Electrocatalytic nitrogen reduction reaction under ambient conditions is a promising pathway for ammonia synthesis.Currently nitrogen reduction reactions are carried out in N_(2)-saturated environments and use high-pu...Electrocatalytic nitrogen reduction reaction under ambient conditions is a promising pathway for ammonia synthesis.Currently nitrogen reduction reactions are carried out in N_(2)-saturated environments and use high-purity nitrogen as feedstock,which is costly.Here,we prepared carbon-coated ultra-low 4d metal Ru-doped liquid metal Ga(Ru_(0.06)/LM@C)for NRR over a wide range of N_(2) concentrations.Comprehensive analyses show that the introduction of the ultra-low 4d element Ru can effectively adjust the electronic structure through orbital interactions,thus enhancing the adsorption of nitrogen-containing intermediates.The liquid catalyst utilized its mobility to provide a higher density of active sites.In addition,the material Ru_(0.06)/Ga@C itself has the ability to promote product desorption.The three act synergistically to optimize the N_(2) mass transfer path,thereby increasing the*NNH coverage and further improving the ammonia yield over a wide range of N_(2) concentrations.The maximum NH_(3) yield of the catalyst can reach 126.0μg h^(-1) mgcat^(-1)(at–0.3 V vs.RHE)with high purity N_(2) as feed gas,and the Faraday efficiency is 60.4%at–0.1 V vs.RHE.Over a wide range of N_(2) concentrations,the NH_(3) yield of the catalyst was greater than 100μg h^(-1) mgcat^(-1) with a Faraday efficiency higher than 47%.The catalytic performance is much higher than that of solid Ga@C and reported p-block metal-based catalysts.展开更多
The polarization switching plays a crucial role in controlling the final products in the catalytic pro-cess.The effect of polarization orientation on nitrogen reduction was investigated by anchoring transition metal a...The polarization switching plays a crucial role in controlling the final products in the catalytic pro-cess.The effect of polarization orientation on nitrogen reduction was investigated by anchoring transition metal atoms to form active centers on ferroelectric material In_(2)Se_(3).During the polariza-tion switching process,the difference in surface electrostatic potential leads to a redistribution of electronic states.This affects the interaction strength between the adsorbed small molecules and the catalyst substrate,thereby altering the reaction barrier.In addition,the surface states must be considered to prevent the adsorption of other small molecules(such as *O,*OH,and *H).Further-more,the V@↓-In_(2)Se_(3) possesses excellent catalytic properties,high electrochemical and thermody-namic stability,which facilitates the catalytic process.Machine learning also helps us further ex-plore the underlying mechanisms.The systematic investigation provides novel insights into the design and application of two-dimensional switchable ferroelectric catalysts for various chemical processes.展开更多
Electrocatalytic reduction of nitrogen into ammonia(NH_(3))is a highly attractive but challenging route for NH_(3)production.We propose to realize a synergetic work of multi reaction sites to overcome the limitation o...Electrocatalytic reduction of nitrogen into ammonia(NH_(3))is a highly attractive but challenging route for NH_(3)production.We propose to realize a synergetic work of multi reaction sites to overcome the limitation of sustainable NH_(3)production.Herein,using ruthenium-sulfur-carbon(Ru-S-C)catalyst as a prototype,we show that the Ru/S dual-site cooperates to catalyse eletrocatalytic nitrogen reduction reaction(eNRR)at ambient conditions.With the combination of theoretical calculations,in situ Raman spectroscopy,and experimental observation,we demonstrate that such Ru/S dual-site cooperation greatly facilitates the activation and first protonation of N_(2)in the rate-determining step of eNRR.As a result,Ru-S-C catalyst exhibits significantly enhanced eNRR performance compared with the routine Ru-N-C catalyst via a single-site catalytic mechanism.We anticipate that our specifically designed dual-site collaborative catalytic mechanism will open up a new way to offers new opportunities for advancing sustainable NH_(3)production.展开更多
