The rational design of Fe–N–C catalysts that possess easily accessible active sites and favorable mass transfer,which are usually determined by the structure of catalyst supports,is crucial for the oxygen reduction ...The rational design of Fe–N–C catalysts that possess easily accessible active sites and favorable mass transfer,which are usually determined by the structure of catalyst supports,is crucial for the oxygen reduction reaction(ORR).In this study,an oleic acid-assisted soft-templating approach is developed to synthesize size-controlled nitrogen-doped carbon nanoparticles(ranging from 130 nm to 60 nm and 35 nm,respectively)that feature spiral mesopores on their surface(SMCs).Next,atomically dispersed Fe–Nx sites are fabricated on the size-tunable SMCs(Fe1/SMC-x,where x represents the SMC size)and the size-dependent activity toward ORR is investigated.It is found that the catalytic performance of Fe1/SMCs is significantly influenced by the size of SMCs,where the Fe1/SMC-60 catalyst shows the highest ORR activity with a half-wave potential of 0.90 V vs.RHE in KOH electrolyte,indicating that the gas-liquid-solid three-phase interface on the Fe1/SMC-60 enhances the accessibility of Fe–Nx sites.In addition,when using Fe1/SMC-60 as the cathode catalyst in aqueous zinc-air batteries(ZABs),it delivers a higher open-circuit voltage(1.514 V),a greater power density(223 mW cm^(−2)),and a larger specific capacity/energy than Pt/C-based counterparts.These results further highlight the potential of Fe1/SMC60 for practical energy devices associated with ORR and the importance of size-controlled synthesis of SMCs.展开更多
Sensitive detection of Staphylococcus aureus enterotoxin B(SEB)is of importance for preventing food poisoning from threatening human health.In this work,an electrochemical and colorimetric dual-signal detection assay ...Sensitive detection of Staphylococcus aureus enterotoxin B(SEB)is of importance for preventing food poisoning from threatening human health.In this work,an electrochemical and colorimetric dual-signal detection assay of SEB was developed.The probe(Ab2/AuPt@Fe-N-C)was bound to SEB captured by Ab1,where the Ab2/AuPt@Fe-N-C triggered methylene blue degradation and resulted in the decrease of electrochemical signal.Furthermore,the probe catalyzed the oxidation of 3,3’,5,5’-tetramethyl biphenyl to generate a colorimetric absorbance at 652 nm.Once the target was captured and formed a sandwich-like complex,the color changed from colorless to blue.SEB detection by colorimetric and electrochemical methods showed a linear relationship in the concentration ranges of 0.0002-10.0000 and 0.0005-10.0000 ng/mL,with limits of detection of 0.0667 and 0.1670 pg/mL,respectively.The dual-signal biosensor was successfully used to detect SEB in milk and water samples,which has great potential in toxin detection in food and the environment.展开更多
生物质碳基材料具有可调的微观结构、丰富的表面活性中心、优良的导电和导热性能以及较大的比表面积,已经成为新能源领域的重要基础材料.然而,应用于锌-空气电池中时,碳基材料高电位下的碳腐蚀问题严重影响了电池的稳定性,因此,开发具...生物质碳基材料具有可调的微观结构、丰富的表面活性中心、优良的导电和导热性能以及较大的比表面积,已经成为新能源领域的重要基础材料.然而,应用于锌-空气电池中时,碳基材料高电位下的碳腐蚀问题严重影响了电池的稳定性,因此,开发具有低过电位的析氧反应(OER)催化剂来降低充电电压是解决该问题的关键.本课题组采用一种低温磷化策略制备了具有低OER过电位的P修饰的Fe_(3)O_(4)/Fe_(2)N和生物质碳复合催化剂(P-Fe_(3)O_(4)/Fe_(2)N@NPC),其具有较好的双功能氧反应活性,氧还原反应(ORR)的半波电位为0.86 V,仅需要280 m V的OER过电位就可以达到10 m Acm-2的电流密度.以P-Fe_(3)O_(4)/Fe_(2)N@NPC作为正极组装的锌-空气电池表现出低的充放电电压差和长期稳定性,在目前报道的碳基催化剂应用于锌-空气电池中具有很大优势.此外,采用X射线光电子能谱(XPS)、拉曼光谱和氧气程序升温脱附(O2-TPD)等技术研究了磷化对催化剂的结构和催化性能带来的差异原因,并利用密度泛函理论(DFT)计算研究了催化剂的OER反应机制.XPS测试结果表明,P-Fe_(3)O_(4)/Fe_(2)N@NPC的P 2p轨道观察到P-M键、P-C键和P-O键,证实P在碳纳米结构中的成功修饰.Fe_(2)pXPS谱显示,P的掺入使Fe_(2)p峰向低结合能方向移动,这表明P的表面改性改变了金属Fe物种的表面电子构型.此外,拉曼光谱结果表明,P掺杂后样品的ID/IG值增加,说明结构中具有更多的缺陷,为ORR反应提供更多的催化活性位.O2-TPD结果表明,两种催化剂在低温区域(<500 ℃)表现为表面缺陷上的化学吸附氧,在高温区域(>500 ℃)表现为晶格氧释放,这说明了催化剂中都存在表面氧空位.与P-Fe_(3)O_(4)/Fe_(2)N@NPC的脱附氧物种相关的峰值温度低于Fe_(3)O_(4)/Fe_(2)N@NPC,证明P修饰可以使催化剂具有更好的吸附/脱附氧能力,进一步降低了吸附氧分子的活化能垒.利用DFT计算分析了OER�展开更多
