The composition of products formed from photooxidation of the aromatic hydrocarbon toluene was investigated. The OH-initiated photooxidation experiments were conducted by irradiating toluene/CH3ONO/NO/air mixtures in ...The composition of products formed from photooxidation of the aromatic hydrocarbon toluene was investigated. The OH-initiated photooxidation experiments were conducted by irradiating toluene/CH3ONO/NO/air mixtures in a smog chamber, the gaseous products were detected under the supersonic beam conditions by utilizing vacuum ultraviolet photoionization mass spectrometer using synchrotron radiation in real-time. And an aerosol time-of-flight mass spectrometer was used to provide on-line measurements of the individual secondary organic aerosol particle resulting from irradiating toluene. The experimental results demonstrated that there were some differences between the gaseous products and that of particle-phase, the products of glyoxal, 2-hydroxyl-3-oxo-butanal, nitrotoluene, and methyl-nitrophenol only existed in the particle-phase. However, furane, methylglyoxal, 2-methylfurane, benzaldehyde, cresol, and benzoic acid were the predominant photooxidation products in both the gas phase and particle phase.展开更多
Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that...Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that the presence of EuOx significantly enhances the redox property,lattice O concentration,and Ce3+ ratio of the Pt/CeO2 material,which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene.Among all catalysts,a sample with an Eu content of 2.5 at.%(Pt/EC-2.5)possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 ℃ under a relatively high GHSV of 50000 h^-1.The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS,which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.展开更多
We found an ultraviolet (UV)-light induced formation of biphenyl and sodium benzoate from benzene and sodium carbonate. The reaction happens in the interface of benzene and aqueous solution at the room temperature. ...We found an ultraviolet (UV)-light induced formation of biphenyl and sodium benzoate from benzene and sodium carbonate. The reaction happens in the interface of benzene and aqueous solution at the room temperature. After 5 h of UV-light exposure, 11.4% of initial amount of 4.4 g (5.0 mL) benzene are converted to biphenyl and sodium benzoate, which are distributed in benzene and aqueous solution, respectively. Using density function theory (DFT) and time dependent DFT, we have investigated the mechanism of this light-induced reaction, and found that the sodium carbonate is not only a reactant for the formation of sodium benzoate, but also a catalyst for the formation of biphenyl.展开更多
Bi2MoO6,a typical Bi-based photocatalyst,has received increasing interests and been widely applied in various fields.However,the visible light photocatalytic activity of Bi2MoO6 is still restricted by some obstacles,s...Bi2MoO6,a typical Bi-based photocatalyst,has received increasing interests and been widely applied in various fields.However,the visible light photocatalytic activity of Bi2MoO6 is still restricted by some obstacles,such as limited photo-response and low charge separation efficiency.In this work,we developed a facile method to introduce artificial oxygen vacancy into Bi2MoO6 microspheres,which could effectively address these problems and realize highly efficient visible light photocatalysis.The experimental and theoretical methods were combined to explore the effects of oxygen vacancy on the electronic structure,photocatalytic activity and the reaction mechanism toward NO removal.The results showed that the addition of NaBH4 during catalyst preparation induced the formation of oxygen vacancy in Bi2MoO6,which plays a significant role in extending the visible light absorption of Bi2MoO6.The visible light photocatalytic activity of Bi2MoO6 with oxygen vacancy was obviously enhanced with a NO removal ratio of 43.5%,in contrast to that of 25.0%with the pristine Bi2MoO6.This can be attributed to the oxygen vacancy that creates a defect energy level in the band gap of Bi2MoO6,thus facilitating the charge separation and transfer processes.Hence,more reactive radicals were generated and participated in the photocatalytic NO oxidation reaction.The in situ FT-IR was used to dynamically monitor the photocatalytic NO oxidation process.The reaction intermediates were observed and the adsorption-reaction mechanism was proposed.It was found that the reaction mechanism was unchanged by introducing the oxygen vacancy in Bi2MoO6.This work could provide new insights into the understanding of the oxygen vacancy in photocatalysis and gas-phase photocatalytic reaction mechanism.展开更多
A series of UiO-66-NH2/Ag2CO3 Z-scheme heterojunctions were prepared by a simple ion-exchange-solution method using UiO-66-NH2 and semiconductor Ag2CO3 as precursors.The photocatalytic activities of UAC-X(UAC-20,50,10...A series of UiO-66-NH2/Ag2CO3 Z-scheme heterojunctions were prepared by a simple ion-exchange-solution method using UiO-66-NH2 and semiconductor Ag2CO3 as precursors.The photocatalytic activities of UAC-X(UAC-20,50,100,150,200)Z-scheme heterojunctions toward the hexavalent chromium(Cr(VI))reduction and UAC-100 toward oxidative degradation of four organic dyes like rhodamine B(RhB),methyl orange(MO),congo red(CR),and methylene blue(MB)under visible light irradiation were investigated.The effects of different pH(pH=2,3,4,6,8),small organic acids(citric acid,tartaric acid,and oxalic acid),and foreign ions(ions in tap water and surface water)on Cr(VI)reduction were explored.The results revealed that the UAC-100 heterojunctions displayed more remarkable Cr(VI)reduction performance than the pristine UiO-66-NH2 and Ag2CO3,resulting from the improved separation of photo-induced electrons and holes.The enhanced photocatalytic activity of UAC-100 was further confirmed by the photoluminescence measurement,electrochemical analysis,and active species trapping experiments.After four cycles’experiments,the photocatalytic Cr(VI)reduction efficiency over UAC-100 was still over 99%,which exhibited that UAC-100 had excellent reusability and stability.Finally,the corresponding photocatalytic reaction mechanism was proposed and tested.展开更多
