Molecular nitrogen is relatively inert and the activation of its triple bond is full of challenges and of significance.Hence,searching for an efficiently heterogeneous catalyst with high stability and dispersion is on...Molecular nitrogen is relatively inert and the activation of its triple bond is full of challenges and of significance.Hence,searching for an efficiently heterogeneous catalyst with high stability and dispersion is one of the important targets of chemical technology.Here,we report a Ba‐K/Ru‐MC catalyst with Ru particle size of 1.5–2.5 nm semi‐embedded in a mesoporous C matrix and with dual promoters of Ba and K that exhibits a higher activity than the supported Ba‐Ru‐K/MC catalyst,although both have similar metal particle sizes for ammonia synthesis.Further,the Ba‐K/Ru‐MC catalyst is more active than commercial fused Fe catalysts and supported Ru catalysts.Characterization techniques such as high‐resolution transmission electron microscopy,N2 physisorption,CO chemisorption,and temperature‐programmed reduction suggest that the Ru nanoparticles have strong interactions with the C matrix in Ba‐K/Ru‐MC,which may facilitate electron transport better than supported nanoparticles.展开更多
A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling t...A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.展开更多
Evaluating the effect of metal surface density on catalytic performance is critical for designing high-activity metal-based catalysts.In this study,a series of ceria(CeCO_(2))-supported Ru catalysts(Ru/CeCO_(2))were p...Evaluating the effect of metal surface density on catalytic performance is critical for designing high-activity metal-based catalysts.In this study,a series of ceria(CeCO_(2))-supported Ru catalysts(Ru/CeCO_(2))were prepared to analyze the effect of Ru surface density on the catalytic performance of Ru/CeCO_(2) for ammonia synthesis.For the Ru/CeCO_(2) catalysts with Ru surface densities lower than 0.68 Ru nm^(-2),the Ru layers were in close contact with CeCO_(2),and electrons were transferred directly from the CeCO_(2) defect sites to the Ru species.In such cases,the adsorption of hydrogen species on the Ru sites in the vicinity of 0 atoms was high,leading to a high ammonia synthesis activity and strong hydrogen poisoning.In contrast,the preferential aggregation of Ru species into large particles on top of the Ru overlayer resulted in the coexistence of Ru clusters and particles,for catalysts with a Ru surface density higher than 1.4 Ru nm^(-2),for which Ru particles were isolated from the direct electronic influence of CeCO_(2).Consequently,the Ru-Ceth interactions were weak,and hydrogen poisoning can be significantly alleviated.Overall,electron transfer and hydrogen adsorption synergistically affected the synthesis of ammonia over Ru/CeCO_(2) catalysts,and catalyst samples with a Ru surface density lower than 0.31 Ru nm^(-2) or exactly 2.1 Ru nm^(-2) exhibited high catalytic activity for ammonia synthesis.展开更多
The metal–support interactions induced by high-temperature hydrogen reduction have a strong influence on the catalytic performance of ceria-supported Ru catalysts. However, the appearance of the strong metal–support...The metal–support interactions induced by high-temperature hydrogen reduction have a strong influence on the catalytic performance of ceria-supported Ru catalysts. However, the appearance of the strong metal–support interaction leads to covering of the Ru species by Ce suboxides, which is detrimental to the ammonia synthesis reaction that requires metallic species as active sites. In the present work, the interaction between Ru and ceria in the Ru/CeO_(2) catalyst was induced by NaBH_(4) treatment. NaBH_(4) treatment enhanced the fraction of metallic Ru, proportion of Ce^(3+), content of exposed Ru species, and amount of surface oxygen species. As a result, a larger amount of hydrogen species would desorb by the H_(2)-formation pathway and the strength of hydrogen adsorption would be weaker, weakening the inhibition effect of the hydrogen species on ammonia synthesis. In addition, the strong electronic metal–support interaction aids in nitrogen dissociation. Consequently, Ru/CeO_(2) with NaBH_(4) treatment showed higher ammonia synthesis rates than that with only hydrogen reduction.展开更多
The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the propertie...The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the properties of CeO2-supported Co catalysts including the surface area, the crystallite size and the morphology of CeO2, the reduction degree of cobalt species and the adsorption performance of hydrogen and nitrogen. As a consequence, the samples promoted with an appropriate amount of Ba show higher ammonia synthesis rates, while the catalysts with high Ba loading or K promoter all exhibit low catalytic activities.展开更多
