Facet-dependent activation of oxalic acid over hematite nanocrystals under the irradiation of visible light for efficient degradation of pollutants.

Naturally occurring hematite has been widely studied in the Fenton-like system for water pollutant remediation due to its abundance and non-toxicity. However, its inadequate catalytic activity results in difficulty in effectively degrading pollutants in the catalytic degradation system that it constitutes. Thus, we constructed a photochemical system composed of hematite with {001} facet of high activity facet and low-cost and non-toxic oxalic acid (OA) for the removal of various types of pollutants. The removal rate for the degradation of metronidazole, tetracycline hydrochloride, Rhodamine B, and hexavalent chromium by hematite nanoplate with the exposed {001} facet activating OA under visible light irradiation was 4.75, 2.25, 2.33, and 2.74 times than that by the exposed {110} facet, respectively. Density functional theory (DFT) calculation proved that the OA molecule was more easily adsorbed on the {001} facet of hematite than that on the {110} facet, which would favor the formation of the more Fe(III)-OA complex and reactive species. In addition, the reactive site of metronidazole for the attraction of radicals was identified on the basis of the DFT calculation on the molecular occupied orbitals, and the possible degradation pathway for metronidazole included carbon chain fracture, hydroxyethyl-cleavage, denitrogenation, and hydroxylation. Thus, this finding may offer a valuable direction in designing an efficient iron-based catalyst based on facet engineering for the improved activity of Fenton-like systems such as OA activation.

2D WO3-x Nanosheet with Rich Oxygen Vacancies for Efficient Visible-Light-Driven Photocatalytic Nitrogen Fixation.

Oxygen vacancy modulation holds great promise for enhancing the photocatalytic activity for efficient nitrogen fixation under mild conditions. In this work, the two-dimensional WO3-x nanosheets with rich oxygen vacancies were prepared using solvothermal synthesis. The WO3-x nanosheets (rich oxygen vacancies) display nice photocatalytic activity for N2 reduction to ammonia with a high yield rate of 82.41 µmol·gcat-1·h-1 under irradiation of visible light (420 nm), which is 3.59 times higher than that of the WO3-x nanoparticles (poor oxygen vacancies). Electron spin resonance (ESR), N2 adsorption-desorption isotherms, and transient photocurrent responses in the N2 or Ar atmosphere experiments proved that the rich oxygen vacancies, which are induced by the nanosheet structure, could serve as active sites for the chemisorption of N2 and facilitate the electron transfer from unsaturated sites to activated N2. Moreover, based on the analysis of banding energy, the oxygen vacancies not only boosted the ability of visible light harvesting but also elevated the defect energy level to the Fermi level, further inhibiting the defect relaxation effect. The findings offer an insight into the design of the efficient photocatalysts via structure engineering and defect engineering for photocatalytic N2 fixation.

Facet-Dependent Activation of Oxalic Acid over Magnetic Recyclable Fe3S4 for Efficient Pollutant Removal under Visible Light Irradiation: Enhanced Catalytic Activity, DFT Calculations, and Mechanism Insight.

Photo-Fenton-like reaction based on oxalic acid (OA) activation is a promising method for the fast degradation of pollutants due to the low cost and safety. Hence, the magnetic recyclable greigite (Fe3S4) with the exposed {011} facet (FS-011) was prepared using a facile one-pot hydrothermal method and activated OA under visible light irradiation for pollutant removal, in which the removal efficiency values of FS-011 for metronidazole (MNZ) and hexavalent chromium were 2.02 and 1.88 times higher than that of Fe3S4 with the exposed {112} facet, respectively. Density functional theory calculations revealed that OA was more easily adsorbed by the {011} facet of Fe3S4 than by the {112} facet, and the in situ-generated H2O2 preferred to diffuse away from the active sites of the {011} facet of Fe3S4 than from that of the {112} facet, which was conducive to the continuous adsorption and efficient activation of OA. Moreover, the analyses of Fukui index and dual descriptor confirmed the degradation mechanism that the imidazole ring of MNZ was easy to be attacked by electrophilic species, while the amino group of MNZ was easy to be attacked by nucleophilic species. These findings deeply analyzed the mechanism of enhanced OA activation by facet engineering and consolidated the theoretical basis for practical application of Fenton-like reactions.

