Existing organic halide synthesis routes typically employ elemental halogens(X_(2),X=Cl or Br),leading to low atom economy and significant environmental pollution.In this work,we developed an atom efficient electrosyn...Existing organic halide synthesis routes typically employ elemental halogens(X_(2),X=Cl or Br),leading to low atom economy and significant environmental pollution.In this work,we developed an atom efficient electrosynthesis and separation strategy for halogenation reagents—N-chlorosuccinimide(NCS)and N-bromosuccinimide(NBS)—at high current densities.Faradic efficiency(FE)of 91.0%and 81.3%was achieved for NCS and NBS generation on RuO_(x)/TiO_(2)/Ti in a batch cell,respectively.Electrosynthesis of NCS likely involves both heterogeneous catalytic and homogeneous tandem pathways,while NBS is likely formed in a Langmuir-Hinshelwood mechanism with a proton-coupled electron transfer as the rate-determining step.A coupled continuous electrocatalytic synthesis and in situ separation setup was developed for the efficient production of NCS and NBS,which yielded 0.77 g of NCS in 12000 s and 0.81 g of NBS in 15000 s,both with relative purity exceeding 95%.The halogenation of acetone using NCS and NBS enabled gram-scale production of the key intermediate in organic synthesis,1-halogenacetone,with over 95%recovery of succinimide.展开更多
Electrocatalysis has been investigated as a promising strategy to utilize green electricity to produce renewable fuels,valuable chemicals,and treat pollutants.Electrode kinetic analysis is a potent technique in interr...Electrocatalysis has been investigated as a promising strategy to utilize green electricity to produce renewable fuels,valuable chemicals,and treat pollutants.Electrode kinetic analysis is a potent technique in interrogating reaction mechanisms and evaluating the electrocatalysts.Electron transfer(ET)and proton‐coupled electron transfer(PCET)processes are widely present in reaction networks of electrocatalysis.pH dependence of the kinetics is frequently employed to evaluate whether an elementary step involves proton participation,which is determined by both the reversibility and the specific reactants of electrode reactions.In this article,we discuss the pH dependence of two widely used formulations of the Butler–Volmer kinetics for a model PCET step and highlight a potential pitfall in kinetic analysis.This work aims to provide guiding principles for distinguishing ET and PCET steps via kinetic measurements in electrolytes in a broad range pH values.展开更多
Electron transfer processes at polymer electrolyte/electrode interfaces play a central role in modern electrochemical devices of energy conversion,however,current understanding of electron transfers through electroche...Electron transfer processes at polymer electrolyte/electrode interfaces play a central role in modern electrochemical devices of energy conversion,however,current understanding of electron transfers through electrochemical interfaces was established exclusively based on the studies of liquid/solid electrochemical interfaces.Thus,similarities and differences of liquid and polymer electrolyte/electrode interfaces need to be mapped out to guide the design of device level electrochemical interfaces.In this work,we employ the sulfonate adsorption/desorption as a probe reaction to understand the electron-transfer steps in polymer and liquid electrolytes.Through cyclic voltametric investigations on the well-define single-crystal Pd_(ML)Pt(111)electrode,we demonstrate that the oxidative adsorption and reductive desorption of sulfonates at the polymer electrolyte/electrode interface are chemically distinct from those in liquid electrolytes,with the former occurring mostly via the proton-coupled pathway while the latter proceeding mainly through the solvation-mediated pathway.Importantly,the sulfonate adsorption/desorption behaviors of alkylsulfonates become increasingly similar to those in Nafion with longer alkyl chains,suggesting that the interfacial hydrophobicity and solvation environment conferred by the perfluorinated polymer play a decisive role in the electron-transfer mechanism.Results reported in this study highlight the mechanistic distinctions between electron-transfer processes at electrochemical interfaces involving polymer and liquid electrolytes,and provide a framework for understanding electron-transfer processes at polymer electrolyte/electrode interfaces.展开更多