The low intrinsic activity of Fe/N/C oxygen catalysts restricts their commercial application in the fuel cells technique;herein,we demonstrated the interface engineering of plasmonic induced Fe/N/C-F catalyst with pri...The low intrinsic activity of Fe/N/C oxygen catalysts restricts their commercial application in the fuel cells technique;herein,we demonstrated the interface engineering of plasmonic induced Fe/N/C-F catalyst with primarily enhanced oxygen reduction performance for fuel cells applications.The strong interaction between F and Fe-N4 active sites modifies the catalyst interfacial properties as revealed by X-ray absorption structure spectrum and density functional theory calculations,which changes the electronic structure of Fe-N active site resulting from more atoms around the active site participating in the reaction as well as super-hydrophobicity from C–F covalent bond.The hybrid contribution from active sites and carbon support is proposed to optimize the three-phase microenvironment efficiently in the catalysis electrode,thereby facilitating efficient oxygen reduction performance.High catalytic performance for oxygen reduction and fuel cells practical application catalyzed by Fe/N/C-F catalyst is thus verified,which offers a novel catalyst system for fuel cells technique.展开更多
An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is ...An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is the carbonization media. The morphology of samples with/without Fe component has been compared by HRTEM, and the result shows that Fe can promote the graphitization of carbon. Further electro-chemical test shows that the oxygen reduction reaction（ORR） catalytic activity of Fe-containing sample（C–Fe N） is much higher than that of the Fe-free sample（C–N）. Additionally, the intermediates of C–Fe N formed during each synthetic procedure have been thoroughly characterized by multiple methods,and the function of each procedure has been discussed. The C–Fe N sample exhibits high electro-catalytic stability and superior electro-catalytic activity toward ORR in alkaline media, with its half-wave potential 20 mV lower than that of commercial Pt/C（40 wt%）. It is further incorporated into alkaline polymer electrolyte fuel cell（APEFC） as the cathode material and led to a power density of 100 m W/cm;.展开更多
Modifying solid catalysts with an ionic liquid layer is an effective approach for boosting the performance of both Pt-based and non-precious metal catalysts toward the oxygen reduction reaction. While most studies ope...Modifying solid catalysts with an ionic liquid layer is an effective approach for boosting the performance of both Pt-based and non-precious metal catalysts toward the oxygen reduction reaction. While most studies operated at room temperature it remains unclear whether the IL-associated boosting effect can be maintained at elevated temperature, which is of high relevance for practical applications in low temperature fuel cells. Herein, Fe-N-C catalysts were modified by introducing small amounts of hydrophobic ionic liquid, resulting in boosted electrocatalytic activity towards the alkaline oxygen reduction reaction at room temperature. It is demonstrated that the boosting effect can be maintained and even strengthened when increasing the electrolyte temperature up to 70℃. These findings show for the first time that the incorporation of ionic liquid is a suited method to obtain advanced noble metal-free electrocatalysts that can be applied at operating temperature condition.展开更多