In this study,TiO_(2) nanosheets(NSs)grown in situ on extremely conductive Ti_(3)C_(2)T_(x) MXene to form TiO_(2)/Ti_(3)C_(2)T_(x) MXene composites with abundant active sites are proposed to effectively achieve elec‐...In this study,TiO_(2) nanosheets(NSs)grown in situ on extremely conductive Ti_(3)C_(2)T_(x) MXene to form TiO_(2)/Ti_(3)C_(2)T_(x) MXene composites with abundant active sites are proposed to effectively achieve elec‐trocatalytic NH_(3) synthesis.Electron transfer can be promoted by Ti_(3)C_(2)T_(x) MXene with high conduc‐tivity.Meanwhile,the TiO_(2) NSs in‐situ formation can not only avoid Ti_(3)C_(2)T_(x) MXene microstacking but also enhance the surface specific area of Ti_(3)C_(2)T_(x) MXene.The TiO_(2)/Ti_(3)C_(2)T_(x) MXene catalyst reach‐es a high Faradaic efϐiciency(FE)of 44.68%at−0.75 V vs.RHE and a large NH3 yield of 44.17µg h^(-1) mg^(-1)cat.at−0.95 V,with strong electrochemical durability.15N isotopic labeling experiments imply that the N in the produced NH3 originated from the N2 of the electrolyte.DFT calculations were conducted to determine the possible NRR reaction pathways for TiO_(2)/Ti_(3)C_(2)T_(x) MXene composites.MXene catalysts combined with other materials have been rationally designed for efficient ammonia production under ambient conditions。展开更多
Oxygen reduction reaction(ORR)plays a crucial role in many energy storage and conversion devices.Currently,the development of inexpensive and high-performance carbon-based non-precious-metal ORR catalysts in alkaline ...Oxygen reduction reaction(ORR)plays a crucial role in many energy storage and conversion devices.Currently,the development of inexpensive and high-performance carbon-based non-precious-metal ORR catalysts in alkaline media still gains a wide attention.In this paper,the mesoporous Fe-N/C catalysts were synthesized through SiO2-mediated templating method using biomass soybeans as the nitrogen and carbon sources.The SiO2 templates create a simultaneous optimization of both the surface functionalities and porous structures of Fe-N/C catalysts.Detailed investigations indicate that the Fe-N/C3 catalyst prepared with the mass ratio of SiO2 to soybean being 3:4 exhibits brilliant electrocatalytic performance,excellent long-term stability and methanol tolerance for the ORR,with the onset potential and the half-wave potential of the ORR being about 0.890 V and 0.783 V(vs RHE),respectively.Meanwhile,the desired 4-electron transfer pathway of the ORR on the catalysts can be observed.It is significantly proposed that the high BET specific surface area and the appropriate pore-size,as well as the high pyridinic-N and total nitrogen loadings may play key roles in enhancing the ORR performance for the Fe-N/C3 catalyst.These results suggest a feasible route based on the economical and sustainable soybean biomass to develop inexpensive and highly efficient non-precious metal electrochemical catalysts for the ORR.展开更多
Owing to its cost‐effectiveness and adjustable eight‐electron distribution in the 3d orbital,nickel oxide(NiO)is considered an effective electrocatalyst for an ambient electrochemical nitrogen reduction reaction(NRR...Owing to its cost‐effectiveness and adjustable eight‐electron distribution in the 3d orbital,nickel oxide(NiO)is considered an effective electrocatalyst for an ambient electrochemical nitrogen reduction reaction(NRR).However,because of the low conductivity of the transition metal oxide electrocatalyst,its application in this field is limited.In this study,we found that the doping of NiO nanosheets with a small amount(3–10 nm)of Pt nanoparticles(Pt/NiO‐NSs)leads to considerable improvements in the Faradaic efficiency(FE)and NH_(3) yield compared with those obtained using pure NiO,breaking the common perception that commercial Pt‐based electrocatalysts demonstrate little potential for NRR due to their high hydrogen evolution tendency.In a 0.1 mol/L Na_(2)SO_(4) solution at−0.2 V vs.RHE,a typical Pt/NiO‐2 sample exhibits an optimum electrochemical NH_(3) yield of 20.59μg h^(–1)mg^(–1)cat.and an FE of 15.56%,which are approximately 5 and 3 times greater,respectively,than those of pure NiO nanosheets at the same applied potential.X‐ray photoelectron spectroscopy analysis revealed that Pt in Pt/NiO‐NSs exist as Pt0,Pt^(2+),and Pt^(4+)and that high‐valence Pt ions are more electropositive,thereby favoring chemisorption and the activation of N2 molecules.Density function theory calculations showed that the d‐band of Pt nanoparticles supported on NiO is significantly tuned compared to that of pure Pt,affording a more favorable electronic structure for NRR.The results of this study show that Pt can be an effective NRR electrochemical catalyst when loaded on an appropriate substrate.Most importantly,it provides a new synthetic avenue for the fabrication of highly active Pt‐based NRR electrocatalysts.展开更多
