Review on inorganic and polymeric materials-coordinated metal-organic-framework photocatalysts for green hydrogen evolution

Metal-organic frameworks(MOFs)possess a distinct advantage over conventional heterogeneous photocatalysts because of their carefully defined architecture and particular pores,which facilitate the targeted incorporation of other efficient cocatalysts or semiconductor materials.The integration of MOFs with other materials has resulted in significant breakthroughs,as the coupled materials improve the performance due to the combined effect.The unique MOF structures allow them to host foreign materials,which results in harvesting the visible region of the solar spectrum and effectively mitigating charge recombination by promoting charge separation.The review presents an evaluation of the latest developments in the utilization of surface and/or pore chemistry of MOF-supported heterojunctions for photocatalytic green-hydrogen generation with a basic understanding of the mechanism involved.The review begins with the basic principles of photocatalysis,the significance of MOFs,their optical properties,the methods used for synthesizing MOFs,and their coordination with other inorganic and polymeric materials.Furthermore,methods to increase photocatalytic H2 evolution using MOF-supported heterojunction have been proposed as standard practice.Lastly,to address environmental challenges,we highlight the future potential of MOF-supported heterojunctions for use in green-energy production.We hope that this review provides guidance to researchers in the development of effective heterojunctions based on MOFs to address challenges in energy applications and catalytic processes.

铝板为基础的S掺杂TiO_2催化分解有毒有机气体(英文)

S-doped TiO2(S-TiO2) films were immobilized on flexible low-cost aluminum sheets(S-TiO2-AS) using a sol-gel dipping process and low post-processing temperatures. The photocatalytic degradation of toxic organic vapors using the prepared films was evaluated using a continuous-flow glass tube under visible light exposure. The surface properties of the S-TiO2-AS and TiO2-AS films were examined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. The photolysis of benzene, toluene, ethyl benzene, and xylene(BTEX) did not occur on the bare AS. In contrast, the photocatalytic degradation efficiencies of the target pollutants using S-TiO2-AS were higher than those obtained using reference TiO2-AS photocatalyst. In particular, the average photocatalytic degradation efficiencies of BTEX using S-TiO2-0.8-AS(S/Ti ratio = 0.8) over a 3-h process were 34%, 78%, 91%, and 94%, respectively, whereas those of TiO2-AS were 2%, 11%, 21%, and 36%, respectively. The photocatalytic decompo-sition efficiencies of BTEX under visible irradiation using S-TiO2-AS increased with increasing S/Ti ratios from 0.2 to 0.8, but decreased when the ratio further increased to 1.6. Thus, S-TiO2-AS can be prepared using optimal S/Ti ratios. The degradation of BTEX over S-TiO2-AS depended on the air flow rates and initial concentrations of the target chemical. Overall, under optimal conditions, S-TiO2-AS can be effectively applied for the purification of toxic organic vapors.

节能发光二极管照射下光催化降解染料的最新进展(英文)

Light emitting diodes(LEDs) are gaining recognition as a convenient and energy-efficient light source for photocatalytic application. This review focuses on recent progress in the research and development of the degradation of dyes in water under LED light irradiation and provides a brief overview of photocatalysis, details of the LEDs commonly employed, a discussion of the advantages of LEDs over traditional ultraviolet sources and their application to photocatalytic dye degradation. We also discuss the experimental conditions used, the reported mechanisms of dye degradation and the various photocatalytic reactor designs and pay attention to the different types of LEDs used, and their power consumption. Based on a literature survey, the feasibility, benefits, limitations, and future prospects of LEDs for use in photocatalytic dye degradation are discussed in detail.

Photocatalytic decomposition of mobile-source related pollutants using a continuous-flow reactor

This study evaluated the application of a continuous-flow photocatalytic reactor for the control of two mobile-derived pollutants, methyl-tertiary butyl ether （MTBE） and naphthalene, present at in-vehicle levels. Variables tested for this study included the hydraulic diameter （HD）, stream flow rate （SFR）, relative humidity （RH）, and feeding type （FT）. The fixed parameters included contaminant concentration, ultraviolet light source, and the weight of TiO2. In all experimental conditions the adsorption process reached equilibrium within 30 to 180 min for the target compounds, and the outlet concentrations of the photocatalytic oxidation （PCO） reactor while operating reached a steady state within 60 to 180 min. The degradation of the target compounds was dependent on RH, HD, FT, or SFR. The PCO system exhibited high degradation （up to nearly 100% for certain conditions） and mineralization efficiencies of target compounds, suggesting that this system can effiectively be employed to improve indoor air quality. Moreover, it was confirmed that trichloroethylene at urban-ambient level also could enhance the degradation efficiency of naphthalene when applying the PCO technology inside vehicles.

