber reactors, and packed bed reactors) were described and differentiated. Lastly, the most noteworthy coverage is dedicated to different types of modification strategies aimed at ameliorating the performance of photocatalysts for degradation of air pollutants, which were proposed and addressed. In addition, the review winds up with a brief deliberation for more exploration into air purification photocatalysis.

Silver based photocatalysts in emerging applications

The infinite availability of solar energy grants the potential of fulfilling the energy demands and environmental sustainability requirements with more feasible and reliant renewable energy forms through photocatalysis. In the past decade, the intensive plasmonic effect, suitable work function, superior electrical conductivity and physiochemical properties have made Ag-based photocatalysts attractive components for emerging applications. The local surface plasmon resonance effect (LSPR) provides extra hot-carriers to participate in the photocatalytic process, and Schottky/Ohmic contacts would facilitate charge transfer. Here, recent studies focused on Ag-based photocatalysts for emerging applications are reviewed. Notably, the mechanisms of LSPR, the Schottky barrier and ohmic contacts are introduced together with urgent issues in CO₂ reduction, antibacterial application, H₂ generation, and environmental hazard removal. Additionally, some perspectives and directions on more comprehensive designs on material system, band alignment and functionalization are given to further the exploration in this research area.

Anti-oil-fouling Au/BiOCl coating for visible light-driven photocatalytic inactivation of bacteria

In this work, gold/bismuth oxychloride (Au/BiOCl) nanocomposites with different morphologies were successfully prepared by simple solvothermal method and sodium borohydride reduction method, which exhibited significantly efficient visible-light-driven photocatalytic disinfection for Staphylococcus aureus (S.aureus). Particularly, the flower-like Au/BiOCl nanocomposite showed the highest photocatalytic bactericidal performance among the prepared Au/BiOCl samples. The radical trapping experiments revealed that the hole was the main reactive species responsible for the inactivation of S.aureus over Au/BiOCl composite. The enhanced photocatalytic bactericidal effect could be attributed to the enhanced adsorption intensity of visible light that originated from the surface plasmon resonance (SPR) effect of Au, rapid transfer and space transport of hot electrons caused by the hierarchical structure of BiOCl layered compound. Furthermore, the Au/BiOCl coating prepared on stainless steel wire mesh via in-situ synthesis method exhibited excellent superhydrophilic/underwater superoleophobic performance, which endowed the coating with anti-oil-fouling in water. More importantly, compared with Au/BiOCl powder catalyst, the prepared Au/BiOCl coating with anti-oil-fouling also possessed high photocatalytic bactericidal activity and stable recycling performance.

Optical and Photocatalytic Properties of Br-Doped BiOCl Nanosheets with Rich Oxygen Vacancies and Dominating {001} Facets

Crystal facet engineering and nonmetal doping are regarded as effective strategies for improving the separation of charge carriers and photocatalytic activity of semiconductor photocatalysts. In this paper, we developed a facial method for fabricating oxygen-deficient Br-doped BiOCl nanosheets with dominating {001} facets through a traditional hydrothermal reaction and explored the impact of the Br doping and specific facets on carrier separation and photocatalytic performance. The morphologies, structures, and optical and photocatalytic properties of the obtained products were characterized systematically. The BiOCl samples prepared by the hydrothermal reaction exhibited square-like shapes with dominating {001} facets. Photodeposition results indicated that photoinduced electrons preferred to transfer to {001} facets because of the strong internal static electric fields in BiOCl nanosheets with dominating {001} facets. Br doping not only contributed to the formation of impurity energy levels that could promote light absorption but introduced a large number of surface oxygen vacancies (VO) in BiOCl photocatalysts, which was beneficial for photocatalytic performance. Moreover, the photocatalytic activities of these products under visible light were tested by degradation of rhodamine B (RhB). Because of the synergistic effect of the dominating {001} facets, Br doping, and rich VO, oxygen-deficient Br-doped BiOCl nanosheets exhibited improved carrier separation, visible light absorption, and photocatalytic efficiency.

Bismuth Oxyhalide-Based Materials (BiOX: X = Cl, Br, I) and Their Application in Photoelectrocatalytic Degradation of Organic Pollutants in Water: A Review

An important target of photoelectrocatalysis (PEC) technology is the development of semiconductor-based photoelectrodes capable of absorbing solar energy (visible light) and promoting oxidation and reduction reactions. Bismuth oxyhalide-based materials BiOX (X = Cl, Br, and I) meet these requirements. Their crystalline structure, optical and electronic properties, and photocatalytic activity under visible light mean that these materials can be coupled to other semiconductors to develop novel heterostructures for photoelectrochemical degradation systems. This review provides a general overview of controlled BiOX powder synthesis methods, and discusses the optical and structural features of BiOX-based materials, focusing on heterojunction photoanodes. In addition, it summarizes the most recent applications in this field, particularly photoelectrochemical performance, experimental conditions and degradation efficiencies reported for some organic pollutants (e.g., pharmaceuticals, organic dyes, phenolic derivatives, etc.). Finally, as this review seeks to serve as a guide for the characteristics and various properties of these interesting semiconductors, it discusses future PEC-related challenges to explore.