Activated carbon-supported Ru-based catalyst and A301 iron catalyst were prepared,and the influences of reaction temperature,space velocity,pressure,and H2/N2 ratio on performance of iron catalyst coupled with Ru cata...Activated carbon-supported Ru-based catalyst and A301 iron catalyst were prepared,and the influences of reaction temperature,space velocity,pressure,and H2/N2 ratio on performance of iron catalyst coupled with Ru catalyst in series for ammonia synthesis were investigated.The activity tests were also performed on the single Ru and Fe catalysts as comparison.Results showed that the activity of the Ru catalyst for ammonia synthesis was higher than that of the iron catalyst by 33.5%-37.6% under the reaction conditions：375-400 °C,10 MPa,10000 h-1,H2︰N2 3,and the Ru catalyst also had better thermal stability when treated at 475 °C for 20 h.The outlet ammonia concentration using Fe-Ru catalyst was increased by 45.6%-63.5% than that of the single-iron catalyst at low tem-perature （375-400 °C）,and the outlet ammonia concentration increased with increasing Ru catalyst loading.展开更多
The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in t...The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in the renewable energy.Generally,ZrO_(2) was regarded as an inferior support for Ru catalyst used in ammonia synthesis.Here we prepare ZrO_(2) with monoclinic phase and carbon species from ZrCl_(4) following the preparation route of UiO-66 as well as ammonia treatment.Owing to the presence of a larger amount of hydrogen adsorption as well as the easier desorption of hydrogen species,the ill effect of hydrogen species on the nitrogen adsorption-desorption and ammonia synthesis can be effectively alleviated.The resulting ZrO_(2)-supported Ru catalyst showed 4 times higher ammonia synthesis activity than the conventional Ru/ZrO_(2) obtained from zirconium nitrate.展开更多
In recent years,photocatalytic N_(2) reduction for ammonia synthesis at room temperature and atmospheric pressure has gradually become a research hotspot,exhibiting extremely high development potential.However,the low...In recent years,photocatalytic N_(2) reduction for ammonia synthesis at room temperature and atmospheric pressure has gradually become a research hotspot,exhibiting extremely high development potential.However,the low photogenerated charge separation efficiency and the lack of effective active sites seriously constrain the reaction efficiencies of semiconductor photocatalysts for N_(2) reduction of ammonia synthesis.Therefore,the rational design of catalytic materials is the key to enhance the photocatalytic N_(2) reduction reaction of ammonia synthesis.Transition metal Ru as the active center not only accelerates the adsorption and activation of N_(2) molecules,but also has good selectivity for N_(2) reduction.Moreover,the interaction between the metal and the support can effectively regulate the electronic structure of the active site,accelerate the photogenerated electron transfer,and significantly enhance the photocatalytic activity.Based on this,this review systematically investigates the Ru co-semiconductors to realize efficient photocatalytic N_(2) reduction for ammonia synthesis,and introduces its basic principles.Specifically,the Ru co-semiconductor photocatalytic material systems are introduced,such as TiO2-based,g-C3N4-based,and metal oxide materials,including the design of catalysts,crystal structures,and other characteristics.In addition,the modification strategies of photocatalytic N_(2) reduction ammonia synthesis materials are also presented,including loading/doping,defect engineering,construction of heterojunctions,and crystal surface modulation.Furthermore,the progress and shortcomings of the application of Ru co-semiconductors in these processes are summarized and comprehensively discussed,and the future outlook of Ru co-semiconductors in photocatalytic N_(2) reduction ammonia synthesis applications is proposed.展开更多
Ammonia serves both as a widely used fertilizer and environmentally friendly energy source due to its high energy density,rich hydrogen content,and emissions-free combustion.Additionally,it offers convenient transport...Ammonia serves both as a widely used fertilizer and environmentally friendly energy source due to its high energy density,rich hydrogen content,and emissions-free combustion.Additionally,it offers convenient transportation and storage as a hydrogen carrier.The dominant method used for large-scale ammonia production is the Haber-Bosch process,which requires high temperatures and pressures and is energy-intensive.However,non-thermal plasma offers an eco-friendly alternative for ammonia synthesis,gaining significant attention.It enables ammonia production at lower temperatures and pressures using plasma technology.This review provides insights into the catalyst and reactor developments,which are pivotal for promoting ammonia efficiency and addressing existing challenges.At first,the reaction kinetics and mechanisms are introduced to gain a comprehensive understanding of the reaction pathways involved in plasma-assisted ammonia synthesis.Thereafter,the enhancement of ammonia synthesis efficiency is discussed by developing and optimizing plasma reactors and effective catalysts.The effect of other feeding sources,such as water and methane,instead of hydrogen is also presented.Finally,the challenges and possible solutions are outlined to facilitate energy-saving and enhance ammonia efficiency in the future.展开更多