Renewable energy-driven bicarbonate conversion to valuable chemicals presents an attractive strategy for mitigating CO_(2)emissions,as bicarbonate can be efficiently generated from the capture of atmospheric CO_(2)usi...Renewable energy-driven bicarbonate conversion to valuable chemicals presents an attractive strategy for mitigating CO_(2)emissions,as bicarbonate can be efficiently generated from the capture of atmospheric CO_(2)using alkaline solutions with reactive absorption.In this work,we present a CO_(2)-mediated bicarbonate conversion to pure formate using a cation exchange membrane-based electrolyzer with a 25 cm^(2)electrode area.Our electrolysis achieved selectivities exceeding 75%for formate at a total current of 2.5 A,achieving formate concentrations up to 1.2 M and yields as high as 95%over extended periods.The techno-economic assessment confirmed the economic viability of the process,highlighting the potential for bicarbonate electrolysis as a sustainable method for producing valuable chemicals.展开更多
Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mecha...Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.展开更多
Electrochemical CO_(2)reduction to formate is a promising approach to store renewable electricity and utilize CO_(2).Tin oxide catalysts are efficient catalysts for this process,while the mechanisms underneath,especia...Electrochemical CO_(2)reduction to formate is a promising approach to store renewable electricity and utilize CO_(2).Tin oxide catalysts are efficient catalysts for this process,while the mechanisms underneath,especially the existence and role of oxidized tin species under CO2 electroreduction conditions remain unclear.In this work,we provide strong evidence on the presence of oxidized tin species on both SnO_(2)and Sn during CO_(2)reduction via in situ surface‐enhanced Raman spectroscopy,while in different nature.Reactivity measurements show similar activity and selectivity to formate production on SnO_(2)and Sn catalysts.Combined analysis of Raman spectra and reactivity results suggests that Sn(IV)and Sn(II)oxide species are unlikely the catalytic species in CO_(2)electroreduction to formate.展开更多
Electrocatalysis offers a promising approach towards chemical synthesis driven by renewable energy.Molecular level understanding of the electrochemical interface remains challenging due to its compositional and struct...Electrocatalysis offers a promising approach towards chemical synthesis driven by renewable energy.Molecular level understanding of the electrochemical interface remains challenging due to its compositional and structural complexity.In situ interfacial specific characterization techniques could help uncover structure-function relationships and reaction mechanism.To this end,electrochemical surface-enhanced Raman spectroscopy(SERS)and surface-enhanced infrared absorption spectroscopy(SEIRAS)thrive as powerful techniques to provide fingerprint information of interfacial species at reaction conditions.In this review,we first introduce the fundamentals of SERS and SEIRAS,followed by discussion regarding the technical challenges and potential solutions.Finally,we highlight future directions for further development of surface-enhanced spectroscopic techniques for electrocatalytic studies.展开更多
Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified ...Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work.Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga_(2)O_(2)^(2+) species corresponding to the infrared GaH band of higher wavenumber(GaHHW)in reduced Ga/H-ZSM-5,instead of the overall Ga_(2)O_(2)^(2+) species,by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio.This disparity in Ga_(2)O_(2)^(2+) species stems from their differing capacity in completing the catalytic cycle.Spectroscopic results suggest that PDH proceeds via a two-step mechanism:(1)C-H bond activation of propane on H-Ga_(2)O_(2)^(2+) species(rate determining step);(2)β-hydride elimination of adsorbed propyl group,which only occurs on active Ga_(2)O_(2)^(2+) species corresponding to GaHHW.展开更多