Facile fabrication of AgI/Sb2O3 heterojunction photocatalyst with enhanced visible-light driven photocatalytic performance for efficient degradation of organic pollutants in water.

The construction of heterojunction is considered as a promising approach to designing highly effective visible-light driven photocatalysts. In this research, the AgI/Sb2O3 heterojunction photocatalyst was synthesized by a simple in situ deposition-precipitation procedure, which was supported by XPS results. Among the prepared samples, the 60% AgI/Sb2O3 samples exhibited the best ARG degradation ratio (98.3%) in 1 h under visible light irradiation, while the pure Sb2O3 and AgI exhibited almost none photocatalytic performance. The trapping experiments and EPR proved that the photo-generated ·O2- and ·OH made major contributions to the photocatalytic degradation of ARG by the 60% AgI/Sb2O3 samples. The enhanced photocatalytic performance of AgI/Sb2O3 heterojunction photocatalysts was ascribed to that the e- produced in the CB of AgI would be transferred to the empty CB of Sb2O3, which could effectively promote separation of photo-induced carries. More importantly, the transfer of electrons from AgI to Sb2O3 would be in favor of restraining the reduction of Ag+ to Ag0 resulting in the good stability of heterojunction photocatalysts. The heterojunction photocatalyst provided in this work might be a prospective candidate for decontamination of water.

Photocatalytic CO2 Conversion of M0.33WO3 Directly from the Air with High Selectivity: Insight into Full Spectrum-Induced Reaction Mechanism.

Natural photosynthesis is a solar light-driven process utilized by plants to convert CO2 and water into carbohydrate molecules. The goal of artificial photosynthesis is the reduction of CO2 directly from air into high purity value-added products at atmospheric pressure. However, its realization, combined with deep mechanism investigation, is a huge challenge. Herein, we demonstrate that hexagonal tungsten bronze M0.33WO3 (M = K, Rb, Cs) series with {010} facets, prepared by a peculiar "water-controllable releasing" solvothermal method, showed excellent full spectrum (UV, visible, and NIR lights)-induced photocatalytic CO2 reduction performance directly from the air at ambient pressure. Particularly, after 4 h near-infrared light irradiation, ca. 4.32% CO2 in the air could be converted into CH3OH with 98.35% selectivity for Rb0.33WO3. The experiments and theoretical calculations unveiled that the introduced alkali metal atom occupied the tunnel of hexagonal structure and donated more free electrons to reconstruct the electronic structure of M0.33WO3, which can enhance the polaron transition, modify the energy band structure, selectively adsorb CO2 rather than O2 from the air, decrease the activation energy of CO2 reaction, and finally make the effective CO2 reduction in the air a reality. This work may provide a new possibility for the practical application of artificial photosynthesis.

Enhanced Generation of Reactive Oxygen Species under Visible Light Irradiation by Adjusting the Exposed Facet of FeWO4 Nanosheets To Activate Oxalic Acid for Organic Pollutant Removal and Cr(VI) Reduction.

In this work, taking FeWO4 nanosheets as an example, the activation of oxalic acid (OA) based on facet engineering for the enhanced generation of active radical species was reported, revealing unprecedented surface Fenton activity for pollutant degradation. Density functional theory calculations confirmed the more efficient generation of reactive oxygen species over FeWO4 nanosheets with the {001} facet exposed (FWO-001) under visible light irradiation compared to the efficiency of FeWO4 nanosheets with the {010} facet exposed (FWO-010), which could be attributed to a higher density of iron and the efficient activation of OA on the {001} facet. The H2O2-derived •OH tended to diffuse away from the active sites of FWO-001 into solution to favor the continuous activation of OA into the active radicals for pollutant redox reactions, but preferred to remain on FWO-010 to hinder the further activation of OA on the {010} facet. Additionally, the generation of •CO2- endowed FeWO4 with a strong reduction ability. Compared with FWO-010, FWO-001 exhibited enhanced redox activity for the catalytic degradation of organic pollutants and Cr(VI) in the optimized conditions. These findings can help in understanding the facet dependent surface Fenton chemistry of catalytic redox reactions and in designing efficient catalysts for environmental decontamination.