The simultaneous integration of heteroatom doping and surface plasmon resonance(SPR) modulation on semiconductor photocatalysts could be capable of improving visible light utilization and charge separation, achieving ...The simultaneous integration of heteroatom doping and surface plasmon resonance(SPR) modulation on semiconductor photocatalysts could be capable of improving visible light utilization and charge separation, achieving better solar light conversion and photocatalysis efficiency. For this purpose, we have designed a novel Bi quantum dots(QDs) implanted C-doped BiOCl photocatalyst(C/BOC/B) for NOx removal. The feasibility was firstly evaluated through density functional theory(DFT) calculations methods, which indicates that the enhanced photocatalytic performance could be expected owing to the synergistic effects of doped C heteroatoms and loaded Bi QDs. Then, the C/BOC/B was synthesized via a facile hydrothermal method and exhibited efficient and stable visible light photocatalytic NO removal. The results found that the doped C atoms can serve as electron guides to induce oriented charge transfer from Bi QDs to BiOCl, while the Bi QDs can act as light-capture and electron-donating sites. The reaction pathway and mechanism for NO conversion was unveiled by in situ Fourier-transform infrared spectroscopy combined with DFT calculation. The enhanced adsorption of reactants and intermediates could promote the overall reaction efficiency and selectivity in photocatalytic NO conversion. This work could provide a new perspective on the mechanistic understanding of the synergistic effects toward non-metal doping and SPR effects in semiconductor photocatalysts, and this presented technique could be extended for other semiconductor materials.展开更多
Heterostructured photocatalysts provide an effective way to achieve enhanced photocatalytic performances through efficient charge separation.Although both wide-and narrow-band-gap photocatalysts have been widely inves...Heterostructured photocatalysts provide an effective way to achieve enhanced photocatalytic performances through efficient charge separation.Although both wide-and narrow-band-gap photocatalysts have been widely investigated,the charge separation and transfer mechanism at the contacting interface of the two has not been fully revealed.Here,a novel SrTiO3/BiOI(STB)heterostructured photocatalyst was successfully fabricated by using a facile method.The heterostructure in the photocatalyst extends the photoabsorption to the visible light range,and thus,high photocatalytic NO removal performance can be achieved under visible light irradiation.A combination of experimental and theoretical evidences indicated that the photogenerated electrons from the BiOI semiconductor can directly transfer to the SrTiO3 surface through a preformed electron delivery channel.Enhanced electron transfer was expected between the SrTiO3 and BiOI surfaces under light irradiation,and leads to efficient ROS generation and thus a high NO conversion rate.Moreover,in situ diffused reflectance infrared Fourier transform spectroscopy revealed that STB can better inhibit the accumulation of the toxic intermediate NO2 and catalyze the NO oxidation more effectively.This work presents a new insight into the mechanism of the interfacial charge separation in heterostructures and provides a simple strategy to promote the photocatalytic technology for efficient and safe air purification.展开更多
As a new organic conjugated semiconductor,graphitic carbon nitride(g-C_(3)N_(4))is emerging as a fascinating material for various photocatalytic applications due to its adjustable electronic structure,outstanding ther...As a new organic conjugated semiconductor,graphitic carbon nitride(g-C_(3)N_(4))is emerging as a fascinating material for various photocatalytic applications due to its adjustable electronic structure,outstanding thermal endurance,appealing chemical stability,low cost,and environmental friendliness.Nevertheless,unmodified bulk g-C_(3)N_(4) possesses some intrinsic limitations related to poor crystallinity,marginal visible-light harvesting,easy recombination of charge pairs,small surface area,and slow charge migration,which give rise to the low quantum efficiency of photocatalytic reactions.One efficient strategy to overcome these shortcomings is the manipulation of the microstructures of g-C_(3)N_(4).Other than the traditional structure control,mimicking the structures of creatures in nature to design and construct bio-inspired structures is a promising approach to improve the photocatalytic performance of g-C_(3)N_(4) and even g-C_(3)N_(4)-based systems.This review summarizes the recent advances of the traditional structure-control of g-C_(3)N_(4)-based systems,and bio-inspired synthesis of g-C_(3)N_(4)-based systems from two aspects of structural bionics and functional bionics.Furthermore,the fundamentals of bio-inspired design and fabrication of g-C_(3)N_(4)-based systems are introduced in detail.Additionally,the different theoretical calculations,diverse photocatalytic applications and various modification strategies of bio-inspired structured g-C_(3)N_(4)-based systems are recapped.We believe that this work will be a guiding star for future research in the new field of biomimetic photocatalysis.展开更多
There is an increasing interest in bismuth carbonate(Bi2O2CO3,BOC)as a semiconductor photocatalyst.However,pure BOC strongly absorbs ultraviolet light,which drives a high recombination rate of charge carriers and ther...There is an increasing interest in bismuth carbonate(Bi2O2CO3,BOC)as a semiconductor photocatalyst.However,pure BOC strongly absorbs ultraviolet light,which drives a high recombination rate of charge carriers and thereby limits the overall photocatalysis efficiency.In this work,artificial oxygen vacancies(OV)were introduced into BOC(OV-BOC)to broaden the optical absorption range,increase the charge separation efficiency,and activate the reactants.The photocatalytic removal ratio of NO was increased significantly from 10.0%for pure BOC to 50.2%for OV-BOC because of the multiple roles played by the oxygen vacancies.These results imply that oxygen vacancies can facilitate the electron exchange between intermediates and the surface oxygen vacancies in OV-BOC,making them more easily destroyed by active radicals.In situ DRIFTS spectra in combination with electron spin resonance spectra and density functional theory calculations enabled unraveling of the conversion pathway for the photocatalytic NO oxidation on OV-BOC.It was found that oxygen vacancies could increase the production of active radicals and promote the transformation of NO into target products instead of toxic byproducts(NO2),thus the selectivity is significantly enhanced.This work provides a new strategy for enhancing photocatalytic activity and selectivity.展开更多
