Non-precious metal electrocatalysts(such as Fe-N-C materials) for the oxygen(O_(2)) reduction reaction demand a high catalyst loading in fuel cell devices to achieve workable performance. However, the extremely low so...Non-precious metal electrocatalysts(such as Fe-N-C materials) for the oxygen(O_(2)) reduction reaction demand a high catalyst loading in fuel cell devices to achieve workable performance. However, the extremely low solubility of O_(2) in water creates severe mass transport resistance in the thick catalyst layer of Fe-N-C catalysts. Here, we introduce silicalite-1 nanocrystals with hydrophobic cavities as sustainable O_(2) reservoirs to overcome the mass transport issue of Fe-N-C catalysts. The extra O_(2) supply to the adjacent catalysts significantly alleviated the negative effects of the severe mass transport resistance. The hybrid catalyst(Fe-N-C@silicalite-1) achieved a higher limiting current density than Fe-N-C in the half-cell test. In the H_(2)-O_(2) and H_2-air proton exchange membrane fuel cells, Fe-N-C@silicalite-1 exhibited a 16.3% and 20.2% increase in peak power density compared with Fe-N-C, respectively. The O_(2)-concentrating additive provides an effective approach for improving the mass transport imposed by the low solubility of O_(2) in water.展开更多
Metal nanoaggregates can simultaneously enhance the activity and stability of Fe-N-C catalysts in proton-exchange-membrane fuel cells(PEMFC).Previous studies on the relevant mechanism have focused on the direct intera...Metal nanoaggregates can simultaneously enhance the activity and stability of Fe-N-C catalysts in proton-exchange-membrane fuel cells(PEMFC).Previous studies on the relevant mechanism have focused on the direct interaction between FeN_(4)active sites and metal nanoaggregates.However,the role of carbon support that hosts metal nanoaggregates and active sites has been overlooked.Here,a Fe-N-C catalyst encapsulating inactive gold nanoparticles is prepared as a model catalyst to investigate the electronic tuning of Au nanoparticles(NPs)towards the carbon support.Au NPs donate electrons to carbon support,making it rich inπelectrons,which reduces the work function and regulates the electronic configuration of the FeN_(4)sites for an enhanced ORR activity.Meanwhile,the electron-rich carbon support can mitigate the electron depletion of FeN_(4)sites caused by carbon support oxidation,thereby preserving its high activity.The yield and accumulation of H_(2)O_(2)are thus alleviated,which delays the oxidation of the catalyst and benefits the stability.Due to the electron-rich carbon support,the composite catalyst achieves a top-level peak power density of 0.74 W/cm^(2) in a 1.5 bar H_(2)-air PEMFC,as well as the improved stability.This work elucidates the key role of carbon support in the performance enhancement of the FeN-C/metal nanoaggregate composite catalysts for fuel cell application.展开更多
Proton exchange membrane fuel cells(PEMFC)have attracted much attention because of their high energy conversion efficiency,high power density and zero emission of pollutants.However,the high cost of the cathode platin...Proton exchange membrane fuel cells(PEMFC)have attracted much attention because of their high energy conversion efficiency,high power density and zero emission of pollutants.However,the high cost of the cathode platinum group metal(PGM)catalysts creates a barrier for the large-scale application of PEMFC.Tremendous efforts have been devoted to the development of low-cost PGM-free catalysts,especially the Fe-N-C catalysts,to replace the expensive PGM catalysts.However,the characterization methods and evaluation standards of the catalysts varies,which is not conducive to the comparison of PGM-free catalysts.U.S.Department of energy(DOE)is the only authority that specifies the testing standards and activity targets for PGM-free catalysts.In this review,the major breakthroughs of Fe-N-C catalysts are outlined with the reference of DOE standards and targets.The preparation and characteristics of these highly active Fe-N-C catalysts are briefly introduced.Moreover,the efforts on improving the mass transfer and the durability issue of Fe-N-C fuel cell are discussed.Finally,the prospective directions concerning the comprehensive evaluation of the Fe-N-C catalysts are proposed.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
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
Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the ac...Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.展开更多