Ammonia(NH 3) is a cornerstone of modern industry and agriculture, serving not only as the primary precursor for synthetic fertilizers but also as a promising carbon-neutral energy carrier [1]. The Haber-Bosch process...Ammonia(NH 3) is a cornerstone of modern industry and agriculture, serving not only as the primary precursor for synthetic fertilizers but also as a promising carbon-neutral energy carrier [1]. The Haber-Bosch process, developed in the early 20th century, revolutionized global agriculture by enabling largescale fertilizer production [2].展开更多
Ruthenium(Ru)serves as a promising catalyst for ammonia synthesis via the Haber-Bosch process,identification of the structure sensitivity to improve the activity of Ru is important but not fully explored yet.We presen...Ruthenium(Ru)serves as a promising catalyst for ammonia synthesis via the Haber-Bosch process,identification of the structure sensitivity to improve the activity of Ru is important but not fully explored yet.We present here density functional theory calculations combined with microkinetic simulations on nitrogen molecule activation,a crucial step in ammonia synthesis,over a variety of hexagonal close-packed(hcp)and face-center cubic(fcc)Ru facets.Hcp{2130}facet exhibits the highest activity toward N_(2) dissociation in hcp Ru,followed by the(0001)monatomic step sites.The other hcp Ru facets have N_(2) dissociation rates at least three orders lower.Fcc{211}facet shows the best performance for N_(2) activation in fcc Ru,followed by{311},which indicates stepped surfaces make great contributions to the overall reactivity.Although hcp Ru{2130}facet and(0001)monatomic step sites have lower or comparable activation barriers compared with fcc Ru{211}facet,fcc Ru is proposed to be more active than hcp Ru for N_(2) conversion due to the exposure of the more favorable active sites over step surfaces in fcc Ru.This work provides new insights into the crystal structure sensitivity of N_(2) activation for mechanistic understanding and rational design of ammonia synthesis over Ru catalysts.展开更多
Achieving green ammonia(NH_(3))synthesis requires developing effective catalysts under mild conditions.However;the competitive adsorption of N2 and H_(2);as well as the strong binding of N-containing intermediates on ...Achieving green ammonia(NH_(3))synthesis requires developing effective catalysts under mild conditions.However;the competitive adsorption of N2 and H_(2);as well as the strong binding of N-containing intermediates on the catalyst;greatly inhibits the active sites for efficient NH_(3) synthesis.Here;we constructed a series of ZrH_(2)-modified Fe catalysts with dual active sites to address these issues and realized efficient NH_(3) synthesis under mild conditions.Our study shows that ZrH_(2) can not only provide active sites for H_(2) activation but also transfer electrons to Fe sites for accelerating N2 activation.The interaction between Fe and ZrH_(2) over 40ZrH_(2)-Fe leads to a decrease in work function and a downward shift of the d-band center;which is conducive to N2 activation and NH_(3) desorption;respectively.The utilization of distinct sites for activating different reactants can avoid the competitive adsorption of N2 and H_(2);leading to excellent NH_(3) synthesis activity of the 40 wt.%ZrH_(2)-mediated Fe catalyst.As a result;40ZrH_(2)-Fe exhibits a high NH_(3) synthesis rate of 23.3 mmol gcat-1h-1at 400℃and 1 MPa and robust stability during 100 h time-on-stream.展开更多
基金supported by the National Natural Science Foundation of China(20803064)the Natural Science Foundation of Zhejiang Provence(LY17B030010)~~
文摘Molecular nitrogen is relatively inert and the activation of its triple bond is full of challenges and of significance.Hence,searching for an efficiently heterogeneous catalyst with high stability and dispersion is one of the important targets of chemical technology.Here,we report a Ba‐K/Ru‐MC catalyst with Ru particle size of 1.5–2.5 nm semi‐embedded in a mesoporous C matrix and with dual promoters of Ba and K that exhibits a higher activity than the supported Ba‐Ru‐K/MC catalyst,although both have similar metal particle sizes for ammonia synthesis.Further,the Ba‐K/Ru‐MC catalyst is more active than commercial fused Fe catalysts and supported Ru catalysts.Characterization techniques such as high‐resolution transmission electron microscopy,N2 physisorption,CO chemisorption,and temperature‐programmed reduction suggest that the Ru nanoparticles have strong interactions with the C matrix in Ba‐K/Ru‐MC,which may facilitate electron transport better than supported nanoparticles.