Biodegradable silver-loaded polycation modified nanodiamonds/polyurethane scaffold with improved antibacterial and mechanical properties for cartilage tissue repairing.

For cartilage tissue repairing, it remains a key challenge to design implant materials with antibacterial activity, proper degradation rate and mechanical property. In this research, antibacterial nanodiamonds (QND, QND-Ag) modified acrylate-terminated polyurethanes (APU) were prepared. By the addition of nanocomposites, the crystallinity of modified APU obviously increased, which indicates a strong interaction between NDs and APU. Tensile and compression tests were carried out to evaluate the improved mechanical properties. Compared with APU, APU(10%PEG)/QND-Ag possessed the increased modulus and strength, a nevertheless slight decrease in elongation at break. Due to the dual actions of contact-killing of cationic polymers and release-killing of the Ag NPs, QND-Ag-containing polyurethane showed excellent antibacterial activity against Staphylococcus aureus. Moreover, APU containing polyethylene glycol showed a significant increase in degradability rates. Consequently, owing to the dual effect of crystallinity and hydrophilicity, our modified APU exhibited the proper degradation rate adaptable to the healing rate of cartilage tissue. Furthermore, the CCK-8 results demonstrated that synthesized samples were low toxic. Therefore, APU(10%PEG)/QND-Ag holds great promise for the application of cartilage tissue repairing.

Vacancy-Rich Monolayer BiO2-x as a Highly Efficient UV, Visible, and Near-Infrared Responsive Photocatalyst.

Vacancy-rich layered materials with good electron-transfer property are of great interest. Herein, a full-spectrum responsive vacancy-rich monolayer BiO2-x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO2-x is responsible for the enhanced photon response and photo-absorption, which were confirmed by UV/Vis-NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO2-x , monolayer BiO2-x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near-infrared light (NIR) irradiation, which can be attributed to the vacancy VBi-O ''' as confirmed by the positron annihilation spectra. The presence of VBi-O ''' defects in monolayer BiO2-x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts.

Longitudinal photosynthetic gradient in crust lichens' thalli.

In order to evaluate the self-shading protection for inner photobionts, the photosynthetic activities of three crust lichens were detected using Microscope-Imaging-PAM. The false color images showed that longitudinal photosynthetic gradient was found in both the green algal lichen Placidium sp. and the cyanolichen Peltula sp. In longitudinal direction, all the four chlorophyll fluorescence parameters Fv/Fm, Yield, qP, and rETR gradually decreased with depth in the thalli of both of these two lichens. In Placidium sp., qN values decreased with depth, whereas an opposite trend was found in Peltula sp. However, no such photosynthetic heterogeneity was found in the thalli of Collema sp. in longitudinal direction. Microscope observation showed that photobiont cells are compactly arranged in Placidium sp. and Peltula sp. while loosely distributed in Collema sp. It was considered that the longitudinal photosynthetic heterogeneity was ascribed to the result of gradual decrease of incidence caused by the compact arrangement of photobiont cells in the thalli. The results indicate a good protection from the self-shading for the inner photobionts against high radiation in crust lichens.

Recent advances in synthesis and applications of clay-based photocatalysts: a review.

Clay materials including clay minerals and layered double hydroxides (LDHs) have attracted great attention because of their special layer structures, large specific surface areas, and remarkable adsorption capacities. In the past few decades, they have been regarded as important components or precursors for making various functional materials. This paper aims to review and summarize the recent advances in the synthesis and photocatalytic applications of clay-based photocatalysts. Moreover, the effects of surface and structural characteristics of clay-based photocatalysts on photocatalytic properties are also discussed. The clay-based photocatalysts show good application prospects for environmental remediation and energy conversion. Especially, H2 generation and reduction of CO2 into carbon sources can be easily achieved using the LDH-based photocatalysts. Meanwhile, the role of clay materials in the photocatalysis is discussed in detail.

The dominant {001} facet-dependent enhanced visible-light photoactivity of ultrathin BiOBr nanosheets.

