Structural regulation of Pd-based electrocatalytic hydrodechlorination(EHDC)catalyst for constructing high-efficient cathode materials with low noble metal content and high atom utilization is crucial but still challe...Structural regulation of Pd-based electrocatalytic hydrodechlorination(EHDC)catalyst for constructing high-efficient cathode materials with low noble metal content and high atom utilization is crucial but still challenging.Herein,a support electron inductive effect of Pd-Mn/Ni foam catalyst was proposed via in-situ Mn doping to optimize the electronic structure of the Ni foam(NF),which can inductive regulation of Pd for improving the EHDC performance.The mass activity and current efficiency of Pd-Mn/NF catalyst are 2.91 and 1.34 times superior to that of Pd/NF with 2,4-dichlorophenol as model compound,respectively.The Mn-doped interlayer optimized the electronic structure of Pd by bringing the d-state closer to the Fermi level than Pd on the NF surface,which optimizied the binding of EHDC intermediates.Additionally,the Mn-doped interlayer acted as a promoter for generating H∗and accelerating the EHDC reaction.This work presents a simple and effective regulation strategy for constructing high-efficient cathode catalyst for the EHDC of chlorinated organic compounds.展开更多
Catalytic nickel was successfully incorporated into nanoscale iron to enhance its dechlorination efficiency for trichloroethylene （TCE）, one of the most commonly detected chlorinated organic compounds in groundwater...Catalytic nickel was successfully incorporated into nanoscale iron to enhance its dechlorination efficiency for trichloroethylene （TCE）, one of the most commonly detected chlorinated organic compounds in groundwater. Ethane was the predominant product. The greatest dechlorination efficiency was achieved at 22 molar percent of nickel. This nanoscale Ni-Fe is poorly ordered and inhomogeneous; iron dissolution occurred whereas nickel was relatively stable during the 24-hr reaction. The morphological characterization provided significant new insights on the mechanism of catalytic hydrodcchlorination by bimetallic nanoparticles. TCE degradation and ethane production rates were greatly affected by environmental parameters such as solution pH, temperature and common groundwater ions. Both rate constants decreased and then increased over the pH range of 6.5 to 8.0, with the minimum value occurring at pH 7.5. TCE degradation rate constant showed an increasing trend over the temperature range of 10 to 25℃. However, ethane production rate constant increased and then decreased over the range, with the maximum value occurring at 20℃, Most salts in the solution appeared to enhance the reaction in the first half hour but overall they displayed an inhibitory effect. Combined ions showed a similar effect as individual salts.展开更多
We report a one‐pot surfactant‐free wet‐chemical reduction approach to the synthesis of palladium/titanium nitride(Pd/TiN)and Pd/carbon(Pd/C)composites,in which^5 nm Pd NPs were uniformly dispersed on TiN or C.In t...We report a one‐pot surfactant‐free wet‐chemical reduction approach to the synthesis of palladium/titanium nitride(Pd/TiN)and Pd/carbon(Pd/C)composites,in which^5 nm Pd NPs were uniformly dispersed on TiN or C.In terms of catalytic performance,Pd/TiN showed enhanced efficiency and stability compared with those of Pd/C and bare TiN in the electrocatalytic hydrodechlorination(EHDC)reaction of 2,4‐dichlorophenol(2,4‐DCP)in aqueous solution.The superior performance of Pd/TiN arises from the promotion effect of TiN.Strong metal‐support interactions modified the electronic structure of Pd,which optimized generation of H*ads and 2,4‐DCP adsorption/activation.The cathode potential plays a vital role in controlling the EHDC efficiency and the product distribution.A working potential of?0.80 V was shown to be optimal for achieving the highest EHDC efficiency and maximizing conversion of 2,4‐DCP to phenol(P).Our studies of the reaction pathway show that EHDC of 2,4‐DCP on Pd/TiN proceeded by 2,4‐DCP→p‐chlorophenol(p‐CP),o‐chlorophenol(o‐CP)→P;however,Pd/TiN presented little selectivity for cleavage of p‐C‐Cl vs o‐C‐Cl.This work presents a new approach to enhancing Pd performance towards EHDC through the effects of a support.The strategy demonstrated here could also be extended to design highly efficient catalysts for other hydrogenation reactions.展开更多