Electrocatalytic production of ammonia from dinitrogen is considered as a sustainable alternative to the energy-demanding and pollutive Haber-Bosch process.A promising class of materials for selective nitrogen reducti...Electrocatalytic production of ammonia from dinitrogen is considered as a sustainable alternative to the energy-demanding and pollutive Haber-Bosch process.A promising class of materials for selective nitrogen reduction(NRR)corresponds to transition-metal oxides given that these electrodes do not show a high activity toward the competing hydrogen evolution reaction.So far,density functional theory calculations have been used to comprehend trends in a class of materials by using the concept of scaling relations and volcano plots.This thermodynamic theory pinpoints that either the formation of the*NNH adsorbate or the formation of ammonia are reconciled with the potential-determining reaction steps.Thus,the development of NRR catalyst has largely focused on the optimization of these two elementary processes.In the present contribution,overpotential and kinetic effects are factored into the volcano plot for the NRR over transition-metal oxides by making use of the recently introduced activity descriptor G_(max)(η).It is illustrated that the thermodynamic volcano picture is too simplistic as the limiting reaction step may alter close to the volcano apex:there,particularly surface reactions may govern the reaction rate.In addition,it is demonstrated how to include the formation of hydrazine as a competing side reaction into the volcano plot,which is of importance for weak binding*NNH catalysts where the formation of hydrazine may compete with the formation of ammonia.Given that the outlined methodology in this manuscript is universal and not restricted to the class of transition-metal oxides,the presented kinetic volcano picture may contribute to the development of NRR catalysts for nitrogen fixation.展开更多
Though touted as a potential way to realize clean ammonia synthesis,electrochemical ammonia synthesis is currently limited by its catalytic efficiency.Great effort has been made to find catalysts with improved activit...Though touted as a potential way to realize clean ammonia synthesis,electrochemical ammonia synthesis is currently limited by its catalytic efficiency.Great effort has been made to find catalysts with improved activity toward electrochemical nitrogen reduction reaction(eNRR).Rational screening of catalysts can be facilitated using the volcano relationship between catalytic activity and adsorption energy of an intermediate,namely,the activity descriptor.In this work,we proposeΔG^(*)_(NH_(2))+ΔG^(*)_(NNH)as a combinatorial descriptor,which shows better predictive power than traditional descriptors using the adsorption free energies of single intermediates.The volcano plots based on the combinatorial descriptor exhibits peak activity fixedly at the descriptor value corresponding to the formation free energy of NH3,regardless of the catalyst types;while the descriptor values correspond to the top activities for eNRR on volcano plots based on single descriptors usually vary with the types of catalysts.展开更多
文摘Electrocatalytic nitrogen reduction reaction under ambient conditions is a promising pathway for ammonia synthesis.Currently nitrogen reduction reactions are carried out in N_(2)-saturated environments and use high-purity nitrogen as feedstock,which is costly.Here,we prepared carbon-coated ultra-low 4d metal Ru-doped liquid metal Ga(Ru_(0.06)/LM@C)for NRR over a wide range of N_(2) concentrations.Comprehensive analyses show that the introduction of the ultra-low 4d element Ru can effectively adjust the electronic structure through orbital interactions,thus enhancing the adsorption of nitrogen-containing intermediates.The liquid catalyst utilized its mobility to provide a higher density of active sites.In addition,the material Ru_(0.06)/Ga@C itself has the ability to promote product desorption.The three act synergistically to optimize the N_(2) mass transfer path,thereby increasing the*NNH coverage and further improving the ammonia yield over a wide range of N_(2) concentrations.The maximum NH_(3) yield of the catalyst can reach 126.0μg h^(-1) mgcat^(-1)(at–0.3 V vs.RHE)with high purity N_(2) as feed gas,and the Faraday efficiency is 60.4%at–0.1 V vs.RHE.Over a wide range of N_(2) concentrations,the NH_(3) yield of the catalyst was greater than 100μg h^(-1) mgcat^(-1) with a Faraday efficiency higher than 47%.The catalytic performance is much higher than that of solid Ga@C and reported p-block metal-based catalysts.
