Light alkanes non-oxidative dehydrogenation is an attractive non-oil route for olefins production.The alkane dehydrogenation reaction is limited by thermodynamic equilibrium,and the C-H bond cleavage is commonly consi...Light alkanes non-oxidative dehydrogenation is an attractive non-oil route for olefins production.The alkane dehydrogenation reaction is limited by thermodynamic equilibrium,and the C-H bond cleavage is commonly considered as the rate-determined step.The valence state of metal sites in catalysts will influence the stabilization of the vital intermediate(i.e.,C_(x)H_(y)...M^(δ+)...H)during the C-H bond cleavage process,which in turn affects the catalytic reactivity.Herein,we explicitly investigated the effect of different valence states of framework-Fe in silicate-1 zeolite on ethane dehydrogenation reaction through the combination of experimental and theoretical study.Fe(Ⅱ)-S-1 and Fe(Ⅲ)-S-1 catalysts are successfully synthesized by ligand-assisted in situ crystallization method,In-situ C_(2)H_6-FTIR shows the higher coverage of hydrocarbon intermediates on Fe(Ⅱ)-S-1,Under the same evaluation co nditio n,Fe(Ⅱ)-S-1 exhibits a higher space time yield of ethylene.Density functional theory(DFT)results reveal that the more coordinate-unsaturated and electron-enriched Fe(Ⅱ)sites boost the first C-H bond activation by slight deformation and efficient electron donation with C_(2)H_(5)^(*)species.Remarkably,the second C-H bond cleavage on Fe(Ⅱ)-S-1 undergoes a spin-crossing process from quintet state to triplet state,which involves a two-electro n-two-orbital interaction,further promoting the formation of ethylene.Microkinetic analysis is consistent with the experimental and DFT results.This work could provide methodology for elucidating the effect of metal valence states on catalytic performance as well as offer guidance for designing more efficient Fe-zeolite catalysts.展开更多
Given the current shortage of resources and environmental pollution,rationally designing and developing low-cost and highefficiency bifunctional electrocatalysts is an urgent and challenging task.It is widely recogniz...Given the current shortage of resources and environmental pollution,rationally designing and developing low-cost and highefficiency bifunctional electrocatalysts is an urgent and challenging task.It is widely recognized that element doping can effectively improve the electrocatalytic activity by adjusting the microstructure,morphology,and electronic structure.Therefore,this work rationally designs and prepares three-dimensional flower-like structured W-doped FeNi_(2)S_(4)/Ni_(3)S_(2)/NF heterojunctions as efficient bifunctional electrocatalysts for overall water splitting.In 1 M KOH,the prepared W-FeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst can effectively drive both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)processes,and only needs overpotentials of 93 and 210 mV to reach current densities of 10 and 50 mA·cm^(−2).In the double electrode cell composed by WFeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst,a low cell voltage of 1.52 V was required to reach a current density of 10 mA·cm^(−2),and 91.6%of this value was preserved after 24 h electrolysis operation.The performance of FeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst is superior to most of the current bifunctional electrocatalytic materials.Density functional theory(DFT)theoretical calculations also revealed a more intense electron transfer process that can be facilitated by constructing FeNi_(2)S_(4)and Ni_(3)S_(2)/NF interface,which may be the main reason for the archived excellent electrochemical performance.展开更多
基金the financial support from the National Natural Science Foundation of China (22035009,22178381)the National Key R&D Program of China (2021YFA1501301,2021YFC2901100)。
文摘Light alkanes non-oxidative dehydrogenation is an attractive non-oil route for olefins production.The alkane dehydrogenation reaction is limited by thermodynamic equilibrium,and the C-H bond cleavage is commonly considered as the rate-determined step.The valence state of metal sites in catalysts will influence the stabilization of the vital intermediate(i.e.,C_(x)H_(y)...M^(δ+)...H)during the C-H bond cleavage process,which in turn affects the catalytic reactivity.Herein,we explicitly investigated the effect of different valence states of framework-Fe in silicate-1 zeolite on ethane dehydrogenation reaction through the combination of experimental and theoretical study.Fe(Ⅱ)-S-1 and Fe(Ⅲ)-S-1 catalysts are successfully synthesized by ligand-assisted in situ crystallization method,In-situ C_(2)H_6-FTIR shows the higher coverage of hydrocarbon intermediates on Fe(Ⅱ)-S-1,Under the same evaluation co nditio n,Fe(Ⅱ)-S-1 exhibits a higher space time yield of ethylene.Density functional theory(DFT)results reveal that the more coordinate-unsaturated and electron-enriched Fe(Ⅱ)sites boost the first C-H bond activation by slight deformation and efficient electron donation with C_(2)H_(5)^(*)species.Remarkably,the second C-H bond cleavage on Fe(Ⅱ)-S-1 undergoes a spin-crossing process from quintet state to triplet state,which involves a two-electro n-two-orbital interaction,further promoting the formation of ethylene.Microkinetic analysis is consistent with the experimental and DFT results.This work could provide methodology for elucidating the effect of metal valence states on catalytic performance as well as offer guidance for designing more efficient Fe-zeolite catalysts.
基金the National Key R&D Program of China(Nos.2021YFA1501300 and 2019YFC1907602)the National Natural Science Foundation of China(Nos.51572295,21273285,and 21003157).
文摘Given the current shortage of resources and environmental pollution,rationally designing and developing low-cost and highefficiency bifunctional electrocatalysts is an urgent and challenging task.It is widely recognized that element doping can effectively improve the electrocatalytic activity by adjusting the microstructure,morphology,and electronic structure.Therefore,this work rationally designs and prepares three-dimensional flower-like structured W-doped FeNi_(2)S_(4)/Ni_(3)S_(2)/NF heterojunctions as efficient bifunctional electrocatalysts for overall water splitting.In 1 M KOH,the prepared W-FeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst can effectively drive both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)processes,and only needs overpotentials of 93 and 210 mV to reach current densities of 10 and 50 mA·cm^(−2).In the double electrode cell composed by WFeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst,a low cell voltage of 1.52 V was required to reach a current density of 10 mA·cm^(−2),and 91.6%of this value was preserved after 24 h electrolysis operation.The performance of FeNi_(2)S_(4)/Ni_(3)S_(2)/NF electrocatalyst is superior to most of the current bifunctional electrocatalytic materials.Density functional theory(DFT)theoretical calculations also revealed a more intense electron transfer process that can be facilitated by constructing FeNi_(2)S_(4)and Ni_(3)S_(2)/NF interface,which may be the main reason for the archived excellent electrochemical performance.