Pd modified electrodes possess problems such as easy agglomeration and low electrolytic ability,and the use of manganese dioxide(MnO_(2)) to facilitate Pd reduction of organic pollutants is just started.However,there ...Pd modified electrodes possess problems such as easy agglomeration and low electrolytic ability,and the use of manganese dioxide(MnO_(2)) to facilitate Pd reduction of organic pollutants is just started.However,there is still a limited understanding of how to match the Pd load and MnO_(2) to realize optimal dechlorination efficiency at minimum cost.Here,a Pd/MnO_(2)/Ni foam cathode was successfully fabricated and applied for the efficient electrochemical dechlorination of 2,4,6-trichlorophenol(2,4,6-TCP).The optimal electrocatalytic hydrodechlorination(ECH)performance with 2,4,6-TCP dechlorination efficiency(92.58%in 180 min)was obtained when the concentration of PdCl_(2) precipitation was 1 mmol/L,the deposition time of MnO_(2) was 300 s and cathode potential was-0.8 V.Performance influenced by the exogenous factors(e.g.,initial pH and coexisted ions)were further investigated.It was found that the neutral pH was the most favorable for ECH and a reduction in dechlorination efficiency(6%~47.6%)was observed in presence of 5 mmol/L of NO_(2)^(-),NO_(3)^(-),S^(2-)or SO_(3)^(2-).Cyclic voltammetry(CV)and quenching experiments verified the existence of three hydrogen species on Pd surface,including adsorbed atomic hydrogen(H^(*)_(ads)),absorbed atomic hydrogen(H^(*)_(abs)),and molecular hydrogen(H_(2)).And the introduction of MnO_(2)promoted the generation of atomic H^(*).Only adsorbed atomic hydrogen(H^(*)_(ads)) was confirmed that it truly facilitated the ECH process.Besides H^(*)_(ads) induced reduction,the direct reduction by cathode electrons also participated in the 2,4,6-TCP dechlorination process.Pd/MnO_(2)/Ni foam cathode shows excellent dechlorination performance,fine stability and recyclable potential,which provides strategies for the effective degradation of persistent halogenated organic pollutants in groundwater.展开更多
Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal’s electrocatalytic hydrodechlo rination perfo rmance in converting 2,4-dichlorophenol...Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal’s electrocatalytic hydrodechlo rination perfo rmance in converting 2,4-dichlorophenol(2,4-DCP)to phenol.The specific activity of the Pd nanoparticles(Pd NPs)on defective polymer carbon nitride(Pd/PCN-x)reaches 0.09 min^(-1) m^-2Pd,which is 1.5 times that of the Pd NPs supported on the perfect PCN(Pd/PCN-0).The combined experimental and theoretical results demonstrate that the strong adsorption of phenol on Pd/PCN-0 passivates the active sites,limiting the dechlorination progress.The PCN-x containing-C≡N defects can effectively mediate the spatial configuration and electronic structure of Pd NPs,and promote the preferential adsorption of 2,4-DCP rather than phenol,resulting in an enhanced dechlorination efficiency.展开更多
A novel supported liquid phase film catalyst: Supported PdCl2-(n-C4H9),N+Cl- molten salts was found to be an effective catalyst with good stability for selective hydrodechlorination of CCl2F2 (CFC-12) to its alternati...A novel supported liquid phase film catalyst: Supported PdCl2-(n-C4H9),N+Cl- molten salts was found to be an effective catalyst with good stability for selective hydrodechlorination of CCl2F2 (CFC-12) to its alternatives CH2F2 and CHClF2. Addition of CoCl2, GaCl3 and CuCl2 to PdCl2-(n-C4H9),N+Cl- modifies the catalytic performance of supported molten salts.展开更多
