Photocatalytic production of H2O2 and its in situ utilization over atomic-scale Au modified MoS2 nanosheets

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%.

Emerging single-atom catalysts in the detection and purification of contaminated gases

Single atom catalysts (SACs) show exceptional molecular adsorption and electron transfer capabilities owing to their remarkable atomic efficiency and tunable electronic structure, thereby providing promising solutions for diverse important processes including photocatalysis, electrocatalysis, thermal catalysis, etc. Consequently, SACs hold great potential in the detection and degradation of pollutants present in contaminated gases. Over the past few years, SACs have made remarkable achievements in the field of contaminated gas detection and purification. In this review, we first provide a concise introduction to the significance and urgency of gas detection and pollutant purification, followed by a comprehensive overview of the structural feature identification methods for SACs. Subsequently, we systematically summarize the three key properties of SACs for detecting contaminated gases and discuss the research progress made in utilizing SACs to purify polluted gases. Finally, we analyze the enhancement mechanism and advantages of SACs in polluted gas detection and purification, and propose strategies to address challenges and expedite the development of SACs in polluted gas detection and purification.

Synergistic effect of photoelectrochemical aptasensor based on staggered gap ZnO/BiFeO3 heterojunction coupled with cDNA-CdS sensitizer enabling ultrasensitive assay of kanamycin

Using staggered-gap ZnO/BiFeO3 heterojunction as photoactive materials and cDNA-CdS as the sensitizer for sensitive Kanamycin (KAN) detection, we have created a unique signal-off biosensing platform. The ZnO/BiFeO3 heterojunction provides active sites for aptamer loading and enhances photocurrent responsiveness. Rapid interfacial charge transfer and the separation efficiency of photo-generated carriers are enhanced by sensitization of the ternary heterojunction ZnO/BiFeO3/CdS. Signal-amplified quenching occurs when sensitizers are replaced with sterically hindered KAN. Because of the aptamer's greater affinity for KAN, the replacement of CdS causes a decrease in photocurrent response. Additionally, the weakly conductive aptamer-KAN complex causes steric hindrance, which exacerbates the photoelectrochemical signal-damping effect even more. The photoelectrochemical aptasensor exhibits excellent selectivity and stability, detecting KAN within the range of 0.00005825-0.233 μg/mL with a detection limit of 0.0466 ng/mL (S/N = 3). This work demonstrates the potential of perovskite oxides and their heterostructures for advanced photoelectrochemical biosensing applications.

Tri-modified ferric alginate gel with high regenerative properties catalysts for efficient degradation of rhodamine B

Water pollution caused by dyes has become a focal point of attention. Among them, the heterogeneous Fenton reaction has emerged as an effective solution to this problem. In this study, we designed a ferric alginate gel (PAGM) tri-modified with poly(vinyl alcohol), graphene oxide, and MoS2 as a heterogeneous Fenton catalyst for organic dye degradation. PAGM addresses the drawbacks of alginate gel, such as poor mechanical properties and gel chain dissolution, thereby significantly extending the catalyst's lifespan. The removal rate of rhodamine B by PAGM reached 95.5 % within 15 min, which was 5.9 times higher than that of unmodified ferric alginate gel. Furthermore, due to the π-π interactions, PAGM exhibits unique adsorption properties for pollutants containing benzene rings. Additionally, PAGM can be regenerated multiple times through a simple soaking procedure without any performance degradation. Finally, the reaction column constructed with PAGM maintained an 83.5 % removal rate even after 319 h of continuous wastewater treatment. This work introduces a novel concept for the study of alginate-based gel catalysts in heterogeneous Fenton reactions.