Due to larger atom utilization,unique electronic properties and unsaturated coordination,atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysi...Due to larger atom utilization,unique electronic properties and unsaturated coordination,atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysis.Considering the challenge of serious aggregation,rational synthesis of an atomic catalyst with good dispersion of atoms is paramount to the development of these catalysts.Herein,we report an enhanced confinement strategy to synthesize a catalyst comprised of atomically dispersed Fe supported on porous nitrogen-doped graphitic carbon from the novel and more cross-linkable Melamine-Glyoxal Resin.Densified isolated grid trapping,excessive melamine restricting,and nitrogen anchoring are strongly combined to ensure the final atomic-level dispersion of metal atoms.Experimental studies revealed enhanced kinetics of the obtained catalyst towards oxygen reduction reaction(ORR).This catalytic activity originates from the highly active surface with atomically dispersed iron sites as well as the multi-level three-dimensional structure with fast mass and electron transfer.The enhanced confinement strategy endows the resin-derived atomic catalyst with a great prospect to develop for commercialization in future.展开更多
Hydrogen peroxide that is produced through the two-electron pathway during the catalysis of oxygen reduction reaction(ORR)is recognized as harmful to the stability of nitrogen-doped carbon and Fe-based nonprecious cat...Hydrogen peroxide that is produced through the two-electron pathway during the catalysis of oxygen reduction reaction(ORR)is recognized as harmful to the stability of nitrogen-doped carbon and Fe-based nonprecious catalyst(Fe-N-C)for fuel cell application.A major remaining scientific question is how fast the removal of these deleterious intermediates can contribute to stability enhancement.Here,we report that the stability of Fe-N-C catalysts is positively correlated with the kinetic constant of hydrogen peroxide decomposition.Modulation of the H_(2)O_(2) decomposition kinetics by applying the frequency factor of the Arrhenius equation from 800 to 30000 s^(-1) for TiO_(2),CeO_(2) and ZrO_(2) reduced the decay rate of Fe-N-C catalysts from 0.151% to ‒0.1% in a 100-hour stability test.Fe-N-C/ZrO_(2) with a frequency factor of 30000 s^(-1) showed a 10% increase in current density during a 100-hour stability test and almost no decay during 15 hours of continuous fuel cell operation at a high potential of 0.7 V.展开更多
The excellent oxygen reduction reaction(ORR)activity of Fe–N–C catalysts in acidic media makes them potential for low-cost proton exchange membrane fuel cells.In recent years,it has been shown that heteroatoms(B,O,S...The excellent oxygen reduction reaction(ORR)activity of Fe–N–C catalysts in acidic media makes them potential for low-cost proton exchange membrane fuel cells.In recent years,it has been shown that heteroatoms(B,O,S,P,Cl,F,etc.)can be used as electron-withdrawing groups to modulate the planar structure and electron distribution of the Fe–Nx active sites to achieve simultaneous improvement of catalytic activity and stability.However,the optimal location of the heteroatoms remains unclear.Here,taking chalcogen heteroatoms(S and Se)as an example,we control the doping positions and investigate their effect on the ORR performance of the Fe–N–C catalysts.The first coordination shell of the iron single atom is identified as the optimal doping position.The optimized catalysts Fe–N_(3)Se_(1)/NC and Fe–N_(3)Se_(1)/NC demonstrate improved activity and stability in both half cells and fuel cells.This work provides insights into the enhancement mechanism of heteroatom doping in single-atom catalysts.展开更多
The introduction of defects can adjust the activity of graphene-based single-atom catalysts for oxygen reduction reactions(ORR).Herein,we for the first time investigate the ORR catalytic activity of FeN_(4)sites embed...The introduction of defects can adjust the activity of graphene-based single-atom catalysts for oxygen reduction reactions(ORR).Herein,we for the first time investigate the ORR catalytic activity of FeN_(4)sites embedded on graphene with four types of line-defective boundary via density functional theory calculations.Our results show that periodic line defects consisting of pentagon-pentagon-octagon(C_(585))or quad-octagon chains(C_(484))can significantly enhance ORR activity,owing to the optimized electronic structures of FeN_(4)sites.The spin magnetic moment and the valence state of the Fe atom are both well correlated with the ORR overpotential.Experimental investigations further corroborate that FeN_(4)with a high degree of defects exhibits better ORR activity and stability compared to FeN_(4)sites of pristine graphene and commercial Pt/C.This work unravels the influence of the periodic defect boundary on the ORR performance of Fe-N-C catalysts and paves the way towards the rational design of highly effective single-atom electrocatalysts.展开更多
[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略...[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略制备了Fe-N-C单原子催化剂,并将其应用于亚硝酸盐制氨反应.[结果]多种结构表征结果显示,Fe-N-C催化剂表面的Fe物种呈现高度分散特征并以单原子形式存在.此外,Fe物种的化学环境主要是+2和+3价混合态,且通过与4个吡啶氮配位而稳定存在,即Fe-N-C催化剂的金属中心微观配位环境为Fe-N4结构.与纯氮碳(N-C)载体相比,本研究制备的Fe-N-C催化剂具有优异的亚硝酸盐还原性能,不仅表现出更高的起始还原电位(0 V vs可逆氢电极),具有接近100%的产氨法拉第效率和高的氨产率[8.4 mg/(h·cm^(2))],并且在连续20次催化循环测试中显示出优异的催化稳定性.[结论]本研究制备的Fe-N-C单原子催化剂对亚硝酸盐还原制氨具有优异的电催化活性,其高活性可能来源于对NO_(2)^(-)的显著吸附,并进一步促进活性氢参与脱氧加氢过程.该Fe-N-C单原子催化亚硝酸盐还原体系可为后续合成氨的活性中心设计提供指导方向.展开更多
Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by ...Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by single-atom catalysts(SACs),which exhibit unique and intricate interactions between atomically dispersed metal atoms and their supports.Recently,bimetallic SACs(bimSACs)have garnered significant attention for leveraging the synergistic functions of two metal ions coordinated on appropriately designed supports.BimSACs offer an avenue for rich metal–metal and metal–support cooperativity,potentially addressing current limitations of SACs in effectively furnishing transformations which involve synchronous proton–electron exchanges,substrate activation with reversible redox cycles,simultaneous multi-electron transfer,regulation of spin states,tuning of electronic properties,and cyclic transition states with low activation energies.This review aims to encapsulate the growing advancements in bimSACs,with an emphasis on their pivotal role in hydrogen generation via water splitting.We subsequently delve into advanced experimental methodologies for the elaborate characterization of SACs,elucidate their electronic properties,and discuss their local coordination environment.Overall,we present comprehensive discussion on the deployment of bimSACs in both hydrogen evolution reaction and oxygen evolution reaction,the two half-reactions of the water electrolysis process.展开更多
Fe-N-C catalysts are potential substitutes to displace electrocatalysts containing noble chemical elements in the oxygen reduction reaction(ORR).However,their application is hampered by unsatisfactory activity and sta...Fe-N-C catalysts are potential substitutes to displace electrocatalysts containing noble chemical elements in the oxygen reduction reaction(ORR).However,their application is hampered by unsatisfactory activity and stability issues.The structures and morphologies of Fe-N-C catalysts have been found to be crucial for the number of active sites and local bonding structures.In this work,dicyandiamide(DCDA)and polyaniline(PANI)are shown to act as dual nitrogen sources to tune the morphology and structure of the catalyst and facilitate the ORR process.The dual nitrogen sources not only increase the amount of nitrogen doping atoms in the electrocatalytic Fe-C-N material,but also maintain a high nitrogen-pyrrole/nitrogen-graphitic:(N-P)/(N-G)value,improving the distribution density of catalytic active sites in the material.With a high surface area and amount of N-doping,the Fe-N-C catalyst developed can achieve an improved half-wave potential of 0.886 V(vs.RHE)in alkaline medium,and a better stability and methanol resistance than commercial Pt/C catalyst.展开更多
S and Co co-doped carbon catalysts were prepared via pyrolysis of MOF-71 and thiourea mixtures at 800℃at a mass ratio of MOF-71 to thiourea of 1:0.1 to effectively activate peroxymonosulfate(PMS)for methylene blue(MB...S and Co co-doped carbon catalysts were prepared via pyrolysis of MOF-71 and thiourea mixtures at 800℃at a mass ratio of MOF-71 to thiourea of 1:0.1 to effectively activate peroxymonosulfate(PMS)for methylene blue(MB)degradation.The effects of two different mixing routes were identified on the MB degradation performance.Particularly,the catalyst obtained by the alcohol solvent evaporation(MOF-AEP)mixing route could degrade 95.60%MB(50 mg/L)within 4 min(degradation rate:K=0.78 min^(-1)),which was faster than that derived from the direct grinding method(MOF-DGP,80.97%,K=0.39 min^(-1)).X-ray photoelectron spectroscopy revealed that the Co-S content of MOF-AEP(43.39at%)was less than that of MOF-DGP(54.73at%),and the proportion of C-S-C in MOF-AEP(13.56at%)was higher than that of MOF-DGP(10.67at%).Density functional theory calculations revealed that the adsorption energy of Co for PMS was -2.94 eV when sulfur was doped as C-S-C on the carbon skeleton,which was higher than that when sulfur was doped next to cobalt in the form of Co-S bond(-2.86 eV).Thus,the C-S-C sites might provide more contributions to activate PMS compared with Co-S.Furthermore,the degradation parameters,including pH and MOF-AEP dosage,were investigated.Finally,radical quenching experiments and electron paramagnetic resonance(EPR)measurements revealed that ^(1)O_(2)might be the primary catalytic species,whereas·O~(2-)might be the secondary one in degrading MB.展开更多
The pursuit of alternative fuel generation technologies has gained momentum due to the diminishing reserves of fossil fuels and global warming from increased CO_(2)emission.Among the proposed methods,the hydrogenation...The pursuit of alternative fuel generation technologies has gained momentum due to the diminishing reserves of fossil fuels and global warming from increased CO_(2)emission.Among the proposed methods,the hydrogenation of CO_(2)to produce marketable carbon-based products like methanol and ethanol is a practical approach that offers great potential to reduce CO_(2)emissions.Although significant volumes of methanol are currently produced from CO_(2),developing highly efficient and stable catalysts is crucial for further enhancing conversion and selectivity,thereby reducing process costs.An in-depth examination of the differences and similarities in the reaction pathways for methanol and ethanol production highlights the key factors that drive C-C coupling.Identifying these factors guides us toward developing more effective catalysts for ethanol synthesis.In this paper,we explore how different catalysts,through the production of various intermediates,can initiate the synthesis of methanol or ethanol.The catalytic mechanisms proposed by spectroscopic techniques and theoretical calculations,including operando X-ray methods,FTIR analysis,and DFT calculations,are summarized and presented.The following discussion explores the structural properties and composition of catalysts that influence C-C coupling and optimize the conversion rate of CO_(2)into ethanol.Lastly,the review examines recent catalysts employed for selective methanol and ethanol production,focusing on single-atom catalysts.展开更多
