An electrochemical study on the redox behavior of indium in the eutectic LiCl-KCl system at 450 ℃ was carried out with the transient techniques of cyclic voltammetry and chronopotentiometry on an inert molybdenum ele...An electrochemical study on the redox behavior of indium in the eutectic LiCl-KCl system at 450 ℃ was carried out with the transient techniques of cyclic voltammetry and chronopotentiometry on an inert molybdenum electrode. The reduction of In(Ⅲ) was found to be a two-step process involving In(Ⅲ)/In(Ⅰ) and In(Ⅰ)/In couples at the potentials of about-0.4 and-0.8 V versus Ag/AgCl, respectively. The redox mechanism was further confirmed by the theoretical evaluation of the number of transferred electrons based on cyclic voltammetry and characterizations of the precipitates generated by the potentiostatic electrolysis. The diffusion coefficients of indium ions in the eutectic LiCl-KCl melt at 450 ℃ were estimated by cyclic voltammetry and chronopotentiometry. The results obtained through the two methods are in fair agreement, delivering an average diffusion coefficient of approximately 1.8×10^(-5)cm^(2)/s for In(Ⅲ), and 1.4×10^(-4)cm^(2)/s for In(Ⅰ).展开更多
The introduction of redox-active ligands into transition metal complexes can lead to novel redox behavior due to the ability of these ligands to serve as electron reservoirs.This feature is especially attractive in ea...The introduction of redox-active ligands into transition metal complexes can lead to novel redox behavior due to the ability of these ligands to serve as electron reservoirs.This feature is especially attractive in earth-abundant transition metal systems that typically favor one-electron redox processes and radical reactivity,as opposed to the two-electron redox cycles common with the noble metals.The redox flexibility afforded by redox-active ligands can enable substrate activation and/or bond forming and breaking processes that would otherwise be inaccessible with traditional redox-innocent ligands.This review discusses key examples of stoichiometric substrate activation and organic transformations facilitated by redox-active ligand-promoted multielectron reactivity at earth-abundant metal complexes.We highlight the electrochemical properties of these systems in relation to their substrate reactivity,where,in many cases,the complexes exhibit sequential one-electron redox events.Only a few examples have achieved electrocatalytic reactivity based on two-electron redox features,which underscores the untapped potential for further development of redox-active ligand systems to expand the capabilities of earth-abundant metal complexes in electrocatalysis.展开更多
The fullerene compound CoC 60(OH) has been prepared by the reaction of C - 60 anion with Co(Ⅱ) hydrous salt under nitrogen atmosphere and refluxing, and the title compound is characterized by FAB-MS, elemental analys...The fullerene compound CoC 60(OH) has been prepared by the reaction of C - 60 anion with Co(Ⅱ) hydrous salt under nitrogen atmosphere and refluxing, and the title compound is characterized by FAB-MS, elemental analysis, FT-IR, XPS, UV-Vis and 1H NMR. The results prove the presence of C-Co and -OH groups in the resultant, and coovalent of Co bonding to C 60. The apparent charge distribution of the resultant appeaers to be Co 2+C - 60(OH) -, and there are three kinds of carbons with different electron density. The result of redox experiment indicates that the reduction potential of the compound is more negative than that of pure C 60.展开更多
Combining the redox properties of Co and the acid properties of Nb in a Co_(3)-Nb-O_(x)catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).Co_(3)O_(4)sh...Combining the redox properties of Co and the acid properties of Nb in a Co_(3)-Nb-O_(x)catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).Co_(3)O_(4)shows average activity,however,it exhibits a poor N_(2)selectivity.Nb_(2)O_(5)is not active for NH_(3)-SCR.However,the mixed Co_(3)-Nb-O_(x) catalyst shows higher NO conversion and N_(2)selectivity than the single Co_(3)O_(4)and Nb_(2)O_(5)catalysts at 100–300℃.The results of temperature programmed reduction by H_(2)and X-ray photoelectron(XP)spectra indicate that the addition of Nb changes the chemical states of Co and decreases the concentration of Co^(3+) and Oa,adjusting the activity for catalytic oxidation to a moderate level.This suppresses the formation of undesired N_(2)O from the over-oxidation of NH_(3).Incorporation of Co and Nb into one solid synergistically couples their redox behavior and surface acidity,ensuring the high catalytic activity and N2 selectivity in NH3-SCR.展开更多