基金supported by the Natural Science Foundation of China(NSFC Grant No.20803064)the Natural Science Foundation of Zhejiang Provence(Y4090348 and LY12B03007)Qianjiang Talent Project in Zhejiang Province(2010R10039 and 2013R10056)
文摘A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.
文摘Evaluating the effect of metal surface density on catalytic performance is critical for designing high-activity metal-based catalysts.In this study,a series of ceria(CeCO_(2))-supported Ru catalysts(Ru/CeCO_(2))were prepared to analyze the effect of Ru surface density on the catalytic performance of Ru/CeCO_(2) for ammonia synthesis.For the Ru/CeCO_(2) catalysts with Ru surface densities lower than 0.68 Ru nm^(-2),the Ru layers were in close contact with CeCO_(2),and electrons were transferred directly from the CeCO_(2) defect sites to the Ru species.In such cases,the adsorption of hydrogen species on the Ru sites in the vicinity of 0 atoms was high,leading to a high ammonia synthesis activity and strong hydrogen poisoning.In contrast,the preferential aggregation of Ru species into large particles on top of the Ru overlayer resulted in the coexistence of Ru clusters and particles,for catalysts with a Ru surface density higher than 1.4 Ru nm^(-2),for which Ru particles were isolated from the direct electronic influence of CeCO_(2).Consequently,the Ru-Ceth interactions were weak,and hydrogen poisoning can be significantly alleviated.Overall,electron transfer and hydrogen adsorption synergistically affected the synthesis of ammonia over Ru/CeCO_(2) catalysts,and catalyst samples with a Ru surface density lower than 0.31 Ru nm^(-2) or exactly 2.1 Ru nm^(-2) exhibited high catalytic activity for ammonia synthesis.
基金financially supported by the National Science Foundation of China (Nos. 21776047, 21825801, 21978051)the Program for Qishan Scholar of Fuzhou University (Grant XRC18033)。
文摘The metal–support interactions induced by high-temperature hydrogen reduction have a strong influence on the catalytic performance of ceria-supported Ru catalysts. However, the appearance of the strong metal–support interaction leads to covering of the Ru species by Ce suboxides, which is detrimental to the ammonia synthesis reaction that requires metallic species as active sites. In the present work, the interaction between Ru and ceria in the Ru/CeO_(2) catalyst was induced by NaBH_(4) treatment. NaBH_(4) treatment enhanced the fraction of metallic Ru, proportion of Ce^(3+), content of exposed Ru species, and amount of surface oxygen species. As a result, a larger amount of hydrogen species would desorb by the H_(2)-formation pathway and the strength of hydrogen adsorption would be weaker, weakening the inhibition effect of the hydrogen species on ammonia synthesis. In addition, the strong electronic metal–support interaction aids in nitrogen dissociation. Consequently, Ru/CeO_(2) with NaBH_(4) treatment showed higher ammonia synthesis rates than that with only hydrogen reduction.
