Atomically dispersed Cu-based single-metal-site catalysts(Cu-N-C)have emerged as a frontier for electrocatalytic oxygen reduction reactions(ORR)because they can effectively optimize the D-band center of the Cu active ...Atomically dispersed Cu-based single-metal-site catalysts(Cu-N-C)have emerged as a frontier for electrocatalytic oxygen reduction reactions(ORR)because they can effectively optimize the D-band center of the Cu active site and provide appropriate adsorption/desorption energy for oxygen-containing intermediates.Metal-organic frameworks(MOFs)show excellent prospects in many fields because of their structural regularity and designability,but their direct use for electrocatalysis has been rarely reported due to the low intrinsic conductivity.Here,a MOF material(Cu-TCNQ)with highly regular single-atom copper active centers was successfully prepared using a solution chemical reaction method.Subsequently,Cu-TCNQ and graphene oxide(GO)were directly self-assembled to form a Cu-TCNQ/GO composite,which improved the conductivity of the catalyst while maintained the atomically precise controllability.The resistivity of the Cu-TCNQ/GO decreased by three orders of magnitude(1663.6-2.7 W/cm)compared with pure Cu-TCNQ.The half-wave potential was as high as 0.92 V in 0.1 mol/L KOH,even better than that of commercial 20%Pt/C.In alkaline polymer electrolyte fuel cells(APEFCs),the open-circuit voltage and power density of Cu-TCNQ/GO electrode reached 0.95 V and 320 m W/cm^(2),respectively,which suggests that Cu-TCNQ/GO has a good potential for application as a cathode ORR catalyst.展开更多
Unremitting and intensive researches about efficient non-precious metal electrocatalysts are necessary for large-scale commercial applications of fuel cells,while iron and nitrogen co-doped carbon(Fe-N-C)materials has...Unremitting and intensive researches about efficient non-precious metal electrocatalysts are necessary for large-scale commercial applications of fuel cells,while iron and nitrogen co-doped carbon(Fe-N-C)materials has become one of the most promising electrocatalysts to replace Pt-based noble metal catalysts.However,the traditional Fe-doped ZIF with rhomb dodecahedron morphology limits the exposure of active sites and the utilization of atoms,even affecting the performance of the catalyst.Herein,a Fe/N co-doped catalyst with a flower-like morphology was prepared using ferric citrate source along with secondary NH_(3)heat treatment.The optimal catalyst(termed as 4Fe_(citrate)-N-C-3)showed distinguished oxygen reduction reaction(ORR)activity with a half-wave potential of 0.8 and 0.9 V(vs.RHE)in acid and alkaline media,respectively.In addition,4Fe_(citrate)-N-C-3 maintained more than 80%of original activity even after 50,000 s which is superior to the benchmark Pt/C.The strategy of controlling morphology and composition is meaningful for the optimization of non-precious metal electrocatalysts for ORR in fuel cells or metal-air batteries.展开更多
The low activity and durability are still the critical barriers for non-precious metal electrocatalyst,mainly involving M-N/C(M=Fe,Co,Mn et al),applied in fuel cell.Constructing bimetallic sites has been explored as a...The low activity and durability are still the critical barriers for non-precious metal electrocatalyst,mainly involving M-N/C(M=Fe,Co,Mn et al),applied in fuel cell.Constructing bimetallic sites has been explored as an effective method to boost the performance of the catalyst for the synergistic effect between metal atoms.However,this synergistic effect is always suppressed in acidic conditions and results in unstable catalytic performance.Here we create novel fluorinated iron(Fe)and cobalt(Co)bimetallic nanoparticles distributed on nitrogen-doped carbon nanofibers(CNFs)for oxygen reduction reaction(ORR).The fluorination strongly increased the charge density of the bimetallic catalyst and resulted in a remarkable catalytic performance with the half-wave potential of 804 m V in 0.1 M HCl O_(4)and 1.6 times power density improvement for the proton exchange membrane fuel cell device.Importantly,the chemical and mechanical robust CNFs support improved the electric conductivity and stability of bimetallic catalysts,which leads to an ultra-stable electrocatalyst.The fuel cell voltage can keep stable even after 110 h,instead of the continuingly decrease in the traditional M-N/C.展开更多
Proton exchange membrane fuel cell(PEMFC)is a device that converts chemical energy into electrical energy,and the design of catalytic layer of its air electrode should not only contain abundant and easily accessible r...Proton exchange membrane fuel cell(PEMFC)is a device that converts chemical energy into electrical energy,and the design of catalytic layer of its air electrode should not only contain abundant and easily accessible reactive sites,but also have highly connected electrons,protons,and reactants mass transfer channels.Therefore,the electrode must possess a specific three-dimensional(3D)geometric structure and orderly distributed functionalized channels to ensure full utilization of catalytic active sites and enable continuous reaction processes.Herein,we review the recent research progress of porous carbon-based oxygen reduction reaction(ORR)catalysts for cathodic catalytic layer in PEMFC.Firstly,the reaction mechanism of PEMFC as well as the optimization principles were briefly introduced,followed by a detailed discussion on the design and preparation of PEMFC cathode ORR catalysts with hierarchical porous structures from the main methods,such as hard template,soft template,combination of hard and soft templates,self-assembled template,electrostatic spinning,and 3D printing.Additionally,the performance characterization of PEMFC cathode catalysts with porous structure was elaborated from three aspects:electrochemical performance testing,numerical investigations of oxygen transport,and in-situ characterization and operation techniques.Finally,the future challenges and opportunities for the PEMFC cathodic catalytic layer were envisioned.展开更多