发光二极管用于活性炭负载光催化剂反应器中挥发性有机化合物的降解(英文)

The applicability of ultraviolet-light emitting diodes(LEDs)as a light source for photocatalysis using granular activated charcoal (GAC)impregnated with transition metal-enhanced photocatalysts for the control of volatile organic compounds(VOCs)was investigated. Two target compounds(toluene and methyl mercaptan)were selected to evaluate the removal activities of the TiO2/GAC composites.The photocatalysts were prepared by a sol-gel method.Methyl trimethoxy silane was added as a precursor sol solution to bind the photocatalyst with the GAC.Metal(Zn 2+ ,Fe 3+ ,Ag + ,and Cu 2+ )enhanced TiO2/GAC composites were prepared and tested for their photocatalytic activities under 400 nm LED irradiation.The specific surface area(SSA)and the surface chemical composition of the prepared composites were investigated.The SSAs of all the impregnated composites were similar to those of pure GAC.Both field emission-scanning electron microscopy and energy dispersive spectroscopic analysis confirmed that titanium and the impregnated metals were deposited on the surface of the adsorbent.The breakthrough time for GAC toward toluene or methyl mercaptan gas increased upon photocatalytic impregnation and LED illumination.Using different binders affected the breakthrough time of the TiO2/GAC composite and the addition of zinc oxide to TiO2 increased the VOC removal capacity of the GAC composite.

Visible-light-activated N-doped CQDs/g-C3N4/Bi2WO6 nanocomposites with different component arrangements for the promoted degradation of hazardous vapors

To investigate whether the arrangement of componentsin multi-composite photocatalysts may affect their photocatalytic properties,due to different charge-transfer routes,two ternary-nanocomposite photocatalysts with different component arrangements,comprising N-doped carbon quantum dots(NCQDs),g-C3N4(CN),and Bi2WO6(BWO)(hereafter referred to as NCQDs/CN/BWO),were developed,and the photocatalytic degradation of model hazardous vapors under visible-light illumination was investigated.Type I NCQDs/CN/BWO,which was developed by the combination of NCQDs/BWO and CN,exhibited photocatalytic ability superior to that of type II NCQDs/CN/BWO,which was developed by the combination of CN/BWO and NCQDs;the superior photocatalytic ability corresponded to the dual properties of NCQDs:charge mediation and upconversion photoluminescence.Moreover,the photocatalytic ability of NCQDs/CN/BWO was greater than those of the reference catalysts;in addition,this photocatalyst exhibited outstanding photochemical stability.Additionally,the effects of CN/(BWO+CN)weight ratio of the CN/BWO dual nanocomposites and the NCQDs/(BWO+CN+NCQDs)weight percentage of NCQDs/CN/BWO ternary nanocomposites on the pollutant removal efficiency were investigated.The plausible mechanisms over the two NCQDs/CN/BWO photocatalysts for the degradation of hazardous vapors were discussed.The component arrangement approach proposed herein afforded a technique toward the perceptive development of novel multi-component heterostructures for the photocatalytic degradation of hazardous vapors.

2D/2D BiOIO_(3)/g-C_(3)N_(4) S-scheme hybrid heterojunction with face-to-face interfacial contact for effective photocatalytic H_(2) production and norfloxacin degradation

A two-dimensional(2D)/2D hybrid heterojunction with face-to-face interfacial assembly is a desirable dimensionality design with significant potential for various photocatalytic applications due to the large interfacial contact area,which facilitates charge migration and separation.Herein,we developed an ef-ficient 2D/2D hybrid heterojunction consisting of BiOIO 3 nanoplates(BIO)and g-C_(3)N_(4) nanosheets(CN)using a simple but effective in situ growth method for photocatalytic aqueous antibiotic degradation and H_(2) generation.The face-to-face interfacial assembly of the BIO and CN components in the BIO/CN hy-brid heterojunction was verified using electron microscopy.Remarkably,the BIO/CN hybrid heterojunc-tion outperformed both the BIO and CN counterparts in terms of norfloxacin degradation and H_(2) gen-eration under simulated solar light irradiation.Moreover,the photocatalytic performance of the hybrid catalyst remained nearly unchanged throughout five consecutive test runs.The exceptional performance and stability of the hybrid catalyst are attributable to its extended optical absorption range,large interfa-cial contact area provided by the face-to-face assembly in the 2D/2D hybrid configuration,and enhanced photoexcited charge separation efficiency and redox power of the separated charges,which are supported by an efficient S-scheme charge transfer mechanism.This study illuminates the rational construction of novel 2D/2D S-scheme hybrid heterojunction photocatalysts with practical applications in environmental remediation and sustainable energy generation.

Bifunctional S-scheme hybrid heterojunction comprising CdS nanorods and BiOIO_(3) nanosheets for efficient solar-induced antibiotic degradation and highly-selective CO_(2) reduction