基金supported by National Natural Science Foundation of China(21776047,21203028)
文摘The Co/CeO2 catalysts promoted with Ba or K were prepared to study the effect of promoter on the catalytic performance of ammonia synthesis. The results show that the presence of Ba or K promoter changes the properties of CeO2-supported Co catalysts including the surface area, the crystallite size and the morphology of CeO2, the reduction degree of cobalt species and the adsorption performance of hydrogen and nitrogen. As a consequence, the samples promoted with an appropriate amount of Ba show higher ammonia synthesis rates, while the catalysts with high Ba loading or K promoter all exhibit low catalytic activities.
基金Supported by the National Natural Science Foundation of China（20803064） the Natural Science Foundation of Zhejiang Province（Y409034）
文摘Activated carbon-supported Ru-based catalyst and A301 iron catalyst were prepared,and the influences of reaction temperature,space velocity,pressure,and H2/N2 ratio on performance of iron catalyst coupled with Ru catalyst in series for ammonia synthesis were investigated.The activity tests were also performed on the single Ru and Fe catalysts as comparison.Results showed that the activity of the Ru catalyst for ammonia synthesis was higher than that of the iron catalyst by 33.5%-37.6% under the reaction conditions：375-400 °C,10 MPa,10000 h-1,H2︰N2 3,and the Ru catalyst also had better thermal stability when treated at 475 °C for 20 h.The outlet ammonia concentration using Fe-Ru catalyst was increased by 45.6%-63.5% than that of the single-iron catalyst at low tem-perature （375-400 °C）,and the outlet ammonia concentration increased with increasing Ru catalyst loading.
基金supported by the National Natural Science Foundation of China(Nos.22178061,21776047,21825801,and 21978051)。
文摘The development of effective Ru catalyst for ammonia synthesis is of important practical value and scientific significance because of the wide application of ammonia as a fertilizer and its promising applications in the renewable energy.Generally,ZrO_(2) was regarded as an inferior support for Ru catalyst used in ammonia synthesis.Here we prepare ZrO_(2) with monoclinic phase and carbon species from ZrCl_(4) following the preparation route of UiO-66 as well as ammonia treatment.Owing to the presence of a larger amount of hydrogen adsorption as well as the easier desorption of hydrogen species,the ill effect of hydrogen species on the nitrogen adsorption-desorption and ammonia synthesis can be effectively alleviated.The resulting ZrO_(2)-supported Ru catalyst showed 4 times higher ammonia synthesis activity than the conventional Ru/ZrO_(2) obtained from zirconium nitrate.
基金supported by Taishan Scholars Foundation of Shandong province(tsqn 201909058)。
文摘In recent years,photocatalytic N_(2) reduction for ammonia synthesis at room temperature and atmospheric pressure has gradually become a research hotspot,exhibiting extremely high development potential.However,the low photogenerated charge separation efficiency and the lack of effective active sites seriously constrain the reaction efficiencies of semiconductor photocatalysts for N_(2) reduction of ammonia synthesis.Therefore,the rational design of catalytic materials is the key to enhance the photocatalytic N_(2) reduction reaction of ammonia synthesis.Transition metal Ru as the active center not only accelerates the adsorption and activation of N_(2) molecules,but also has good selectivity for N_(2) reduction.Moreover,the interaction between the metal and the support can effectively regulate the electronic structure of the active site,accelerate the photogenerated electron transfer,and significantly enhance the photocatalytic activity.Based on this,this review systematically investigates the Ru co-semiconductors to realize efficient photocatalytic N_(2) reduction for ammonia synthesis,and introduces its basic principles.Specifically,the Ru co-semiconductor photocatalytic material systems are introduced,such as TiO2-based,g-C3N4-based,and metal oxide materials,including the design of catalysts,crystal structures,and other characteristics.In addition,the modification strategies of photocatalytic N_(2) reduction ammonia synthesis materials are also presented,including loading/doping,defect engineering,construction of heterojunctions,and crystal surface modulation.Furthermore,the progress and shortcomings of the application of Ru co-semiconductors in these processes are summarized and comprehensively discussed,and the future outlook of Ru co-semiconductors in photocatalytic N_(2) reduction ammonia synthesis applications is proposed.