Renewable-energy-powered electrochemical CO or CO_(2)reduction reactions(CO_(2)RR)provide one of the most promising strategies to upgrade CO_(2)to valuable products.In the past decade,the existence and the mechanistic...Renewable-energy-powered electrochemical CO or CO_(2)reduction reactions(CO_(2)RR)provide one of the most promising strategies to upgrade CO_(2)to valuable products.In the past decade,the existence and the mechanistic role of oxygen-containing species,such as(sub)surface oxide,hydroxide and oxyhydroxide species,at the electrode–electrolyte interface under reductive conditions have emerged as a topic of acute discussion within the CO_(2)RR field.Oxide-derived Cu attracted the most attention,while other surfaces,including Au,Ag and Sn,were also widely investigated.This review identifies likely causes for contrasting results and views in the literature,summarizes possible oxygen sources for the interfacial oxygen-containing species at the CO_(2)RR conditions,and discusses potential roles these species could play in affecting the rate and product distribution.Finally,perspectives on future efforts to reveal the identity and role of oxygen-containing species in the CO_(2)RR are presented.展开更多
Cu-based catalysts have attracted widespread attention for its capability in electrocatalytically reducing CO_(2)to a variety of products.Surface modification of Cu has become an interesting method for tuning the cata...Cu-based catalysts have attracted widespread attention for its capability in electrocatalytically reducing CO_(2)to a variety of products.Surface modification of Cu has become an interesting method for tuning the catalytic performance.Here,we use Zrbased metal-organic layers(MOLs)as the additive of the Cu surface,which enhanced the Faradaic efficiency of CH4 by two times as compared to the untreated polycrystalline Cu foil.Unexpectedly,the MOLs were found to induce in situ nano-structuring of the Cu foil surface within seconds in the electrolysis,as revealed by a combination of scanning electron microscopy(SEM),grazing incidence X-ray diffractometry(GIXRD),and linear sweep voltammetry(LSV)measurements.These surface changes are responsible for the shift of product selectivity.Control experiments suggest that negatively chargedμ3-O−on the Zr-cluster in the MOL might interact with CO-covered Cu surface and induce roughing and nano-structuring.This work reveals a potential role of additive on Cu to induce surface nano-structuring that tunes catalytic activity and selectivity.展开更多
Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,h...Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,highly desirable since each process step is costly,both energetically and economically.Here,we report a CO_(2)direct air capture(DAC)and fixation process that produces methane.Low concentrations of CO_(2)(∼400 ppm)in the air are captured by an aqueous solution of sodium hydroxide to form carbonate.The carbonate is subsequently hydrogenated to methane,which is easily separated from the reaction system,catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9%among gas-phase products.The concurrent regenerated hydroxide,in turn,increases the alkalinity of the aqueous solution for further CO_(2)capture,thereby enabling this one-ofits-kind continuous CO_(2)capture and methanation process.Engineering simulations demonstrate the energy feasibility of this CO_(2)DAC and methanation process,highlighting its promise for potential largescale applications.展开更多
High selectivity toward alkenes in oxidative dehydrogenation(ODH)of light alkanes makes boron-based materials promising Catalysts.However,many key mechanistic aspects are still debated due to the challenge of capturin...High selectivity toward alkenes in oxidative dehydrogenation(ODH)of light alkanes makes boron-based materials promising Catalysts.However,many key mechanistic aspects are still debated due to the challenge of capturing fleeting reaction intermediates.Kinetic analysis,including determining reaction orders and activation energy,could be informative for reactions involving radical intermediates but has not been extensively exploited.This Review summarizes the current understanding of the apparent alkane reaction order and the apparent activation energy in the boron-catalyzed ODH.Despite varying compositions and structures,a majority of boron-based catalysts share many common features,induding alkene selectivity,the evolution and the formation of active site,and the apparent kinetic properties.These common trends could be attributed to the shared gas-phase radical mediated reaction pathways and the formation of active hydroxylated boron oxide species on boron-containing materials under ODH conditions.Values of apparent alkane reaction orders and apparent activation energies are sensitive and reliable experimental measures of the contributions of the gas-phase radical-mediated and surface mediated pathways,suggesting the outline of a general mechanistic framework of the boron-catalyzed ODH.展开更多