Unveiling the charge transfer dynamics steered by built-in electric fields in BiOBr photocatalysts

Construction of internal electric fields (IEFs) is crucial to realize efficient charge separation for charge-induced redox reactions, such as water splitting and CO₂ reduction. However, a quantitative understanding of the charge transfer dynamics modulated by IEFs remains elusive. Here, electron microscopy study unveils that the non-equilibrium photo-excited electrons are collectively steered by two contiguous IEFs within binary (001)/(200) facet junctions of BiOBr platelets, and they exhibit characteristic Gaussian distribution profiles on reduction facets by using metal co-catalysts as probes. An analytical model justifies the Gaussian curve and allows us to measure the diffusion length and drift distance of electrons. The charge separation efficiency, as well as photocatalytic performances, are maximized when the platelet size is about twice the drift distance, either by tailoring particle dimensions or tuning IEF-dependent drift distances. The work offers great flexibility for precisely constructing high-performance particulate photocatalysts by understanding charge transfer dynamics.

Recent advances and perspectives for solar-driven water splitting using particulate photocatalysts

The conversion and storage of solar energy to chemical energy via artificial photosynthesis holds significant potential for optimizing the energy situation and mitigating the global warming effect. Photocatalytic water splitting utilizing particulate semiconductors offers great potential for the production of renewable hydrogen, while this cross-road among biology, chemistry, and physics features a topic with fascinating interdisciplinary challenges. Progress in photocatalytic water splitting has been achieved in recent years, ranging from fundamental scientific research to pioneering scalable practical applications. In this review, we focus mainly on the recent advancements in terms of the development of new light-absorption materials, insights and strategies for photogenerated charge separation, and studies towards surface catalytic reactions and mechanisms. In particular, we emphasize several efficient charge separation strategies such as surface-phase junction, spatial charge separation between facets, and polarity-induced charge separation, and also discuss their unique properties including ferroelectric and photo-Dember effects on spatial charge separation. By integrating time- and space-resolved characterization techniques, critical issues in photocatalytic water splitting including photoinduced charge generation, separation and transfer, and catalytic reactions are analyzed and reviewed. In addition, photocatalysts with state-of-art efficiencies in the laboratory stage and pioneering scalable solar water splitting systems for hydrogen production using particulate photocatalysts are presented. Finally, some perspectives and outlooks on the future development of photocatalytic water splitting using particulate photocatalysts are proposed.

Recent advances in degradation of organic pollutant in aqueous solutions using bismuth based photocatalysts: A review

Today, a major concern associated with the environment is the water pollution occurred due to the introduction of variety of persistent organic pollutants and residual dyes from different sources (e.g., dye and dye intermediates industries, paper and pulp industries, textile industries, tannery and craft bleaching industries, pharmaceutical industries, etc.) into our natural water resources. Recently, advanced oxidation processes (AOPs) by photocatalyst have garnered great attention as a new frontier promising eco-friendly and sustainable wastewater treatment technology. Utilization of the photocatalytic technology efficiently is significant for cleaner environment. Bismuth based photocatalyst have aroused widespread attention as a visible light responsive photocatalyst for waste water treatment due to their non-toxicity, low cost, modifiable morphology, and outstanding optical and chemical properties. In this review, we have dealt with the research progress on bismuth-based photocatalysts for waste water treatment. However, it seems to give limitation over pristine photocatalysts such as slow migration of charge carriers, charge carrier recombination, low visible light absorption, etc., Various bismuth based photocatalyst and its modifications via doping, heterojunction, Z-scheme etc., are discussed in detail. Further, the strategies adopted to improve the photocatalytic activity of bismuth based photocatalyst to improve the waste water treatment (mostly drugs and dyes) are critically reviewed. Also, we have discussed the bacterial inactivation by bismuth based photocatalyst. Finally, the challenges and future aspects against bismuth based photocatalyst are explored for further research.

Bulk Superlattice Analogues for Energy Conversion

Energy storage and conversion in a clean, efficient, and safe way is the core appeal of a modern sustainable society, which is built on the development of multifunctional materials. Superlattice structures can integrate the advantage of their sublayers while new phenomena may arise from the interface, which play key roles in modern semiconductor technology; however, additional concerns such as stability and yield challenge their large-scale applications in industrial products. In this Perspective we focus our interest on a distinctive category of easily available multilayered inorganic materials that have well-defined subunit structures and can be regarded as bulk superlattice analogues. We illustrate several specific combining forms of subunits in bulk superlattice analogues, including soft/rigid sublayers, electron/phonon transport sublayers, quasi-two-dimensional layers, and intercalated metal layers. We hope to provide insights into material design and broaden the application scope in the field of energy conversion by integrating the versatility of subunits into these bulk superlattice analogues.

