The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffu...The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I-1 versus ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.展开更多
Sintered （300℃） porous pellets of Fe2O3 were electrolyzed to Fe in molten CaCl2 （800-900℃） under argon at 1.8-3.2 V for 2-20 h. The laboratory scale experiments show that it was a potentially direct green method...Sintered （300℃） porous pellets of Fe2O3 were electrolyzed to Fe in molten CaCl2 （800-900℃） under argon at 1.8-3.2 V for 2-20 h. The laboratory scale experiments show that it was a potentially direct green method to produce Fe powder. At lower electrolysis voltage （〈2.2 V）, higher current efficiency （〉90%） and smaller energy consumption （-3.0 kWh/kg） can be obtained. When the electrolysis voltage was above 2.4 V, the deposition of metal Ca from the salt lowered the current efficiency and increased the energy consumption. The electrolysis voltage also had effects on the micrographs of the reduced powder. The cubic particles can be seen in the products at the voltage lower than 2.2 V; when the voltage was higher than 2.2 V, it was nodular. The reduction proceeds at the cathode in two steps, i.e., from Fe2O3 to FeO and then to Fe. The oxygen emits at the anode. The process is potentially free of carbon emission and produces two useful products at both cathode and anode, promising a zero-emission technology for the extractive metallurgical industry.展开更多
Electrocatalytic synthesis of ammonia as an environment-friendly and sustainable development method has received widespread attention in recent years.Two-dimensional(2D)materials are a promising catalyst for ammonia s...Electrocatalytic synthesis of ammonia as an environment-friendly and sustainable development method has received widespread attention in recent years.Two-dimensional(2D)materials are a promising catalyst for ammonia synthesis due to their large surface area.In this work,we have constructed a series of 2D metal borides(MBenes)with transition metal(TM)defects(TMd-MBenes)and comprehensively calculated the reactivity of electrocatalytic synthesis of ammonia-based on density functional theory.The results have demonstrated that the TMd-MBenes can effectively activate nitrogen oxide(NO)and nitrogen(N2)molecules thermodynamically.Particularly interesting,the co-chemisorption of O atoms,dissociated from NO,can facilitate the spilled of the inert N2 molecules into single N atoms,which can further hydrogenate into ammonia easily with an ultralow limiting potential of 0.59 V on TMd-MnB.Our research has not only provided clues for catalyst design for experimental study but also paved the way for the industrial application of electrocatalytic ammonia synthesis.展开更多
In this study,for the first time,direct copper production from copper sulfide was carried out via direct electrochemical reduction method using inexpensive and stable molten borax electrolyte.The effects of current de...In this study,for the first time,direct copper production from copper sulfide was carried out via direct electrochemical reduction method using inexpensive and stable molten borax electrolyte.The effects of current density(100–800 mA/cm^2)and electrolysis time(15–90 min)on both the cathodic current efficiency and copper yield were systematically investigated in consideration of possible electrochemical/chemical reactions at 1200℃.The copper production yield reached 98.09%after 90 min of electrolysis at a current density of 600 mA/cm^2.Direct metal production was shown to be possible with 6 kWh/kg energy consumption at a 600 mA/cm2 current density,at which the highest current efficiency(41%)was obtained.The suggested method can also be applied to metal/alloy production from single-and mixed-metal sulfides coming from primary production and precipitated sulfides,which are produced in the mining and metallurgical industries during treatment of process solutions or wastewaters.展开更多
Electrochemical reduction of CO_(2) is a novel research field towards a CO_(2)-neutral global economy and combating fast accelerating and disastrous climate changes while finding new solutions to store renewable energ...Electrochemical reduction of CO_(2) is a novel research field towards a CO_(2)-neutral global economy and combating fast accelerating and disastrous climate changes while finding new solutions to store renewable energy in value-added chemicals and fuels.Ionic liquids(ILs),as medium and catalysts(or supporting part of catalysts)have been given wide attention in the electrochemical CO_(2) reduction reaction(CO_(2) RR)due to their unique advantages in lowering overpotential and improving the product selectivity,as well as their designable and tunable properties.In this review,we have summarized the recent progress of CO_(2) electro-reduction in IL-based electrolytes to produce higher-value chemicals.We then have highlighted the unique enhancing effect of ILs on CO_(2) RR as templates,precursors,and surface functional moieties of electrocatalytic materials.Finally,computational chemistry tools utilized to understand how the ILs facilitate the CO_(2) RR or to propose the reaction mechanisms,generated intermediates and products have been discussed.展开更多