Surface plasmon resonance(SPR)of metals may provide a way to improve light absorption and utilization of semiconductors,achieving better solar light conversion and photocatalysis efficiency.This study uses the advanta...Surface plasmon resonance(SPR)of metals may provide a way to improve light absorption and utilization of semiconductors,achieving better solar light conversion and photocatalysis efficiency.This study uses the advantages of SPR in metallic Bi and artificial defects to cooperatively enhance the photocatalytic performance of BiOI.The catalysts were prepared by partial reduction of BiOI to form Bi@defective BiOI,which showed highly enhanced visible photocatalytic activity for NOx removal.The effects of reductant quantity on the photocatalytic performance of Bi@defective BiOI were investigated.The as-prepared photocatalyst(Bi/BiOI-2)using 2 mmol of reductant NaBH4 showed the most efficient visible light photocatalytic activity.This enhanced activity can be ascribed to the synergistic effects of metallic Bi and oxygen vacancies.The electrons from the valence band tend to accumulate at vacancy states;therefore,the increased charge density would cause the adsorbed oxygen to transform more easily into superoxide radicals and,further,into hydroxyl radicals.These radicals are the main active species that oxidize NO into final products.The SPR effect of elemental Bi enables the improvement of visible light absorption efficiency and the promotion of charge carrier separation,which are crucial factors in boosting photocatalysis.NO adsorption and reaction processes on Bi/BiOI-2 were dynamically monitored by in situ infrared spectroscopy(FT-IR).The Bi/BiOI photocatalysis mechanism co-mediated by elemental Bi and oxygen vacancies was proposed based on the analysis of intermediate products and DFT calculations.This present work could provide new insights into the design of high-performance photocatalysts and understanding of the photocatalysis reaction mechanism for air-purification applications.展开更多
Spectroscopic characterization of clusters is crucial to understanding the structures and reaction mechanisms at the microscopic level,but it has been proven to be a grand challenge for neutral clusters because the ab...Spectroscopic characterization of clusters is crucial to understanding the structures and reaction mechanisms at the microscopic level,but it has been proven to be a grand challenge for neutral clusters because the absence of a charge makes it di伍cult for the size selection and detection.Infrared(IR)spectroscopy based on threshold photoionization using a tunable vacuum ultraviolet free electron laser(VUV-FEL)has recently been developed in the lab.The IR-VUV depletion and IR+VUV enhancement spectroscopic techniques open new avenues for size-selected IR spectroscopies of a large variety of neutral clusters without confinement(i.e.,an ultraviolet chromophore,a messenger tag,or a host matrix).The spectroscopic principles have been demonstrated by investigations of some neutral water clusters and some metal carbonyls.Here,the spectroscopic principles and their applications for neutral clusters are reviewed.展开更多
Based on the mechanism analysis of the polychlorination of long chain n-alkanes by photo-initiation,a kinetic model was developed. The model parameters were obtained by the method of non-linear fitting. The influences...Based on the mechanism analysis of the polychlorination of long chain n-alkanes by photo-initiation,a kinetic model was developed. The model parameters were obtained by the method of non-linear fitting. The influences of luminous intensity and concentration of molecular chlorine on the rate of polychlorination are demonstrated by the model. If the luminous intensity is adequate, the polychlorination rate of n-alkane is only controlled by the flow rate of molecular chlorine in a wide range of temperature, and the changes of temperature and luminous intensity have less effect on the reaction rate. In addition, the predictions of chlorine content of polychlorinated n-alkane calculated with the model agree very well with experimental results.展开更多
Hydrogen peroxide has attracted increasing interest as an environmentally benign and green oxidant that can also be used as a solar fuel in fuel cells.This review focuses on recent progress in production of hydrogen p...Hydrogen peroxide has attracted increasing interest as an environmentally benign and green oxidant that can also be used as a solar fuel in fuel cells.This review focuses on recent progress in production of hydrogen peroxide by solar-light-driven oxidation of water by dioxygen and its usage as a green oxidant and fuel.The photocatalytic production of hydrogen peroxide is made possible by combining the e^(-)and 4e-oxidation of water with the e^(-)reduction of dioxygen using solar energy.The catalytic control of the selectivity of the e^(-)vs.4e-oxidation of water is discussed together with the selectivity of the e^(-)vs.4e-reduction of dioxygen.The combination of the photocatalytic e^(-)oxidation of water and the e^(-)reduction of dioxygen provides the best efficiency because both processes afford hydrogen peroxide.The solar-light-driven hydrogen peroxide production by oxidation of water and by reduction of dioxygen is combined with the catalytic oxidation of substrates with hydrogen peroxides,in which dioxygen is used as the greenest oxidant.展开更多