Chlorotrifluoroethylene(CTFE)is a vital fluorinated olefinic monomer produced through the catalytic hydrodechlorination of trichlorotrifluoroethane(CFC-113),an eco-friendly process.However,hydrodechlorination catalyst...Chlorotrifluoroethylene(CTFE)is a vital fluorinated olefinic monomer produced through the catalytic hydrodechlorination of trichlorotrifluoroethane(CFC-113),an eco-friendly process.However,hydrodechlorination catalysts for olefin production often suffer from poor stability.The Pd/AC catalyst and Pd-Cu/AC catalyst prepared by co-impregnation method exhibited poor stability,Pd-Cu/AC catalyst with CFC-113 conversion dropping to around 37%after 50 h of hydrodechlorination reaction.Brunauer-Emmett-Teller,transmission electron microscopy,X-ray photoelectron spectroscopy,and X-ray diffraction of fresh and deactivated Pd/AC catalysts indicate that the deactivation of Pd/AC catalysts is due to high-temperature agglomeration of Pd.Comparative analysis of fresh and deactivated Pd-Cu/AC catalysts using Brunauer-Emmett-Teller,transmission electron microscopy,and thermogravimetric analysis techniques revealed decreased dispersion of active sites,reduced surface area,catalyst aggregation deactivation,and a significant decrease in Cu content.Furthermore,the results of NH3-TPD revealed that the acid sites of the catalyst increased significantly.X-ray diffraction spectra indicated the formation of new species,basic copper chloride(Cu_(2)(OH)_(3)Cl),during the reaction.As the reaction progressed,these new species agglomerated,leading to a gradual loss of catalyst activity.Moreover,the deactivated catalyst was successfully reactivated using a simple alkaline washing method.展开更多
Electrocatalysis technology can effectively promote the hydrodechlorination of chloramphenicol(CAP)to reduce the bio-toxicity.However,there are still some challenges such as low degradation rate and poor stability.Her...Electrocatalysis technology can effectively promote the hydrodechlorination of chloramphenicol(CAP)to reduce the bio-toxicity.However,there are still some challenges such as low degradation rate and poor stability.Here,we prepared porous N,O co-doped carbon supported Pd nanoparticles composites(Pd NPs/NO-C)for electrocatalytic degradation of CAP.The doping of N and O not only effectively enhanced the interaction between substrate and CAP,promoting the mass transfer process,but also enhanced the anchoring effect on Pd nanoparticles,avoiding the occurrence of aggregation.The prepared composites achieved removal efficiency of CAP over 99%within 1 h,and the rate constant was as high as 6.72 h^(–1),outperforming previous reported electrocatalysts.Additionally,Pd NPs/NO-C composites showed a wide range of pH tolerance,excellent ion interference resistance and long-term stability.Our work unravels the importance of mass transfer processes in solution to electrocatalytic hydrodechlorination and provides new research ideas for catalysts design.展开更多
In this study, stabilized Pd, Pt and Au nanoparticles were successfully prepared in aqueous phase using sodium carboxymethyl cellulose （CMC） as a capping agent. These metal nanoparticles were then tested for catalyt...In this study, stabilized Pd, Pt and Au nanoparticles were successfully prepared in aqueous phase using sodium carboxymethyl cellulose （CMC） as a capping agent. These metal nanoparticles were then tested for catalytic hydrodechlorination toward two classes of organochlorinated compounds （vinyl polychlorides includ- ing trichloroethylene （TCE）, tetrachloroethylene （PCE）, and alkyl polychlorides including 1,1,1-trichloroethane （1,1,1-TCA）, and 1,1,1,2-tetrachloroethane （1,1,1,2- TeCA）） to determine the rate-limiting steps and to explore the reaction mechanisms. The surface area normalized reaction rate constant, ksA, showed a systematic depen- dence on the electronic structure （the density of states at the Fermi level） of the metals, suggesting that adsorption of organochlorinated reactants on the metal catalyst surfaces is the rate-limiting step for catalytic