文摘The polarization switching plays a crucial role in controlling the final products in the catalytic pro-cess.The effect of polarization orientation on nitrogen reduction was investigated by anchoring transition metal atoms to form active centers on ferroelectric material In_(2)Se_(3).During the polariza-tion switching process,the difference in surface electrostatic potential leads to a redistribution of electronic states.This affects the interaction strength between the adsorbed small molecules and the catalyst substrate,thereby altering the reaction barrier.In addition,the surface states must be considered to prevent the adsorption of other small molecules(such as *O,*OH,and *H).Further-more,the V@↓-In_(2)Se_(3) possesses excellent catalytic properties,high electrochemical and thermody-namic stability,which facilitates the catalytic process.Machine learning also helps us further ex-plore the underlying mechanisms.The systematic investigation provides novel insights into the design and application of two-dimensional switchable ferroelectric catalysts for various chemical processes.
文摘Electrocatalytic reduction of nitrogen into ammonia(NH_(3))is a highly attractive but challenging route for NH_(3)production.We propose to realize a synergetic work of multi reaction sites to overcome the limitation of sustainable NH_(3)production.Herein,using ruthenium-sulfur-carbon(Ru-S-C)catalyst as a prototype,we show that the Ru/S dual-site cooperates to catalyse eletrocatalytic nitrogen reduction reaction(eNRR)at ambient conditions.With the combination of theoretical calculations,in situ Raman spectroscopy,and experimental observation,we demonstrate that such Ru/S dual-site cooperation greatly facilitates the activation and first protonation of N_(2)in the rate-determining step of eNRR.As a result,Ru-S-C catalyst exhibits significantly enhanced eNRR performance compared with the routine Ru-N-C catalyst via a single-site catalytic mechanism.We anticipate that our specifically designed dual-site collaborative catalytic mechanism will open up a new way to offers new opportunities for advancing sustainable NH_(3)production.
文摘In this study,TiO_(2) nanosheets(NSs)grown in situ on extremely conductive Ti_(3)C_(2)T_(x) MXene to form TiO_(2)/Ti_(3)C_(2)T_(x) MXene composites with abundant active sites are proposed to effectively achieve elec‐trocatalytic NH_(3) synthesis.Electron transfer can be promoted by Ti_(3)C_(2)T_(x) MXene with high conduc‐tivity.Meanwhile,the TiO_(2) NSs in‐situ formation can not only avoid Ti_(3)C_(2)T_(x) MXene microstacking but also enhance the surface specific area of Ti_(3)C_(2)T_(x) MXene.The TiO_(2)/Ti_(3)C_(2)T_(x) MXene catalyst reach‐es a high Faradaic efϐiciency(FE)of 44.68%at−0.75 V vs.RHE and a large NH3 yield of 44.17µg h^(-1) mg^(-1)cat.at−0.95 V,with strong electrochemical durability.15N isotopic labeling experiments imply that the N in the produced NH3 originated from the N2 of the electrolyte.DFT calculations were conducted to determine the possible NRR reaction pathways for TiO_(2)/Ti_(3)C_(2)T_(x) MXene composites.MXene catalysts combined with other materials have been rationally designed for efficient ammonia production under ambient conditions。
基金Project(21406273)supported by the National Natural Science Foundation of China
文摘Oxygen reduction reaction(ORR)plays a crucial role in many energy storage and conversion devices.Currently,the development of inexpensive and high-performance carbon-based non-precious-metal ORR catalysts in alkaline media still gains a wide attention.In this paper,the mesoporous Fe-N/C catalysts were synthesized through SiO2-mediated templating method using biomass soybeans as the nitrogen and carbon sources.The SiO2 templates create a simultaneous optimization of both the surface functionalities and porous structures of Fe-N/C catalysts.Detailed investigations indicate that the Fe-N/C3 catalyst prepared with the mass ratio of SiO2 to soybean being 3:4 exhibits brilliant electrocatalytic performance,excellent long-term stability and methanol tolerance for the ORR,with the onset potential and the half-wave potential of the ORR being about 0.890 V and 0.783 V(vs RHE),respectively.Meanwhile,the desired 4-electron transfer pathway of the ORR on the catalysts can be observed.It is significantly proposed that the high BET specific surface area and the appropriate pore-size,as well as the high pyridinic-N and total nitrogen loadings may play key roles in enhancing the ORR performance for the Fe-N/C3 catalyst.These results suggest a feasible route based on the economical and sustainable soybean biomass to develop inexpensive and highly efficient non-precious metal electrochemical catalysts for the ORR.