CuO was synthesized by thermal decomposition of Cu(NO3)2·3H2O at various temperatures and characterized by powder X-ray diffractometry(XRD) as well as scanning electron microscopy(SEM).The effects of calcination ...CuO was synthesized by thermal decomposition of Cu(NO3)2·3H2O at various temperatures and characterized by powder X-ray diffractometry(XRD) as well as scanning electron microscopy(SEM).The effects of calcination temperature,category of sacrificial reagent,initial sacrificial reagent concentration,and Ag loading content on the photocatalytic activity of the as-obtained CuO sample were investigated.The results show that the as-obtained CuO exhibits high activity for photocatalysis of H2 evolution reaction(HER) in oxalic acid solution under simulated sunlight irradiation.The highest photocatalytic activity of the as-obtained CuO was achieved at the calcination temperature of 1000℃,and oxalic acid was used as the sacrificial reagent with the concentration 0.05 mol/L.H2 evolution rate is as high as 2.98 mmol/(h·g) with 2%(mass fraction) loaded Ag.The possible photocatalytic reaction mechanism on the CuO photocatalyst for HER in oxalic acid solution was also discussed.展开更多
A comprehensive experimental study of the premixed ethylene/oxygen/argon flame at 2.667 kPa with a stoichiometric equivalence ratio (Ф=1) was performed with the tunable synchrotron photoionization and molecular-bea...A comprehensive experimental study of the premixed ethylene/oxygen/argon flame at 2.667 kPa with a stoichiometric equivalence ratio (Ф=1) was performed with the tunable synchrotron photoionization and molecular-beam sampling mass spectrometry techniques. The isomers of most observed species in the flame were unambiguously identified by measurements of the photoionization etticiency spectra, e.g. C3H4, C2H4O and C4H4. The mole fraction profiles of species up to C7H8 were measured by scanning the burner position at the selected photon energies near ionization thresholds, and the flame temperature profile was obtained by using Pt/Pt-13%Rh thermocouple. Compared with the previous studies, a lot of new flame species: C3H2, C3H3, C3H5, C2H6O, C4H2, C4H4, C4H6, C3H4O, C3H6O, C3H8O, C5H6, C4H8O and C7H8, were observed. A series of free radicals in the flame are detected to be CH3, C2H3, C2H5, HCO, C3H3 and C3H5. Based on the experimental work, a reduced reaction mechanism was developed including 40 species and 223 reactions. Modeling and measurements agree well for the major species and most intermediates. A detailed kinetic model is desired for this flame.展开更多
The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction,both in terms of practical applications(e.g.models of combustion or atmosphere chemistry...The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction,both in terms of practical applications(e.g.models of combustion or atmosphere chemistry)in understanding the fundamental mechanisms of such chemical reactions.A global ground state potential energy surface for the dissociation reaction of deuterated alkyl halide CD_(3)CH_(2)F was computed at the CCSD(T)/CBS//B3 LYP/aug-cc-p VDZ level of theory for all species.The decomposition of CD_(3)CH_(2)F is controversial concerning C-F bond dissociation reaction and molecular(HF,DF,H_(2),D_(2),HD)elimination reaction.RiceRamsperger-Kassel-Marcus(RRKM)calculations were applied to compute the rate constants for individual reaction steps and the relative product branching ratios for the dissociation products were calculated using the steady-state approach.At the different energies studied,the RRKM method predicts that the main channel for DF or HF elimination from1,2-elimination of CD_(3)CH_(2)F is through a four-center transition state,whereas D_(2) or H_(2) elimination from 1,1-elimination of CD_(3)CH_(2)F occurs through a direct three-center elimination.At 266,248,and 193 nm photodissociation,the main product CD_(2)CH_(2)+DF branching ratios are computed to be 96.57%,91.47%,and 48.52%,respectively;however,at 157 nm photodissociation,the product branching ratio is computed to be 16.11%.Based on these transition state structures and energies,the following photodissociation mechanisms are suggested:at 266,248,193 nm,CD_(3)CH_(2)F→absorption of a photon→TS5→the formation of the major product CD_(2)CH_(2)+DF;at 157 nm,CD_(3)CH_(2)F→absorption of a photon→D/F interchange of TS1→CDH_(2)CDF→H/F interchange of TS2→CHD_(2)CHDF→the formation of the major product CHD_(2)+CHDF.展开更多
Benzofuran is an essential structural component found in a wide range of natural products,agrochemicals and drugs,possessing a range of biological activities.In recent years,there have been numerous reports of success...Benzofuran is an essential structural component found in a wide range of natural products,agrochemicals and drugs,possessing a range of biological activities.In recent years,there have been numerous reports of successful syntheses of benzofuran derivatives via intra-and inter-molecular cyclizations using diverse catalysts.This review gives an exhaustive and methodical survey of the procedures for making benzofurans.展开更多
Theoretical investigations have been carried out on the mechanism and kinetics for the reaction of CF 3 CHO + Cl using duallevel direct dynamics method. The potential energy surface information was obtained at the MCQ...Theoretical investigations have been carried out on the mechanism and kinetics for the reaction of CF 3 CHO + Cl using duallevel direct dynamics method. The potential energy surface information was obtained at the MCQCISD/3//MP2/cc-pVDZ level and the kinetic calculations were done using variational transition state theory with interpolated single-point energy (VTST-ISPE) approach. The calculated results show that the reaction proceeds primarily via the H-abstraction channel, while the Cl-addition channel is unfavorable due to the higher barriers. The improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling correction (SCT) was used to calculate the rate constants. The theoretical rate constants at room temperature are in general agreement with the experimental values. A three-parameter rate constant expression was fitted over a wide temperature range of 200-2000 K.展开更多
基金This work was supported by the Open Research Fund of Key Laboratory of Atmospheric Composition and Optical Radiation, Chinese Academy of Sciences (No.J J-10-04), Knowledge Innovation Foundation of Chinese Academy of Sciences (KJCX2-YW-N24), and the National Natural Science Foundation of China (No.40975080 and No.10979061).