Constructing Schottky junctions via Pd nanosheets on DUT-67 surfaces to accelerate charge transfer

The separation, transfer and recombination of charge often affect the rate of photocatalytic reduction of CO₂. Schottky junctions can promote the rapid separation of space charge. Therefore, in this paper, Pd nanosheets were grown on the surface of DUT-67 by a hydrothermal method, and a Schottky junction was constructed between DUT-67 and Pd. Under the action of the Schottky junction, the CO yield of 0.3-Pd/DUT-67 reached 12.15 μmol/g/h, which was 17 times higher than that of DUT-67. Efficient charge transfer was demonstrated in photochemical experiments. The large specific surface area and the increased light utilization rate also contributed to the increase in the CO₂ reduction efficiency. In addition, the mechanism of Pd/DUT-67 photocatalytic reduction of CO₂ was proposed.

Interface Dynamics in Ag-Cu3P Nanoparticle Heterostructures

Earth-abundant transition metal phosphides are promising materials for energy-related applications. Specifically, copper(I) phosphide is such a material and shows excellent photocatalytic activity. Currently, there are substantial research efforts to synthesize well-defined metal-semiconductor nanoparticle heterostructures to enhance the photocatalytic performance by an efficient separation of charge carriers. The involved crystal facets and heterointerfaces have a major impact on the efficiency of a heterostructured photocatalyst, which points out the importance of synthesizing potential photocatalysts in a controlled manner and characterizing their structural and morphological properties in detail. In this study, we investigated the interface dynamics occurring around the synthesis of Ag-Cu3P nanoparticle heterostructures by a chemical reaction between Ag-Cu nanoparticle heterostructures and phosphine in an environmental transmission electron microscope. The major product of the Cu-Cu3P phase transformation using Ag-Cu nanoparticle heterostructures with a defined interface as a template preserved the initially present Ag{111} facet of the heterointerface. After the complete transformation, corner truncation of the faceted Cu3P phase led to a physical transformation of the nanoparticle heterostructure. In some cases, the structural rearrangement toward an energetically more favorable heterointerface has been observed and analyzed in detail at the atomic level. The herein-reported results will help better understand dynamic processes in Ag-Cu3P nanoparticle heterostructures and enable facet-engineered surface and heterointerface design to tailor their physical properties.

Porous direct Z-scheme heterostructures of S-deficient CoS/CdS hexagonal nanoplates for robust photocatalytic H2 generation

Unique porous S-deficient CoS/CdS hexagonal nanoplates exhibited an outstanding photocatalytic capability for H2 production, due to excellent visible-light response, efficient Z-scheme charge separation, and abundant H2-evolving active sites.

The selective production of CH4via photocatalytic CO2 reduction over Pd-modified BiOCl

The selective production of CH4via photocatalytic CO2 reduction was achieved over Pd-modified BiOCl.

Crystal facet and phase engineering for advanced water splitting

This review covers the principles and recent advances in facet and phase engineering of catalysts for photocatalytic, photoelectrochemical, and electrochemical water splitting. It suggests the basis of catalyst design for advanced water splitting.

General In Situ Photoactivation Route with IPCE over 80% toward CdS Photoanodes for Photoelectrochemical Applications

Cost-effective photoanodes with remarkable electronic properties are highly demanded for practical photoelectrochemical (PEC) water splitting. The ability to manipulate the surface carrier separation and recombination is pivotal for achieving high PEC performance for water splitting. Here, a facile and economical approach is reported for substantially improving the surface charge separation property of CdS photoanodes through in situ photoactivation, which significantly reduces surface charge recombination through the formation of thiosulfate ion which is favorable to the transfer of photogenerated holes and a uniform nanoporous morphology via the dissolving Cd²⁺ with phosphate ions on the surface of CdS. The resulting CdS electrodes through scalable particle transfer method exhibit nearly tripled photocurrents, with an incident-photon-to-current conversion efficiency (IPCE) at 480 nm exceeding 80% at 0.6 V versus reversible hydrogen electrode (RHE). And the CdS thin films prepared from chemical bath deposition display quadrupled photocurrents after the stir and PEC activation, with an IPCE of 91.7% at 455 nm and 0.6 V versus RHE. With the suppression of photocorrosion in alkaline borate buffer, the activated photoanodes show great stability for solar hydrogen production at the sacrifice of sulfite. This work brings insights into the design of nanoporous metal sulfide semiconductors for solar water splitting.