Metal sulphides and their heterojunctions for photocatalytic degradation of organic dyes-A comprehensive review

Water pollution caused by organic dyes is one of the greatest threats to the ecosystem. The removal of dyes from water has remained a challenge for scientists. Recently, metal sulphides have emerged as a potential candidate for water remediation applications. The efficient charge transportation, greater surface-active sites, and low bandgap of metal sulphides make them an excellent choice of semiconductor photocatalysts for degradation of dyes. This review summarises the potential application of metal sulphides and their heterojunctions for the photocatalytic degradation of organic dyes from wastewater. A detailed study has been presented on the synthesis, basics of photodegradation and heterojunctions and photocatalytic activity. The effect of the use of templates, doping agents, synthesis route, and various other factors affecting the photocatalytic activity of metal sulphides have been summarised in this review. The synthesis techniques, characterisation techniques, mechanism of degradation of organic dyes by Z-scheme heterojunction photocatalyst, reusability and stability of metal sulphides, and the scope of future research are also discussed. This study indicates that Scopus-based core gathered data could be used to give an objective overview of the global dye degradation research from 2008 to 2023 (15 years). All data (articles, authors, keywords, and publications) is compiled in the Scopus database. For the bibliometric study, 1962 papers relevant to dye photodegradation by sulfide-based photocatalysts were found, and this number rises yearly. A bibliometric analysis provides a 15-year evaluation of the state-of-the-art research on the impact of metal sulfide-based photocatalysts on the photodegradation of dyes.

Recent Progress of Single-Atom Photocatalysts Applied in Energy Conversion and Environmental Protection

Photocatalysis driven by solar energy is a feasible strategy to alleviate energy crises and environmental problems. In recent years, significant progress has been made in developing advanced photocatalysts for efficient solar-to-chemical energy conversion. Single-atom catalysts have the advantages of highly dispersed active sites, maximum atomic utilization, unique coordination environment, and electronic structure, which have become a research hotspot in heterogeneous photocatalysis. This paper introduces the potential supports, preparation, and characterization methods of single-atom photocatalysts in detail. Subsequently, the fascinating effects of single-atom photocatalysts on three critical steps of photocatalysis (the absorption of incident light to produce electron-hole pairs, carrier separation and migration, and interface reactions) are analyzed. At the same time, the applications of single-atom photocatalysts in energy conversion and environmental protection (CO₂ reduction, water splitting, N₂ fixation, organic macromolecule reforming, air pollutant removal, and water pollutant degradation) are systematically summarized. Finally, the opportunities and challenges of single-atom catalysts in heterogeneous photocatalysis are discussed. It is hoped that this work can provide insights into the design, synthesis, and application of single-atom photocatalysts and promote the development of high-performance photocatalytic systems.

Photocatalytic Synthesis of Hydrogen Peroxide from Molecular Oxygen and Water

Hydrogen peroxide is a powerful and green oxidant that allows for the oxidation of a wide span of organic and inorganic substrates in liquid media under mild reaction conditions, and forms only molecular water and oxygen as end products. Hydrogen peroxide is therefore used in a wide range of applications, for which the well-documented and established anthraquinone autoxidation process is by far the dominating production method at the industrial scale. As this method is highly energy consuming and environmentally costly, the search for more sustainable synthesis methods is of high interest. To this end, the article reviews the basis and the recent development of the photocatalytic synthesis of hydrogen peroxide. Different oxygen reduction and water oxidation mechanisms are discussed, as well as several kinetic models, and the influence of the main key reaction parameters is itemized. A large range of photocatalytic materials is reviewed, with emphasis on titania-based photocatalysts and on high-prospect graphitic carbon nitride-based systems that take advantage of advanced bulk and surface synthetic approaches. Strategies for enhancing the performances of solar-driven photocatalysts are reported, and the search for new, alternative, photocatalytic materials is detailed. Finally, the promise of in situ photocatalytic synthesis of hydrogen peroxide for water treatment and organic synthesis is described, as well as its coupling with enzymes and the direct in situ synthesis of other technical peroxides.

Single-Atom Catalysts in Environmental Engineering: Progress, Outlook and Challenges

Recently, single-atom catalysts (SACs) have attracted wide attention in the field of environmental engineering. Compared with their nanoparticle counterparts, SACs possess high atomic efficiency, unique catalytic activity, and selectivity. This review summarizes recent studies on the environmental remediation applications of SACs in (1) gaseous: volatile organic compounds (VOCs) treatment, NO_x reduction, CO₂ reduction, and CO oxidation; (2) aqueous: Fenton-like advanced oxidation processes (AOPs), hydrodehalogenation, and nitrate/nitrite reduction. We present the treatment activities and reaction mechanisms of various SACs and propose challenges and future opportunities. We believe that this review will provide constructive inspiration and direction for future SAC research in environmental engineering.