文摘Owing to its cost‐effectiveness and adjustable eight‐electron distribution in the 3d orbital,nickel oxide(NiO)is considered an effective electrocatalyst for an ambient electrochemical nitrogen reduction reaction(NRR).However,because of the low conductivity of the transition metal oxide electrocatalyst,its application in this field is limited.In this study,we found that the doping of NiO nanosheets with a small amount(3–10 nm)of Pt nanoparticles(Pt/NiO‐NSs)leads to considerable improvements in the Faradaic efficiency(FE)and NH_(3) yield compared with those obtained using pure NiO,breaking the common perception that commercial Pt‐based electrocatalysts demonstrate little potential for NRR due to their high hydrogen evolution tendency.In a 0.1 mol/L Na_(2)SO_(4) solution at−0.2 V vs.RHE,a typical Pt/NiO‐2 sample exhibits an optimum electrochemical NH_(3) yield of 20.59μg h^(–1)mg^(–1)cat.and an FE of 15.56%,which are approximately 5 and 3 times greater,respectively,than those of pure NiO nanosheets at the same applied potential.X‐ray photoelectron spectroscopy analysis revealed that Pt in Pt/NiO‐NSs exist as Pt0,Pt^(2+),and Pt^(4+)and that high‐valence Pt ions are more electropositive,thereby favoring chemisorption and the activation of N2 molecules.Density function theory calculations showed that the d‐band of Pt nanoparticles supported on NiO is significantly tuned compared to that of pure Pt,affording a more favorable electronic structure for NRR.The results of this study show that Pt can be an effective NRR electrochemical catalyst when loaded on an appropriate substrate.Most importantly,it provides a new synthetic avenue for the fabrication of highly active Pt‐based NRR electrocatalysts.
文摘Electrocatalytic production of ammonia from dinitrogen is considered as a sustainable alternative to the energy-demanding and pollutive Haber-Bosch process.A promising class of materials for selective nitrogen reduction(NRR)corresponds to transition-metal oxides given that these electrodes do not show a high activity toward the competing hydrogen evolution reaction.So far,density functional theory calculations have been used to comprehend trends in a class of materials by using the concept of scaling relations and volcano plots.This thermodynamic theory pinpoints that either the formation of the*NNH adsorbate or the formation of ammonia are reconciled with the potential-determining reaction steps.Thus,the development of NRR catalyst has largely focused on the optimization of these two elementary processes.In the present contribution,overpotential and kinetic effects are factored into the volcano plot for the NRR over transition-metal oxides by making use of the recently introduced activity descriptor G_(max)(η).It is illustrated that the thermodynamic volcano picture is too simplistic as the limiting reaction step may alter close to the volcano apex:there,particularly surface reactions may govern the reaction rate.In addition,it is demonstrated how to include the formation of hydrazine as a competing side reaction into the volcano plot,which is of importance for weak binding*NNH catalysts where the formation of hydrazine may compete with the formation of ammonia.Given that the outlined methodology in this manuscript is universal and not restricted to the class of transition-metal oxides,the presented kinetic volcano picture may contribute to the development of NRR catalysts for nitrogen fixation.
文摘Though touted as a potential way to realize clean ammonia synthesis,electrochemical ammonia synthesis is currently limited by its catalytic efficiency.Great effort has been made to find catalysts with improved activity toward electrochemical nitrogen reduction reaction(eNRR).Rational screening of catalysts can be facilitated using the volcano relationship between catalytic activity and adsorption energy of an intermediate,namely,the activity descriptor.In this work,we proposeΔG^(*)_(NH_(2))+ΔG^(*)_(NNH)as a combinatorial descriptor,which shows better predictive power than traditional descriptors using the adsorption free energies of single intermediates.The volcano plots based on the combinatorial descriptor exhibits peak activity fixedly at the descriptor value corresponding to the formation free energy of NH3,regardless of the catalyst types;while the descriptor values correspond to the top activities for eNRR on volcano plots based on single descriptors usually vary with the types of catalysts.