Weakly binding organic species have been shown to significantly impact the electrocatalytic activities of metal surfaces;however,molecular level mechanisms remain elusive.The ambiguity of whether these weakly binding ...Weakly binding organic species have been shown to significantly impact the electrocatalytic activities of metal surfaces;however,molecular level mechanisms remain elusive.The ambiguity of whether these weakly binding species are specifically adsorbed is a key challenge as there are few experimental tech niques with sufficient sensitivity.The vibrational Stark effect of interfacial species offers a feasible way to achieve this goal with vibrational spectroscopy techniques,such as surface enhanced infrared absorption spectroscopy(SEIRAS)and surface enhanced Raman spectroscopy(SERS).In this work,we employed a library of bifunctional molecules with an isocyano group designed to anchor on the Au surface and an unbound cyano or isocyano group to investigate the effect of variations in the electric field on the Stark tuning rate of both functional groups.The surface bound isocyano group shows pronounced Stark tuning rates(2.4–4.7 cm^(−1)(MV cm^(−1))^(−1))while the Stark tuning rates of the free functional groups are comparable to or below the spectral resolution(<0.6 cm^(−1)(MV cm^(−1))^(−1)).Contributions from variations in the bond force constant,induced by an electric field or a Fermi level shift,and the anharmonicity effect on the observed Stark tuning rates were deconvoluted.A shift in the vibrational peak of a specifically adsorbed functional group is more sensitive to the change in the electrode potential,which could be used to ident ify surface adsorbates at electrochemical interfaces.Our results suggest that Stark tuning rates above 0.6 cm^(−1)(MV cm^(−1))^(−1)can be considered as strong evidence for specific adsorption on the electrode surface.展开更多
文摘Existing organic halide synthesis routes typically employ elemental halogens(X_(2),X=Cl or Br),leading to low atom economy and significant environmental pollution.In this work,we developed an atom efficient electrosynthesis and separation strategy for halogenation reagents—N-chlorosuccinimide(NCS)and N-bromosuccinimide(NBS)—at high current densities.Faradic efficiency(FE)of 91.0%and 81.3%was achieved for NCS and NBS generation on RuO_(x)/TiO_(2)/Ti in a batch cell,respectively.Electrosynthesis of NCS likely involves both heterogeneous catalytic and homogeneous tandem pathways,while NBS is likely formed in a Langmuir-Hinshelwood mechanism with a proton-coupled electron transfer as the rate-determining step.A coupled continuous electrocatalytic synthesis and in situ separation setup was developed for the efficient production of NCS and NBS,which yielded 0.77 g of NCS in 12000 s and 0.81 g of NBS in 15000 s,both with relative purity exceeding 95%.The halogenation of acetone using NCS and NBS enabled gram-scale production of the key intermediate in organic synthesis,1-halogenacetone,with over 95%recovery of succinimide.
基金supported by the Beijing Natural Science Foundation Key Research Program(Grant Z240026)the Beijing National Laboratory for Molecular Sciences.
文摘Electrocatalysis has been investigated as a promising strategy to utilize green electricity to produce renewable fuels,valuable chemicals,and treat pollutants.Electrode kinetic analysis is a potent technique in interrogating reaction mechanisms and evaluating the electrocatalysts.Electron transfer(ET)and proton‐coupled electron transfer(PCET)processes are widely present in reaction networks of electrocatalysis.pH dependence of the kinetics is frequently employed to evaluate whether an elementary step involves proton participation,which is determined by both the reversibility and the specific reactants of electrode reactions.In this article,we discuss the pH dependence of two widely used formulations of the Butler–Volmer kinetics for a model PCET step and highlight a potential pitfall in kinetic analysis.This work aims to provide guiding principles for distinguishing ET and PCET steps via kinetic measurements in electrolytes in a broad range pH values.