文摘The composition of products formed from photooxidation of the aromatic hydrocarbon toluene was investigated. The OH-initiated photooxidation experiments were conducted by irradiating toluene/CH3ONO/NO/air mixtures in a smog chamber, the gaseous products were detected under the supersonic beam conditions by utilizing vacuum ultraviolet photoionization mass spectrometer using synchrotron radiation in real-time. And an aerosol time-of-flight mass spectrometer was used to provide on-line measurements of the individual secondary organic aerosol particle resulting from irradiating toluene. The experimental results demonstrated that there were some differences between the gaseous products and that of particle-phase, the products of glyoxal, 2-hydroxyl-3-oxo-butanal, nitrotoluene, and methyl-nitrophenol only existed in the particle-phase. However, furane, methylglyoxal, 2-methylfurane, benzaldehyde, cresol, and benzoic acid were the predominant photooxidation products in both the gas phase and particle phase.
基金financially supported by the National Key R&D Program of China (2016YFC0204201)the National Natural Science Foundation of China (21677114, 21477095, 21876139)the Fundamental Research Funds for the Central Universities (xjj2017170)~~
文摘Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that the presence of EuOx significantly enhances the redox property,lattice O concentration,and Ce3+ ratio of the Pt/CeO2 material,which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene.Among all catalysts,a sample with an Eu content of 2.5 at.%(Pt/EC-2.5)possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 ℃ under a relatively high GHSV of 50000 h^-1.The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS,which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.
文摘We found an ultraviolet (UV)-light induced formation of biphenyl and sodium benzoate from benzene and sodium carbonate. The reaction happens in the interface of benzene and aqueous solution at the room temperature. After 5 h of UV-light exposure, 11.4% of initial amount of 4.4 g (5.0 mL) benzene are converted to biphenyl and sodium benzoate, which are distributed in benzene and aqueous solution, respectively. Using density function theory (DFT) and time dependent DFT, we have investigated the mechanism of this light-induced reaction, and found that the sodium carbonate is not only a reactant for the formation of sodium benzoate, but also a catalyst for the formation of biphenyl.
基金supported by the National Natural Science Foundation of China(21501016,51501024,51871037 and 21822601)the Fundamental Research Funds for the Central Universities(2018CDQYCL0027)~~
文摘Bi2MoO6,a typical Bi-based photocatalyst,has received increasing interests and been widely applied in various fields.However,the visible light photocatalytic activity of Bi2MoO6 is still restricted by some obstacles,such as limited photo-response and low charge separation efficiency.In this work,we developed a facile method to introduce artificial oxygen vacancy into Bi2MoO6 microspheres,which could effectively address these problems and realize highly efficient visible light photocatalysis.The experimental and theoretical methods were combined to explore the effects of oxygen vacancy on the electronic structure,photocatalytic activity and the reaction mechanism toward NO removal.The results showed that the addition of NaBH4 during catalyst preparation induced the formation of oxygen vacancy in Bi2MoO6,which plays a significant role in extending the visible light absorption of Bi2MoO6.The visible light photocatalytic activity of Bi2MoO6 with oxygen vacancy was obviously enhanced with a NO removal ratio of 43.5%,in contrast to that of 25.0%with the pristine Bi2MoO6.This can be attributed to the oxygen vacancy that creates a defect energy level in the band gap of Bi2MoO6,thus facilitating the charge separation and transfer processes.Hence,more reactive radicals were generated and participated in the photocatalytic NO oxidation reaction.The in situ FT-IR was used to dynamically monitor the photocatalytic NO oxidation process.The reaction intermediates were observed and the adsorption-reaction mechanism was proposed.It was found that the reaction mechanism was unchanged by introducing the oxygen vacancy in Bi2MoO6.This work could provide new insights into the understanding of the oxygen vacancy in photocatalysis and gas-phase photocatalytic reaction mechanism.
基金supported by the National Natural Science Foundation of China(51878023,51578034)Great Wall Scholars Training Program Project of Beijing Municipality Universities(CIT&TCD20180323)+2 种基金Project of Construction of Innovation Teams and Teacher Career Development for Universities and Colleges Under Beijing Municipality(IDHT20170508)Beijing Talent Project(2018A35)BUCEA Post Graduate Innovation Project(PG2019039)~~
文摘A series of UiO-66-NH2/Ag2CO3 Z-scheme heterojunctions were prepared by a simple ion-exchange-solution method using UiO-66-NH2 and semiconductor Ag2CO3 as precursors.The photocatalytic activities of UAC-X(UAC-20,50,100,150,200)Z-scheme heterojunctions toward the hexavalent chromium(Cr(VI))reduction and UAC-100 toward oxidative degradation of four organic dyes like rhodamine B(RhB),methyl orange(MO),congo red(CR),and methylene blue(MB)under visible light irradiation were investigated.The effects of different pH(pH=2,3,4,6,8),small organic acids(citric acid,tartaric acid,and oxalic acid),and foreign ions(ions in tap water and surface water)on Cr(VI)reduction were explored.The results revealed that the UAC-100 heterojunctions displayed more remarkable Cr(VI)reduction performance than the pristine UiO-66-NH2 and Ag2CO3,resulting from the improved separation of photo-induced electrons and holes.The enhanced photocatalytic activity of UAC-100 was further confirmed by the photoluminescence measurement,electrochemical analysis,and active species trapping experiments.After four cycles’experiments,the photocatalytic Cr(VI)reduction efficiency over UAC-100 was still over 99%,which exhibited that UAC-100 had excellent reusability and stability.Finally,the corresponding photocatalytic reaction mechanism was proposed and tested.