Mo-Based Heterogeneous Interface and Sulfur Vacancy Synergistic Effect Enhances the Fenton-like Catalytic Performance for Organic Pollutant Degradation

Heterogeneous Fenton-like reactions (HFLRs) based on the in situ electrochemical generation of hydrogen peroxide (H₂O₂) are one of the green methods to remediate organic pollutants in wastewater. However, the design of Fenton-like catalysts with specific active sites and high pollutant degradation rate is still challenging. Here, MoS₂-MoC and MoS₂-Mo₂N catalytic cathodes with heterojunctions were successfully prepared, and the mechanism by which hydroxyl radicals and singlet oxygen (¹O₂) were generated cleanly without adding chemical additives other than oxygen was clarified. The composite catalysts contained more sulfur vacancies, and the catalytic cathode achieved a high paracetamol pollutant degradation efficiency with 0.17 kWh g^-1 TOC specific energy consumption. And almost 5 times higher activity was achieved compared to a pure MoS₂ catalytic cathode. Experimental studies confirmed that the production of ¹O₂ was based on the transformation of superoxide radicals by Mo⁶⁺, and ¹O₂ accounted for approximately 66% of the total degradation and enhanced the nonradical behavior in the reaction. This work provides a sustainable strategy for pollutant utilization, which is valuable for solving the difficult problems of HFLRs and developing new environmental remediation technologies.

Visible Light-Active Ternary Heterojunction Photocatalyst for Efficient CO2 Reduction with Simultaneous Amine Oxidation and Sustainable H2O2 Production

The present work described a unique approach for CO₂ reduction to methanol along with the oxidation of various amines to the corresponding imines and photocatalytic H₂O₂ production from H₂O and molecular O₂ using a heterojunction photocatalyst made up of ZnIn₂S₄/Ni₁₂P₅/g-C₃N₄(NCZ) under visible light irradiation. The photocatalysts were synthesized via a high-temperature treatment of nickel and phosphorous precursors with g-C₃N₄ followed by decoration of ZnIn₂S₄. The synthesized photocatalysts were characterized using various spectroscopic and microscopic techniques. The density functional theory (DFT) studies suggested the participation of the valence band maximum (VBM) from Ni₁₂P₅ and the conduction band maximum (CBM) from ZnIn₂S₄ in the ternary NCZ heterojunction. The ternary composite exhibited superior photocatalytic activity compared to that of its individual components due to the formation of a heterojunction, thereby enhancing the transfer efficiency of electrons from the conduction band of g-C₃N₄ to that of ZnIn₂S₄ using Ni₁₂P₅ as an electron bridge. Moreover, the reduced band gap of the ternary heterojunction played a key role in its higher efficiency.

Recent progress in the design of photocatalytic H2O2 synthesis system

Photocatalytic synthesis of hydrogen peroxide under mild reaction conditions is a promising technology. This article will review the recent research progress in the design of photocatalytic H₂O₂ synthesis systems. A comprehensive discussion of the strategies that could solve two essential issues related to H₂O₂ synthesis. That is, how to improve the reaction kinetics of H₂O₂ formation via 2e^- oxygen reduction reaction and inhibit the H₂O₂ decomposition through a variety of surface functionalization methods. The photocatalyst design and the reaction mechanism will be especially stressed in this work which will be concluded with an outlook to show the possible ways for synthesizing high-concentration H₂O₂ solution in the future.

Visible light-driven H2O2 synthesis over Au/C3N4: medium-sized Au nanoparticles exhibiting suitable built-in electric fields and inhibiting reverse H2O2 decomposition