基金supported by the National Key R&D Program of China(No.2021YFA1501003)。
文摘Electron transfer processes at polymer electrolyte/electrode interfaces play a central role in modern electrochemical devices of energy conversion,however,current understanding of electron transfers through electrochemical interfaces was established exclusively based on the studies of liquid/solid electrochemical interfaces.Thus,similarities and differences of liquid and polymer electrolyte/electrode interfaces need to be mapped out to guide the design of device level electrochemical interfaces.In this work,we employ the sulfonate adsorption/desorption as a probe reaction to understand the electron-transfer steps in polymer and liquid electrolytes.Through cyclic voltametric investigations on the well-define single-crystal Pd_(ML)Pt(111)electrode,we demonstrate that the oxidative adsorption and reductive desorption of sulfonates at the polymer electrolyte/electrode interface are chemically distinct from those in liquid electrolytes,with the former occurring mostly via the proton-coupled pathway while the latter proceeding mainly through the solvation-mediated pathway.Importantly,the sulfonate adsorption/desorption behaviors of alkylsulfonates become increasingly similar to those in Nafion with longer alkyl chains,suggesting that the interfacial hydrophobicity and solvation environment conferred by the perfluorinated polymer play a decisive role in the electron-transfer mechanism.Results reported in this study highlight the mechanistic distinctions between electron-transfer processes at electrochemical interfaces involving polymer and liquid electrolytes,and provide a framework for understanding electron-transfer processes at polymer electrolyte/electrode interfaces.
基金National Natural Science Foundation of China(22379083)State Key Laboratory of Chemical Engineering(SKL-ChE-23T02)+2 种基金financial support from Beijing National Laboratory for Molecular Sciencessupport from Tsinghua International School’s Research Mentoring Programsupport from Tsinglan School’s Research Mentoring Program。
文摘Renewable energy-driven bicarbonate conversion to valuable chemicals presents an attractive strategy for mitigating CO_(2)emissions,as bicarbonate can be efficiently generated from the capture of atmospheric CO_(2)using alkaline solutions with reactive absorption.In this work,we present a CO_(2)-mediated bicarbonate conversion to pure formate using a cation exchange membrane-based electrolyzer with a 25 cm^(2)electrode area.Our electrolysis achieved selectivities exceeding 75%for formate at a total current of 2.5 A,achieving formate concentrations up to 1.2 M and yields as high as 95%over extended periods.The techno-economic assessment confirmed the economic viability of the process,highlighting the potential for bicarbonate electrolysis as a sustainable method for producing valuable chemicals.
文摘Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.
文摘Electrochemical CO_(2)reduction to formate is a promising approach to store renewable electricity and utilize CO_(2).Tin oxide catalysts are efficient catalysts for this process,while the mechanisms underneath,especially the existence and role of oxidized tin species under CO2 electroreduction conditions remain unclear.In this work,we provide strong evidence on the presence of oxidized tin species on both SnO_(2)and Sn during CO_(2)reduction via in situ surface‐enhanced Raman spectroscopy,while in different nature.Reactivity measurements show similar activity and selectivity to formate production on SnO_(2)and Sn catalysts.Combined analysis of Raman spectra and reactivity results suggests that Sn(IV)and Sn(II)oxide species are unlikely the catalytic species in CO_(2)electroreduction to formate.
文摘Electrocatalysis offers a promising approach towards chemical synthesis driven by renewable energy.Molecular level understanding of the electrochemical interface remains challenging due to its compositional and structural complexity.In situ interfacial specific characterization techniques could help uncover structure-function relationships and reaction mechanism.To this end,electrochemical surface-enhanced Raman spectroscopy(SERS)and surface-enhanced infrared absorption spectroscopy(SEIRAS)thrive as powerful techniques to provide fingerprint information of interfacial species at reaction conditions.In this review,we first introduce the fundamentals of SERS and SEIRAS,followed by discussion regarding the technical challenges and potential solutions.Finally,we highlight future directions for further development of surface-enhanced spectroscopic techniques for electrocatalytic studies.