hydrodechlorination. Hydrodechlorination rates of 1,1,1-TCA and 1,1,1,2-TeCA agreed with the bond strength of the first （weakest） dissociated C-C1 bond, suggesting that C-C1 bond cleavage, which is the first step for dissociative adsorption of the alkyl polychlorides, controlled the catalytic hydro- dechlorination rate. However, hydrodechlorination rates of TCE and PCE correlated with the adsorption energies of their molecular （non-dissociative） adsorption on the noble metals rather than with the first C-C1 bond strength, suggesting that molecular adsorption governs the reaction rate for hydrodechlorination of the vinyl polychlorides.展开更多
Catalytic hydrodechlorination(HDC)is an innovative means of transforming chlorinated waste streams into a recyclable product. In this study,the gas phase HDC of chlorobenzene(CB)has been studied over bulk Pd and Ni an...Catalytic hydrodechlorination(HDC)is an innovative means of transforming chlorinated waste streams into a recyclable product. In this study,the gas phase HDC of chlorobenzene(CB)has been studied over bulk Pd and Ni and((8±1)wt%)Pd and Ni supported on activated carbon(AC),graphite,graphitic nanofibers(GNF),Al2O3,and SiO2.Catalyst activation was examined by temperature-programmed reduction(TPR)analysis and the activated catalysts characterized in terms of BET area,transmission electron microscopy,scanning electron microscopy,H2 chemisorption/temperature-programmed desorption,and X-ray diffraction measurements.Metal surface area(1-19 m 2 /g), TPR,and H2 uptake/release exhibited a dependence on both metal and support.The Pd system delivered specific HDC rates that were up to three orders of magnitude greater than that recorded for the Ni catalysts,a result that we link to the higher H2 diffusivity in Pd.HDC was 100%selective over Ni while Pd also produced cyclohexane(selectivity<4%)as a result of a combined HDC/hydrogenation.Bulk Pd outperformed carbon supported Pd but was less active than Pd on the oxide supports.In contrast,unsupported Ni presented no measurable activity when compared with supported Ni.The specific HDC rate was found to increase with decreasing metal surface area where spillover hydrogen served to enhance HDC performance.展开更多
Monochloroacetic acid(MCAA)is identified as a highly carcinogenic disinfection by-product in chlorinated drinking water.In this study,a series of CeO_(2)-supported Pd catalysts(Pd/MCeO_(2))were synthesized through one...Monochloroacetic acid(MCAA)is identified as a highly carcinogenic disinfection by-product in chlorinated drinking water.In this study,a series of CeO_(2)-supported Pd catalysts(Pd/MCeO_(2))were synthesized through one-step calcination of Pd-loaded Ce-UiO-66-BDC(CeMOF),and the liquid-phase catalytic hydrodechlorination of MCA A was explored using these catalysts.For comparison,Pd/CeO_(2)catalysts were additionally synthesized using the conventional impregnation method.The characterization results reveal that the catalysts exhibit strong metal-support interaction,leading to high Pd dispersion and Pd^(n+)content.Additionally,the calcination temperature significantly influences catalytic performance,with the catalyst calcined at 500℃(Pd/MCeO_(2)-500)demonstrating the highest catalytic activity and achieving complete dechlorination of MCA A within 50 min.Furthermore,it is found that the catalytic MCAA hydrodechlorination using the catalysts adheres to the Langmuir-Hinshelwood model.Accordingly,low reaction pH is favorable for the catalytic hydrodechlorination of MCAA,enhancing MCAA adsorption on the catalyst surface due to the electrostatic interaction between MCAA and the catalyst surface.Theoretical results suggest that the presence of Pd^(n+)efficiently facilitates MCAA adsorption and C-Cl cleavage,thus significantly enhancing the liquid-phase catalytic hydrodechlorination.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22178388 and 22108306)Taishan Scholars Program of Shandong Province(No.tsqn201909065)Chongqing Science and Technology Bureau(No.cstc2019jscx-gksb X0032).
