Membrane distillation(MD)is a promising alternative desalination technology,but the hydrophobic membrane cannot intercept volatile organic compounds(VOCs),resulting in aggravation in the quality of permeate.In term of...Membrane distillation(MD)is a promising alternative desalination technology,but the hydrophobic membrane cannot intercept volatile organic compounds(VOCs),resulting in aggravation in the quality of permeate.In term of this,electro-Fenton(EF)was coupled with sweeping gas membrane distillation(SGMD)in a more efficient way to construct an advanced oxidation barrier at the gas-liquid interface,so that the VOCs could be trapped in this layer to guarantee the water quality of the distillate.During the so-called EF-MD process,an interfacial interception barrier containing hydroxyl radical formed on the hydrophobic membrane surface.It contributed to the high phenol rejection of 90.2% with the permeate phenol concentration lower than 1.50 mg/L.Effective interceptions can be achieved in a wide temperature range,even though the permeate flux of phenol was also intensified.The EF-MD system was robust to high salinity and could electrochemically regenerate ferrous ions,which endowed the long-term stability of the system.This novel EF-MD configuration proposed a valuable strategy to intercept VOCs in MD and will broaden the application of MD in hypersaline wastewater treatment.展开更多
Unlike inorganic quantum dots,fluorescent graphene quantum dots(GQDs)display excitation-dependent multiple color emission.In this study,we report N-doped GQDs(N-GQDs)with tailored single color emission by tuning p-con...Unlike inorganic quantum dots,fluorescent graphene quantum dots(GQDs)display excitation-dependent multiple color emission.In this study,we report N-doped GQDs(N-GQDs)with tailored single color emission by tuning p-conjugation degree,which is comparable to the inorganic quantum dot.Starting from citric acid and diethylenetriamine,as prepared N-GQDs display blue,green,and yellow light emission by changing the reaction solvent from water,dimethylformamide(DMF),and solvent free.The X-ray photoelectron spectroscopy,ultraviolet-visible spectra results clearly show the N-GQDs with blue emission(N-GQDs-B)have relatively short effective conjugation length and more carboxyl group because H_(2)O is a polar protic solvent,which tends to donate proton to the reagent to depress the H_(2)O elimination reaction.On the other hand,the polar aprotic solvent(DMF)cannot donate hydrogen,the elimination of H_(2)O is promoted and more nitrogen units enter GQD framework.With the increase of effective p-conjugation length and N content,the emission band of N-GQDS red-shifts to green and yellow.We also demonstrate that N-GQDs could be a potential great biomarker for fluorescent bioimaging.展开更多
Hydrous manganese dioxide (HMO) synthesized by redox of potassium permanganate and hydrogen peroxide was used as an adsorbent for Pb(Ⅱ) removal.The specific surface area,pore volume and BJH pore diameter of the H...Hydrous manganese dioxide (HMO) synthesized by redox of potassium permanganate and hydrogen peroxide was used as an adsorbent for Pb(Ⅱ) removal.The specific surface area,pore volume and BJH pore diameter of the HMO were 79.31m2/g,0.07cm3/g and 3.38 nm,respectively.The adsorption equilibrium at 298K could be well described by the Langmuir isotherm equation with q max value of 352.55mg/g.The negative values of G and the positive values of H and S indicated the adsorption process was spontaneous and endothermic.The pseudo second-order equation could best fit the adsorption data.The value of the calculated activation energy for Pb(Ⅱ) adsorption onto the HMO was 38.23 kJ/mol.The uptake of Pb(Ⅱ) by HMO was correlated with increasing surface hydroxyl group content and the main adsorbed speciation was PbOH+.The final chemical state of Pb(Ⅱ) on the surface of HMO was similar to PbO.HMO was a promising candidate for Pb(Ⅱ) removal from aqueous solution.展开更多
太阳能水蒸发对于解决净水危机潜力无限.随着研究的深入,研发高效光热转换材料和合理的材料结构设计均可以提高光热蒸发速率.因此,我们设计合成了一种双层碳基水凝胶复合材料.在一个太阳光照条件下,其最大蒸发速率可达2.19 kg m^(−2)h^(...太阳能水蒸发对于解决净水危机潜力无限.随着研究的深入,研发高效光热转换材料和合理的材料结构设计均可以提高光热蒸发速率.因此,我们设计合成了一种双层碳基水凝胶复合材料.在一个太阳光照条件下,其最大蒸发速率可达2.19 kg m^(−2)h^(−1),光热转换效率可达93.7%.同时,该复合材料展现了优异的海水淡化性能及良好的稳定性,扩展了实际应用范围.除此之外,其可控规模化及便携性可以自如面对多种复杂的应用环境,成本低廉可以使其大规模应用于经济落后地区,为复合结构水凝胶蒸发器的生产提供了可供参考的设计思路和策略.展开更多