基金the financial support provided by the Canada Research Chair program and the Natural Science and Engineering Research Council of Canada (NSERC)
文摘Ammonia serves both as a widely used fertilizer and environmentally friendly energy source due to its high energy density,rich hydrogen content,and emissions-free combustion.Additionally,it offers convenient transportation and storage as a hydrogen carrier.The dominant method used for large-scale ammonia production is the Haber-Bosch process,which requires high temperatures and pressures and is energy-intensive.However,non-thermal plasma offers an eco-friendly alternative for ammonia synthesis,gaining significant attention.It enables ammonia production at lower temperatures and pressures using plasma technology.This review provides insights into the catalyst and reactor developments,which are pivotal for promoting ammonia efficiency and addressing existing challenges.At first,the reaction kinetics and mechanisms are introduced to gain a comprehensive understanding of the reaction pathways involved in plasma-assisted ammonia synthesis.Thereafter,the enhancement of ammonia synthesis efficiency is discussed by developing and optimizing plasma reactors and effective catalysts.The effect of other feeding sources,such as water and methane,instead of hydrogen is also presented.Finally,the challenges and possible solutions are outlined to facilitate energy-saving and enhance ammonia efficiency in the future.
文摘Ammonia(NH 3) is a cornerstone of modern industry and agriculture, serving not only as the primary precursor for synthetic fertilizers but also as a promising carbon-neutral energy carrier [1]. The Haber-Bosch process, developed in the early 20th century, revolutionized global agriculture by enabling largescale fertilizer production [2].
基金supported by the National Natural Science Foundation of China(No.91645202 and No.91945302)the Key Technologies R&D Program of China(2017YFB0602205 and 2018YFA0208603)+1 种基金the Chinese Academy of Sciences Key Project(QYZDJSSW-SLH054)the Super Computing Center of USTC is gratefully acknowledged。
文摘Ruthenium(Ru)serves as a promising catalyst for ammonia synthesis via the Haber-Bosch process,identification of the structure sensitivity to improve the activity of Ru is important but not fully explored yet.We present here density functional theory calculations combined with microkinetic simulations on nitrogen molecule activation,a crucial step in ammonia synthesis,over a variety of hexagonal close-packed(hcp)and face-center cubic(fcc)Ru facets.Hcp{2130}facet exhibits the highest activity toward N_(2) dissociation in hcp Ru,followed by the(0001)monatomic step sites.The other hcp Ru facets have N_(2) dissociation rates at least three orders lower.Fcc{211}facet shows the best performance for N_(2) activation in fcc Ru,followed by{311},which indicates stepped surfaces make great contributions to the overall reactivity.Although hcp Ru{2130}facet and(0001)monatomic step sites have lower or comparable activation barriers compared with fcc Ru{211}facet,fcc Ru is proposed to be more active than hcp Ru for N_(2) conversion due to the exposure of the more favorable active sites over step surfaces in fcc Ru.This work provides new insights into the crystal structure sensitivity of N_(2) activation for mechanistic understanding and rational design of ammonia synthesis over Ru catalysts.
基金supported by the National Key Research and Development Program of China(2021YFB4000400)the National Natural Science Foundation of China(22222801,22038002,92361303,22478075,22472028,and 22108037)the Key R&D Plan of Shanghai Science and Technology Commission(21DZ1209002).
文摘Achieving green ammonia(NH_(3))synthesis requires developing effective catalysts under mild conditions.However;the competitive adsorption of N2 and H_(2);as well as the strong binding of N-containing intermediates on the catalyst;greatly inhibits the active sites for efficient NH_(3) synthesis.Here;we constructed a series of ZrH_(2)-modified Fe catalysts with dual active sites to address these issues and realized efficient NH_(3) synthesis under mild conditions.Our study shows that ZrH_(2) can not only provide active sites for H_(2) activation but also transfer electrons to Fe sites for accelerating N2 activation.The interaction between Fe and ZrH_(2) over 40ZrH_(2)-Fe leads to a decrease in work function and a downward shift of the d-band center;which is conducive to N2 activation and NH_(3) desorption;respectively.The utilization of distinct sites for activating different reactants can avoid the competitive adsorption of N2 and H_(2);leading to excellent NH_(3) synthesis activity of the 40 wt.%ZrH_(2)-mediated Fe catalyst.As a result;40ZrH_(2)-Fe exhibits a high NH_(3) synthesis rate of 23.3 mmol gcat-1h-1at 400℃and 1 MPa and robust stability during 100 h time-on-stream.