Ni-based catalysts are widely applied in the hydrodeoxygenation of lignin derivatives via C-O cleavage for the production of cycloalkanes.However,they often have difficulty in achieving high activity under mild condit...Ni-based catalysts are widely applied in the hydrodeoxygenation of lignin derivatives via C-O cleavage for the production of cycloalkanes.However,they often have difficulty in achieving high activity under mild conditions and exhibit relatively poor stability,and rare studies focus on the cleavage of the stubborn interunit C-C linkages.To address this issue,we developed a Ni@AlPO_(4)/Al_(2)O_(3)catalyst in which the surface of Ni nanoparticles was decorated by AlPO_(4)species,demonstrating excellent catalytic activity and stability in the C-C and C-O cleavages.In the hydrodeoxygenation of guaiacol,this catalyst afforded99.1%conversion and 92.9%yield of cyclohexane under 1 MPa H_(2)at 230℃ for 2 h.More important,this catalyst maintained unchanged performance even after 6 runs with the conversion controlled at about50%,Mecha nistic investigations revealed that the moderate surface coverage of AlPO_(4)on Ni with the formation of Ni^(δ+)-AlPO_(4)interface significantly facilitated the conversion of methoxycyclohexanol and cyclohexanol to cyclohexane,whereas,excess coverage would also block the access to Ni site.Moreover,Ni@AlPO_(4)/Al_(2)O_(3)demonstrated broad applicability in the C-O cleavage of various typical lignin monomers and dimers into cycloalkanes.To our delight,this catalyst also displayed pretty good activity even in the simultaneous cleavage of C-C linkages and C-O bonds for the lignin-derived C-C dimers,achieving cycloalkanes as final products.As a consequence,a 27.1 wt%yield of monocycloalkanes was obtained in the depolymerization of poplar lignin with both C-C and C-O cleavages.展开更多
Exploiting non-precious metal catalysts with excellent oxygen reduction reaction(ORR)performance for energy devices is paramount essential for the green and sustainable society development.Herein,low-cost,high-perform...Exploiting non-precious metal catalysts with excellent oxygen reduction reaction(ORR)performance for energy devices is paramount essential for the green and sustainable society development.Herein,low-cost,high-performance biomass-derived ORR catalysts with an asymmetric Fe-N_(3)P configuration was prepared by a simple pyrolysis-etching technique,where carboxymethyl cellulose(CMC)was used as the carbon source,urea and 1,10-phenanthroline iron complex(FePhen)as additives,and Na_(3)PO_(4)as the phosphorus dopant and a pore-forming agent.The CMC-derived FeNPC catalyst displayed a large specific area(BET:1235 m^(2)g^(-1))with atomically dispersed Fe-N_(3)P active sites,which exhibited superior ORR activity and stability in alkaline solution(E_(1/2)=0.90 V vs.RHE)and Zn-air batteries(P_(max)=149 mW cm^(-2))to commercial Pt/C catalyst(E_(1/2)=0.87 V,P_(max)=118 mW cm^(-2))under similar experimental conditions.This work provides a feasible and costeffective route toward highly efficient ORR catalysts and their application to Zn-air batteries for energy conversion.展开更多
基金financially supported by the Natural Science Foundation of Beijing Municipality(No.Z200012)the National Natural Science Foundation of China(Nos.U21A20328 and 21975010)+2 种基金the National Key Research and Development Program of China(No. 2021YFB4000601)the China Postdoctoral Science Foundation(No.2022M720013)the Postdoctoral Fellowship Program of CPSF(No.GZB20230926)。
文摘Non-precious metal electrocatalysts(such as Fe-N-C materials) for the oxygen(O_(2)) reduction reaction demand a high catalyst loading in fuel cell devices to achieve workable performance. However, the extremely low solubility of O_(2) in water creates severe mass transport resistance in the thick catalyst layer of Fe-N-C catalysts. Here, we introduce silicalite-1 nanocrystals with hydrophobic cavities as sustainable O_(2) reservoirs to overcome the mass transport issue of Fe-N-C catalysts. The extra O_(2) supply to the adjacent catalysts significantly alleviated the negative effects of the severe mass transport resistance. The hybrid catalyst(Fe-N-C@silicalite-1) achieved a higher limiting current density than Fe-N-C in the half-cell test. In the H_(2)-O_(2) and H_2-air proton exchange membrane fuel cells, Fe-N-C@silicalite-1 exhibited a 16.3% and 20.2% increase in peak power density compared with Fe-N-C, respectively. The O_(2)-concentrating additive provides an effective approach for improving the mass transport imposed by the low solubility of O_(2) in water.