An extensive analysis of iron-nitrogen-carbon(Fe-N-C)electrocatalysts synthesis and activity is presented concerning synthesis conditions such as initial Fe content,pyrolysis temperature and atmosphere(inert N_(2),red...An extensive analysis of iron-nitrogen-carbon(Fe-N-C)electrocatalysts synthesis and activity is presented concerning synthesis conditions such as initial Fe content,pyrolysis temperature and atmosphere(inert N_(2),reducing NH_(3),oxidizing Cl_(2) and their sequential combinations)and the influence of an external magnetic field on their performance in oxygen reduction reaction(ORR).Thermosetting porous polymers doped with FeCl_(3) were utilized as the Fe-N-C catalysts precursors.The pyrolysis temperature was varied within a 700-900℃range.The temperature and atmosphere of pyrolysis strongly affect the porosity and compositi on of the resultant Fe-N-C catalysts,while the in itial amount of Fe precursor shows much weaker impact.Pyrolysis under NH_(3) yields materials similar to those pyrolyzed under an inert atmosphere(N_(2)).In contrast,pyrolysis under Cl_(2) yields carbon of peculiar character with highly disordered structure and extensive microporosity.The application of a static external magnetic field strongly enhances the ORR process(herein studied in an alkaline environment)and the enhancement correlates with the Fe content in the Fe-N-C catalysts.The Fe-N-C materials containing ferromagnetic iron phase embedded in N-doped microporous carbon constitute attractive catalysts for magnetic field-aided anion exchange membrane fuel cell technology.展开更多
In recent years,Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction(ORR)activity and low cost for proton exchange membrane fuel cells(PEMFCs).However,the durability problems still pose...In recent years,Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction(ORR)activity and low cost for proton exchange membrane fuel cells(PEMFCs).However,the durability problems still pose challenge to the application of Fe-N-C catalyst.Although considerable work has been done to investigate the degradation mechanisms of Fe-N-C catalyst,most of them are simply focused on the active-site decay,the carbon oxidation,and the demetalation problems.In fact,the 2e−pathway in the ORR process of Fe-N-C catalyst would result in the formation of H2O2,which is proved to be a key degradation source.In this paper,a new insight into the effect of potential on degradation of Fe-N-C catalyst was provided by quantifying the H2O2 intermediate.In this case,stability tests were conducted by the potential-static method in O2 saturated 0.1 mol/L HClO4.During the tests,H2O2 was quantified by rotating ring disk electrode(RRDE).The results show that compared with the loading voltage of 0.4 V,0.8 V,and 1.0 V,the catalysts being kept at 0.6 V exhibit a highest H2O2 yield.It is found that it is the combined effect of electrochemical oxidation and chemical oxidation(by aggressive radicals like H2O2/radicals)that triggered the highest H2O2 release rate,with the latter as the major cause.展开更多