The ability to suppress the recombination of the photoinduced charges is the key prerequisite for an excellent photocatalyst, which has attracted extensive and continuous interest in the field of photocatalysis. Herein, we presented a convenient strategy for the one-step selective synthesis of ultrathin BiOBr nanosheets with atomic thickness through a simple solvothermal method. These ultrathin BiOBr nanosheets not only show high exposure percentage of active (001) facets but also have an optimized band structure, which synergistically facilitates the electron-hole pair separation to realize significantly promoted visible-light photocatalytic activity. Our results provide a new avenue and direction for the design of photocatalysts with high visible-light photocatalytic performance.

Degradation of microplastic in water by advanced oxidation processes.

Plastic products have gained global popularity due to their lightweight, excellent ductility, high durability, and portability. However, out of the 8.3 billion tons of plastic waste generated by human activities, 80% of plastic waste is discarded due to improper disposal, and then transformed into microplastic pollution under the combined influence of environmental factors and microorganisms. In this comprehensive study, we present a thorough review of recent advancements in research on the source, distribution, and effect of microplastics. More importantly, we conducted deep research on the catalytic degradation technologies of microplastics in water, including advanced oxidation and photocatalytic technologies, and elaborated on the mechanisms of microplastics degradation in water. Besides, various strategies for mitigating microplastic pollution in aquatic ecosystems are discussed, ranging from policy interventions, the initiative for plastic recycling, the development of efficient catalytic materials, and the integration of multiple technological approaches. This review serves as a valuable resource for addressing the challenge of removing microplastic contaminants from water bodies, offering insights into effective and sustainable solutions.

Study on the Effect of Foam Stability on the Properties of Foamed Lightweight Soils.

The properties of prepared foamed lightweight soils (FLSs) using prefabricated foam requires high foam stability. This paper investigates the geometrical characteristics of different foam densities, different types of foaming agents in the air, and the presence of slurry. Then, it studies their effects on the pore structure and mechanical properties of FLS. Results show that with the increase in foam density the bleeding rate of foam in the air for 1 h increases and the foam with a foam density of 50 kg/m3 is the most stable in the air. The stability of foam in slurry is not directly related to the property of foam in the air. The FLS prepared with the same foaming agent had the best performance with the FLS designed with a foam density of 50 kg/m3, which had the smallest average pore size and the most minor pore size distribution, and had the highest compressive strength. Among the three different foaming agents, Type-S was the best, and the slurry had the lowest rate of increase in wet density after the defoaming test, indicating that the foam had the best stability in the cement slurry. The FLS prepared with the density of 50 kg/m3 using the Type-S foaming agent and mixed with the slurry of cement, fly ash:slag:water = 105:105:140:227.5, was hardened to a mean pore size of 299 µm, and the 7 days, 28 days, and 56 days compressive strengths were 0.92 MPa, 2.04 MPa, and 2.48 MPa, respectively, which had the smallest average pore size and the highest compressive strength among the FLSs prepared using the three foaming agents.

Novel Z-scheme AgI/Sb2WO6 heterostructure for efficient photocatalytic degradation of organic pollutants under visible light: Interfacial electron transfer pathway, DFT calculation and mechanism unveiling.

Developing highly efficient heterostructured photocatalysts with robust redox ability is of great significance to wastewater purification. Herein, a novel Z-scheme AgI/Sb2WO6 heterojunction was successfully constructed via a chemical-precipitation method. The Z-scheme system can serve as a highly efficient photocatalyst for degradation of organic pollutants in water. Under visible light illumination, the degradation efficiency of rhodamine B and tetracycline over the optimal Z-scheme heterojunction can achieve 95% in 12 min and 80% in 8 min, which is 10.8 and 11.4 times higher than that over single Sb2WO6, respectively. Interestingly, low amounts of Ag0 can be generated and attached on the surface of Sb2WO6 during the photocatalytic process, further enhancing the photocatalytic activity of the Z-scheme heterojunction. Based on theoretical calculations, the interfacial internal electric field (IEF) can facilitate the photoexcited electrons at the conduction band (CB) of AgI to consume the photoexcited holes at the valence band (VB) of Sb2WO6, which greatly promotes the Z-scheme charge transfer path. Quenching experiments and electron spin resonance analyses demonstrate superoxide radicals play a major role in the photocatalytic reactions. The concept of constructing a Z-scheme heterojunction photocatalyst with efficient interfacial charge transfer shall provide a design guide for wastewater purification.