基金supported by the Natural Science Foundation of Beijing Municipality (Z200012)the National Natural Science Foundation of China (U21A20328,22225903)the National Key Research and Development Program of China (2021YFB4000601)。
文摘Metal nanoaggregates can simultaneously enhance the activity and stability of Fe-N-C catalysts in proton-exchange-membrane fuel cells(PEMFC).Previous studies on the relevant mechanism have focused on the direct interaction between FeN_(4)active sites and metal nanoaggregates.However,the role of carbon support that hosts metal nanoaggregates and active sites has been overlooked.Here,a Fe-N-C catalyst encapsulating inactive gold nanoparticles is prepared as a model catalyst to investigate the electronic tuning of Au nanoparticles(NPs)towards the carbon support.Au NPs donate electrons to carbon support,making it rich inπelectrons,which reduces the work function and regulates the electronic configuration of the FeN_(4)sites for an enhanced ORR activity.Meanwhile,the electron-rich carbon support can mitigate the electron depletion of FeN_(4)sites caused by carbon support oxidation,thereby preserving its high activity.The yield and accumulation of H_(2)O_(2)are thus alleviated,which delays the oxidation of the catalyst and benefits the stability.Due to the electron-rich carbon support,the composite catalyst achieves a top-level peak power density of 0.74 W/cm^(2) in a 1.5 bar H_(2)-air PEMFC,as well as the improved stability.This work elucidates the key role of carbon support in the performance enhancement of the FeN-C/metal nanoaggregate composite catalysts for fuel cell application.
基金supported by the National Thousand Talents Plan of Chinathe National Natural Science Foundation of China(Grant Nos.21673014 and U1766216)+1 种基金the 111 project(B17002)funded by the Ministry of Education of Chinathe Fundamental Research Funds for the Central Universities of China
文摘Proton exchange membrane fuel cells(PEMFC)have attracted much attention because of their high energy conversion efficiency,high power density and zero emission of pollutants.However,the high cost of the cathode platinum group metal(PGM)catalysts creates a barrier for the large-scale application of PEMFC.Tremendous efforts have been devoted to the development of low-cost PGM-free catalysts,especially the Fe-N-C catalysts,to replace the expensive PGM catalysts.However,the characterization methods and evaluation standards of the catalysts varies,which is not conducive to the comparison of PGM-free catalysts.U.S.Department of energy(DOE)is the only authority that specifies the testing standards and activity targets for PGM-free catalysts.In this review,the major breakthroughs of Fe-N-C catalysts are outlined with the reference of DOE standards and targets.The preparation and characteristics of these highly active Fe-N-C catalysts are briefly introduced.Moreover,the efforts on improving the mass transfer and the durability issue of Fe-N-C fuel cell are discussed.Finally,the prospective directions concerning the comprehensive evaluation of the Fe-N-C catalysts are proposed.
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 Natural Science Foundation of China(21633008,21433003,U1601211,21733004)National Science and Technology Major Project(2016YFB0101202)+1 种基金Jilin Province Science and Technology Development Program(20150101066JC,20160622037JC,20170203003SF,20170520150JH)Hundred Talents Program of Chinese Academy of Sciences and the Recruitment Program of Foreign Experts(WQ20122200077)
文摘Rational regulation on pore structure and active site density plays critical roles in enhancing the performance of Fe-N-C catalysts. As the microporous structure of the carbon substrate is generally regarded as the active site hosts, its hostility to electron/mass transfer could lead to the incomplete fulfillment of the catalytic activity. Besides, the formation of inactive metallic Fe particles during the conventional catalyst synthesis could also decrease the active site density and complicate the identification of real active site. Herein, we developed a facial hydrogen etching methodology to yield single site Fe-N-C catalysts featured with micro/mesoporous hierarchical structure. The hydrogen concentration in pyrolysis process was designated to effectively regulate the pore structure and active site density of the resulted catalysts.The optimized sample achieves excellent ORR catalytic performance with an ultralow H2O2 yield(1%)and superb stability over 10,000 cycles. Our finding provides new thoughts for the rational design of hierarchically porous carbon-based materials and highly promising non-precious metal ORR catalysts.
基金financially supported by the Hebei Province Natural Science Foundation Innovation Group Project(B2021203016)the National Natural Science Foundation of China(51674221 and 51704261)+1 种基金the Provincial Graduate Innovation Assistant Project of Yanshan University(023000309)partially supported by the ARC Future Fellowship(FT180100705)of Australia。
文摘Due to larger atom utilization,unique electronic properties and unsaturated coordination,atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysis.Considering the challenge of serious aggregation,rational synthesis of an atomic catalyst with good dispersion of atoms is paramount to the development of these catalysts.Herein,we report an enhanced confinement strategy to synthesize a catalyst comprised of atomically dispersed Fe supported on porous nitrogen-doped graphitic carbon from the novel and more cross-linkable Melamine-Glyoxal Resin.Densified isolated grid trapping,excessive melamine restricting,and nitrogen anchoring are strongly combined to ensure the final atomic-level dispersion of metal atoms.Experimental studies revealed enhanced kinetics of the obtained catalyst towards oxygen reduction reaction(ORR).This catalytic activity originates from the highly active surface with atomically dispersed iron sites as well as the multi-level three-dimensional structure with fast mass and electron transfer.The enhanced confinement strategy endows the resin-derived atomic catalyst with a great prospect to develop for commercialization in future.