A novel gas-phase electrocatalytic cell containing a low-temperature proton exchange membrane(PEM)was developed to electrochemically convert CO_2into organic compounds.Two different Cu-based cathode catalysts(Cu and C...A novel gas-phase electrocatalytic cell containing a low-temperature proton exchange membrane(PEM)was developed to electrochemically convert CO_2into organic compounds.Two different Cu-based cathode catalysts(Cu and Cu–C)were prepared by physical vapor deposition method(sputtering)and subsequently employed for the gas-phase electroreduction of CO_2at different temperatures(70–90°C).The prepared electrodes Cu and Cu–C were characterized by X-ray diffraction(XRD),X-ray photoemission spectroscopy(XPS)and scanning electron microscopy(SEM).As revealed,Cu is partially oxidized on the surface of the samples and the Cu and Cu–C cathodic catalysts were comprised of a porous,continuous,and homogeneous film with nanocrystalline Cu with a grain size of 16 and 8 nm,respectively.The influence of the applied current and temperature on the electro-catalytic activity and selectivity of these materials was investigated.Among the two investigated electrodes,the pure Cu catalyst film showed the highest CO_2specific electrocatalytic reduction rates and higher selectivity to methanol formation compared to the Cu–C electrode,which was attributed to the higher particle size of the former and lower Cu O/Cu ratio.The obtained results show potential interest for the possible use of electrical renewable energy for the transformation of CO_2into valuable products using low metal loading Cu based electrodes(0.5 mg Cu cm^(-2))prepared by sputtering.展开更多
Nitrogen electro-reduction reaction(NERR)is a promising alternative method for ammonia production to the Haber-Bosch approach due to mild reaction conditions and free harmful by-product emission.A formidable challenge...Nitrogen electro-reduction reaction(NERR)is a promising alternative method for ammonia production to the Haber-Bosch approach due to mild reaction conditions and free harmful by-product emission.A formidable challenge in bringing NERR closer to the practical application is developing an electrocatalyst which can simultaneously improve the Faraday efficiency and reduce the reaction over-potential.Herein,we fabricated a catalyst of nitrogen-doped carbon dots modified copper-phosphate nanoflower petals(Cu Po-NCDs NF)via a self-assembly method.The flower structure endowed the Cu Po-NCDs NF with large specific surface area,and thus enabled more active sites to be exposed.In particular,we demonstrated that the NCDs modified Cu Po petals with flower-like structure can accelerate the interfacial proton-electron transfer,suppressing the competing hydrogen evolution reaction and promoting the desired NERR process.Ultimately,for the CuPo-NCDs NF catalyzed NERR,the FE_(NH_(3))and the reaction potential both were boosted,the resultant energy efficiency of NERR reached a record-breaking value of 56.5%,and the NH_(3)yield rate increased by 7 times compared to NCDs.This study provides a novel catalyst with a new pathway to boost the NERR.展开更多
Ionic liquid,1-butyl-3-methylimidazolium acetate（BMImAc）,was used in the electrochemical reduction of nitrobenzene.The electro-reduction of nitrobenzene on platinum electrode was studied by cyclic voltammetry（CV）,...Ionic liquid,1-butyl-3-methylimidazolium acetate（BMImAc）,was used in the electrochemical reduction of nitrobenzene.The electro-reduction of nitrobenzene on platinum electrode was studied by cyclic voltammetry（CV）,in situ Fourier transform infrared（FTIR） spectroscopy and constant-potential electrolysis.The experimental results show that electrochemical reduction process of nitrobenzene was controlled by diffusion,the main reduction product was azobenzen at-1.45 V,and the influences of scan rate and temperature on the electrochemical behaviors were obviously.A reduction mechanism of nitrobenzene in an ionic liquid was a probable ‘nitrobenzene→nitrosobenzene→azobenzene→aniline＇ main reductive reaction route.展开更多
文摘The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I-1 versus ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.