Preparation and Properties of Low-Carbon Foamed Lightweight Soil with High Resistance to Sulphate Erosion Environments.

Foamed lightweight soil (FLS) is a lightweight cementitious material containing a large number of tiny closed pores and has been widely used as a filler in places such as railways, roads and airports. However, there has been little research into the resistance of FLS to sulphate attack in practical engineering applications. The performance of FLS against different sulphate erosion concentrations was studied to elucidate the engineering characteristics of using large volumes of FLS as fill material for the road base in the construction of intelligent networked vehicle test sites. The results showed that the compressive strength of FLS prepared using 30% Portland cement (C), 30% granulated blast furnace slag (GBFS), 40% fly ash (FA) and a small amount of a concrete antiseptic agent (CA) as cementitious materials reached 0.8 and 1.9 MPa at 7 and 28 d, respectively, when the wet density was about 600 kg/m3, which met the design requirements. The FLS prepared via the above-mentioned cementitious system had a low carbon emission, with a CO2 emission reduction rate of up to 70%. It also had excellent sulphate attack resistance: the corrosion resistance coefficient of the cementitious material system reached 0.97, which was considerably better than that of C (0.83). For an erosion medium environment with SO42- concentrations of less than 1000 mg/L (moderate), 40% GBFS or FA can be used to prepare FLS. When the concentration of SO42- is less than 4000 mg/L (severe), 30% C, 30% GBFS and 40% FA can be used as cementitious materials, preferably in combination with an appropriate amount of CA, to prepare FLS.

Long-range hydrophobic force enhanced interfacial photocatalysis for the submerged surface anti-biofouling.

Developing anti-biofouling and anti-biofilm techniques is of great importance for protecting water-contact surfaces. In this study, we developed a novel double-layer system consisting of a bottom immobilized TiO2 nanoflower arrays (TNFs) unit and an upper superhydrophobic (SHB) coating along with the assistance of nanobubbles (NBs), which can significantly elevate the interfacial oxygen level by establishing the long-range hydrophobic force between NBs and SHB and effectively maximize the photocatalytic reaction brought by the bottom TNFs. The developed NBs-SHB/TNFs system demonstrated the highest bulk chemical oxygen demand (COD) reduction efficiency at approximately 80% and achieved significant E. coli and Chlorella sp. inhibition efficiencies of 5.38 and 1.99 logs. Meanwhile, the system showed a sevenfold higher resistance to biofilm formation when testing in a wastewater matrix using a wildly collected biofilm seeding solution. These findings provide insights for implementing nanobubble-integrated techniques for submerged surface protection.

Fabrication of 1D/2D BiPO4/g-C3N4 heterostructured photocatalyst with enhanced photocatalytic efficiency for NO removal.

The visible light photocatalytic removal of NO in air is a promising way. BiPO4 is restricted by its wide band gap and can only be responded to ultraviolet light. Herein, 1D BiPO4 nanorod/2D g-C3N4 heterostructured photocatalyst was successfully synthesized via a facile one-step hydrothermal process for efficient visible light photocatalytic removal of NO. With simulated sunlight irradiation, the photocatalytic NO removal activity of the BiPO4/g-C3N4 (64%) is much higher than that of the pure BiPO4 (7.2%) and g-C3N4 (50%). Its excellent photocatalytic performance was ascribed to broadening the light response range to visible light and boosting the separation and transfer of photogenerated electrons and holes. The NO photocatalytic removal mechanism was proposed by the free radical trapping experiment and in situ DRIFTS research. The present study might induce a new means to design BiPO4-based heterostructured photocatalysts for the removal of NO from air pollution under simulated solar light irradiation.

Advances in single-atom catalysts: Design, synthesis and environmental applications.