基金financially supported by the National Key Research and Development Program of China(2021YFA1502000)the National Natural Science Foundation of China(22022502 and 22179012)Natural Science Foundation of Chongqing,China(CSTB2023NSCQLZX0084).
文摘Hydrogen peroxide that is produced through the two-electron pathway during the catalysis of oxygen reduction reaction(ORR)is recognized as harmful to the stability of nitrogen-doped carbon and Fe-based nonprecious catalyst(Fe-N-C)for fuel cell application.A major remaining scientific question is how fast the removal of these deleterious intermediates can contribute to stability enhancement.Here,we report that the stability of Fe-N-C catalysts is positively correlated with the kinetic constant of hydrogen peroxide decomposition.Modulation of the H_(2)O_(2) decomposition kinetics by applying the frequency factor of the Arrhenius equation from 800 to 30000 s^(-1) for TiO_(2),CeO_(2) and ZrO_(2) reduced the decay rate of Fe-N-C catalysts from 0.151% to ‒0.1% in a 100-hour stability test.Fe-N-C/ZrO_(2) with a frequency factor of 30000 s^(-1) showed a 10% increase in current density during a 100-hour stability test and almost no decay during 15 hours of continuous fuel cell operation at a high potential of 0.7 V.
基金supported by the National Key Research and Development Program of China(grant No.2021YFB4000601)Natural Science Foundation of Beijing Municipality(grant No.Z200012)+1 种基金National Natural Science Foundation of China(grant No.21975010,U21A20328)the China Postdoctoral Science Foundation(grant No.2022M720013).
文摘The excellent oxygen reduction reaction(ORR)activity of Fe–N–C catalysts in acidic media makes them potential for low-cost proton exchange membrane fuel cells.In recent years,it has been shown that heteroatoms(B,O,S,P,Cl,F,etc.)can be used as electron-withdrawing groups to modulate the planar structure and electron distribution of the Fe–Nx active sites to achieve simultaneous improvement of catalytic activity and stability.However,the optimal location of the heteroatoms remains unclear.Here,taking chalcogen heteroatoms(S and Se)as an example,we control the doping positions and investigate their effect on the ORR performance of the Fe–N–C catalysts.The first coordination shell of the iron single atom is identified as the optimal doping position.The optimized catalysts Fe–N_(3)Se_(1)/NC and Fe–N_(3)Se_(1)/NC demonstrate improved activity and stability in both half cells and fuel cells.This work provides insights into the enhancement mechanism of heteroatom doping in single-atom catalysts.
文摘The introduction of defects can adjust the activity of graphene-based single-atom catalysts for oxygen reduction reactions(ORR).Herein,we for the first time investigate the ORR catalytic activity of FeN_(4)sites embedded on graphene with four types of line-defective boundary via density functional theory calculations.Our results show that periodic line defects consisting of pentagon-pentagon-octagon(C_(585))or quad-octagon chains(C_(484))can significantly enhance ORR activity,owing to the optimized electronic structures of FeN_(4)sites.The spin magnetic moment and the valence state of the Fe atom are both well correlated with the ORR overpotential.Experimental investigations further corroborate that FeN_(4)with a high degree of defects exhibits better ORR activity and stability compared to FeN_(4)sites of pristine graphene and commercial Pt/C.This work unravels the influence of the periodic defect boundary on the ORR performance of Fe-N-C catalysts and paves the way towards the rational design of highly effective single-atom electrocatalysts.
文摘[目的]为进一步拓展单原子催化剂在亚硝酸盐还原制氨领域的应用,提出了一种铁-氮-碳(Fe-N-C)单原子催化剂电催化亚硝酸盐还原制氨的新体系.[方法]以二氧化硅为硬模板,2,6-二氨基吡啶为碳氮前驱体,硝酸铁为金属盐,通过“热解-刻蚀”策略制备了Fe-N-C单原子催化剂,并将其应用于亚硝酸盐制氨反应.[结果]多种结构表征结果显示,Fe-N-C催化剂表面的Fe物种呈现高度分散特征并以单原子形式存在.此外,Fe物种的化学环境主要是+2和+3价混合态,且通过与4个吡啶氮配位而稳定存在,即Fe-N-C催化剂的金属中心微观配位环境为Fe-N4结构.与纯氮碳(N-C)载体相比,本研究制备的Fe-N-C催化剂具有优异的亚硝酸盐还原性能,不仅表现出更高的起始还原电位(0 V vs可逆氢电极),具有接近100%的产氨法拉第效率和高的氨产率[8.4 mg/(h·cm^(2))],并且在连续20次催化循环测试中显示出优异的催化稳定性.[结论]本研究制备的Fe-N-C单原子催化剂对亚硝酸盐还原制氨具有优异的电催化活性,其高活性可能来源于对NO_(2)^(-)的显著吸附,并进一步促进活性氢参与脱氧加氢过程.该Fe-N-C单原子催化亚硝酸盐还原体系可为后续合成氨的活性中心设计提供指导方向.