Nitrogen-coordinated iron atoms on carbon supports(Fe-N-C)are among the most promising noble-metal-free electrocatalysts for oxygen reduction reaction(ORR).However,their unsatisfactory stability limits their prac-tica...Nitrogen-coordinated iron atoms on carbon supports(Fe-N-C)are among the most promising noble-metal-free electrocatalysts for oxygen reduction reaction(ORR).However,their unsatisfactory stability limits their prac-tical application.Herein,we demonstrate a dual-shell Fe-N-C electrocatalyst with excellent catalytic activity and long-term stability.Pyrrole and dopamine are sequentially polymerized on a fumed silica nanoparticle template.Metal precursor(FeCl_(3))and pore formation agent(ZnCl_(2))were loaded on the inner polypyrrole shell.During carbonization,the Zn evaporation creates abundant mesopores in the polydopamine-derived outer carbon shell,forming a "chain mail"like outer shell that protects Fe-N-C active sites loaded on the inner carbon shell and enables efficient mass transfer.Systematical tuning of the shield thickness and porosity affords the optimal electrocatalyst with a large surface area of 934 m^(2)g^(-1) and a high Fe loading of 2.04 wt%.This electrocatalyst delivers excellent ORR activity and superior stability in both acidic and alkaline electrolytes.Primary Zn-air batteries fabricated from this electrocatalyst delivers a high-power density of 257 mW cm^(-2) and impressive durability of continuous discharging over 250 h.Creating a graphitic and porous carbon protective shell can be further extended to other electrocatalysts to enable their practical applications in energy conversion and storage.展开更多
以苯胺为原料,二氧化硅球为硬模板,采用原位聚合法制备出具有多孔结构的氮掺杂碳球,然后以三氯化铁为铁源,利用沉淀法制备出球状多孔Fe-N-C复合催化剂.通过SEM、TEM、EDS等分析手段对Fe-N-C的形貌结构及组成进行了表征,使用旋转圆盘电...以苯胺为原料,二氧化硅球为硬模板,采用原位聚合法制备出具有多孔结构的氮掺杂碳球,然后以三氯化铁为铁源,利用沉淀法制备出球状多孔Fe-N-C复合催化剂.通过SEM、TEM、EDS等分析手段对Fe-N-C的形貌结构及组成进行了表征,使用旋转圆盘电极测试了其在碱性条件下对氧还原反应的催化活性.结果表明,其起始电位(0.961 V vs RHE)与半波电位(0.835 V vs RHE)与商业化Pt/C相近,经过7 000 s后,Fe-N-C仍保持93.53%的相对电流,显示出优异的氧还原催化稳定性.展开更多
Atomically dispersed iron-nitrogen-carbon(Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction(ORR) in proton exchange membrane fuel ce...Atomically dispersed iron-nitrogen-carbon(Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction(ORR) in proton exchange membrane fuel cells(PEMFCs),however suffer from low site density of active Fe-N4 moiety and limited mass transport during the catalytic reaction.To address these challenges,we report a three-dimensional(3D) metal-organic frameworks(MOF)-derived Fe-N-C single-atom catalyst.In this well-designed Fe-N-C catalyst,the micro-scale interconnected skeleton,the nano-scale ordered pores and the atomic-scale abundant carbon edge defects inside the skeleton significantly enhance the site density of active Fe-N4 moiety,thus improving the Fe utilization in the final catalyst.Moreover,the combination of the above mentioned micro-and nano-scale structures greatly facilitates the mass transport in the 3D Fe-N-C catalyst.Therefore,the multiscale engineered Fe-N-C single-atom catalyst achieves excellent ORR performance under acidic condition and affords a significantly enhanced current density and power density in PEMFC.Our findings may open new opportunities for the rational design of FeN-C catalysts through multiscale structural engineering.展开更多
基金supported by Major Basic Research Program of Natural Science Foundation of Shandong Province under Grant(ZR2022ZD30)Qingdao New Energy Shandong Laboratory Open Project(Grant:QNESL OP 202307)+2 种基金Natural Science Foundation of Shandong Province(ZR2023QB103)China Postdoctoral Science Foundation(2023M733609)Qingdao Postdoctoral Applied Research Project(QDBSH20230202075).