The solar H_(2)generation directly from natural seawater is a sustainable way of green energy.However,it is limited by a low H_(2)generation rate even compared to fresh water.In this report,TiO_(2)is chosen as a model...The solar H_(2)generation directly from natural seawater is a sustainable way of green energy.However,it is limited by a low H_(2)generation rate even compared to fresh water.In this report,TiO_(2)is chosen as a model photocatalyst to disclose the critical factor to deteriorate the H_(2)generation rate from seawater.The simulated seawater(SSW),which is composed of eight ions(Na^(+),K^(+),Ca^(2+),Mg^(2+),Cl^(−),Br^(−),SO_(4)^(2−),and CO_(3)^(2−)),is investigated the effect of each ion on the H_(2)production.The results indicate that all ions have a negative effect at the same concentration as in the seawater except Br−.The CO_(3)^(2−)has the most serious deterioration,and the H_(2)production rate lowers near 40%even at[CO_(3)^(2−)]of 1.5 mmol·L^(−1).The H_(2)production rate can be recovered to 85%if the CO_(3)^(2−)is excluded from the SSW.To understand the reason,the zeta potential of the TiO_(2)treated with different ions aqueous solution reveals that the zeta potential decreases when it is treated with CO_(3)^(2−)and SO_(4)^(2−)due to they can adsorb on the surface of TiO_(2)nanoparticles.Fourier transform infrared(FTIR)and thermogravimetric analysis-mass spectroscopy(TGA-MS)further confirm that the adsorbed ion is mainly from CO_(3)^(2−).Since the pH of seawater is about 8.9 between pKa1(6.37)and pKa2(10.3)of H_(2)CO3,the CO_(3)^(2−)should exist in the form of HCO3−in the seawater.We proposed a simple method to remove the adsorbed HCO3−from the TiO_(2)surface by adjusting the pH below the pKa1.The results indicate that if a trace amount of HCl(adjusting pH~6.0)is added to the SSW,the H_(2)production rate can be recovered to 85%of that in pure water.展开更多
Photocatalysis is considered to be a clean, green and efficient method to purify water. In this report, we first developed a highly efficient ultrafine TiO_2 nanorods/g-C3 N4 nanosheets(TiO_2 NR/CN NS) composites via ...Photocatalysis is considered to be a clean, green and efficient method to purify water. In this report, we first developed a highly efficient ultrafine TiO_2 nanorods/g-C3 N4 nanosheets(TiO_2 NR/CN NS) composites via a simple hydrothermal method. Tiny TiO_2 nanorods(diameter:~1.5 nm and length:~8.3 nm) were first loaded in situ on the CN NS by adding graphitic carbon nitride(g-C3 N4) to the reaction solution.The TiO_2 NR/CN NS composites present high charge separation efficiency and broader light absorbance than P25 TiO_2. Furthermore, we illustrate that the Ti0_2 NR/CN NS catalyst possesses high performance for the photocatalytic degradation of the common and stubborn pollutants in water, such as the rhodamine B(RhB) dye and phenol. Under visible light(λ> 420 nm) irradiation, the apparent rate of the TiO_2 NR/CN NR is 172 and 41 times higher than that of the P25 TiO_2 and TiO_2 NR, respectively.Additionally, we speculated that the heterojunction formed between TiO_2 NR and CN NS, which is the basis for the experiments we have designed and the corresponding results. We demonstrated that reactive oxidative species such as superoxide anion radical and holes play critical roles in the degradation,and the hydroxyl radical contributes nothing to the degradation.展开更多
Carbon dots(Cdots)with a broad light absorption range could be a potential stable sensitizer for TiO2,which is an excellent ultraviolet(UV)response photocatalyst.Herein,we systematically investigated the different col...Carbon dots(Cdots)with a broad light absorption range could be a potential stable sensitizer for TiO2,which is an excellent ultraviolet(UV)response photocatalyst.Herein,we systematically investigated the different color emissive Cdots-sensitized TiO2 for H2 production.Firstly,all kinds of Cdots enhanced the photocatalytic properties of TiO2.All the Cdots-sensitized TiO2 exhibits visible light H2 production due to their absorption in the visible light region.The photocurrent and H2 production amount display strong dependence on the light absorption range of Cdots.The blue-emissive Cdots endow the weak H2 production rate due to its weak absorption in the visible light.The enhanced photocatalytic activities are mainly contributed to the strong light absorbance and high-efficient charge separation.The light absorption of green-and red-emissive Cdots is another main factor for the high catalytic activities besides charge separation.展开更多