文摘Propane dehydrogenation(PDH)on Ga/H-ZSM-5 catalysts is a promising reaction for propylene production,while the detail mechanism remains debatable.Ga_(2)O_(2)^(2+) stabilized by framework Al pairs have been identified as the most active species in Ga/H-ZSM-5 for PDH in our recent work.Here we demonstrate a strong correlation between the PDH activity and a fraction of Ga_(2)O_(2)^(2+) species corresponding to the infrared GaH band of higher wavenumber(GaHHW)in reduced Ga/H-ZSM-5,instead of the overall Ga_(2)O_(2)^(2+) species,by employing five H-ZSM-5 supports sourced differently with comparable Si/Al ratio.This disparity in Ga_(2)O_(2)^(2+) species stems from their differing capacity in completing the catalytic cycle.Spectroscopic results suggest that PDH proceeds via a two-step mechanism:(1)C-H bond activation of propane on H-Ga_(2)O_(2)^(2+) species(rate determining step);(2)β-hydride elimination of adsorbed propyl group,which only occurs on active Ga_(2)O_(2)^(2+) species corresponding to GaHHW.
基金supported by Beijing National Laboratory for Molecular Sciences and the National Natural Science Foundation of China(21872079)。
文摘Renewable-energy-powered electrochemical CO or CO_(2)reduction reactions(CO_(2)RR)provide one of the most promising strategies to upgrade CO_(2)to valuable products.In the past decade,the existence and the mechanistic role of oxygen-containing species,such as(sub)surface oxide,hydroxide and oxyhydroxide species,at the electrode–electrolyte interface under reductive conditions have emerged as a topic of acute discussion within the CO_(2)RR field.Oxide-derived Cu attracted the most attention,while other surfaces,including Au,Ag and Sn,were also widely investigated.This review identifies likely causes for contrasting results and views in the literature,summarizes possible oxygen sources for the interfacial oxygen-containing species at the CO_(2)RR conditions,and discusses potential roles these species could play in affecting the rate and product distribution.Finally,perspectives on future efforts to reveal the identity and role of oxygen-containing species in the CO_(2)RR are presented.
基金support from the National Natural Science Foundation of China(Nos.22125502,22071207,22121001,and 21721001)and NFFTBS(No.J1310024)。
文摘Cu-based catalysts have attracted widespread attention for its capability in electrocatalytically reducing CO_(2)to a variety of products.Surface modification of Cu has become an interesting method for tuning the catalytic performance.Here,we use Zrbased metal-organic layers(MOLs)as the additive of the Cu surface,which enhanced the Faradaic efficiency of CH4 by two times as compared to the untreated polycrystalline Cu foil.Unexpectedly,the MOLs were found to induce in situ nano-structuring of the Cu foil surface within seconds in the electrolysis,as revealed by a combination of scanning electron microscopy(SEM),grazing incidence X-ray diffractometry(GIXRD),and linear sweep voltammetry(LSV)measurements.These surface changes are responsible for the shift of product selectivity.Control experiments suggest that negatively chargedμ3-O−on the Zr-cluster in the MOL might interact with CO-covered Cu surface and induce roughing and nano-structuring.This work reveals a potential role of additive on Cu to induce surface nano-structuring that tunes catalytic activity and selectivity.
基金the Natural Science Foundation of China(grant nos.21725301,21932002,21821004,91645115,51872008,22172183,22172150,and 22222306)the National Key R&D Program of China(grant nos.2017YFB060220 and 2021YFA-1502804)+3 种基金the Beijing Outstanding Young Scientists Projects(grant nos.BJJWZYJH01201910005018 and BJJWZYJH01201914430039)the Strategic Priority Research Program of the Chinese Academy of Science(grant no.XDB0450102)the K.C.Wong Education Foundation(grant no.GJTD-2020-15)the Innovation Program for Quantum Science and Technology(grant no.2021ZD0303302).