基金support from the Czech Science Foundation,project EXPRO,No 19-27454Xsupport by the European Union under the REFRESH—Research Excellence For Region Sustainability and High-tech Industries project number CZ.10.03.01/00/22_003/0000048 via the Operational Programme Just Transition from the Ministry of the Environment of the Czech Republic+1 种基金Horizon Europe project EIC Pathfinder Open 2023,“GlaS-A-Fuels”(No.101130717)supported from ERDF/ESF,project TECHSCALE No.CZ.02.01.01/00/22_008/0004587).
文摘Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society.The field of catalysis has been revolutionized by single-atom catalysts(SACs),which exhibit unique and intricate interactions between atomically dispersed metal atoms and their supports.Recently,bimetallic SACs(bimSACs)have garnered significant attention for leveraging the synergistic functions of two metal ions coordinated on appropriately designed supports.BimSACs offer an avenue for rich metal–metal and metal–support cooperativity,potentially addressing current limitations of SACs in effectively furnishing transformations which involve synchronous proton–electron exchanges,substrate activation with reversible redox cycles,simultaneous multi-electron transfer,regulation of spin states,tuning of electronic properties,and cyclic transition states with low activation energies.This review aims to encapsulate the growing advancements in bimSACs,with an emphasis on their pivotal role in hydrogen generation via water splitting.We subsequently delve into advanced experimental methodologies for the elaborate characterization of SACs,elucidate their electronic properties,and discuss their local coordination environment.Overall,we present comprehensive discussion on the deployment of bimSACs in both hydrogen evolution reaction and oxygen evolution reaction,the two half-reactions of the water electrolysis process.
基金supported by the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.23KJD430007)Qinglan Project of Jiangsu Province,Innovative Research Group Project of the National Natural Science Foundation of China(Grant No.51902145)+1 种基金Nanjing Technology Innovation Team of Optometric Materials and Application and Doctoral Start-up Fund Research supported by Jinling Institute of Technology(jit-b-202026)the European Union(ERDF)and Région Nouvelle Aquitaine.
文摘Fe-N-C catalysts are potential substitutes to displace electrocatalysts containing noble chemical elements in the oxygen reduction reaction(ORR).However,their application is hampered by unsatisfactory activity and stability issues.The structures and morphologies of Fe-N-C catalysts have been found to be crucial for the number of active sites and local bonding structures.In this work,dicyandiamide(DCDA)and polyaniline(PANI)are shown to act as dual nitrogen sources to tune the morphology and structure of the catalyst and facilitate the ORR process.The dual nitrogen sources not only increase the amount of nitrogen doping atoms in the electrocatalytic Fe-C-N material,but also maintain a high nitrogen-pyrrole/nitrogen-graphitic:(N-P)/(N-G)value,improving the distribution density of catalytic active sites in the material.With a high surface area and amount of N-doping,the Fe-N-C catalyst developed can achieve an improved half-wave potential of 0.886 V(vs.RHE)in alkaline medium,and a better stability and methanol resistance than commercial Pt/C catalyst.
基金financially supported by the National Natural Science Foundation of China(Nos.51602018 and 51902018)the Natural Science Foundation of Beijing Municipality(No.2154052)+3 种基金the China Postdoctoral Science Foundation(No.2014M560044)the Fundamental Research Funds for the Central Universities(No.FRF-MP-20-22)USTB Research Center for International People-to-people Exchange in Science,Technology and Civilization(No.2022KFYB007)Education and Teaching Reform Foundation at University of Science and Technology Beijing(Nos.2023JGC027,KC2022QYW06,and KC2022TS09)。
文摘S and Co co-doped carbon catalysts were prepared via pyrolysis of MOF-71 and thiourea mixtures at 800℃at a mass ratio of MOF-71 to thiourea of 1:0.1 to effectively activate peroxymonosulfate(PMS)for methylene blue(MB)degradation.The effects of two different mixing routes were identified on the MB degradation performance.Particularly,the catalyst obtained by the alcohol solvent evaporation(MOF-AEP)mixing route could degrade 95.60%MB(50 mg/L)within 4 min(degradation rate:K=0.78 min^(-1)),which was faster than that derived from the direct grinding method(MOF-DGP,80.97%,K=0.39 min^(-1)).X-ray photoelectron spectroscopy revealed that the Co-S content of MOF-AEP(43.39at%)was less than that of MOF-DGP(54.73at%),and the proportion of C-S-C in MOF-AEP(13.56at%)was higher than that of MOF-DGP(10.67at%).Density functional theory calculations revealed that the adsorption energy of Co for PMS was -2.94 eV when sulfur was doped as C-S-C on the carbon skeleton,which was higher than that when sulfur was doped next to cobalt in the form of Co-S bond(-2.86 eV).Thus,the C-S-C sites might provide more contributions to activate PMS compared with Co-S.Furthermore,the degradation parameters,including pH and MOF-AEP dosage,were investigated.Finally,radical quenching experiments and electron paramagnetic resonance(EPR)measurements revealed that ^(1)O_(2)might be the primary catalytic species,whereas·O~(2-)might be the secondary one in degrading MB.