Transition metal oxides are regarded as an economical and efficient catalytic alternate for catalytic oxidation of volatile organic compounds(VOCs)emissions.The morphological decoration and the incorporation of extrin...Transition metal oxides are regarded as an economical and efficient catalytic alternate for catalytic oxidation of volatile organic compounds(VOCs)emissions.The morphological decoration and the incorporation of extrinsic metals were demonstrated to be effective strategies for achieving noticeable catalytic improvement.In this work,a novel Co-Ce composite oxides catalyst was obtained by the pyrolysis of ZIF-67 template with the impregnation of certain cerium cations(denoted as ZIF-CoCe).Compared with the reference Co-Ce composite oxides by the sol-gel(denoted as SG-CoCe)and physical mixing(denoted as MIX-CoCe)methods,ZIF-CoCe delivers significantly higher catalytic activity for vinyl chloride oxidation,which are demonstrated to be closely related with its superior redox capacity,more abundance of surface active Co^(3+)sites and adsorbed active oxygen species from oxygen vacancies.In addition,the unique cage-like morphological feature of the Co-based catalysts derived from ZIF-67 template plays a crucial function in kinetically facilitating the mass transfer of catalytic reaction and promoting the catalytic VC oxidation activity.With regard to in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTs)analysis,enol and carboxylic acid species are identified to be the key organic intermediates during catalytic vinyl chloride oxidation.展开更多
The CeO_(2),Ce-Nb-O_(x) and Nb_(2)O_(5) catalysts were synthesized by citric acid method and the promotion effect of Nb on ceria for selective catalytic reduction(SCR)of NO with NH_(3) was investigated.The catalytic a...The CeO_(2),Ce-Nb-O_(x) and Nb_(2)O_(5) catalysts were synthesized by citric acid method and the promotion effect of Nb on ceria for selective catalytic reduction(SCR)of NO with NH_(3) was investigated.The catalytic activity measurements indicate that the mixed oxide Ce-Nb-O_(x) presents a higher SCR activity than the single oxide CeO_(2) or Nb_(2)O_(5) catalyst.In addition,the Ce-Nb-O_(x) catalyst shows high resistance towards H_(2)O and SO_(2) at 280℃.The Raman,X-ray photoelectron spectra and temperature programmed reduction with H_(2) results indicate that the incorporation of Nb provides abundant oxygen vacancies for capturing more surface adsorbed oxygen,which provides a superior redox capability and accelerates the renewal of active sites.Furthermore,the Fourier transform infrared spectra and temperature programmed desorption of NH_(3) results suggest that niobium pentoxide shows high surface acidity,which is partly retained in the Ce-Nb-O_(x) catalyst possessing a high content of Lewis and Br?nsted acid sites.Therefore,the incorporation of Nb improves both the redox and acidic capacities of Ce-Nb-O_(x) catalyst for the SCR reaction.Here,the redox behavior is primarily taken on Ce and the acidity is well improved by Nb,so the synergistic effect should exist between Ce and Nb.In terms of the reaction mechanism,in situ DRIFT experiments suggest that both NH_(3) on Lewis acid sites and NH_(4)^(+) on Bronsted acid sites can react with NO species,and adsorbed NO and NO_(2) species can both be reduced by NH_(3).In the SCR process,O_(2) primarily acts as the accelerant to improve the redox and acid cycles and plays an important role.This work proves that the combination of redox and acidic properties of different constituents can be feasible for catalyst design to obtain a superior SCR performance.展开更多
Morphologically controlled synthesis of metal oxide-based materials has attracted significant attention to enable the capacity and redox performance of faradaic-type hybrid supercapacitors(H-SCs).In this work,we desig...Morphologically controlled synthesis of metal oxide-based materials has attracted significant attention to enable the capacity and redox performance of faradaic-type hybrid supercapacitors(H-SCs).In this work,we designed hollow-structured copper molybdate(Cu_(3)Mo_(2)O_(9)) with hollow flowers(CM HFs) and hollow spheres(HSs) were facilely prepared by solvent-mediated hydrothermal method.The aqueous environment in the hydrothermal system facilitates anisotropic crystal growth and self-assembly of nanoplates into three-dimensional CM HFs architecture,which showed high surface area and enhanced electrolyte accessibility.The electrochemical performance revealed that the CM HFs showed better redox behavior with longer charge-discharge times,and lower resistance compared to CM HSs.As a result,the CM HFs showed a higher specific capacitance of 530 F g^(-1) at 2 A g^(-1) and faster ion diffusion with a capacitance retention of 94.1%after 10,000 cycles.Moreover,a two-electrode H-SC was fabricated using CM HFs as the positive electrode and activated carbon as the negative electrode,which achieved a high energy density of 33.24 Wh kg^(-1) and a power density of 5250 W kg^(-1) along with excellent cycling stability.Aiding from the high energy storage performance of H-SC,the devices in series successfully powered LEDs,demonstrating their potential for flexible and durable energy storage applications.展开更多
基金the National Natural Science Foundation of China(Nos.51904003,U1703130,51704011)the China Postdoctoral Science Foundation(No.2019M651466)the Foundation of Anhui Province Key Laboratory of Metallurgical Engineering&Resources Recycling of China(Nos.SKF18-01,SKF19-05).