Visible light-driven H₂O₂ production presents the unique merits of sustainability and environmental friendliness. The size of noble metal nanoparticles (NPs) determines their dispersion and electronic structure and greatly affects their photocatalytic activity. In this work, a series of sized Au NPs over C₃N₄ were modulated for H₂O₂ production. The results show that there is a volcanic trend in H₂O₂ with the decrease of Au particle size, and the highest H₂O₂ production rate of 1052 μmol g^-1 h^-1 is obtained from medium-sized Au particles (∼8.7 nm). The relationship between structure and catalytic performance is supported by experimental and theoretical methods. (1) First, medium-sized Au NPs promote photon absorption, and have a suitable built-in electric field at the heterojunction, which can be successfully tuned to achieve a more efficient h⁺-e^- spatial separation. (2) Second, medium-sized Au NPs enhance O₂ adsorption, and create selective 2e^- O₂ reduction reaction sites. (3) Particularly, medium-sized Au NPs promote the desorption of produced H₂O₂ and inhibit H₂O₂ decomposition, finally leading to the highest H₂O₂ selectivity. Excellent catalytic performance will be obtained by finely optimizing the particle size in a certain range. This work provides a new idea for preparing high efficiently photocatalysts for H₂O₂ production.

Single-atom site catalysts for environmental remediation: Recent advances

Single-atom site catalysts (SACs) can maximize the utilization of active metal species and provide an attractive way to regulate the activity and selectivity of catalytic reactions. The adjustable coordination configuration and atomic structure of SACs enable them to be an ideal candidate for revealing reaction mechanisms in various catalytic processes. The minimum use of metals and relatively tight anchoring of the metal atoms significantly reduce leaching and environmental risks. Additionally, the unique physicochemical properties of single atom sites endow SACs with superior activity in various catalytic processes for environmental remediation (ER). Generally, SACs are burgeoning and promising materials in the application of ER. However, a systematic and critical review on the mechanism and broad application of SACs-based ER is lacking. Herein, we review emerging studies applying SACs for different ERs, such as eliminating organic pollutants in water, removing volatile organic compounds, purifying automobile exhaust, and others (hydrodefluorination and disinfection). We have summarized the synthesis, characterization, reaction mechanism and structural-function relationship of SACs in ER. In addition, the perspectives and challenges of SACs for ER are also analyzed. We expect that this review can provide constructive inspiration for discoveries and applications of SACs in environmental catalysis in the future.

A self-sufficient photo-Fenton system with coupling in-situ production H2O2 of ultrathin porous g-C3N4 nanosheets and amorphous FeOOH quantum dots

Photo-Fenton degradation of pollutants in wastewater involving hydrogen peroxide (H₂O₂) and Fe²⁺ ions to produce hydroxyl radicals (·OH) with high oxidative activity is an ideal and feasible choice in advanced oxidation processes (AOPs). However, the photo-Fenton degradation application is limited by the range of acidic pH and the external introduction of H₂O₂ and Fe²⁺ ions. Herein, a self-sufficient photo-Fenton system was developed by coupled ultrathin porous g-C₃N₄ (UPCN) nanosheets that spontaneously produce H₂O₂ with amorphous FeOOH quantum dots (QDs) via in-situ deposition method for efficient photo-Fenton degradation of oxytetracycline (OTC) under natural pH condition. The enhancement of photocatalytic degradation activity comes from the synergistic effect of amorphous FeOOH QDs and UPCN nanosheets as follows: on the one hand, the formation of photo-Fenton system combining in-situ generation H₂O₂ of UPCN with amorphous FeOOH QDs can better boost photocatalytic activity for degrading OTC solution in natural pH under light illumination; on the other hand, the ultrathin porous structure of UPCN can better promote the rapid transfer and dispersion of photo-generated electrons from UPCN to amorphous FeOOH QDs and then Fe³⁺ is reduced to Fe²⁺ to participate in the Fenton catalytic reaction.