Photocatalytic N2 fixation involves a nitrogen reduction reaction on the surface of the photocatalyst to convert N2 into ammonia.Currently,the adsorption of N2 is the limiting step for the N2 reduction reaction on the...Photocatalytic N2 fixation involves a nitrogen reduction reaction on the surface of the photocatalyst to convert N2 into ammonia.Currently,the adsorption of N2 is the limiting step for the N2 reduction reaction on the surface of the catalyst.Based on the concept of photocatalytic water splitting,the photocatalytic efficiency can be greatly enhanced by introducing a co-catalyst.In this report,we proposed a new strategy,namely,the loading of a NiS co-catalyst on CdS nanorods for photocatalytic N2 fixation.Theoretical calculation results indicated that N2 was effectively adsorbed onto the NiS/CdS surface.Temperature programmed desorption studies confirmed that the N2 molecules preferred to adsorb onto the NiS/CdS surface.Linear sweep voltammetry results revealed that the overpotential of the N2 reduction reaction was reduced by loading NiS.Furthermore,transient photocurrent and electrochemical impedance spectroscopy indicated that the charge separation was enhanced by introducing NiS.Photocatalytic N2 fixation was carried out in the presence of the catalyst dispersed in water without any sacrificial agent.As a result,1.0 wt% NiS/CdS achieved an ammonia production rate of 2.8 and 1.7 mg L-1 for the first hour under full spectrum and visible light(λ>420 nm),respectively.The catalyst demonstrated apparent quantum efficiencies of 0.76%,0.39% and 0.09% at 420,475 and 520 nm,res pectively.This study provides a new method to promote the photocatalytic efficiency of N2 fixation.展开更多
Carbon dots(Cdots)has been proved to possess the catalytic decomposition of H_(2)O_(2) in the photocatalytic system.It is a potential photo-Fenton catalyst.Since multiple emissive Cdots have different light response r...Carbon dots(Cdots)has been proved to possess the catalytic decomposition of H_(2)O_(2) in the photocatalytic system.It is a potential photo-Fenton catalyst.Since multiple emissive Cdots have different light response range.There is rarely investigation on the performance of Cdots based photo-Fenton on the light wavelength.Herein,blue,green and red emissive carbon dots were synthesized from the different ratio of o-phenylenediamine and catechol by the solvothermal method.They exhibit different light adsorption range from UV to visible light.Furthermore,the photo-Fenton reactivity of Cdots was studied for catalyzing the decomposition of H_(2)O_(2) to generate free hydroxyl radicals and consequently applying for the removal of methyl blue.The results exhibit that Cdots with the broader light adsorption rang possess the stro nger catalytic activity for the photo-Fenton reaction.The H_(2)O_(2) decomposition rate of red emissive Cdots is 0.074 min^(-1),which is 2.64 and 1.46 times than the blue and green emissive Cdots,respectively.And the radical detection results confirm that the photo-Fenton happens in the reaction.In addition,the Cdots photo-Fenton can be carried out in the broad pH range from acidic to basic solution,which has a great potential to treat wastewater in the neutral system.展开更多
In this study,direct contact membrane distillation(DCMD)was used for treating fermentation wastewater with high organic concentrations.DCMD performance characteristics including permeate flux,permeate water quality ...In this study,direct contact membrane distillation(DCMD)was used for treating fermentation wastewater with high organic concentrations.DCMD performance characteristics including permeate flux,permeate water quality as well as membrane fouling were investigated systematically.Experimental results showed that,after 12 hr DCMD,the feed wastewater was concentrated by about a factor of 3.7 on a volumetric basis,with the permeate flux decreasing