文摘An electrochemical study on the redox behavior of indium in the eutectic LiCl-KCl system at 450 ℃ was carried out with the transient techniques of cyclic voltammetry and chronopotentiometry on an inert molybdenum electrode. The reduction of In(Ⅲ) was found to be a two-step process involving In(Ⅲ)/In(Ⅰ) and In(Ⅰ)/In couples at the potentials of about-0.4 and-0.8 V versus Ag/AgCl, respectively. The redox mechanism was further confirmed by the theoretical evaluation of the number of transferred electrons based on cyclic voltammetry and characterizations of the precipitates generated by the potentiostatic electrolysis. The diffusion coefficients of indium ions in the eutectic LiCl-KCl melt at 450 ℃ were estimated by cyclic voltammetry and chronopotentiometry. The results obtained through the two methods are in fair agreement, delivering an average diffusion coefficient of approximately 1.8×10^(-5)cm^(2)/s for In(Ⅲ), and 1.4×10^(-4)cm^(2)/s for In(Ⅰ).
基金supported the ACS Petroleum Research Fund(65171-DNI3)Rutgers,The State University of New Jersey.
文摘The introduction of redox-active ligands into transition metal complexes can lead to novel redox behavior due to the ability of these ligands to serve as electron reservoirs.This feature is especially attractive in earth-abundant transition metal systems that typically favor one-electron redox processes and radical reactivity,as opposed to the two-electron redox cycles common with the noble metals.The redox flexibility afforded by redox-active ligands can enable substrate activation and/or bond forming and breaking processes that would otherwise be inaccessible with traditional redox-innocent ligands.This review discusses key examples of stoichiometric substrate activation and organic transformations facilitated by redox-active ligand-promoted multielectron reactivity at earth-abundant metal complexes.We highlight the electrochemical properties of these systems in relation to their substrate reactivity,where,in many cases,the complexes exhibit sequential one-electron redox events.Only a few examples have achieved electrocatalytic reactivity based on two-electron redox features,which underscores the untapped potential for further development of redox-active ligand systems to expand the capabilities of earth-abundant metal complexes in electrocatalysis.
文摘The fullerene compound CoC 60(OH) has been prepared by the reaction of C - 60 anion with Co(Ⅱ) hydrous salt under nitrogen atmosphere and refluxing, and the title compound is characterized by FAB-MS, elemental analysis, FT-IR, XPS, UV-Vis and 1H NMR. The results prove the presence of C-Co and -OH groups in the resultant, and coovalent of Co bonding to C 60. The apparent charge distribution of the resultant appeaers to be Co 2+C - 60(OH) -, and there are three kinds of carbons with different electron density. The result of redox experiment indicates that the reduction potential of the compound is more negative than that of pure C 60.
基金This work was financially supported by the National Key R&D Projects(No.2019YFC1907101)the National Natural Science Foundation of China(No.U2002212)+2 种基金the State Key Laboratory for Advanced Metals and Materials(No.2019Z-05)the Fundamental Research Funds for the Central Universities(Nos.FRFIDRY-20-005 and FRF-TP-20-097A1Z)the Postdoctor Research Foundation of Shunde Graduate School of University of Science and Technology Beijing(No.2020BH012).
文摘Combining the redox properties of Co and the acid properties of Nb in a Co_(3)-Nb-O_(x)catalyst is shown to provide superior performance in the selective catalytic reduction of NO with NH_(3)(NH_(3)-SCR).Co_(3)O_(4)shows average activity,however,it exhibits a poor N_(2)selectivity.Nb_(2)O_(5)is not active for NH_(3)-SCR.However,the mixed Co_(3)-Nb-O_(x) catalyst shows higher NO conversion and N_(2)selectivity than the single Co_(3)O_(4)and Nb_(2)O_(5)catalysts at 100–300℃.The results of temperature programmed reduction by H_(2)and X-ray photoelectron(XP)spectra indicate that the addition of Nb changes the chemical states of Co and decreases the concentration of Co^(3+) and Oa,adjusting the activity for catalytic oxidation to a moderate level.This suppresses the formation of undesired N_(2)O from the over-oxidation of NH_(3).Incorporation of Co and Nb into one solid synergistically couples their redox behavior and surface acidity,ensuring the high catalytic activity and N2 selectivity in NH3-SCR.
基金Project supported by the National Natural Science Foundation of China(22076088,21607163).