The development of a bifunctional photocatalyst that can be utilized for both energy conversion and envi-ronmental remediation is of great practical significance.In addition,an S-scheme charge transfer process can assist a photocatalyst in efficiently separating photoexcited electrons and holes while maintaining the strong reducibility and oxidizability of the former and the latter,respectively.We developed a bifunctional S-scheme hybrid photocatalyst comprising CdS nanorods and BiOIO_(3)(BIO) nanosheets for efficient antibi-otic degradation and cocatalyst-and sacrificial reagent-free CO_(2) reduction.The combination of visible-light-responsive one-dimensional(1D)CdS and UV-light-responsive 2D BIO resulted in a CdS/BIO hybrid photocatalyst with effective 1D/2D(line)interfacial contact and a broadened optical absorption range.Notably,the CdS/BIO hybrid exhibited exceptional diclofenac degradation and mineralization as well as outstanding CO_(2) reduction activity for CO production,with 95.4%CO selectivity over H_(2)production.The exceptional performance of the hybrid catalyst is primarily attributed to the accelerated photoexcited charge transfer caused by the 1D/2D line interfacial contact and the high charge separation and strong redox power of the separated charges,both of which stem from the effective S-scheme charge transfer process.In addition,photocorrosion of CdS was substantially mitigated,resulting in the high photocat-alytic performance of the hybrid catalyst even after repeated test runs.This study provides insight into the rational design of bifunctional S-scheme hybrid photocatalysts for CO_(2) reduction and pollutant degra-dation.

Porous g-C_(3)N_(4)-encapsulated TiO_(2) hollow sphere as a high-performance Z-scheme hybrid for solar-induced photocatalytic abatement of environmentally toxic pharmaceuticals

Herein,we rationally constructed a hybrid heterostructure comprising porous g-C_(3)N_(4)(CN)-encapsulated anatase TiO_(2) hollow spheres(TOHS)via a synthesis method that involves hydrothermal and calcination treatments.The fabricated hybrid,termed CN/TOHS,demonstrated extraordinary activity toward the degradation of environmentally toxic pharmaceutical substances(acetaminophen and ciprofloxacin)in aqueous solutions under simulated sunlight irradiation;the activity of CN/TOHS was superior to that attained for individual TOHS and CN counterparts.In particular,the CN/TOHS hybrid containing 13.3 wt.%of CN on TOHS displayed the optimum degradation activity among the tested catalysts used in this study,and it also possessed exceptional recyclability and stability during consecutive degradation tests.The remarkable photocatalytic activity and stability of the hybrid were predominantly ascribed to the large solid interfacial contact between constituents,TOHS and CN,induced by effective hybrid structure,which boosted the interfacial charge transfer and impeded with the direct recombination of photo-induced charges.Notably,the results of the liquid chromatography-mass spectrometry analysis corroborated the effective mineralization of model pharmaceutical pollutants in the presence of the CN/TOHS hybrid.The simple interfacial engineering strategy presented in this study offers a potential route for the rational design of novel catalysts for application in environmental remediation and solar energy conversion.

One-dimensional titania nanotubes annealed at various temperatures for the photocatalytic degradation of low concentration gaseous pollutants

In this study, one-dimensional titania nanotubes （TNTs） were synthesized using a combined process of chemical and hydrothermal treatments, and their activities for the photocatalytic reactions of selected gaseous pollutants at sub-ppm levels were determined. Additionally, the properties of the TNTs were examined using selected spectroscopic methods. The annealed TNTs showed higher photocatalytic activities for the four target compounds than did the unannealed TNTs. For all the target compounds except benzene, the effect of the annealing temperature on the degradation efficiency was difficult to determine because all degradation efficiencies were very high. However, for benzene, which decomposed with a low efficiency, the degradation activities of the TNTs increased as the treatment temperature was increased from 250 to 300 ℃, while they decreased slightly when the temperature was increased from 300 to 400 ℃. These findings confirm the presence of an optimal annealing temperature for the synthesis of TNTs. Moreover, the average degradation extents for benzene, toluene, ethylbenzene, and o-xylene decreased from 92%, 96%, 99%, and 98% to 77%, 86%, 92%, and 94%, respectively, as the airstream flow rate increased within the range of 1-4L/min. The average degradation extents decreased from 12%, 75%, 87%, and 88% to 3%, 29%, 46%, and 51%, respectively, as the input concentration increased from 0.4 to 1.9 ppm. Overall, these findings suggest that one-dimensional TNTs can be effectively utilized for the degradation of gaseous pollutants under optimal operational conditions.

2D reduced graphene oxide-titania nanocomposites synthesized under different hydrothermal conditions for treatment of hazardous organic pollutants

Two-dimensional reduced graphene oxide-titania （RGO-TiO2） composites were prepared using a single- step hydrothermal method under various hydrothermal reaction conditions. The morphological and surface characteristics of the RGO-TiO2 composites and reference materials were determined. The RGO-TiO2 composites showed photocatalytic activity for the decomposition of two target pollutants that was superior to both pure TiO2 and RGO under fluorescent daylight lamp illumination. The photo- catalytic activity of the RGO-TiO2 composite increased as the hydrothermal treatment time increased from 1 to 24 h, but then it decreased as the time increased to 36 h, which indicated the presence of an optimal treatment time. RGO-TiO2 composites activated by violet light-emitting diodes （LEDs） displayed lower decomposition efficiency than those activated by a daylight lamp, likely because of the lower light intensity of violet LEDs （0.2 mW/cm2） when compared with that of the daylight lamp （1.4mW/cm2）. However, the photocatalytic decomposition of the target pollutants using the RGO-TiO2 composite was more energy-efficient using the violet LEDs. The photocatalytic reaction rates increased as the residence time decreased, whereas the reverse was true for the decomposition efficiency.