Based on the volcanic relationship between catalytic activity and key adsorption energies,Pt-Co alloy materials have been widely studied as cathode oxygen reduction reaction(ORR)catalysts in proton exchange membrane f...Based on the volcanic relationship between catalytic activity and key adsorption energies,Pt-Co alloy materials have been widely studied as cathode oxygen reduction reaction(ORR)catalysts in proton exchange membrane fuel cells(PEMFCs)due to their higher active surface area and adjustable D-band energy levels compared to Pt/C.However,how to balance the alloying degree and ORR performance of Pt-Co catalyst remains a great challenge.Herein,we first synthesized a well-dispersed Pt/Co/C precursor by using a mild dimethylamine borane(DMAB)as the reducing agent.The precursor was calcined at high temperature under H_(2)/Ar mixed gas by a secondary reduction strategy to obtain an ordered Pt_(3)Co intermetallic compound nanoparticle catalyst with a high degree of alloying.The optimization of elec-tronic structure due to Pt-Co alloying and the strong metal-carrier interaction ensure the high kinetic activity of the cell membrane electrode.Additionally,the high degree of graphitization increases the electrical conductivity during the reaction.As a result,the activity and stability of the catalyst were significantly improved,with a half-wave potential as high as 0.87 V,which decreased by only 20 mV after 10000 potential cycles.Single-cell tests further validate the high intrinsic activity of the ordered Pt_(3)Co catalyst with mass activity up to 0.67 A mg_(pt)^(-1),exceeding the United States Department of Energy(US DOE)standard(0.44 A mg_(pt)^(-1)),and a rated power of 5.93 W mg_(pt)^(-1).展开更多
Metal-organic frameworks(MOFs)have attracted a lot of attention due to their diverse structures,favorable porous properties,and tunable chemical compositions in the multiple fields.Notably,MOF-based materials(includin...Metal-organic frameworks(MOFs)have attracted a lot of attention due to their diverse structures,favorable porous properties,and tunable chemical compositions in the multiple fields.Notably,MOF-based materials(including pristine MOFs,MOF composites,and their derivatives)play the vital role in electrochemical energy storage and conversion systems,due to their ability for regulating chemical composition at the molecular level and their highly porous frameworks for facilitating the mass and charge transfer.Supercapacitors and fuel cells are used as one of energy storage and conversion systems respectively,and it is unstoppable to design and synthesize high-efficiency electrode materials for them.This review starts with the strategies for designing targeted MOF-based materials in electrochemical energy storage and conversion applications followed by the state-ofthe-art MOF-based materials discussed as to their potential applications in supercapacitors and electrocatalytic oxygen reduction reaction(ORR).Finally,the challenges and perspectives of MOF-based materials applied for supercapacitors and electrocatalytic ORR are discussed.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFB3807500)the National Natural Science Foundation of China(No.22220102003)+1 种基金the Beijing Natural Science Foundation(No.JL23003)“Double-First-Class”construction projects(Nos.XK180301 and XK1804-02)。
文摘Atomically dispersed Cu-based single-metal-site catalysts(Cu-N-C)have emerged as a frontier for electrocatalytic oxygen reduction reactions(ORR)because they can effectively optimize the D-band center of the Cu active site and provide appropriate adsorption/desorption energy for oxygen-containing intermediates.Metal-organic frameworks(MOFs)show excellent prospects in many fields because of their structural regularity and designability,but their direct use for electrocatalysis has been rarely reported due to the low intrinsic conductivity.Here,a MOF material(Cu-TCNQ)with highly regular single-atom copper active centers was successfully prepared using a solution chemical reaction method.Subsequently,Cu-TCNQ and graphene oxide(GO)were directly self-assembled to form a Cu-TCNQ/GO composite,which improved the conductivity of the catalyst while maintained the atomically precise controllability.The resistivity of the Cu-TCNQ/GO decreased by three orders of magnitude(1663.6-2.7 W/cm)compared with pure Cu-TCNQ.The half-wave potential was as high as 0.92 V in 0.1 mol/L KOH,even better than that of commercial 20%Pt/C.In alkaline polymer electrolyte fuel cells(APEFCs),the open-circuit voltage and power density of Cu-TCNQ/GO electrode reached 0.95 V and 320 m W/cm^(2),respectively,which suggests that Cu-TCNQ/GO has a good potential for application as a cathode ORR catalyst.