from the initial 8.7 L/m^2/hr to the final 4.3 L/m^2/hr due to membrane fouling;the protein concentration in the feed wastewater was increased by about 3.5 times and achieved a value of 6178 mg/L,which is suitable for reutilization.Although COD and TOC in permeate water increased continuously due to the transfer of volatile components from wastewater,organic rejection of over 95%was achieved in wastewater.GC–MS results suggested that the fermentation wastewater contained 128kinds of organics,in which 14 organics dominated.After 12 hr DCMD,not only volatile organics including trimethyl pyrazine,2-acetyl pyrrole,phenethyl alcohol and phenylacetic acid,but also non-volatile dibutyl phthalate was detected in permeate water due to membrane wetting.FT-IR and SEM–EDS results indicated that the deposits formed on the membrane inner surface mainly consisted of Ca,Mg,and amine,carboxylic acid and aromatic groups.The fouled membrane could be recovered,as most of the deposits could be removed using a HCl/Na OH chemical cleaning method.展开更多
Electrocatalytic nitrogen reduction reaction(NRR)is a sustainable approach for NH_(3)production with low energy consumption.However,competing hydrogen reduction reaction(HER)in aqueous solution results in low NH_(3)pr...Electrocatalytic nitrogen reduction reaction(NRR)is a sustainable approach for NH_(3)production with low energy consumption.However,competing hydrogen reduction reaction(HER)in aqueous solution results in low NH_(3)production and Faraday efficiency(FE).Here,MoS_(2)nanostructures with a hydrophobic surface are synthesized by alkyl thiols modification.Aerophilic and hydrophobic surface facilitates an efficient three-phase contact of N_(2),H_(2)O,and catalyst.Thus,localized concentrated N_(2)molecules can overcome the mass transfer limitation of N2 and depress the HER due to lowering the proton contacts.Although the active-sites decrease with the increase of the alkyl chain since the thiol may cover the active site,the optimized electrocatalyst achieves NH_(3)yield of 12.86×10^(-11)mol·cm^(-2)·s^(-1)at-0.25 V and 22.23%FE,which are 4.3 and 24 times higher than those of MoS2-CP electrocatalyst,respectively.The increased catalytic performance is attributed to the high N_(2)adsorption and depressed HER.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52200111,51978651,and 51878049)the China Postdoctoral Science Foundation(No.2021M703407)the special fund from the State Key Joint Laboratory of Environment Simulation and Pollution Control(Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences(No.21Z01ESPCR)。
文摘Membrane distillation(MD)is a promising alternative desalination technology,but the hydrophobic membrane cannot intercept volatile organic compounds(VOCs),resulting in aggravation in the quality of permeate.In term of this,electro-Fenton(EF)was coupled with sweeping gas membrane distillation(SGMD)in a more efficient way to construct an advanced oxidation barrier at the gas-liquid interface,so that the VOCs could be trapped in this layer to guarantee the water quality of the distillate.During the so-called EF-MD process,an interfacial interception barrier containing hydroxyl radical formed on the hydrophobic membrane surface.It contributed to the high phenol rejection of 90.2% with the permeate phenol concentration lower than 1.50 mg/L.Effective interceptions can be achieved in a wide temperature range,even though the permeate flux of phenol was also intensified.The EF-MD system was robust to high salinity and could electrochemically regenerate ferrous ions,which endowed the long-term stability of the system.This novel EF-MD configuration proposed a valuable strategy to intercept VOCs in MD and will broaden the application of MD in hypersaline wastewater treatment.
基金The authors thank the National Natural Science Foundation of China(No.21301166,21201159,61306081,and 61176016)Science and Technology Department of Jilin Province(No.20130522127JH)are gratefully acknowledged+1 种基金ZS thanks the support of the‘Hundred Talent Program’of CAS and Innovation and Entrepreneurship Program of JilinThe project was supported by Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry and the open research fund program of the State Key Laboratory of Luminescence and Applications.