文摘Reducing the ever-growing level of CO_(2)in the atmosphere is critical for the sustainable development of human society in the context of global warming.Integration of the capture and upgrading of CO_(2)is,therefore,highly desirable since each process step is costly,both energetically and economically.Here,we report a CO_(2)direct air capture(DAC)and fixation process that produces methane.Low concentrations of CO_(2)(∼400 ppm)in the air are captured by an aqueous solution of sodium hydroxide to form carbonate.The carbonate is subsequently hydrogenated to methane,which is easily separated from the reaction system,catalyzed by TiO2-supported Ru in the aqueous phase with a selectivity of 99.9%among gas-phase products.The concurrent regenerated hydroxide,in turn,increases the alkalinity of the aqueous solution for further CO_(2)capture,thereby enabling this one-ofits-kind continuous CO_(2)capture and methanation process.Engineering simulations demonstrate the energy feasibility of this CO_(2)DAC and methanation process,highlighting its promise for potential largescale applications.
基金National Natural Science Foundation of China(22172001 and 22108006)Beijing National Laboratory for Molecular Sciences.
文摘High selectivity toward alkenes in oxidative dehydrogenation(ODH)of light alkanes makes boron-based materials promising Catalysts.However,many key mechanistic aspects are still debated due to the challenge of capturing fleeting reaction intermediates.Kinetic analysis,including determining reaction orders and activation energy,could be informative for reactions involving radical intermediates but has not been extensively exploited.This Review summarizes the current understanding of the apparent alkane reaction order and the apparent activation energy in the boron-catalyzed ODH.Despite varying compositions and structures,a majority of boron-based catalysts share many common features,induding alkene selectivity,the evolution and the formation of active site,and the apparent kinetic properties.These common trends could be attributed to the shared gas-phase radical mediated reaction pathways and the formation of active hydroxylated boron oxide species on boron-containing materials under ODH conditions.Values of apparent alkane reaction orders and apparent activation energies are sensitive and reliable experimental measures of the contributions of the gas-phase radical-mediated and surface mediated pathways,suggesting the outline of a general mechanistic framework of the boron-catalyzed ODH.
基金supported by the National Key R&D Program of China(No.2021YFA1501003)。
文摘Weakly binding organic species have been shown to significantly impact the electrocatalytic activities of metal surfaces;however,molecular level mechanisms remain elusive.The ambiguity of whether these weakly binding species are specifically adsorbed is a key challenge as there are few experimental tech niques with sufficient sensitivity.The vibrational Stark effect of interfacial species offers a feasible way to achieve this goal with vibrational spectroscopy techniques,such as surface enhanced infrared absorption spectroscopy(SEIRAS)and surface enhanced Raman spectroscopy(SERS).In this work,we employed a library of bifunctional molecules with an isocyano group designed to anchor on the Au surface and an unbound cyano or isocyano group to investigate the effect of variations in the electric field on the Stark tuning rate of both functional groups.The surface bound isocyano group shows pronounced Stark tuning rates(2.4–4.7 cm^(−1)(MV cm^(−1))^(−1))while the Stark tuning rates of the free functional groups are comparable to or below the spectral resolution(<0.6 cm^(−1)(MV cm^(−1))^(−1)).Contributions from variations in the bond force constant,induced by an electric field or a Fermi level shift,and the anharmonicity effect on the observed Stark tuning rates were deconvoluted.A shift in the vibrational peak of a specifically adsorbed functional group is more sensitive to the change in the electrode potential,which could be used to ident ify surface adsorbates at electrochemical interfaces.Our results suggest that Stark tuning rates above 0.6 cm^(−1)(MV cm^(−1))^(−1)can be considered as strong evidence for specific adsorption on the electrode surface.