基金supported by the National Key Research and Development Program of China(No.2019YFA0210300)the Natural Science Foundation of China(Nos.21922802,52074119)+3 种基金the Beijing Natural Science Foundation(No.JQ19007)the Joint Funds of the National Natural Science Foundation of China(No.U20A20280)Talent cultivation of State Key Laboratory of OrganicInorganic Composites,“Double-First-Class”construction projects(Nos.XK180301,XK1804–02)Distinguished Scientist Program at BUCT(No.buctylkxj02)。
文摘Unremitting and intensive researches about efficient non-precious metal electrocatalysts are necessary for large-scale commercial applications of fuel cells,while iron and nitrogen co-doped carbon(Fe-N-C)materials has become one of the most promising electrocatalysts to replace Pt-based noble metal catalysts.However,the traditional Fe-doped ZIF with rhomb dodecahedron morphology limits the exposure of active sites and the utilization of atoms,even affecting the performance of the catalyst.Herein,a Fe/N co-doped catalyst with a flower-like morphology was prepared using ferric citrate source along with secondary NH_(3)heat treatment.The optimal catalyst(termed as 4Fe_(citrate)-N-C-3)showed distinguished oxygen reduction reaction(ORR)activity with a half-wave potential of 0.8 and 0.9 V(vs.RHE)in acid and alkaline media,respectively.In addition,4Fe_(citrate)-N-C-3 maintained more than 80%of original activity even after 50,000 s which is superior to the benchmark Pt/C.The strategy of controlling morphology and composition is meaningful for the optimization of non-precious metal electrocatalysts for ORR in fuel cells or metal-air batteries.
基金supported by the National Key Research and Development Program of China(2019YFA0210300)the NSF of China(21922802)+2 种基金the talent cultivation of State Key Laboratory of Organic-Inorganic Compositesthe‘‘Double-First-Class”construction projects(XK180301,XK1804-02)the Distinguished Scientist Program at BUCT(buctylkxj02)。
文摘The low activity and durability are still the critical barriers for non-precious metal electrocatalyst,mainly involving M-N/C(M=Fe,Co,Mn et al),applied in fuel cell.Constructing bimetallic sites has been explored as an effective method to boost the performance of the catalyst for the synergistic effect between metal atoms.However,this synergistic effect is always suppressed in acidic conditions and results in unstable catalytic performance.Here we create novel fluorinated iron(Fe)and cobalt(Co)bimetallic nanoparticles distributed on nitrogen-doped carbon nanofibers(CNFs)for oxygen reduction reaction(ORR).The fluorination strongly increased the charge density of the bimetallic catalyst and resulted in a remarkable catalytic performance with the half-wave potential of 804 m V in 0.1 M HCl O_(4)and 1.6 times power density improvement for the proton exchange membrane fuel cell device.Importantly,the chemical and mechanical robust CNFs support improved the electric conductivity and stability of bimetallic catalysts,which leads to an ultra-stable electrocatalyst.The fuel cell voltage can keep stable even after 110 h,instead of the continuingly decrease in the traditional M-N/C.
基金supported by the Natural Science Special Project of Scientific Research Program of Shaanxi Provincial Department of Education(No.24JK0468)the Youth Innovation Team of Shaanxi Universities(No.2022TD071)Xi’an Key Laboratory of Textile and Chemical Additives Performance Assessment Reward and Subsidy Project(No.2021JH-201-0004).