文摘Unlike inorganic quantum dots,fluorescent graphene quantum dots(GQDs)display excitation-dependent multiple color emission.In this study,we report N-doped GQDs(N-GQDs)with tailored single color emission by tuning p-conjugation degree,which is comparable to the inorganic quantum dot.Starting from citric acid and diethylenetriamine,as prepared N-GQDs display blue,green,and yellow light emission by changing the reaction solvent from water,dimethylformamide(DMF),and solvent free.The X-ray photoelectron spectroscopy,ultraviolet-visible spectra results clearly show the N-GQDs with blue emission(N-GQDs-B)have relatively short effective conjugation length and more carboxyl group because H_(2)O is a polar protic solvent,which tends to donate proton to the reagent to depress the H_(2)O elimination reaction.On the other hand,the polar aprotic solvent(DMF)cannot donate hydrogen,the elimination of H_(2)O is promoted and more nitrogen units enter GQD framework.With the increase of effective p-conjugation length and N content,the emission band of N-GQDS red-shifts to green and yellow.We also demonstrate that N-GQDs could be a potential great biomarker for fluorescent bioimaging.
基金supported by the Fundamental Research Funds for the Central Universities(No.TD2010-5)the National Natural Science Research Fund(No.51078034,51278051)Beijing Forestry University Young Scientist Fund(No.BLX2009018)
文摘Hydrous manganese dioxide (HMO) synthesized by redox of potassium permanganate and hydrogen peroxide was used as an adsorbent for Pb(Ⅱ) removal.The specific surface area,pore volume and BJH pore diameter of the HMO were 79.31m2/g,0.07cm3/g and 3.38 nm,respectively.The adsorption equilibrium at 298K could be well described by the Langmuir isotherm equation with q max value of 352.55mg/g.The negative values of G and the positive values of H and S indicated the adsorption process was spontaneous and endothermic.The pseudo second-order equation could best fit the adsorption data.The value of the calculated activation energy for Pb(Ⅱ) adsorption onto the HMO was 38.23 kJ/mol.The uptake of Pb(Ⅱ) by HMO was correlated with increasing surface hydroxyl group content and the main adsorbed speciation was PbOH+.The final chemical state of Pb(Ⅱ) on the surface of HMO was similar to PbO.HMO was a promising candidate for Pb(Ⅱ) removal from aqueous solution.
基金supported by the National Natural Science Foundation of China(21872001,51801006,21805004,and 21671011)Beijing Municipal High Level Innovative Team Building Program(IDHT20180504)+2 种基金Beijing Outstanding Young Scientists Program(BJJWZYJH01201910005017)Beijing Natural Science Foundation(2192005)Beijing Municipal Science and Natural Science Fund Project(KM201910005016)。
文摘水体污染是当前造成淡水短缺的主要原因之一.利用太阳能水蒸发装置从海水或污水中生产淡水是一种简单有效且节能的解决淡水危机的方式,引起了广泛的关注.然而,污染物的共同蒸发或沉积可能会降低水蒸发过程中的效率和淡水质量.本文基于天然木质纤维素(NCF)、聚苯胺(PANI)和二氧化钛(TiO_(2))开发了自清洁太阳能水蒸发器,其具有宽吸收、亲水性强、导热系数低等优点.通过在聚合物溶液中加入木质纤维素,聚苯胺纳米纤维在NCF表面聚合形成介孔网络.P25 TiO_(2)纳米颗粒作为光催化剂分散到上述反应液中,通过简单的过滤形成PANI/TiO_(2)/NCF复合材料.由于太阳水蒸发器装置中PANI的光热效应与TiO_(2)纳米颗粒的光催化降解的协同作用,水蒸发速率可达2.36 kg m^(-2)h^(-1)(1个太阳光照射下),且可有效降解污染物(100 ppm四环素).更重要的是,在工作10 h后,该太阳能水蒸发器装置仍然保持稳定的水蒸发速率,且没有污染物的积聚.光催化和光热效应相结合的双功能太阳能水蒸发装置在有机污染物水中具有自清洁作用,具有很大的应用潜力.
基金financially supported by the National Natural Science Foundation of China(21805004,21872001,51801006,and 21671011)Beijing Municipal High-Level Innovative Team Building Program(IDHT20180504)+2 种基金Beijing Outstanding Young Scientists Program(BJJWZYJH01201910005017)Beijing Natural Science Foundation(2192005)Beijing Municipal Science and Natural Science Fund Project(KM201910005016).