文摘Sintered （300℃） porous pellets of Fe2O3 were electrolyzed to Fe in molten CaCl2 （800-900℃） under argon at 1.8-3.2 V for 2-20 h. The laboratory scale experiments show that it was a potentially direct green method to produce Fe powder. At lower electrolysis voltage （〈2.2 V）, higher current efficiency （〉90%） and smaller energy consumption （-3.0 kWh/kg） can be obtained. When the electrolysis voltage was above 2.4 V, the deposition of metal Ca from the salt lowered the current efficiency and increased the energy consumption. The electrolysis voltage also had effects on the micrographs of the reduced powder. The cubic particles can be seen in the products at the voltage lower than 2.2 V; when the voltage was higher than 2.2 V, it was nodular. The reduction proceeds at the cathode in two steps, i.e., from Fe2O3 to FeO and then to Fe. The oxygen emits at the anode. The process is potentially free of carbon emission and produces two useful products at both cathode and anode, promising a zero-emission technology for the extractive metallurgical industry.
基金funded by the Natural Science Foundation of China(No.21603109)the Henan Joint Fund of the National Natural Science Foundation of China(No.U1404216)+2 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0676)the Science and Technology Innovation Talents in Universities of Henan Province(No.22HASTIT028)supported by Natural Science Basic Research Program of Shanxi(Nos.2022JQ-108,2022JQ-096).
文摘Electrocatalytic synthesis of ammonia as an environment-friendly and sustainable development method has received widespread attention in recent years.Two-dimensional(2D)materials are a promising catalyst for ammonia synthesis due to their large surface area.In this work,we have constructed a series of 2D metal borides(MBenes)with transition metal(TM)defects(TMd-MBenes)and comprehensively calculated the reactivity of electrocatalytic synthesis of ammonia-based on density functional theory.The results have demonstrated that the TMd-MBenes can effectively activate nitrogen oxide(NO)and nitrogen(N2)molecules thermodynamically.Particularly interesting,the co-chemisorption of O atoms,dissociated from NO,can facilitate the spilled of the inert N2 molecules into single N atoms,which can further hydrogenate into ammonia easily with an ultralow limiting potential of 0.59 V on TMd-MnB.Our research has not only provided clues for catalyst design for experimental study but also paved the way for the industrial application of electrocatalytic ammonia synthesis.
文摘In this study,for the first time,direct copper production from copper sulfide was carried out via direct electrochemical reduction method using inexpensive and stable molten borax electrolyte.The effects of current density(100–800 mA/cm^2)and electrolysis time(15–90 min)on both the cathodic current efficiency and copper yield were systematically investigated in consideration of possible electrochemical/chemical reactions at 1200℃.The copper production yield reached 98.09%after 90 min of electrolysis at a current density of 600 mA/cm^2.Direct metal production was shown to be possible with 6 kWh/kg energy consumption at a 600 mA/cm2 current density,at which the highest current efficiency(41%)was obtained.The suggested method can also be applied to metal/alloy production from single-and mixed-metal sulfides coming from primary production and precipitated sulfides,which are produced in the mining and metallurgical industries during treatment of process solutions or wastewaters.
基金F.Li and X.Ji thank the financial support from the Swedish Energy Agency(P47500-1)A.Laaksonen acknowledges the Swedish Research Council for financial support(2019-03865)+1 种基金partial support from a grant from Ministry of Research and Innovation of Romania(CNCS-UEFISCDI,project number PN-IIIP4-ID-PCCF-2016-0050,within PNCDI III)F.Mocci thanks the Fondazione di Sardegna,Project:“Precious metal-free complexes for catalytic CO2 reduction”(CUP:F71I17000170002)for the financial support.
文摘Electrochemical reduction of CO_(2) is a novel research field towards a CO_(2)-neutral global economy and combating fast accelerating and disastrous climate changes while finding new solutions to store renewable energy in value-added chemicals and fuels.Ionic liquids(ILs),as medium and catalysts(or supporting part of catalysts)have been given wide attention in the electrochemical CO_(2) reduction reaction(CO_(2) RR)due to their unique advantages in lowering overpotential and improving the product selectivity,as well as their designable and tunable properties.In this review,we have summarized the recent progress of CO_(2) electro-reduction in IL-based electrolytes to produce higher-value chemicals.We then have highlighted the unique enhancing effect of ILs on CO_(2) RR as templates,precursors,and surface functional moieties of electrocatalytic materials.Finally,computational chemistry tools utilized to understand how the ILs facilitate the CO_(2) RR or to propose the reaction mechanisms,generated intermediates and products have been discussed.