文摘Structural regulation of Pd-based electrocatalytic hydrodechlorination(EHDC)catalyst for constructing high-efficient cathode materials with low noble metal content and high atom utilization is crucial but still challenging.Herein,a support electron inductive effect of Pd-Mn/Ni foam catalyst was proposed via in-situ Mn doping to optimize the electronic structure of the Ni foam(NF),which can inductive regulation of Pd for improving the EHDC performance.The mass activity and current efficiency of Pd-Mn/NF catalyst are 2.91 and 1.34 times superior to that of Pd/NF with 2,4-dichlorophenol as model compound,respectively.The Mn-doped interlayer optimized the electronic structure of Pd by bringing the d-state closer to the Fermi level than Pd on the NF surface,which optimizied the binding of EHDC intermediates.Additionally,the Mn-doped interlayer acted as a promoter for generating H∗and accelerating the EHDC reaction.This work presents a simple and effective regulation strategy for constructing high-efficient cathode catalyst for the EHDC of chlorinated organic compounds.
基金supported by the National Natural Science Foundation of China(No.20807004)the General Research an Development Founding for Universities directly under the Ministry of Education of China(BUCTZZ1202)
文摘Catalytic nickel was successfully incorporated into nanoscale iron to enhance its dechlorination efficiency for trichloroethylene （TCE）, one of the most commonly detected chlorinated organic compounds in groundwater. Ethane was the predominant product. The greatest dechlorination efficiency was achieved at 22 molar percent of nickel. This nanoscale Ni-Fe is poorly ordered and inhomogeneous; iron dissolution occurred whereas nickel was relatively stable during the 24-hr reaction. The morphological characterization provided significant new insights on the mechanism of catalytic hydrodcchlorination by bimetallic nanoparticles. TCE degradation and ethane production rates were greatly affected by environmental parameters such as solution pH, temperature and common groundwater ions. Both rate constants decreased and then increased over the pH range of 6.5 to 8.0, with the minimum value occurring at pH 7.5. TCE degradation rate constant showed an increasing trend over the temperature range of 10 to 25℃. However, ethane production rate constant increased and then decreased over the range, with the maximum value occurring at 20℃, Most salts in the solution appeared to enhance the reaction in the first half hour but overall they displayed an inhibitory effect. Combined ions showed a similar effect as individual salts.
基金supported by the National Natural Science Foundation of China(51508055,51502277)Chongqing Postdoctoral Science Foundation(Xm2016020)+2 种基金China Postdoctoral Science Foundation(2016M602660)Natural Science Foundation of Chongqing Science and Technology Commission(cstc2016jcyjA0154)Innovative Research Team of Chongqing(CXTDG201602014)~~
文摘We report a one‐pot surfactant‐free wet‐chemical reduction approach to the synthesis of palladium/titanium nitride(Pd/TiN)and Pd/carbon(Pd/C)composites,in which^5 nm Pd NPs were uniformly dispersed on TiN or C.In terms of catalytic performance,Pd/TiN showed enhanced efficiency and stability compared with those of Pd/C and bare TiN in the electrocatalytic hydrodechlorination(EHDC)reaction of 2,4‐dichlorophenol(2,4‐DCP)in aqueous solution.The superior performance of Pd/TiN arises from the promotion effect of TiN.Strong metal‐support interactions modified the electronic structure of Pd,which optimized generation of H*ads and 2,4‐DCP adsorption/activation.The cathode potential plays a vital role in controlling the EHDC efficiency and the product distribution.A working potential of?0.80 V was shown to be optimal for achieving the highest EHDC efficiency and maximizing conversion of 2,4‐DCP to phenol(P).Our studies of the reaction pathway show that EHDC of 2,4‐DCP on Pd/TiN proceeded by 2,4‐DCP→p‐chlorophenol(p‐CP),o‐chlorophenol(o‐CP)→P;however,Pd/TiN presented little selectivity for cleavage of p‐C‐Cl vs o‐C‐Cl.This work presents a new approach to enhancing Pd performance towards EHDC through the effects of a support.The strategy demonstrated here could also be extended to design highly efficient catalysts for other hydrogenation reactions.