文摘太阳能水蒸发对于解决净水危机潜力无限.随着研究的深入,研发高效光热转换材料和合理的材料结构设计均可以提高光热蒸发速率.因此,我们设计合成了一种双层碳基水凝胶复合材料.在一个太阳光照条件下,其最大蒸发速率可达2.19 kg m^(−2)h^(−1),光热转换效率可达93.7%.同时,该复合材料展现了优异的海水淡化性能及良好的稳定性,扩展了实际应用范围.除此之外,其可控规模化及便携性可以自如面对多种复杂的应用环境,成本低廉可以使其大规模应用于经济落后地区,为复合结构水凝胶蒸发器的生产提供了可供参考的设计思路和策略.
基金financially supported by the National Natural Science Foundation of China(21872001,51801006,21805004,and 21671011)Beijing Municipal High Level Innovative Team Building Program(IDHT20180504)+2 种基金Beijing Outstanding Young Scientists Program(BJJWZYJH01201910005017)Beijing Natural Science Foundation(2192005)Beijing Municipal Science and Natural Science Fund Project(KM201910005016)。
基金supported by the National Natural Science Foundation of China(Nos.21872001,22272003,21805004,and 51801006)the Beijing Municipal High-Level Innovative Team Building Program(No.IDHT 20180504)+3 种基金Beijing Outstanding Young Scientists Program(No.BJJWZYJH0201910005017)Beijing Natural Science Foundation(Nos.KZ201710005002 and 2192005)Beijing Municipal Science and Natural Science Fund Project(No.KM201910005016)these funding agencies are acknowledged.
文摘The solar H_(2)generation directly from natural seawater is a sustainable way of green energy.However,it is limited by a low H_(2)generation rate even compared to fresh water.In this report,TiO_(2)is chosen as a model photocatalyst to disclose the critical factor to deteriorate the H_(2)generation rate from seawater.The simulated seawater(SSW),which is composed of eight ions(Na^(+),K^(+),Ca^(2+),Mg^(2+),Cl^(−),Br^(−),SO_(4)^(2−),and CO_(3)^(2−)),is investigated the effect of each ion on the H_(2)production.The results indicate that all ions have a negative effect at the same concentration as in the seawater except Br−.The CO_(3)^(2−)has the most serious deterioration,and the H_(2)production rate lowers near 40%even at[CO_(3)^(2−)]of 1.5 mmol·L^(−1).The H_(2)production rate can be recovered to 85%if the CO_(3)^(2−)is excluded from the SSW.To understand the reason,the zeta potential of the TiO_(2)treated with different ions aqueous solution reveals that the zeta potential decreases when it is treated with CO_(3)^(2−)and SO_(4)^(2−)due to they can adsorb on the surface of TiO_(2)nanoparticles.Fourier transform infrared(FTIR)and thermogravimetric analysis-mass spectroscopy(TGA-MS)further confirm that the adsorbed ion is mainly from CO_(3)^(2−).Since the pH of seawater is about 8.9 between pKa1(6.37)and pKa2(10.3)of H_(2)CO3,the CO_(3)^(2−)should exist in the form of HCO3−in the seawater.We proposed a simple method to remove the adsorbed HCO3−from the TiO_(2)surface by adjusting the pH below the pKa1.The results indicate that if a trace amount of HCl(adjusting pH~6.0)is added to the SSW,the H_(2)production rate can be recovered to 85%of that in pure water.
基金supported by the Beijing Municipal High Level Innovative Team Building Program(IDHT20180504)the National Natural Science Foundation of China(21671011)+4 种基金Beijing High Talent ProgramBeijing Natural Science Foundation(KZ201710005002)the Large-scale Instrument and Equipment Platform of Beijing University of TechnologyChina Postdoctoral Science FoundationBeijing Postdoctoral Research Foundation
文摘Photocatalysis is considered to be a clean, green and efficient method to purify water. In this report, we first developed a highly efficient ultrafine TiO_2 nanorods/g-C3 N4 nanosheets(TiO_2 NR/CN NS) composites via a simple hydrothermal method. Tiny TiO_2 nanorods(diameter:~1.5 nm and length:~8.3 nm) were first loaded in situ on the CN NS by adding graphitic carbon nitride(g-C3 N4) to the reaction solution.The TiO_2 NR/CN NS composites present high charge separation efficiency and broader light absorbance than P25 TiO_2. Furthermore, we illustrate that the Ti0_2 NR/CN NS catalyst possesses high performance for the photocatalytic degradation of the common and stubborn pollutants in water, such as the rhodamine B(RhB) dye and phenol. Under visible light(λ> 420 nm) irradiation, the apparent rate of the TiO_2 NR/CN NR is 172 and 41 times higher than that of the P25 TiO_2 and TiO_2 NR, respectively.Additionally, we speculated that the heterojunction formed between TiO_2 NR and CN NS, which is the basis for the experiments we have designed and the corresponding results. We demonstrated that reactive oxidative species such as superoxide anion radical and holes play critical roles in the degradation,and the hydroxyl radical contributes nothing to the degradation.