Protonated g-C3N4 coated Co9S8 heterojunction for photocatalytic H2O2 production

Photocatalytic H₂O₂ production is an eco-friendly technique because only H₂O, molecular O₂ and light are involved. However, it still confronts the challenges of the unsatisfactory productivity of H₂O₂ and the dependence on organic electron donors or high purity O₂, which restrict the practical application. Herein, we construct a type-II heterojunction of the protonated g-C₃N₄ coated Co₉S₈ semiconductor for photocatalytic H₂O₂ production. The ultrathin g-C₃N₄ uniformly spreads on the surface of the dispersed Co₉S₈ nanosheets by a two-step method of protonation and dip-coating, and exhibits improved photogenerated electrons transportability and e^--h⁺ pairs separation ability. The photocatalytic system can achieve a considerable productivity of H₂O₂ to 2.17 mM for 5 h in alkaline medium in the absence of the organic electron donors and pure O₂. The optimal photocatalyst also obtains the highest apparent quantum yield (AQY) of 18.10% under 450 nm of light irradiation, as well as a good reusability. The contribution of the type-II heterojunction is that the migrations of electrons and holes within the interface between g-C₃N₄ and Co₉S₈ matrix promote the separation of photocarriers, and another channel is also opened for H₂O₂ generation. The accumulated electrons in conduction band (CB) of Co₉S₈ contribute to the major channel of two-electron reduction of O₂ for H₂O₂ production. Meanwhile, the electrons in CB of g-C₃N₄ participate in the single electron reduction of O₂ as an auxiliary channel to enhance the H₂O₂ production.

In-situ production and activation of H2O2 for enhanced degradation of roxarsone by FeS2 decorated resorcinol-formaldehyde resins

Fenton technology performs well in high-risk roxarsone (ROX) removal, but it is limited by the high H₂O₂ transportation and storage risks. Herein, FeS₂ decorated resorcinol-formaldehyde resins (FeS₂-RFR) were successfully prepared to in-situ produce and utilize H₂O₂ for efficient removal of ROX. Under solar light illumination, resorcinol-formaldehyde resins (RFR) efficiently generated a high concentration of H₂O₂, with a yield of 500 μmol g^-1 h^-1. FeS₂ can in-situ decompose H₂O₂ to generate ·OH, participating in the oxidation of ROX. As a result, the FeS₂-RFR catalyst degraded more than 97% of ROX within 2 h and ROX was selectively degraded into low-toxic As(V), which can be simply removed by traditional adsorption or precipitation processes. During the degradation of ROX, ·OH played a dominant role. Moreover, the cations (Na⁺, K⁺, and Ca²⁺), anions (SO₄^2-, Cl^-), and humic acid had no noticeable inhibition effect on ROX removal. Furthermore, FeS₂-RFR can still remove 70% of ROX even after three cycles, proving that this in-situ photo-Fenton system exhibited stability. This study innovatively proposed a double-active site FeS₂-RFR photocatalyst for in-situ production and activation of H₂O₂ and showed a sustainable and eco-friendly way for organoarsenic compounds degradation.

Lignin-Supported Heterogeneous Photocatalyst for the Direct Generation of H2O2 from Seawater

The development of smart and sustainable photocatalysts is in high priority for the synthesis of H₂O₂ because the global demand for H₂O₂ is sharply rising. Currently, the global market share for H₂O₂ is around 4 billion US$ and is expected to grow by about 5.2 billion US$ by 2026. Traditional synthesis of H₂O₂ via the anthraquinone method is associated with the generation of substantial chemical waste as well as the requirement of a high energy input. In this respect, the oxidative transformation of pure water is a sustainable solution to meet the global demand. In fact, several photocatalysts have been developed to achieve this chemistry. However, 97% of the water on our planet is seawater, and it contains 3.0-5.0% of salts. The presence of salts in water deactivates the existing photocatalysts, and therefore, the existing photocatalysts have rarely shown reactivity toward seawater. Considering this, a sustainable heterogeneous photocatalyst, derived from hydrolysis lignin, has been developed, showing an excellent reactivity toward generating H₂O₂ directly from seawater under air. In fact, in the presence of this catalyst, we have been able to achieve 4085 μM of H₂O₂. Expediently, the catalyst has shown longer durability and can be recycled more than five times to generate H₂O₂ from seawater. Finally, full characterizations of this smart photocatalyst and a detailed mechanism have been proposed on the basis of the experimental evidence and multiscale/level calculations.