文摘The simultaneous integration of heteroatom doping and surface plasmon resonance(SPR) modulation on semiconductor photocatalysts could be capable of improving visible light utilization and charge separation, achieving better solar light conversion and photocatalysis efficiency. For this purpose, we have designed a novel Bi quantum dots(QDs) implanted C-doped BiOCl photocatalyst(C/BOC/B) for NOx removal. The feasibility was firstly evaluated through density functional theory(DFT) calculations methods, which indicates that the enhanced photocatalytic performance could be expected owing to the synergistic effects of doped C heteroatoms and loaded Bi QDs. Then, the C/BOC/B was synthesized via a facile hydrothermal method and exhibited efficient and stable visible light photocatalytic NO removal. The results found that the doped C atoms can serve as electron guides to induce oriented charge transfer from Bi QDs to BiOCl, while the Bi QDs can act as light-capture and electron-donating sites. The reaction pathway and mechanism for NO conversion was unveiled by in situ Fourier-transform infrared spectroscopy combined with DFT calculation. The enhanced adsorption of reactants and intermediates could promote the overall reaction efficiency and selectivity in photocatalytic NO conversion. This work could provide a new perspective on the mechanistic understanding of the synergistic effects toward non-metal doping and SPR effects in semiconductor photocatalysts, and this presented technique could be extended for other semiconductor materials.
基金supported by the National Natural Science Foundation of China(21822601,21501016,21777011)the National R&D Program of China(2016YFC02047)+1 种基金the Innovative Research Team of Chongqing(CXTDG201602014)the Natural Science Foundation of Chongqing(cstc2017jcyj BX0052)~~
文摘Heterostructured photocatalysts provide an effective way to achieve enhanced photocatalytic performances through efficient charge separation.Although both wide-and narrow-band-gap photocatalysts have been widely investigated,the charge separation and transfer mechanism at the contacting interface of the two has not been fully revealed.Here,a novel SrTiO3/BiOI(STB)heterostructured photocatalyst was successfully fabricated by using a facile method.The heterostructure in the photocatalyst extends the photoabsorption to the visible light range,and thus,high photocatalytic NO removal performance can be achieved under visible light irradiation.A combination of experimental and theoretical evidences indicated that the photogenerated electrons from the BiOI semiconductor can directly transfer to the SrTiO3 surface through a preformed electron delivery channel.Enhanced electron transfer was expected between the SrTiO3 and BiOI surfaces under light irradiation,and leads to efficient ROS generation and thus a high NO conversion rate.Moreover,in situ diffused reflectance infrared Fourier transform spectroscopy revealed that STB can better inhibit the accumulation of the toxic intermediate NO2 and catalyze the NO oxidation more effectively.This work presents a new insight into the mechanism of the interfacial charge separation in heterostructures and provides a simple strategy to promote the photocatalytic technology for efficient and safe air purification.
文摘As a new organic conjugated semiconductor,graphitic carbon nitride(g-C_(3)N_(4))is emerging as a fascinating material for various photocatalytic applications due to its adjustable electronic structure,outstanding thermal endurance,appealing chemical stability,low cost,and environmental friendliness.Nevertheless,unmodified bulk g-C_(3)N_(4) possesses some intrinsic limitations related to poor crystallinity,marginal visible-light harvesting,easy recombination of charge pairs,small surface area,and slow charge migration,which give rise to the low quantum efficiency of photocatalytic reactions.One efficient strategy to overcome these shortcomings is the manipulation of the microstructures of g-C_(3)N_(4).Other than the traditional structure control,mimicking the structures of creatures in nature to design and construct bio-inspired structures is a promising approach to improve the photocatalytic performance of g-C_(3)N_(4) and even g-C_(3)N_(4)-based systems.This review summarizes the recent advances of the traditional structure-control of g-C_(3)N_(4)-based systems,and bio-inspired synthesis of g-C_(3)N_(4)-based systems from two aspects of structural bionics and functional bionics.Furthermore,the fundamentals of bio-inspired design and fabrication of g-C_(3)N_(4)-based systems are introduced in detail.Additionally,the different theoretical calculations,diverse photocatalytic applications and various modification strategies of bio-inspired structured g-C_(3)N_(4)-based systems are recapped.We believe that this work will be a guiding star for future research in the new field of biomimetic photocatalysis.
基金supported by the National Key R&D Program of China(2016YFC02047)the National Natural Science Foundation of China(21822601,21777011,and 21501016)+3 种基金the Graduate Research and Innovation Foundation of Chongqing(CYS18019)the Innovative Research Team of Chongqing(CXTDG201602014)the Natural Science Foundation of Chongqing(cstc2017jcyjBX0052)the National Special Supporting National Plan for High-Level~~
文摘There is an increasing interest in bismuth carbonate(Bi2O2CO3,BOC)as a semiconductor photocatalyst.However,pure BOC strongly absorbs ultraviolet light,which drives a high recombination rate of charge carriers and thereby limits the overall photocatalysis efficiency.In this work,artificial oxygen vacancies(OV)were introduced into BOC(OV-BOC)to broaden the optical absorption range,increase the charge separation efficiency,and activate the reactants.The photocatalytic removal ratio of NO was increased significantly from 10.0%for pure BOC to 50.2%for OV-BOC because of the multiple roles played by the oxygen vacancies.These results imply that oxygen vacancies can facilitate the electron exchange between intermediates and the surface oxygen vacancies in OV-BOC,making them more easily destroyed by active radicals.In situ DRIFTS spectra in combination with electron spin resonance spectra and density functional theory calculations enabled unraveling of the conversion pathway for the photocatalytic NO oxidation on OV-BOC.It was found that oxygen vacancies could increase the production of active radicals and promote the transformation of NO into target products instead of toxic byproducts(NO2),thus the selectivity is significantly enhanced.This work provides a new strategy for enhancing photocatalytic activity and selectivity.