文摘The rational design of Fe–N–C catalysts that possess easily accessible active sites and favorable mass transfer,which are usually determined by the structure of catalyst supports,is crucial for the oxygen reduction reaction(ORR).In this study,an oleic acid-assisted soft-templating approach is developed to synthesize size-controlled nitrogen-doped carbon nanoparticles(ranging from 130 nm to 60 nm and 35 nm,respectively)that feature spiral mesopores on their surface(SMCs).Next,atomically dispersed Fe–Nx sites are fabricated on the size-tunable SMCs(Fe1/SMC-x,where x represents the SMC size)and the size-dependent activity toward ORR is investigated.It is found that the catalytic performance of Fe1/SMCs is significantly influenced by the size of SMCs,where the Fe1/SMC-60 catalyst shows the highest ORR activity with a half-wave potential of 0.90 V vs.RHE in KOH electrolyte,indicating that the gas-liquid-solid three-phase interface on the Fe1/SMC-60 enhances the accessibility of Fe–Nx sites.In addition,when using Fe1/SMC-60 as the cathode catalyst in aqueous zinc-air batteries(ZABs),it delivers a higher open-circuit voltage(1.514 V),a greater power density(223 mW cm^(−2)),and a larger specific capacity/energy than Pt/C-based counterparts.These results further highlight the potential of Fe1/SMC60 for practical energy devices associated with ORR and the importance of size-controlled synthesis of SMCs.
基金This work was financially supported by Major Science and Technology Project of Yunnan Province(202302AE090022)Key Research and Development Program of Yunnan(202203AC100010)+4 种基金the National Natural Science Foundation of China(32160597,32160236,32371463)National Key Research and Development Program of China(2022YFC2601604)Cardiovascular Ultrasound Innovation Team of Yunnan Province(202305AS350021)Spring City Plan:the High-level Talent Promotion and Training Project of Kunming(2022SCP001)the second phase of“Double-First Class”Program Construction of Yunnan University.
文摘Sensitive detection of Staphylococcus aureus enterotoxin B(SEB)is of importance for preventing food poisoning from threatening human health.In this work,an electrochemical and colorimetric dual-signal detection assay of SEB was developed.The probe(Ab2/AuPt@Fe-N-C)was bound to SEB captured by Ab1,where the Ab2/AuPt@Fe-N-C triggered methylene blue degradation and resulted in the decrease of electrochemical signal.Furthermore,the probe catalyzed the oxidation of 3,3’,5,5’-tetramethyl biphenyl to generate a colorimetric absorbance at 652 nm.Once the target was captured and formed a sandwich-like complex,the color changed from colorless to blue.SEB detection by colorimetric and electrochemical methods showed a linear relationship in the concentration ranges of 0.0002-10.0000 and 0.0005-10.0000 ng/mL,with limits of detection of 0.0667 and 0.1670 pg/mL,respectively.The dual-signal biosensor was successfully used to detect SEB in milk and water samples,which has great potential in toxin detection in food and the environment.