Photocatalytic H2O2 production and removal of Cr (VI) via a novel Lu3NbO7: Yb, Ho/CQDs/AgInS2/In2S3 heterostructure with broad spectral response

The low-usage of solar energy and the sluggish separation efficiency of the photogenerated electrons/holes pairs are the obstacles in the practical application of photocatalysts. The integration of upconversion and Z-scheme heterojunction is expected to break the barriers to achieve the efficient charge separation and broaden near-infrared light absorption. Herein, an effective indirect Z scheme AgInS₂/In₂S₃ heterostructure with carbon quantum dots (CQDs, as the electron conduction medium) and Lu₃NbO₇:Yb, Ho (as upconversion function) has been successfully synthesized. Consequently, the Lu₃NbO₇: Yb, Ho/CQDs/AgInS₂/In₂S₃ heterostructure exhibited superior photocatalytic activities for Cr(VI) reduction and H₂O₂ production, reducing 99.9% of Cr(VI)(20 ppm, 15 min) and 78.5% of Cr(VI) (40 ppm, 30 min) with visible light irradiation as well as 94.0% of Cr(VI) (20 ppm, 39 min) under NIR light irradiation. Simultaneously, the heterostructure could generate 902.9 μM H₂O₂ for 5 h under visible light irradiation. The intensive photocatalytic properties could primarily be attributed to the boosted light absorption capacity, the improved solar-to-energy conversion by the remarkable upconversion capacity of Lu₃NbO₇: Yb, Ho/CQDs and the faster charge transfer through a Z-schematic pathway. This work is anticipated to open a novel "window" for designing the efficient photocatalysts by coupling of Lu₃NbO₇: Yb, Ho and CQDs.

Recent progress of noble metals with tailored features in catalytic oxidation for organic pollutants degradation

With the increasing serious water pollutions, an increasing interest has given for the nanocomposites as environmental catalysts. To date, noble metals-based nanocomposites have been extensively studied by researchers in environmental catalysis. In detail, serving as key functional parts, noble metals are usually combined with other nanomaterials for rationally designing nanocomposites, which exhibit enhanced catalytic properties in pollutants removal. Noble metals in the nanocomposites possess tailored properties, thus playing different important roles in catalytic oxidation reactions for pollutants removal. To motivate the research and elaborate the progress of noble metals, this review (i) summarizes advanced characterization techniques and rising technology of theoretical calculation for evaluating noble metal, and (ii) classifies the roles according to their disparate mechanism in different catalytic oxidation reactions. Meanwhile, the enhanced mechanism and influence factors are discussed. (iii) The conclusions, facing challenges and perspectives are proposed for further development of noble metals-based nanocomposites as environmental catalysts.

Metal-Support Interactions of Single-Atom Catalysts for Biomedical Applications

The development of single-atom catalysts (SACs) has become a rapidly growing research field. It is a critical challenge to understand the interactions between the single-atom metal active sites and the support materials. Recently, original research reports of SACs in biomedical applications have emerged in the literature, yet this topic has seldom been reviewed. Here, this review focuses on the latest advances in single-atom catalysis for biomedical applications and highlights the keys for the design of SACs, such as understanding the interactions between metals and supports and classifying various enzyme-like activities. This review helps bridge the knowledge of multiple disciplines and provides prospects regarding the development of SACs for biomedicine.

Boosting photocatalytic degradation of tetracycline under visible light over hierarchical carbon nitride microrods with carbon vacancies

Graphitic carbon nitride is considered as one of the promising photocatalysts for pollution elimination from wastewater. Manipulating the microstructure of carbon nitride remains a challengeable task, which is essential for improving light absorption, separating photogenerated carrier and creating reactive sites. Herein, a carbon vacancy modified hierarchical carbon nitride microrod (CN1.5) has been prepared templated from a melamine-NH₂OH·HCl complex. The hierarchical microrods are demonstrated to be comprised of interconnected nanosheets with rich carbon vacancies, which endows it with high specific surface area, enhanced light utilization efficiency, available reactive sites, improved charge carrier separation and numerous mass-transport channels. The resultant photocatalyst CN1.5 exhibits an excellent photodegradation efficiency of 87.9% towards tetracycline under visible light irradiation. The remarkable apparent rate constant of 4.91 × 10^-2 min^-1 is 7.3 times higher than that of bulk CN. In addition, the degradation pathways are deduced base on the observation of degradation intermediates generating in the photocatalytic process. Mechanism investigation indicates that the major contribution for photodegradation is attributed to ·O₂^-, ¹O₂ and H₂O₂ species. This work provides new insights into advancing carbon nitride's microstructure to improve photocatalytic degradation performance for highly efficient antibiotic removal and environment remediation.