基金supported by the National Natural Science Foundation of China(21501016,21777011 and 21822601)the National Key R&D Program of China(2016YFC02047)+2 种基金the Innovative Research Team of Chongqing(CXTDG201602014)the Key Natural Science Foundation of Chongqing(cstc2017jcyj BX0052)the National Ten Thousand Talent Program of China~~
文摘Surface plasmon resonance(SPR)of metals may provide a way to improve light absorption and utilization of semiconductors,achieving better solar light conversion and photocatalysis efficiency.This study uses the advantages of SPR in metallic Bi and artificial defects to cooperatively enhance the photocatalytic performance of BiOI.The catalysts were prepared by partial reduction of BiOI to form Bi@defective BiOI,which showed highly enhanced visible photocatalytic activity for NOx removal.The effects of reductant quantity on the photocatalytic performance of Bi@defective BiOI were investigated.The as-prepared photocatalyst(Bi/BiOI-2)using 2 mmol of reductant NaBH4 showed the most efficient visible light photocatalytic activity.This enhanced activity can be ascribed to the synergistic effects of metallic Bi and oxygen vacancies.The electrons from the valence band tend to accumulate at vacancy states;therefore,the increased charge density would cause the adsorbed oxygen to transform more easily into superoxide radicals and,further,into hydroxyl radicals.These radicals are the main active species that oxidize NO into final products.The SPR effect of elemental Bi enables the improvement of visible light absorption efficiency and the promotion of charge carrier separation,which are crucial factors in boosting photocatalysis.NO adsorption and reaction processes on Bi/BiOI-2 were dynamically monitored by in situ infrared spectroscopy(FT-IR).The Bi/BiOI photocatalysis mechanism co-mediated by elemental Bi and oxygen vacancies was proposed based on the analysis of intermediate products and DFT calculations.This present work could provide new insights into the design of high-performance photocatalysts and understanding of the photocatalysis reaction mechanism for air-purification applications.
基金This work was supported by the National Natural Science Foundation of China(No.92061203 and No.21688102)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB17000000)+3 种基金International Partnership Program of Chinese Academy of Sciences(121421KYSB20170012)Chinese Academy of Sciences(GJJSTD20190002)K.C.Wong Education Foundation(GJTD-2018-06)Dalian Institute of Chemical Physics(DICP DCLS201702).
文摘Spectroscopic characterization of clusters is crucial to understanding the structures and reaction mechanisms at the microscopic level,but it has been proven to be a grand challenge for neutral clusters because the absence of a charge makes it di伍cult for the size selection and detection.Infrared(IR)spectroscopy based on threshold photoionization using a tunable vacuum ultraviolet free electron laser(VUV-FEL)has recently been developed in the lab.The IR-VUV depletion and IR+VUV enhancement spectroscopic techniques open new avenues for size-selected IR spectroscopies of a large variety of neutral clusters without confinement(i.e.,an ultraviolet chromophore,a messenger tag,or a host matrix).The spectroscopic principles have been demonstrated by investigations of some neutral water clusters and some metal carbonyls.Here,the spectroscopic principles and their applications for neutral clusters are reviewed.
文摘Based on the mechanism analysis of the polychlorination of long chain n-alkanes by photo-initiation,a kinetic model was developed. The model parameters were obtained by the method of non-linear fitting. The influences of luminous intensity and concentration of molecular chlorine on the rate of polychlorination are demonstrated by the model. If the luminous intensity is adequate, the polychlorination rate of n-alkane is only controlled by the flow rate of molecular chlorine in a wide range of temperature, and the changes of temperature and luminous intensity have less effect on the reaction rate. In addition, the predictions of chlorine content of polychlorinated n-alkane calculated with the model agree very well with experimental results.
基金supported by the JSPS KAKENHI(16H02268)from MEXTJapan and by the CRI(2012R1A3A2048842)Basic Science Research Program(NRF-2020R1I1A1A01074630)through NRF of Korea.
文摘Hydrogen peroxide has attracted increasing interest as an environmentally benign and green oxidant that can also be used as a solar fuel in fuel cells.This review focuses on recent progress in production of hydrogen peroxide by solar-light-driven oxidation of water by dioxygen and its usage as a green oxidant and fuel.The photocatalytic production of hydrogen peroxide is made possible by combining the e^(-)and 4e-oxidation of water with the e^(-)reduction of dioxygen using solar energy.The catalytic control of the selectivity of the e^(-)vs.4e-oxidation of water is discussed together with the selectivity of the e^(-)vs.4e-reduction of dioxygen.The combination of the photocatalytic e^(-)oxidation of water and the e^(-)reduction of dioxygen provides the best efficiency because both processes afford hydrogen peroxide.The solar-light-driven hydrogen peroxide production by oxidation of water and by reduction of dioxygen is combined with the catalytic oxidation of substrates with hydrogen peroxides,in which dioxygen is used as the greenest oxidant.