文摘生物质碳基材料具有可调的微观结构、丰富的表面活性中心、优良的导电和导热性能以及较大的比表面积,已经成为新能源领域的重要基础材料.然而,应用于锌-空气电池中时,碳基材料高电位下的碳腐蚀问题严重影响了电池的稳定性,因此,开发具有低过电位的析氧反应(OER)催化剂来降低充电电压是解决该问题的关键.本课题组采用一种低温磷化策略制备了具有低OER过电位的P修饰的Fe_(3)O_(4)/Fe_(2)N和生物质碳复合催化剂(P-Fe_(3)O_(4)/Fe_(2)N@NPC),其具有较好的双功能氧反应活性,氧还原反应(ORR)的半波电位为0.86 V,仅需要280 m V的OER过电位就可以达到10 m Acm-2的电流密度.以P-Fe_(3)O_(4)/Fe_(2)N@NPC作为正极组装的锌-空气电池表现出低的充放电电压差和长期稳定性,在目前报道的碳基催化剂应用于锌-空气电池中具有很大优势.此外,采用X射线光电子能谱(XPS)、拉曼光谱和氧气程序升温脱附(O2-TPD)等技术研究了磷化对催化剂的结构和催化性能带来的差异原因,并利用密度泛函理论(DFT)计算研究了催化剂的OER反应机制.XPS测试结果表明,P-Fe_(3)O_(4)/Fe_(2)N@NPC的P 2p轨道观察到P-M键、P-C键和P-O键,证实P在碳纳米结构中的成功修饰.Fe_(2)pXPS谱显示,P的掺入使Fe_(2)p峰向低结合能方向移动,这表明P的表面改性改变了金属Fe物种的表面电子构型.此外,拉曼光谱结果表明,P掺杂后样品的ID/IG值增加,说明结构中具有更多的缺陷,为ORR反应提供更多的催化活性位.O2-TPD结果表明,两种催化剂在低温区域(<500 ℃)表现为表面缺陷上的化学吸附氧,在高温区域(>500 ℃)表现为晶格氧释放,这说明了催化剂中都存在表面氧空位.与P-Fe_(3)O_(4)/Fe_(2)N@NPC的脱附氧物种相关的峰值温度低于Fe_(3)O_(4)/Fe_(2)N@NPC,证明P修饰可以使催化剂具有更好的吸附/脱附氧能力,进一步降低了吸附氧分子的活化能垒.利用DFT计算分析了OER�
基金the National Natural Science Foundation of China(Nos.21203008 and 21975025)Beijing Nature Science Foundation(No.2172051)+1 种基金State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University,and Shenzhen Science and Technology Innovation Committee(No.JCYJ20170817161445322)Thanks for Dr.Lirong Zheng(1W1B@Beijing Synchrotron Radiation Facility)for providing measurement time.We appreciate help from Dr.Jiaou Wang(4B9B@Beijing Synchrotron Radiation Facility)for XANES measurement.XPS measurements were performed in the Analysis&Testing Center,Beijing Institute of Technology.
文摘The low intrinsic activity of Fe/N/C oxygen catalysts restricts their commercial application in the fuel cells technique;herein,we demonstrated the interface engineering of plasmonic induced Fe/N/C-F catalyst with primarily enhanced oxygen reduction performance for fuel cells applications.The strong interaction between F and Fe-N4 active sites modifies the catalyst interfacial properties as revealed by X-ray absorption structure spectrum and density functional theory calculations,which changes the electronic structure of Fe-N active site resulting from more atoms around the active site participating in the reaction as well as super-hydrophobicity from C–F covalent bond.The hybrid contribution from active sites and carbon support is proposed to optimize the three-phase microenvironment efficiently in the catalysis electrode,thereby facilitating efficient oxygen reduction performance.High catalytic performance for oxygen reduction and fuel cells practical application catalyzed by Fe/N/C-F catalyst is thus verified,which offers a novel catalyst system for fuel cells technique.
基金financially supported by the National Natural Science Foundation of China(21573167,21633008,91545205,21125312)National Key Research and Development Program(2016YFB0101203)+2 种基金the National Basic Research Program(2012CB932800,2012CB215500)the Doctoral Fund of Ministry of Education of China(20110141130002)the Fundamental Research Funds for the Central Universities(2014203020207)
文摘An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is the carbonization media. The morphology of samples with/without Fe component has been compared by HRTEM, and the result shows that Fe can promote the graphitization of carbon. Further electro-chemical test shows that the oxygen reduction reaction（ORR） catalytic activity of Fe-containing sample（C–Fe N） is much higher than that of the Fe-free sample（C–N）. Additionally, the intermediates of C–Fe N formed during each synthetic procedure have been thoroughly characterized by multiple methods,and the function of each procedure has been discussed. The C–Fe N sample exhibits high electro-catalytic stability and superior electro-catalytic activity toward ORR in alkaline media, with its half-wave potential 20 mV lower than that of commercial Pt/C（40 wt%）. It is further incorporated into alkaline polymer electrolyte fuel cell（APEFC） as the cathode material and led to a power density of 100 m W/cm;.