基金Financial support from the "Spanish Ministry of Economy, Industry, and Competitiveness" (Project CTQ2016-75491-R)from Abengoa Researchthe Spanish Ministry of Economy, Industry, and Competitiveness for financial support through the Ramón y Cajal Program, Grant: RYC-2015-19230
文摘A novel gas-phase electrocatalytic cell containing a low-temperature proton exchange membrane(PEM)was developed to electrochemically convert CO_2into organic compounds.Two different Cu-based cathode catalysts(Cu and Cu–C)were prepared by physical vapor deposition method(sputtering)and subsequently employed for the gas-phase electroreduction of CO_2at different temperatures(70–90°C).The prepared electrodes Cu and Cu–C were characterized by X-ray diffraction(XRD),X-ray photoemission spectroscopy(XPS)and scanning electron microscopy(SEM).As revealed,Cu is partially oxidized on the surface of the samples and the Cu and Cu–C cathodic catalysts were comprised of a porous,continuous,and homogeneous film with nanocrystalline Cu with a grain size of 16 and 8 nm,respectively.The influence of the applied current and temperature on the electro-catalytic activity and selectivity of these materials was investigated.Among the two investigated electrodes,the pure Cu catalyst film showed the highest CO_2specific electrocatalytic reduction rates and higher selectivity to methanol formation compared to the Cu–C electrode,which was attributed to the higher particle size of the former and lower Cu O/Cu ratio.The obtained results show potential interest for the possible use of electrical renewable energy for the transformation of CO_2into valuable products using low metal loading Cu based electrodes(0.5 mg Cu cm^(-2))prepared by sputtering.
基金the financial support from the National Natural Science Foundation of China(Nos.22004060,22074062,22276100)the Natural Science Foundation of Jiangsu Province(No.SBK2022044384)the financial support from Research startup fund of Nanjing University of Posts and Telecommunications(NJUPT)。
文摘Nitrogen electro-reduction reaction(NERR)is a promising alternative method for ammonia production to the Haber-Bosch approach due to mild reaction conditions and free harmful by-product emission.A formidable challenge in bringing NERR closer to the practical application is developing an electrocatalyst which can simultaneously improve the Faraday efficiency and reduce the reaction over-potential.Herein,we fabricated a catalyst of nitrogen-doped carbon dots modified copper-phosphate nanoflower petals(Cu Po-NCDs NF)via a self-assembly method.The flower structure endowed the Cu Po-NCDs NF with large specific surface area,and thus enabled more active sites to be exposed.In particular,we demonstrated that the NCDs modified Cu Po petals with flower-like structure can accelerate the interfacial proton-electron transfer,suppressing the competing hydrogen evolution reaction and promoting the desired NERR process.Ultimately,for the CuPo-NCDs NF catalyzed NERR,the FE_(NH_(3))and the reaction potential both were boosted,the resultant energy efficiency of NERR reached a record-breaking value of 56.5%,and the NH_(3)yield rate increased by 7 times compared to NCDs.This study provides a novel catalyst with a new pathway to boost the NERR.
基金Supported by the National Basic Research Program of China（No.2012CB722604） and the National Natural Science Foundation of China（No.21076192）.
文摘Ionic liquid,1-butyl-3-methylimidazolium acetate（BMImAc）,was used in the electrochemical reduction of nitrobenzene.The electro-reduction of nitrobenzene on platinum electrode was studied by cyclic voltammetry（CV）,in situ Fourier transform infrared（FTIR） spectroscopy and constant-potential electrolysis.The experimental results show that electrochemical reduction process of nitrobenzene was controlled by diffusion,the main reduction product was azobenzen at-1.45 V,and the influences of scan rate and temperature on the electrochemical behaviors were obviously.A reduction mechanism of nitrobenzene in an ionic liquid was a probable ‘nitrobenzene→nitrosobenzene→azobenzene→aniline＇ main reductive reaction route.
基金supported by National Science Foundation of China(20873083,21003088 and 21173144)Funding of Shanghai education commission fifth key disciplines(J50102)+1 种基金State Key Laboratory of Chemical Engineering(SKL-ChE-08A01)Innovation Foundation of Shanghai University(SHUCX112038)