基金Project(20876039) supported by the National Natural Science Foundation of ChinaProject(09JJ3023) supported by Natural Science Foundation of Hunan Province, China
文摘CuO was synthesized by thermal decomposition of Cu(NO3)2·3H2O at various temperatures and characterized by powder X-ray diffractometry(XRD) as well as scanning electron microscopy(SEM).The effects of calcination temperature,category of sacrificial reagent,initial sacrificial reagent concentration,and Ag loading content on the photocatalytic activity of the as-obtained CuO sample were investigated.The results show that the as-obtained CuO exhibits high activity for photocatalysis of H2 evolution reaction(HER) in oxalic acid solution under simulated sunlight irradiation.The highest photocatalytic activity of the as-obtained CuO was achieved at the calcination temperature of 1000℃,and oxalic acid was used as the sacrificial reagent with the concentration 0.05 mol/L.H2 evolution rate is as high as 2.98 mmol/(h·g) with 2%(mass fraction) loaded Ag.The possible photocatalytic reaction mechanism on the CuO photocatalyst for HER in oxalic acid solution was also discussed.
基金Ⅵ. ACKN0WLEDGMENTS This work was supported by the National Natural Science Foundation of China (No.20473081 and No.20533040), and Chinese Academy of Sciences. The authors are also thankful for the valuable help in the experimental work from Aigou Zhu. Fei Qi thanks the Combustion Research Facility of Sandia National Labs to provide a Chemkin program package for kinetic modeling study.
文摘A comprehensive experimental study of the premixed ethylene/oxygen/argon flame at 2.667 kPa with a stoichiometric equivalence ratio (Ф=1) was performed with the tunable synchrotron photoionization and molecular-beam sampling mass spectrometry techniques. The isomers of most observed species in the flame were unambiguously identified by measurements of the photoionization etticiency spectra, e.g. C3H4, C2H4O and C4H4. The mole fraction profiles of species up to C7H8 were measured by scanning the burner position at the selected photon energies near ionization thresholds, and the flame temperature profile was obtained by using Pt/Pt-13%Rh thermocouple. Compared with the previous studies, a lot of new flame species: C3H2, C3H3, C3H5, C2H6O, C4H2, C4H4, C4H6, C3H4O, C3H6O, C3H8O, C5H6, C4H8O and C7H8, were observed. A series of free radicals in the flame are detected to be CH3, C2H3, C2H5, HCO, C3H3 and C3H5. Based on the experimental work, a reduced reaction mechanism was developed including 40 species and 223 reactions. Modeling and measurements agree well for the major species and most intermediates. A detailed kinetic model is desired for this flame.
基金supported by the National Natural Science Foundation of China(No.91641116,No.21433004,No.91753103,and No.21933010)the NYU Global Seed Grantthe Laboratory and Equipment Management Office of ECNU。
文摘The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction,both in terms of practical applications(e.g.models of combustion or atmosphere chemistry)in understanding the fundamental mechanisms of such chemical reactions.A global ground state potential energy surface for the dissociation reaction of deuterated alkyl halide CD_(3)CH_(2)F was computed at the CCSD(T)/CBS//B3 LYP/aug-cc-p VDZ level of theory for all species.The decomposition of CD_(3)CH_(2)F is controversial concerning C-F bond dissociation reaction and molecular(HF,DF,H_(2),D_(2),HD)elimination reaction.RiceRamsperger-Kassel-Marcus(RRKM)calculations were applied to compute the rate constants for individual reaction steps and the relative product branching ratios for the dissociation products were calculated using the steady-state approach.At the different energies studied,the RRKM method predicts that the main channel for DF or HF elimination from1,2-elimination of CD_(3)CH_(2)F is through a four-center transition state,whereas D_(2) or H_(2) elimination from 1,1-elimination of CD_(3)CH_(2)F occurs through a direct three-center elimination.At 266,248,and 193 nm photodissociation,the main product CD_(2)CH_(2)+DF branching ratios are computed to be 96.57%,91.47%,and 48.52%,respectively;however,at 157 nm photodissociation,the product branching ratio is computed to be 16.11%.Based on these transition state structures and energies,the following photodissociation mechanisms are suggested:at 266,248,193 nm,CD_(3)CH_(2)F→absorption of a photon→TS5→the formation of the major product CD_(2)CH_(2)+DF;at 157 nm,CD_(3)CH_(2)F→absorption of a photon→D/F interchange of TS1→CDH_(2)CDF→H/F interchange of TS2→CHD_(2)CHDF→the formation of the major product CHD_(2)+CHDF.
文摘Benzofuran is an essential structural component found in a wide range of natural products,agrochemicals and drugs,possessing a range of biological activities.In recent years,there have been numerous reports of successful syntheses of benzofuran derivatives via intra-and inter-molecular cyclizations using diverse catalysts.This review gives an exhaustive and methodical survey of the procedures for making benzofurans.
基金supported by the National Natural Science Foundation of China (20973077, 20303007)the Program for New Century Excellent Talents in University (NCET)
文摘Theoretical investigations have been carried out on the mechanism and kinetics for the reaction of CF 3 CHO + Cl using duallevel direct dynamics method. The potential energy surface information was obtained at the MCQCISD/3//MP2/cc-pVDZ level and the kinetic calculations were done using variational transition state theory with interpolated single-point energy (VTST-ISPE) approach. The calculated results show that the reaction proceeds primarily via the H-abstraction channel, while the Cl-addition channel is unfavorable due to the higher barriers. The improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling correction (SCT) was used to calculate the rate constants. The theoretical rate constants at room temperature are in general agreement with the experimental values. A three-parameter rate constant expression was fitted over a wide temperature range of 200-2000 K.