CO oxidation at ceria surfaces has been studied for decades,and many efforts have been devoted to understanding the effect of surface reduction on the catalytic activity.In this work,we theoretically studied the CO ox...CO oxidation at ceria surfaces has been studied for decades,and many efforts have been devoted to understanding the effect of surface reduction on the catalytic activity.In this work,we theoretically studied the CO oxidation on the clean and reduced CeO_(2)(111)surfaces using different surface cells to dete rmine the relationships between the reduction degrees and calculated reaction energetics.It is found that the calculated barrier for the direct reaction between CO and surface lattice O drastically decreases with the increase of surface reduction degree.From electronic analysis,we found that the surface reduction can lead to the occurrence of localized electrons at the surface Ce,which affects the charge distribution at surface O.As the result,the surface O becomes more negatively charged and therefore more active in reacting with CO.This work then suggests that the localized 4 f electron reservoir of Ce can act as the"pseudo-anion"at reduced CeO_(2) surfaces to activate surface lattice O for catalytic oxidative reactions.展开更多
Iron-containing zeolite catalysts(Fe-zeolites)demonstrate exceptional performance in selective oxidation of methane to C1 oxygenates,while aerobic C-C coupling to C_(2) hydrocarbons has remained elusive.The heterogene...Iron-containing zeolite catalysts(Fe-zeolites)demonstrate exceptional performance in selective oxidation of methane to C1 oxygenates,while aerobic C-C coupling to C_(2) hydrocarbons has remained elusive.The heterogeneity of Fe species within zeolites,intertwined with kinetically competing over-oxidation processes,engenders ambiguities in determining catalytic pathways,thereby fundamentally impeding rational design of the catalyst.Here,we report that continuous aerobic C-C coupling of methane can be achieved under oxygen-lean conditions over tailored Fezeolites.Crucially,the oxygen-lean environment enables clear identification of distinct active-site roles:CO is directly generated on low-coordinated monomeric Fe sites,while C_(2) hydrocarbons formation predominantly occurs on coordinatively saturated monomeric Fe sites.Detailed spectroscopic studies and density functional theory(DFT)calculation reveals that steric effect of octahedral-coordinated monomeric Fe^(3+) Lewis acid sites(LAS)compels ^(*)CH_(3) species to preferentially bind to the Brønsted acid sites(BAS),facilitating C-C coupling and suppressing overoxidation.Furthermore,the Mars-van Krevelen(MvK)mechanism is verified as a feasible pathway for methane-to-ethane conversion.This work elucidates the critical role of Fe site coordination in dictating reaction pathways during oxygen-mediated methane conversion.展开更多
基金financial support from the National Key R&D Program of China(No.2018YFA0208602)National Natural Science Foundation of China(No.21825301)。
文摘CO oxidation at ceria surfaces has been studied for decades,and many efforts have been devoted to understanding the effect of surface reduction on the catalytic activity.In this work,we theoretically studied the CO oxidation on the clean and reduced CeO_(2)(111)surfaces using different surface cells to dete rmine the relationships between the reduction degrees and calculated reaction energetics.It is found that the calculated barrier for the direct reaction between CO and surface lattice O drastically decreases with the increase of surface reduction degree.From electronic analysis,we found that the surface reduction can lead to the occurrence of localized electrons at the surface Ce,which affects the charge distribution at surface O.As the result,the surface O becomes more negatively charged and therefore more active in reacting with CO.This work then suggests that the localized 4 f electron reservoir of Ce can act as the"pseudo-anion"at reduced CeO_(2) surfaces to activate surface lattice O for catalytic oxidative reactions.
基金supported by the National Key R&D Program of China(No.2022YFA1504700)the National Natural Science Foundation of China(Nos.22378414 and 21908236)the Youth Innovation Promotion Association CAS(No.2022287).
文摘Iron-containing zeolite catalysts(Fe-zeolites)demonstrate exceptional performance in selective oxidation of methane to C1 oxygenates,while aerobic C-C coupling to C_(2) hydrocarbons has remained elusive.The heterogeneity of Fe species within zeolites,intertwined with kinetically competing over-oxidation processes,engenders ambiguities in determining catalytic pathways,thereby fundamentally impeding rational design of the catalyst.Here,we report that continuous aerobic C-C coupling of methane can be achieved under oxygen-lean conditions over tailored Fezeolites.Crucially,the oxygen-lean environment enables clear identification of distinct active-site roles:CO is directly generated on low-coordinated monomeric Fe sites,while C_(2) hydrocarbons formation predominantly occurs on coordinatively saturated monomeric Fe sites.Detailed spectroscopic studies and density functional theory(DFT)calculation reveals that steric effect of octahedral-coordinated monomeric Fe^(3+) Lewis acid sites(LAS)compels ^(*)CH_(3) species to preferentially bind to the Brønsted acid sites(BAS),facilitating C-C coupling and suppressing overoxidation.Furthermore,the Mars-van Krevelen(MvK)mechanism is verified as a feasible pathway for methane-to-ethane conversion.This work elucidates the critical role of Fe site coordination in dictating reaction pathways during oxygen-mediated methane conversion.
