Cyclohexane is a high-valued chemical receivingsignificant interest in liquid hydrogen storage technology.TiO_(2)-based catalysts show high performance in the photocatalytic dehydrogenation of cyclohexane under mild c...Cyclohexane is a high-valued chemical receivingsignificant interest in liquid hydrogen storage technology.TiO_(2)-based catalysts show high performance in the photocatalytic dehydrogenation of cyclohexane under mild conditions,but the detailed reaction mechanism is not well understood.With the surface science approaches,we have studied the adsorption and surface chemistry of cyclohexane on rutile TiO_(2)(110).The thermal desorption spectroscopy and X-ray photoelectron spectroscopy results both demonstrate the molecular adsorption of cyclohexane on rutile TiO_(2)(110).Upon the UV Hg light irradiation,photodesorption of cyclohexane occurs from both the chemisorbed monolayer and the multilayer.No decomposition nor dehydrogenation of cyclohexane occurs on rutile TiO_(2)(110).These results deepen the fundamental understanding of the surface chemistry of cyclohexane on the TiO_(2)surface.展开更多
The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling ...The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling the coverage of molecular O_(2)on the surface via increasing or decreasing O_(2)exposure,two chemisorbed O_(2)species on the surface are confirmed,one at the bridging oxygen vacancy(Ov)site(O_(2)^(2-)/Ov)and the other at the five-fold coordinated titanium(Ti_(5c))site(O^(2-)/Ti_(5c)).At low O_(2)exposure,O^(2-)/Ov is the main species on the surface,which only leads to the O-H bond cleavage of CH_(3)OH,producing methoxy groups(CHgO).However,after the Ov sites are nearly filled by O_(2)at about 0.1 L O_(2)exposure,O_(2)/Tisc species begins to appear on R-TiO_(2)(110)surface,resulting in the formation of formaldehyde(CH_(2)O)via the reaction of O_(2)/Tisc species with CH_(3)OH or CH3O to break the C-H bond at low surface temperature.Moreover,the yield of CH_(2)O increases linearly with that of H_(2)O.In addition,when the 1 L O_(2)covered surface is irradiated with 355 nm UV irradiation to desorb and dissociate O_(2)/Ti_(5c)species,the yield of CH_(2)O decreases linearly with that of H_(2)O.Further analysis suggests that the charge state of O_(2)/Ti_(5c)may not change as the exposure of O_(2)changes on the R-TiO_(2)(110)surface,and O_(2)is most likely to adsorb on the Ti_(5c)sites in the form of O_(2)^(2-),not O_(2)^(-),The result not only advances our understanding on the adsorption state of O_(2)on TiO_(2),but also provides clues for low temperature C-H bond activation with O_(2)on TiO_(2).展开更多
基金supported by the National Key R&D Program of China(No.2018YFE0203002)the National Natural Science Foundation of China(No.22173041,No.22173042,No.21973037,NSFC Center for Chemical Dynamics)+4 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB17000000)the Shenzhen Science and Technology Innovation Committee(No.JCYJ2019080914021660,No.ZDSYS20200421111001787)the Guangdong Innovative&Entrepreneurial Research Team Program(No.2019ZT08L455,No.2019JC01X091)the International Partnership Program of Chinese Academy of Science(No.121421KYSB 20170012)Innovation Program for Quantum Science and Technology(No.2021ZD0303304).
基金This work is supported by the National Natural Science Foundation of China(No.22202191).
文摘Cyclohexane is a high-valued chemical receivingsignificant interest in liquid hydrogen storage technology.TiO_(2)-based catalysts show high performance in the photocatalytic dehydrogenation of cyclohexane under mild conditions,but the detailed reaction mechanism is not well understood.With the surface science approaches,we have studied the adsorption and surface chemistry of cyclohexane on rutile TiO_(2)(110).The thermal desorption spectroscopy and X-ray photoelectron spectroscopy results both demonstrate the molecular adsorption of cyclohexane on rutile TiO_(2)(110).Upon the UV Hg light irradiation,photodesorption of cyclohexane occurs from both the chemisorbed monolayer and the multilayer.No decomposition nor dehydrogenation of cyclohexane occurs on rutile TiO_(2)(110).These results deepen the fundamental understanding of the surface chemistry of cyclohexane on the TiO_(2)surface.
基金This work was supported by the National Natural Science Foundation of China(No.21973010)Liaoning Revitalization Talents Program(No.XLYC1907032)The authors thank Qing Guo at Southern University of Science and Technolog for many insightful discussions。
文摘The activity and adsorption behavior of oxygen on rutile TiO_(2)(110)(RTiO_(2)(110))were investigated using the temperature programmed desorption(TPD)method with methanol(CH_(3)OH)as the probe molecule.By controlling the coverage of molecular O_(2)on the surface via increasing or decreasing O_(2)exposure,two chemisorbed O_(2)species on the surface are confirmed,one at the bridging oxygen vacancy(Ov)site(O_(2)^(2-)/Ov)and the other at the five-fold coordinated titanium(Ti_(5c))site(O^(2-)/Ti_(5c)).At low O_(2)exposure,O^(2-)/Ov is the main species on the surface,which only leads to the O-H bond cleavage of CH_(3)OH,producing methoxy groups(CHgO).However,after the Ov sites are nearly filled by O_(2)at about 0.1 L O_(2)exposure,O_(2)/Tisc species begins to appear on R-TiO_(2)(110)surface,resulting in the formation of formaldehyde(CH_(2)O)via the reaction of O_(2)/Tisc species with CH_(3)OH or CH3O to break the C-H bond at low surface temperature.Moreover,the yield of CH_(2)O increases linearly with that of H_(2)O.In addition,when the 1 L O_(2)covered surface is irradiated with 355 nm UV irradiation to desorb and dissociate O_(2)/Ti_(5c)species,the yield of CH_(2)O decreases linearly with that of H_(2)O.Further analysis suggests that the charge state of O_(2)/Ti_(5c)may not change as the exposure of O_(2)changes on the R-TiO_(2)(110)surface,and O_(2)is most likely to adsorb on the Ti_(5c)sites in the form of O_(2)^(2-),not O_(2)^(-),The result not only advances our understanding on the adsorption state of O_(2)on TiO_(2),but also provides clues for low temperature C-H bond activation with O_(2)on TiO_(2).