Efficient photocatalytic hydrogen peroxide generation coupled with selective benzylamine oxidation over defective ZrS3 nanobelts

Photocatalytic hydrogen peroxide (H₂O₂) generation represents a promising approach for artificial photosynthesis. However, the sluggish half-reaction of water oxidation significantly limits the efficiency of H₂O₂ generation. Here, a benzylamine oxidation with more favorable thermodynamics is employed as the half-reaction to couple with H₂O₂ generation in water by using defective zirconium trisulfide (ZrS₃) nanobelts as a photocatalyst. The ZrS₃ nanobelts with disulfide (S₂^2-) and sulfide anion (S^2-) vacancies exhibit an excellent photocatalytic performance for H₂O₂ generation and simultaneous oxidation of benzylamine to benzonitrile with a high selectivity of >99%. More importantly, the S₂^2- and S^2- vacancies can be separately introduced into ZrS₃ nanobelts in a controlled manner. The S₂^2- vacancies are further revealed to facilitate the separation of photogenerated charge carriers. The S^2- vacancies can significantly improve the electron conduction, hole extraction, and kinetics of benzylamine oxidation. As a result, the use of defective ZrS₃ nanobelts yields a high production rate of 78.1 ± 1.5 and 32.0 ± 1.2 μmol h^-1 for H₂O₂ and benzonitrile, respectively, under a simulated sunlight irradiation.

Fenton/Fenton-like processes with in-situ production of hydrogen peroxide/hydroxyl radical for degradation of emerging contaminants: Advances and prospects

Fenton processes based on the reaction between Fe²⁺ and H₂O₂ to produce hydroxyl radicals, have been widely studied and applied for the degradation of toxic organic contaminants in wastewater due to its high efficiency, mild condition and simple operation. However, H₂O₂ is usually added by bulk feeding, which suffers from the potential risks during the storage and transportation of H₂O₂ as well as its low utilization efficiency. Therefore, Fenton/Fenton-like processes with in-situ production of H₂O₂ have received increasing attention, in which H₂O₂ was in-situ produced through O₂ activation, then decomposed into hydroxyl radicals by Fenton catalysts. In this review, the in situ production of H₂O₂ for Fenton oxidation was introduced, the strategies for activation of O₂ to generate H₂O₂ were summarized, including chemical reduction, electro-catalysis and photo-catalysis, the influencing factors and the mechanisms of the in situ production and utilization of H₂O₂ in various Fenton/Fenton-like processes were analyzed and discussed, and the applications of these processes for the degradation of toxic organic contaminants were summarized. This review will deepen the understanding of the tacit cooperation between the in situ production and utilization of H₂O₂ in Fenton process, and provide the further insight into this promising process for degradation of emerging contaminants in industrial wastewater.

Metal-Organic-Framework-Based Photocatalysts Optimized by Spatially Separated Cocatalysts for Overall Water Splitting

Efficient charge separation and utilization are critical factors in photocatalysis. Herein, it is demonstrated that the complete spatial separation of oxidation and reduction cocatalysts enhances the efficacy of charge separation and surface reaction. Specifically, a Pt@NH₂ -UiO-66@MnO_x (PUM) heterostructured photocatalyst with Pt and MnO_x as cocatalysts is designed for the optimization of the NH₂ -UiO-66 photocatalyst. Compared with the pristine NH₂ -UiO-66, Pt@NH₂ -UiO-66 (PU), and NH₂ -UiO-66@MnO_x (UM) samples, the PUM sample exhibits the highest hydrogen production activity. As cocatalysts, Pt favors trapping of electrons, while MnO_x tends to collect holes. Upon generation from NH₂ -UiO-66, electrons and holes flow inward and outward of the metal-organic framework photocatalyst, accumulating on the corresponding cocatalysts, and then take part in the redox reactions. The PUM photocatalyst greatly prolongs the lifetime of the photogenerated electrons and holes, which favors the electron-hole separation. Furthermore, the PUM sample facilitates overall water splitting in the absence of sacrificial agents, thereby demonstrating its potential as a modification method of MOF-type semiconductors for the overall water-splitting reaction.

Single-Atom Catalysts across the Periodic Table

Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.