基金financially supported by the Beijing Municipal High Level Innovative Team Building Program (No. IDHT20180504)the National Natural Science Foundation of China (Nos. 21805004, 21671011, 21872001 and 51801006)+3 种基金Beijing Natural Science Foundation (No. KZ201710005002 and 2192005)the Natural Science Foundation of the Beijing Municipal Education Committee, China Postdoctoral Science Foundation (No. 2018M641133)Beijing Postdoctoral Research Foundation (No. 2018-ZZ-021)Chaoyang District Postdoctoral Research Foundation (No. 2018-ZZ-026)
文摘Carbon dots(Cdots)with a broad light absorption range could be a potential stable sensitizer for TiO2,which is an excellent ultraviolet(UV)response photocatalyst.Herein,we systematically investigated the different color emissive Cdots-sensitized TiO2 for H2 production.Firstly,all kinds of Cdots enhanced the photocatalytic properties of TiO2.All the Cdots-sensitized TiO2 exhibits visible light H2 production due to their absorption in the visible light region.The photocurrent and H2 production amount display strong dependence on the light absorption range of Cdots.The blue-emissive Cdots endow the weak H2 production rate due to its weak absorption in the visible light.The enhanced photocatalytic activities are mainly contributed to the strong light absorbance and high-efficient charge separation.The light absorption of green-and red-emissive Cdots is another main factor for the high catalytic activities besides charge separation.
基金financially supported by the Beijing Municipal High-Level Innovative Team Building Program (IDHT20180504)the National Natural Science Foundation of China (21805004, 21671011, 21872001 and 51801006)+3 种基金the Beijing Natural Science Foundation (KZ201710005002 and 2192005)the China Postdoctoral Science Foundation (2018M641133)the Beijing Postdoctoral Research Foundation (2018-ZZ-021)the Chaoyang District Postdoctoral Research Foundation, China (2018-ZZ-026)
文摘Photocatalytic N2 fixation involves a nitrogen reduction reaction on the surface of the photocatalyst to convert N2 into ammonia.Currently,the adsorption of N2 is the limiting step for the N2 reduction reaction on the surface of the catalyst.Based on the concept of photocatalytic water splitting,the photocatalytic efficiency can be greatly enhanced by introducing a co-catalyst.In this report,we proposed a new strategy,namely,the loading of a NiS co-catalyst on CdS nanorods for photocatalytic N2 fixation.Theoretical calculation results indicated that N2 was effectively adsorbed onto the NiS/CdS surface.Temperature programmed desorption studies confirmed that the N2 molecules preferred to adsorb onto the NiS/CdS surface.Linear sweep voltammetry results revealed that the overpotential of the N2 reduction reaction was reduced by loading NiS.Furthermore,transient photocurrent and electrochemical impedance spectroscopy indicated that the charge separation was enhanced by introducing NiS.Photocatalytic N2 fixation was carried out in the presence of the catalyst dispersed in water without any sacrificial agent.As a result,1.0 wt% NiS/CdS achieved an ammonia production rate of 2.8 and 1.7 mg L-1 for the first hour under full spectrum and visible light(λ>420 nm),respectively.The catalyst demonstrated apparent quantum efficiencies of 0.76%,0.39% and 0.09% at 420,475 and 520 nm,res pectively.This study provides a new method to promote the photocatalytic efficiency of N2 fixation.
