Understanding the effect of H_(2)O adsorption on reactant activation is of great importance in heterogeneous catalysis,which remains a grand challenge particularly in oxide catalyst systems with structural complexity....Understanding the effect of H_(2)O adsorption on reactant activation is of great importance in heterogeneous catalysis,which remains a grand challenge particularly in oxide catalyst systems with structural complexity.Herein,the effect of D_(2)O adsorption on D_(2)activation over MgO nanocatalysts at different temperatures has been investigated by transmission Fourier transform infrared(FT-IR)and temperature-programmed desorption(TPD).Two sets of hydride and hydroxyl species produced from D_(2)dissociation at more active and less active Mg-O pairs can be observed by FT-IR,which all desorb via the product of D_(2)as confirmed by TPD experiments.We find that the physically adsorbed D_(2)O overlayer does not affect the dissociation of D_(2)since D_(2)may pass through the molecular layer and access the surface-active sites.When D_(2)O is partially dissociated on the MgO surface,D_(2)can only dissociate at the remaining active sites until that dissociated-ODw groups from D_(2)O occupy all active sites.These findings provide a fundamental understanding of the effect of water adsorption on D_(2)activation on oxide catalysts.展开更多
Ultrathin ZnO nano structures prese nt in teresti ng two-dimensi on al(2D)graphene-like structure in contrast to wurtzite structure in bulk ZnO.Growth on Au(111)has been regarded as a well-established route to the 2D ...Ultrathin ZnO nano structures prese nt in teresti ng two-dimensi on al(2D)graphene-like structure in contrast to wurtzite structure in bulk ZnO.Growth on Au(111)has been regarded as a well-established route to the 2D ZnO layers while controlled growth of uniform ZnO nano structures remains as a challe nge.Here,reactive deposition of Zn in O3 and NO2 was employed,which is investigated by sea nning tunneling microscopy and X-ray photoelectr on spectroscopy(XPS).We dem on strate that uniform ZnO mono layer nanoislands and films can be obtained on Au(111)using O3 and uniform ZnO bilayer nanoislands and films form on Au(111)using NO2,respectively.Formation of atomic oxyge n overlayers on Au(111)via exposure to O3 is critical to the formatio n of uniform ZnO mono layer nano structures atop.Near ambient pressure XPS studies revealed that n early full hydroxy lati on occurs on mono layer ZnO structures upon exposure to near ambient pressure water vapor or atomic hydrogen species,while partial surface hydroxylation happens on bilayer ZnO under the same gaseous exposure conditions.展开更多
基金This work was financially supported by the National Key R&D Program of China(Nos.2021YFA1502800,2022YFA1504800 and 2022YFA1504500)the National Natural Science Foundation of China(Nos.91945302,22272162,22288201 and 21825203).
文摘Understanding the effect of H_(2)O adsorption on reactant activation is of great importance in heterogeneous catalysis,which remains a grand challenge particularly in oxide catalyst systems with structural complexity.Herein,the effect of D_(2)O adsorption on D_(2)activation over MgO nanocatalysts at different temperatures has been investigated by transmission Fourier transform infrared(FT-IR)and temperature-programmed desorption(TPD).Two sets of hydride and hydroxyl species produced from D_(2)dissociation at more active and less active Mg-O pairs can be observed by FT-IR,which all desorb via the product of D_(2)as confirmed by TPD experiments.We find that the physically adsorbed D_(2)O overlayer does not affect the dissociation of D_(2)since D_(2)may pass through the molecular layer and access the surface-active sites.When D_(2)O is partially dissociated on the MgO surface,D_(2)can only dissociate at the remaining active sites until that dissociated-ODw groups from D_(2)O occupy all active sites.These findings provide a fundamental understanding of the effect of water adsorption on D_(2)activation on oxide catalysts.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.21825203,91545204,21688102,and 21621063)the National Key Research and Development Program of China(Nos.2016YFA0200200 and 2017YFB0602205)+1 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17020000)The authors thank the support for Nano-X from Suzhou Institute of Nano-Tech and Nano-Bionics(SINANO).The fruitful discussion with Yuemin Wang in Karlsruhe Institute of Technology(KIT)is highly appreciated.
文摘Ultrathin ZnO nano structures prese nt in teresti ng two-dimensi on al(2D)graphene-like structure in contrast to wurtzite structure in bulk ZnO.Growth on Au(111)has been regarded as a well-established route to the 2D ZnO layers while controlled growth of uniform ZnO nano structures remains as a challe nge.Here,reactive deposition of Zn in O3 and NO2 was employed,which is investigated by sea nning tunneling microscopy and X-ray photoelectr on spectroscopy(XPS).We dem on strate that uniform ZnO mono layer nanoislands and films can be obtained on Au(111)using O3 and uniform ZnO bilayer nanoislands and films form on Au(111)using NO2,respectively.Formation of atomic oxyge n overlayers on Au(111)via exposure to O3 is critical to the formatio n of uniform ZnO mono layer nano structures atop.Near ambient pressure XPS studies revealed that n early full hydroxy lati on occurs on mono layer ZnO structures upon exposure to near ambient pressure water vapor or atomic hydrogen species,while partial surface hydroxylation happens on bilayer ZnO under the same gaseous exposure conditions.