基金supported by the NSFC-JSPS joint research program(No.51961145202)the Natural Science Foundation of Heilongjiang Province,China(No.C2018035)。
文摘Pd modified electrodes possess problems such as easy agglomeration and low electrolytic ability,and the use of manganese dioxide(MnO_(2)) to facilitate Pd reduction of organic pollutants is just started.However,there is still a limited understanding of how to match the Pd load and MnO_(2) to realize optimal dechlorination efficiency at minimum cost.Here,a Pd/MnO_(2)/Ni foam cathode was successfully fabricated and applied for the efficient electrochemical dechlorination of 2,4,6-trichlorophenol(2,4,6-TCP).The optimal electrocatalytic hydrodechlorination(ECH)performance with 2,4,6-TCP dechlorination efficiency(92.58%in 180 min)was obtained when the concentration of PdCl_(2) precipitation was 1 mmol/L,the deposition time of MnO_(2) was 300 s and cathode potential was-0.8 V.Performance influenced by the exogenous factors(e.g.,initial pH and coexisted ions)were further investigated.It was found that the neutral pH was the most favorable for ECH and a reduction in dechlorination efficiency(6%~47.6%)was observed in presence of 5 mmol/L of NO_(2)^(-),NO_(3)^(-),S^(2-)or SO_(3)^(2-).Cyclic voltammetry(CV)and quenching experiments verified the existence of three hydrogen species on Pd surface,including adsorbed atomic hydrogen(H^(*)_(ads)),absorbed atomic hydrogen(H^(*)_(abs)),and molecular hydrogen(H_(2)).And the introduction of MnO_(2)promoted the generation of atomic H^(*).Only adsorbed atomic hydrogen(H^(*)_(ads)) was confirmed that it truly facilitated the ECH process.Besides H^(*)_(ads) induced reduction,the direct reduction by cathode electrons also participated in the 2,4,6-TCP dechlorination process.Pd/MnO_(2)/Ni foam cathode shows excellent dechlorination performance,fine stability and recyclable potential,which provides strategies for the effective degradation of persistent halogenated organic pollutants in groundwater.
基金the National Key R&D Program of China(No.2019YFD1100300)National Natural Science Foundation of China(Nos.41877396,51708157)+2 种基金Shenzhen Key Technology R&D Program of China(No.JSGG20180507183210868)the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(Nos.ES201905,2020TS02)State Key Laboratory of Separation Membranes and Membrane Processes(Tianjin Polytechnic University,No.M2-201701)。
文摘Here we report a facile defect-engineering strategy on the support to optimize the metal-support interaction and enhance the metal’s electrocatalytic hydrodechlo rination perfo rmance in converting 2,4-dichlorophenol(2,4-DCP)to phenol.The specific activity of the Pd nanoparticles(Pd NPs)on defective polymer carbon nitride(Pd/PCN-x)reaches 0.09 min^(-1) m^-2Pd,which is 1.5 times that of the Pd NPs supported on the perfect PCN(Pd/PCN-0).The combined experimental and theoretical results demonstrate that the strong adsorption of phenol on Pd/PCN-0 passivates the active sites,limiting the dechlorination progress.The PCN-x containing-C≡N defects can effectively mediate the spatial configuration and electronic structure of Pd NPs,and promote the preferential adsorption of 2,4-DCP rather than phenol,resulting in an enhanced dechlorination efficiency.