基金supported by the National Natural Science Foundation of China(Nos.21805004,21671011,21872001 and 51801006)the Beijing Municipal High Level Innovative Team Building Program(No.IDHT20180504)+2 种基金the Beijing Outstanding Young Scientists Program(No.BJJWZYJH01201910005017)the Beijing Natural Science Foundation(No.2192005)the Beijing Municipal Science and Natural Science Fund Project(No.KM201910005016)。
文摘Carbon dots(Cdots)has been proved to possess the catalytic decomposition of H_(2)O_(2) in the photocatalytic system.It is a potential photo-Fenton catalyst.Since multiple emissive Cdots have different light response range.There is rarely investigation on the performance of Cdots based photo-Fenton on the light wavelength.Herein,blue,green and red emissive carbon dots were synthesized from the different ratio of o-phenylenediamine and catechol by the solvothermal method.They exhibit different light adsorption range from UV to visible light.Furthermore,the photo-Fenton reactivity of Cdots was studied for catalyzing the decomposition of H_(2)O_(2) to generate free hydroxyl radicals and consequently applying for the removal of methyl blue.The results exhibit that Cdots with the broader light adsorption rang possess the stro nger catalytic activity for the photo-Fenton reaction.The H_(2)O_(2) decomposition rate of red emissive Cdots is 0.074 min^(-1),which is 2.64 and 1.46 times than the blue and green emissive Cdots,respectively.And the radical detection results confirm that the photo-Fenton happens in the reaction.In addition,the Cdots photo-Fenton can be carried out in the broad pH range from acidic to basic solution,which has a great potential to treat wastewater in the neutral system.
基金supported by the Special S&T Project on Treatment and Control of Water Pollution (No. 2013ZX07201007-003)
文摘In this study,direct contact membrane distillation(DCMD)was used for treating fermentation wastewater with high organic concentrations.DCMD performance characteristics including permeate flux,permeate water quality as well as membrane fouling were investigated systematically.Experimental results showed that,after 12 hr DCMD,the feed wastewater was concentrated by about a factor of 3.7 on a volumetric basis,with the permeate flux decreasing from the initial 8.7 L/m^2/hr to the final 4.3 L/m^2/hr due to membrane fouling;the protein concentration in the feed wastewater was increased by about 3.5 times and achieved a value of 6178 mg/L,which is suitable for reutilization.Although COD and TOC in permeate water increased continuously due to the transfer of volatile components from wastewater,organic rejection of over 95%was achieved in wastewater.GC–MS results suggested that the fermentation wastewater contained 128kinds of organics,in which 14 organics dominated.After 12 hr DCMD,not only volatile organics including trimethyl pyrazine,2-acetyl pyrrole,phenethyl alcohol and phenylacetic acid,but also non-volatile dibutyl phthalate was detected in permeate water due to membrane wetting.FT-IR and SEM–EDS results indicated that the deposits formed on the membrane inner surface mainly consisted of Ca,Mg,and amine,carboxylic acid and aromatic groups.The fouled membrane could be recovered,as most of the deposits could be removed using a HCl/Na OH chemical cleaning method.
基金We acknowledge financial support from the Beijing Municipal High Level Innovative Team Building Program(No.IDHT20180504)Beijing Outstanding Young Scientist Program(No.BJJWZYJH01201910005017)+2 种基金the National Natural Science Foundation of China(Nos.51801006,21805004,21872001,and 21936001)Beijing Natural Science Foundation(No.2192005)Beijing Municipal Science and Natural Science Fund Project(Nos.KM201910005016 and 2017000020124G085).
文摘Electrocatalytic nitrogen reduction reaction(NRR)is a sustainable approach for NH_(3)production with low energy consumption.However,competing hydrogen reduction reaction(HER)in aqueous solution results in low NH_(3)production and Faraday efficiency(FE).Here,MoS_(2)nanostructures with a hydrophobic surface are synthesized by alkyl thiols modification.Aerophilic and hydrophobic surface facilitates an efficient three-phase contact of N_(2),H_(2)O,and catalyst.Thus,localized concentrated N_(2)molecules can overcome the mass transfer limitation of N2 and depress the HER due to lowering the proton contacts.Although the active-sites decrease with the increase of the alkyl chain since the thiol may cover the active site,the optimized electrocatalyst achieves NH_(3)yield of 12.86×10^(-11)mol·cm^(-2)·s^(-1)at-0.25 V and 22.23%FE,which are 4.3 and 24 times higher than those of MoS2-CP electrocatalyst,respectively.The increased catalytic performance is attributed to the high N_(2)adsorption and depressed HER.