Over the past few years, single-atom catalysts (SACs) on the horizon have driven rapid and extensive scientific advances in heterogeneous catalysis. Nevertheless, large-scale applications of SACs in the environment have been hindered by the problematic synthesis of catalysts, because the atomic-scale materials with high activation energy are easy to form nanoclusters and nanoparticles in the synthesis stage. The catalytic stability and catalytic activity of SACs in the treatment of complex environmental pollutants also need to be further researched. Herein, the review is built on a comprehensive discussion of the design and synthesis strategies of SACs. The shortcomings of traditional methods and the improvement from different angles like defect regulation are analyzed. Furthermore, the reaction mechanism of SACs in different reactions was summarized, and the environmental applications of SACs, such as wastewater treatment, carbon dioxide reduction, nitrogen reduction, hydrogen evolution, NOx reduction and oxidation, volatile organic compounds removing and environmental monitoring are exemplified to deeply evaluate the prospects and challenges of SACs in the field of environmental protection.

Enhanced visible-light-driven photocatalysis of in-situ reduced of bismuth on BiOCl nanosheets and montmorillonite loading: Synergistic effect and mechanism insight.

Various improvement strategies have been developed to enhance the visible light photocatalytic properties of materials. In these enhancement strategies, bismuth, a non-noble metal-based plasma metal, is deposited on the surface of the photocatalyst, which can improve the visible light response and photocatalytic performance of the photocatalyst. Herein, we constructed montmorillonite loaded BiOCl nanosheets with in situ reduced bismuth by one-step hydrothermal method. As for the results of TEM analysis, the in-situ reduced bismuth nanoparticles with diameters of 5-20 nm were evenly distributed on the surface of BiOCl nanosheets. Due to the surface plasmon resonance (SPR) effect of semi metallic bismuth nanoparticles on the BiOCl nanosheets, the light absorption range of the modified photocatalyst was expanded and its absorption band gap (Eg) was reduced from 3.16 eV (pure BiOCl) to 2.26 eV. Besides, the results of dark adsorption experiments confirmed that the montmorillonite supporter greatly enhanced the adsorption capacity of the modified photocatalyst for pollutants. Moreover, the radical species trapping tests revealed that •O2- and h+ were the pivotal active agents in the pollutant degradation process. The visible light driven photocatalytic degradation rate of TCs and RhB by the modified photocatalyst was 3 and 4 times higher than that of pure BiOCl because of the synergistic effect of montmorillonite supporter and bismuth nanoparticles. The present work provides an innovative strategy for the great feasibility of fabricating low-cost clay and effective bismuth nanoparticles as a substitute for noble metal in environmental pollutants degradation.

Efficient degradation of organic pollutants by activated peroxymonosulfate over TiO2@C decorated Mg-Fe layered double oxides: Degradation pathways and mechanism.

To activate peroxymonosulfate (PMS) is an efficient way for decomposition of non-biodegradable organic pollutants. Herein, Mg-Fe layered double oxides decorated with Ti3C2 MXene-derived TiO2@C (T/LDOs) were fabricated to efficiently activate PMS for the degradation of Rhodamine B (RhB), acid red 1 (AR1), methylene blue (MB), and tetracycline hydrochloride (TC). The T/LDOs catalyst could decompose 95.8% of RhB, 94.8% of AR1, 84.9% of MB within 10 min, and 82.4% of TC within 60 min. The degradation rate constant of RhB in the optimal T/LDOs/PMS system was approximately 2.5 and 15.7 times higher than that in the Mg-Fe LDOs/PMS system and Mg-Fe LDH/PMS system, respectively. Importantly, the T/LDOs exhibited a wide working pH range (3.1-11.0) and high stability with low metal ions leaching, indicating its potential practical applications. Quenching experiments and electronic spin resonance results confirmed that both •O2- and 1O2 were the dominant active species in the T/LDOs/PMS system. In addition, the possible degradation pathway of RhB in the 5%-T/LDOs/PMS system was proposed. Finally, the catalytic mechanism study revealed that the T/LDOs with abundant surface hydroxyl groups and a certain amount of TiO2@C facilitated the electron transfer between ≡Fe(Ⅲ)‒OH complex and HSO5-, boosting the generation of •O2- and 1O2. This study provides an insight into exploiting highly efficient catalysts for PMS activation towards the degradation of organic pollutants.