文摘A novel supported liquid phase film catalyst: Supported PdCl2-(n-C4H9),N+Cl- molten salts was found to be an effective catalyst with good stability for selective hydrodechlorination of CCl2F2 (CFC-12) to its alternatives CH2F2 and CHClF2. Addition of CoCl2, GaCl3 and CuCl2 to PdCl2-(n-C4H9),N+Cl- modifies the catalytic performance of supported molten salts.
基金supported by the National Natural Science Foundation of China(22008212,22078292,21902124)Natural Science Basic Research Planning Shaanxi Province of China(2017ZDJC-29)+2 种基金Key Research and Development Project of Shaanxi Province(2018ZDXM-GY-173)China Postdoctoral Science Foundation(2019 M663848)Open cooperative innovation fund of Xi'an Institute of modern chemistry(SYJJ48).
文摘Chlorotrifluoroethylene(CTFE)is a vital fluorinated olefinic monomer produced through the catalytic hydrodechlorination of trichlorotrifluoroethane(CFC-113),an eco-friendly process.However,hydrodechlorination catalysts for olefin production often suffer from poor stability.The Pd/AC catalyst and Pd-Cu/AC catalyst prepared by co-impregnation method exhibited poor stability,Pd-Cu/AC catalyst with CFC-113 conversion dropping to around 37%after 50 h of hydrodechlorination reaction.Brunauer-Emmett-Teller,transmission electron microscopy,X-ray photoelectron spectroscopy,and X-ray diffraction of fresh and deactivated Pd/AC catalysts indicate that the deactivation of Pd/AC catalysts is due to high-temperature agglomeration of Pd.Comparative analysis of fresh and deactivated Pd-Cu/AC catalysts using Brunauer-Emmett-Teller,transmission electron microscopy,and thermogravimetric analysis techniques revealed decreased dispersion of active sites,reduced surface area,catalyst aggregation deactivation,and a significant decrease in Cu content.Furthermore,the results of NH3-TPD revealed that the acid sites of the catalyst increased significantly.X-ray diffraction spectra indicated the formation of new species,basic copper chloride(Cu_(2)(OH)_(3)Cl),during the reaction.As the reaction progressed,these new species agglomerated,leading to a gradual loss of catalyst activity.Moreover,the deactivated catalyst was successfully reactivated using a simple alkaline washing method.
基金support received from the Basic Research Project of Leading Technology in Jiangsu Province(BK20202012)the National Natural Science Foundation of China(21938006and 21776190)+1 种基金China Postdoctoral Science Foundation(2020M681714)the Priority Academic Program Development of Higher Education Institutions(PAPD)in Jiangsu.
文摘Electrocatalysis technology can effectively promote the hydrodechlorination of chloramphenicol(CAP)to reduce the bio-toxicity.However,there are still some challenges such as low degradation rate and poor stability.Here,we prepared porous N,O co-doped carbon supported Pd nanoparticles composites(Pd NPs/NO-C)for electrocatalytic degradation of CAP.The doping of N and O not only effectively enhanced the interaction between substrate and CAP,promoting the mass transfer process,but also enhanced the anchoring effect on Pd nanoparticles,avoiding the occurrence of aggregation.The prepared composites achieved removal efficiency of CAP over 99%within 1 h,and the rate constant was as high as 6.72 h^(–1),outperforming previous reported electrocatalysts.Additionally,Pd NPs/NO-C composites showed a wide range of pH tolerance,excellent ion interference resistance and long-term stability.Our work unravels the importance of mass transfer processes in solution to electrocatalytic hydrodechlorination and provides new research ideas for catalysts design.
基金This work was partially supported by the National Natural Science Foundation of China （Grant Nos. 51308312 and 41230638）.