文摘Proton exchange membrane fuel cell(PEMFC)is a device that converts chemical energy into electrical energy,and the design of catalytic layer of its air electrode should not only contain abundant and easily accessible reactive sites,but also have highly connected electrons,protons,and reactants mass transfer channels.Therefore,the electrode must possess a specific three-dimensional(3D)geometric structure and orderly distributed functionalized channels to ensure full utilization of catalytic active sites and enable continuous reaction processes.Herein,we review the recent research progress of porous carbon-based oxygen reduction reaction(ORR)catalysts for cathodic catalytic layer in PEMFC.Firstly,the reaction mechanism of PEMFC as well as the optimization principles were briefly introduced,followed by a detailed discussion on the design and preparation of PEMFC cathode ORR catalysts with hierarchical porous structures from the main methods,such as hard template,soft template,combination of hard and soft templates,self-assembled template,electrostatic spinning,and 3D printing.Additionally,the performance characterization of PEMFC cathode catalysts with porous structure was elaborated from three aspects:electrochemical performance testing,numerical investigations of oxygen transport,and in-situ characterization and operation techniques.Finally,the future challenges and opportunities for the PEMFC cathodic catalytic layer were envisioned.
基金supported by the National Key Research and Development Program of China(grant No.2022YFB3807500)the National Natural Science Foundation of China(grant No.21922802,22220102003)+1 种基金the Beijing Natural Science Foundation(grant No.JQ19007)“Double-First-Class”construction projects(grant No.XK180301,XK1804-02).
文摘Based on the volcanic relationship between catalytic activity and key adsorption energies,Pt-Co alloy materials have been widely studied as cathode oxygen reduction reaction(ORR)catalysts in proton exchange membrane fuel cells(PEMFCs)due to their higher active surface area and adjustable D-band energy levels compared to Pt/C.However,how to balance the alloying degree and ORR performance of Pt-Co catalyst remains a great challenge.Herein,we first synthesized a well-dispersed Pt/Co/C precursor by using a mild dimethylamine borane(DMAB)as the reducing agent.The precursor was calcined at high temperature under H_(2)/Ar mixed gas by a secondary reduction strategy to obtain an ordered Pt_(3)Co intermetallic compound nanoparticle catalyst with a high degree of alloying.The optimization of elec-tronic structure due to Pt-Co alloying and the strong metal-carrier interaction ensure the high kinetic activity of the cell membrane electrode.Additionally,the high degree of graphitization increases the electrical conductivity during the reaction.As a result,the activity and stability of the catalyst were significantly improved,with a half-wave potential as high as 0.87 V,which decreased by only 20 mV after 10000 potential cycles.Single-cell tests further validate the high intrinsic activity of the ordered Pt_(3)Co catalyst with mass activity up to 0.67 A mg_(pt)^(-1),exceeding the United States Department of Energy(US DOE)standard(0.44 A mg_(pt)^(-1)),and a rated power of 5.93 W mg_(pt)^(-1).
基金This work was supported by the National Key Research and Development Program of China(No.2019YFA0210300)the Natural Science Foundation of China(No.21922802)+3 种基金the Beijing Natural Science Foundation(No.JQ19007)Talent Cultivation and Open Project(No.OIC-201801007)of State Key Laboratory of Organic-Inorganic Composites“Double-First-Class”Construction Projects(Nos.XK180301 and XK1804-02)the Distinguished Scientist Program at BUCT(No.buctylkxj02).
文摘Metal-organic frameworks(MOFs)have attracted a lot of attention due to their diverse structures,favorable porous properties,and tunable chemical compositions in the multiple fields.Notably,MOF-based materials(including pristine MOFs,MOF composites,and their derivatives)play the vital role in electrochemical energy storage and conversion systems,due to their ability for regulating chemical composition at the molecular level and their highly porous frameworks for facilitating the mass and charge transfer.Supercapacitors and fuel cells are used as one of energy storage and conversion systems respectively,and it is unstoppable to design and synthesize high-efficiency electrode materials for them.This review starts with the strategies for designing targeted MOF-based materials in electrochemical energy storage and conversion applications followed by the state-ofthe-art MOF-based materials discussed as to their potential applications in supercapacitors and electrocatalytic oxygen reduction reaction(ORR).Finally,the challenges and perspectives of MOF-based materials applied for supercapacitors and electrocatalytic ORR are discussed.