基金funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Program (Grant No. 681719)the German Research Foundation (Grant No.GSC1070) for financial support。
文摘Modifying solid catalysts with an ionic liquid layer is an effective approach for boosting the performance of both Pt-based and non-precious metal catalysts toward the oxygen reduction reaction. While most studies operated at room temperature it remains unclear whether the IL-associated boosting effect can be maintained at elevated temperature, which is of high relevance for practical applications in low temperature fuel cells. Herein, Fe-N-C catalysts were modified by introducing small amounts of hydrophobic ionic liquid, resulting in boosted electrocatalytic activity towards the alkaline oxygen reduction reaction at room temperature. It is demonstrated that the boosting effect can be maintained and even strengthened when increasing the electrolyte temperature up to 70℃. These findings show for the first time that the incorporation of ionic liquid is a suited method to obtain advanced noble metal-free electrocatalysts that can be applied at operating temperature condition.
基金supported by the National Science Centre,Poland,UMO-2016/23/B/ST5/00127。
文摘An extensive analysis of iron-nitrogen-carbon(Fe-N-C)electrocatalysts synthesis and activity is presented concerning synthesis conditions such as initial Fe content,pyrolysis temperature and atmosphere(inert N_(2),reducing NH_(3),oxidizing Cl_(2) and their sequential combinations)and the influence of an external magnetic field on their performance in oxygen reduction reaction(ORR).Thermosetting porous polymers doped with FeCl_(3) were utilized as the Fe-N-C catalysts precursors.The pyrolysis temperature was varied within a 700-900℃range.The temperature and atmosphere of pyrolysis strongly affect the porosity and compositi on of the resultant Fe-N-C catalysts,while the in itial amount of Fe precursor shows much weaker impact.Pyrolysis under NH_(3) yields materials similar to those pyrolyzed under an inert atmosphere(N_(2)).In contrast,pyrolysis under Cl_(2) yields carbon of peculiar character with highly disordered structure and extensive microporosity.The application of a static external magnetic field strongly enhances the ORR process(herein studied in an alkaline environment)and the enhancement correlates with the Fe content in the Fe-N-C catalysts.The Fe-N-C materials containing ferromagnetic iron phase embedded in N-doped microporous carbon constitute attractive catalysts for magnetic field-aided anion exchange membrane fuel cell technology.
基金The work was supported by the Thirteenth National Key Point Research and Invention Program(No.2016YFB0101302)。
文摘In recent years,Fe-N-C catalyst is particularly attractive due to its high oxygen reduction reaction(ORR)activity and low cost for proton exchange membrane fuel cells(PEMFCs).However,the durability problems still pose challenge to the application of Fe-N-C catalyst.Although considerable work has been done to investigate the degradation mechanisms of Fe-N-C catalyst,most of them are simply focused on the active-site decay,the carbon oxidation,and the demetalation problems.In fact,the 2e−pathway in the ORR process of Fe-N-C catalyst would result in the formation of H2O2,which is proved to be a key degradation source.In this paper,a new insight into the effect of potential on degradation of Fe-N-C catalyst was provided by quantifying the H2O2 intermediate.In this case,stability tests were conducted by the potential-static method in O2 saturated 0.1 mol/L HClO4.During the tests,H2O2 was quantified by rotating ring disk electrode(RRDE).The results show that compared with the loading voltage of 0.4 V,0.8 V,and 1.0 V,the catalysts being kept at 0.6 V exhibit a highest H2O2 yield.It is found that it is the combined effect of electrochemical oxidation and chemical oxidation(by aggressive radicals like H2O2/radicals)that triggered the highest H2O2 release rate,with the latter as the major cause.