文摘In this study, stabilized Pd, Pt and Au nanoparticles were successfully prepared in aqueous phase using sodium carboxymethyl cellulose （CMC） as a capping agent. These metal nanoparticles were then tested for catalytic hydrodechlorination toward two classes of organochlorinated compounds （vinyl polychlorides includ- ing trichloroethylene （TCE）, tetrachloroethylene （PCE）, and alkyl polychlorides including 1,1,1-trichloroethane （1,1,1-TCA）, and 1,1,1,2-tetrachloroethane （1,1,1,2- TeCA）） to determine the rate-limiting steps and to explore the reaction mechanisms. The surface area normalized reaction rate constant, ksA, showed a systematic depen- dence on the electronic structure （the density of states at the Fermi level） of the metals, suggesting that adsorption of organochlorinated reactants on the metal catalyst surfaces is the rate-limiting step for catalytic hydrodechlorination. Hydrodechlorination rates of 1,1,1-TCA and 1,1,1,2-TeCA agreed with the bond strength of the first （weakest） dissociated C-C1 bond, suggesting that C-C1 bond cleavage, which is the first step for dissociative adsorption of the alkyl polychlorides, controlled the catalytic hydro- dechlorination rate. However, hydrodechlorination rates of TCE and PCE correlated with the adsorption energies of their molecular （non-dissociative） adsorption on the noble metals rather than with the first C-C1 bond strength, suggesting that molecular adsorption governs the reaction rate for hydrodechlorination of the vinyl polychlorides.
基金supported by the National Science Foundation through Grant CTS-0218591
文摘Catalytic hydrodechlorination(HDC)is an innovative means of transforming chlorinated waste streams into a recyclable product. In this study,the gas phase HDC of chlorobenzene(CB)has been studied over bulk Pd and Ni and((8±1)wt%)Pd and Ni supported on activated carbon(AC),graphite,graphitic nanofibers(GNF),Al2O3,and SiO2.Catalyst activation was examined by temperature-programmed reduction(TPR)analysis and the activated catalysts characterized in terms of BET area,transmission electron microscopy,scanning electron microscopy,H2 chemisorption/temperature-programmed desorption,and X-ray diffraction measurements.Metal surface area(1-19 m 2 /g), TPR,and H2 uptake/release exhibited a dependence on both metal and support.The Pd system delivered specific HDC rates that were up to three orders of magnitude greater than that recorded for the Ni catalysts,a result that we link to the higher H2 diffusivity in Pd.HDC was 100%selective over Ni while Pd also produced cyclohexane(selectivity<4%)as a result of a combined HDC/hydrogenation.Bulk Pd outperformed carbon supported Pd but was less active than Pd on the oxide supports.In contrast,unsupported Ni presented no measurable activity when compared with supported Ni.The specific HDC rate was found to increase with decreasing metal surface area where spillover hydrogen served to enhance HDC performance.
基金financially supported by the National Natural Science Foundation of China(Nos.21976086 and 22002059)。
文摘Monochloroacetic acid(MCAA)is identified as a highly carcinogenic disinfection by-product in chlorinated drinking water.In this study,a series of CeO_(2)-supported Pd catalysts(Pd/MCeO_(2))were synthesized through one-step calcination of Pd-loaded Ce-UiO-66-BDC(CeMOF),and the liquid-phase catalytic hydrodechlorination of MCA A was explored using these catalysts.For comparison,Pd/CeO_(2)catalysts were additionally synthesized using the conventional impregnation method.The characterization results reveal that the catalysts exhibit strong metal-support interaction,leading to high Pd dispersion and Pd^(n+)content.Additionally,the calcination temperature significantly influences catalytic performance,with the catalyst calcined at 500℃(Pd/MCeO_(2)-500)demonstrating the highest catalytic activity and achieving complete dechlorination of MCA A within 50 min.Furthermore,it is found that the catalytic MCAA hydrodechlorination using the catalysts adheres to the Langmuir-Hinshelwood model.Accordingly,low reaction pH is favorable for the catalytic hydrodechlorination of MCAA,enhancing MCAA adsorption on the catalyst surface due to the electrostatic interaction between MCAA and the catalyst surface.Theoretical results suggest that the presence of Pd^(n+)efficiently facilitates MCAA adsorption and C-Cl cleavage,thus significantly enhancing the liquid-phase catalytic hydrodechlorination.