文摘Transition metal oxides are regarded as an economical and efficient catalytic alternate for catalytic oxidation of volatile organic compounds(VOCs)emissions.The morphological decoration and the incorporation of extrinsic metals were demonstrated to be effective strategies for achieving noticeable catalytic improvement.In this work,a novel Co-Ce composite oxides catalyst was obtained by the pyrolysis of ZIF-67 template with the impregnation of certain cerium cations(denoted as ZIF-CoCe).Compared with the reference Co-Ce composite oxides by the sol-gel(denoted as SG-CoCe)and physical mixing(denoted as MIX-CoCe)methods,ZIF-CoCe delivers significantly higher catalytic activity for vinyl chloride oxidation,which are demonstrated to be closely related with its superior redox capacity,more abundance of surface active Co^(3+)sites and adsorbed active oxygen species from oxygen vacancies.In addition,the unique cage-like morphological feature of the Co-based catalysts derived from ZIF-67 template plays a crucial function in kinetically facilitating the mass transfer of catalytic reaction and promoting the catalytic VC oxidation activity.With regard to in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTs)analysis,enol and carboxylic acid species are identified to be the key organic intermediates during catalytic vinyl chloride oxidation.
基金Project supported by the Postdoctor Research Foundation of Shunde Graduate School of University of Science and Technology Beijing(2020BH012)the National Key Research&Development Projects(2021YFC1910504)+1 种基金the National Natural Science Foundation of China(U2002212)the Fundamental Research Funds for the Central Universities(FRF-IDRY-20-005)。
文摘The CeO_(2),Ce-Nb-O_(x) and Nb_(2)O_(5) catalysts were synthesized by citric acid method and the promotion effect of Nb on ceria for selective catalytic reduction(SCR)of NO with NH_(3) was investigated.The catalytic activity measurements indicate that the mixed oxide Ce-Nb-O_(x) presents a higher SCR activity than the single oxide CeO_(2) or Nb_(2)O_(5) catalyst.In addition,the Ce-Nb-O_(x) catalyst shows high resistance towards H_(2)O and SO_(2) at 280℃.The Raman,X-ray photoelectron spectra and temperature programmed reduction with H_(2) results indicate that the incorporation of Nb provides abundant oxygen vacancies for capturing more surface adsorbed oxygen,which provides a superior redox capability and accelerates the renewal of active sites.Furthermore,the Fourier transform infrared spectra and temperature programmed desorption of NH_(3) results suggest that niobium pentoxide shows high surface acidity,which is partly retained in the Ce-Nb-O_(x) catalyst possessing a high content of Lewis and Br?nsted acid sites.Therefore,the incorporation of Nb improves both the redox and acidic capacities of Ce-Nb-O_(x) catalyst for the SCR reaction.Here,the redox behavior is primarily taken on Ce and the acidity is well improved by Nb,so the synergistic effect should exist between Ce and Nb.In terms of the reaction mechanism,in situ DRIFT experiments suggest that both NH_(3) on Lewis acid sites and NH_(4)^(+) on Bronsted acid sites can react with NO species,and adsorbed NO and NO_(2) species can both be reduced by NH_(3).In the SCR process,O_(2) primarily acts as the accelerant to improve the redox and acid cycles and plays an important role.This work proves that the combination of redox and acidic properties of different constituents can be feasible for catalyst design to obtain a superior SCR performance.
基金supported and funded by the Deanship of the Scientific Research at Imam Mohammad Ibn Saud Islamic University(IMSIU)(No.IMSIU-DDRSP2503)
文摘Morphologically controlled synthesis of metal oxide-based materials has attracted significant attention to enable the capacity and redox performance of faradaic-type hybrid supercapacitors(H-SCs).In this work,we designed hollow-structured copper molybdate(Cu_(3)Mo_(2)O_(9)) with hollow flowers(CM HFs) and hollow spheres(HSs) were facilely prepared by solvent-mediated hydrothermal method.The aqueous environment in the hydrothermal system facilitates anisotropic crystal growth and self-assembly of nanoplates into three-dimensional CM HFs architecture,which showed high surface area and enhanced electrolyte accessibility.The electrochemical performance revealed that the CM HFs showed better redox behavior with longer charge-discharge times,and lower resistance compared to CM HSs.As a result,the CM HFs showed a higher specific capacitance of 530 F g^(-1) at 2 A g^(-1) and faster ion diffusion with a capacitance retention of 94.1%after 10,000 cycles.Moreover,a two-electrode H-SC was fabricated using CM HFs as the positive electrode and activated carbon as the negative electrode,which achieved a high energy density of 33.24 Wh kg^(-1) and a power density of 5250 W kg^(-1) along with excellent cycling stability.Aiding from the high energy storage performance of H-SC,the devices in series successfully powered LEDs,demonstrating their potential for flexible and durable energy storage applications.