文摘Fe-N-C材料是目前非常有潜力的一类非贵金属氧还原电极催化剂。本论文分别以导电碳黑(HG-1F)、苯胺、Fe Cl3为碳载体、含氮前驱体、铁前驱体,依次经过聚合、热处理和酸处理获得了多孔Fe-N-C材料。电化学测试结果表明,多孔Fe-N-C材料在0.1 M KOH中催化氧还原反应(ORR)的活性随酸处理时间呈火山型变化,其中酸处理4 h的样品对ORR具有较高的催化活性,促使ORR主要以4电子反应途径进行。
基金the Australian Research Council under the Future Fellowships scheme(FT160100107)Discovery Programme(DP180102210)The University of Sydney under the Commercial Development and Industry Partnerships fund CDIP 332020.
文摘Nitrogen-coordinated iron atoms on carbon supports(Fe-N-C)are among the most promising noble-metal-free electrocatalysts for oxygen reduction reaction(ORR).However,their unsatisfactory stability limits their prac-tical application.Herein,we demonstrate a dual-shell Fe-N-C electrocatalyst with excellent catalytic activity and long-term stability.Pyrrole and dopamine are sequentially polymerized on a fumed silica nanoparticle template.Metal precursor(FeCl_(3))and pore formation agent(ZnCl_(2))were loaded on the inner polypyrrole shell.During carbonization,the Zn evaporation creates abundant mesopores in the polydopamine-derived outer carbon shell,forming a "chain mail"like outer shell that protects Fe-N-C active sites loaded on the inner carbon shell and enables efficient mass transfer.Systematical tuning of the shield thickness and porosity affords the optimal electrocatalyst with a large surface area of 934 m^(2)g^(-1) and a high Fe loading of 2.04 wt%.This electrocatalyst delivers excellent ORR activity and superior stability in both acidic and alkaline electrolytes.Primary Zn-air batteries fabricated from this electrocatalyst delivers a high-power density of 257 mW cm^(-2) and impressive durability of continuous discharging over 250 h.Creating a graphitic and porous carbon protective shell can be further extended to other electrocatalysts to enable their practical applications in energy conversion and storage.
文摘以苯胺为原料,二氧化硅球为硬模板,采用原位聚合法制备出具有多孔结构的氮掺杂碳球,然后以三氯化铁为铁源,利用沉淀法制备出球状多孔Fe-N-C复合催化剂.通过SEM、TEM、EDS等分析手段对Fe-N-C的形貌结构及组成进行了表征,使用旋转圆盘电极测试了其在碱性条件下对氧还原反应的催化活性.结果表明,其起始电位(0.961 V vs RHE)与半波电位(0.835 V vs RHE)与商业化Pt/C相近,经过7 000 s后,Fe-N-C仍保持93.53%的相对电流,显示出优异的氧还原催化稳定性.
基金supported by the National Natural Science Foundation of China(51722103,52071231 and 51571149)the Natural Science Foundation of Tianjin City(19JCJQJC61900)。
文摘Atomically dispersed iron-nitrogen-carbon(Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction(ORR) in proton exchange membrane fuel cells(PEMFCs),however suffer from low site density of active Fe-N4 moiety and limited mass transport during the catalytic reaction.To address these challenges,we report a three-dimensional(3D) metal-organic frameworks(MOF)-derived Fe-N-C single-atom catalyst.In this well-designed Fe-N-C catalyst,the micro-scale interconnected skeleton,the nano-scale ordered pores and the atomic-scale abundant carbon edge defects inside the skeleton significantly enhance the site density of active Fe-N4 moiety,thus improving the Fe utilization in the final catalyst.Moreover,the combination of the above mentioned micro-and nano-scale structures greatly facilitates the mass transport in the 3D Fe-N-C catalyst.Therefore,the multiscale engineered Fe-N-C single-atom catalyst achieves excellent ORR performance under acidic condition and affords a significantly enhanced current density and power density in PEMFC.Our findings may open new opportunities for the rational design of FeN-C catalysts through multiscale structural engineering.