基金the Canadian NRCan OERD Energy Innovation Programthe Natural Sciences and Engineering Research Council of Canada,and the Carbon Solution Program for their financial support.
文摘The pursuit of alternative fuel generation technologies has gained momentum due to the diminishing reserves of fossil fuels and global warming from increased CO_(2)emission.Among the proposed methods,the hydrogenation of CO_(2)to produce marketable carbon-based products like methanol and ethanol is a practical approach that offers great potential to reduce CO_(2)emissions.Although significant volumes of methanol are currently produced from CO_(2),developing highly efficient and stable catalysts is crucial for further enhancing conversion and selectivity,thereby reducing process costs.An in-depth examination of the differences and similarities in the reaction pathways for methanol and ethanol production highlights the key factors that drive C-C coupling.Identifying these factors guides us toward developing more effective catalysts for ethanol synthesis.In this paper,we explore how different catalysts,through the production of various intermediates,can initiate the synthesis of methanol or ethanol.The catalytic mechanisms proposed by spectroscopic techniques and theoretical calculations,including operando X-ray methods,FTIR analysis,and DFT calculations,are summarized and presented.The following discussion explores the structural properties and composition of catalysts that influence C-C coupling and optimize the conversion rate of CO_(2)into ethanol.Lastly,the review examines recent catalysts employed for selective methanol and ethanol production,focusing on single-atom catalysts.
基金supported by National Natural Science Foundation of China(22178258,22308254)China Postdoctoral Science Foundation(2023M742593,2024T170642)+1 种基金Independent Innova-tion Fund of Tianjin University(2024XQM-0021)the Open Fund of the Key Laboratory of Functional Molecular Solids(FMS2023006)。
文摘Ni-based catalysts are widely applied in the hydrodeoxygenation of lignin derivatives via C-O cleavage for the production of cycloalkanes.However,they often have difficulty in achieving high activity under mild conditions and exhibit relatively poor stability,and rare studies focus on the cleavage of the stubborn interunit C-C linkages.To address this issue,we developed a Ni@AlPO_(4)/Al_(2)O_(3)catalyst in which the surface of Ni nanoparticles was decorated by AlPO_(4)species,demonstrating excellent catalytic activity and stability in the C-C and C-O cleavages.In the hydrodeoxygenation of guaiacol,this catalyst afforded99.1%conversion and 92.9%yield of cyclohexane under 1 MPa H_(2)at 230℃ for 2 h.More important,this catalyst maintained unchanged performance even after 6 runs with the conversion controlled at about50%,Mecha nistic investigations revealed that the moderate surface coverage of AlPO_(4)on Ni with the formation of Ni^(δ+)-AlPO_(4)interface significantly facilitated the conversion of methoxycyclohexanol and cyclohexanol to cyclohexane,whereas,excess coverage would also block the access to Ni site.Moreover,Ni@AlPO_(4)/Al_(2)O_(3)demonstrated broad applicability in the C-O cleavage of various typical lignin monomers and dimers into cycloalkanes.To our delight,this catalyst also displayed pretty good activity even in the simultaneous cleavage of C-C linkages and C-O bonds for the lignin-derived C-C dimers,achieving cycloalkanes as final products.As a consequence,a 27.1 wt%yield of monocycloalkanes was obtained in the depolymerization of poplar lignin with both C-C and C-O cleavages.
基金supported by the National Natural Science Foundation of China(No.21571062)the Program for Professor of Special Appointment(Eastern Scholar)at the Shanghai Institutions of Higher Learning to JGL,and the Fundamental Research Funds for the Central Universities(No.222201717003)。
文摘Exploiting non-precious metal catalysts with excellent oxygen reduction reaction(ORR)performance for energy devices is paramount essential for the green and sustainable society development.Herein,low-cost,high-performance biomass-derived ORR catalysts with an asymmetric Fe-N_(3)P configuration was prepared by a simple pyrolysis-etching technique,where carboxymethyl cellulose(CMC)was used as the carbon source,urea and 1,10-phenanthroline iron complex(FePhen)as additives,and Na_(3)PO_(4)as the phosphorus dopant and a pore-forming agent.The CMC-derived FeNPC catalyst displayed a large specific area(BET:1235 m^(2)g^(-1))with atomically dispersed Fe-N_(3)P active sites,which exhibited superior ORR activity and stability in alkaline solution(E_(1/2)=0.90 V vs.RHE)and Zn-air batteries(P_(max)=149 mW cm^(-2))to commercial Pt/C catalyst(E_(1/2)=0.87 V,P_(max)=118 mW cm^(-2))under similar experimental conditions.This work provides a feasible and costeffective route toward highly efficient ORR catalysts and their application to Zn-air batteries for energy conversion.
