Abstract
The photocatalytic activity of anatase TiO2 decorated with metal clusters has been widely documented, but the nature of the metal–metal oxide interface and reaction intermediates in catalytic processes are still not well understood. This in part is due to the fact that use of photoelectron spectroscopy to deduce the surface chemistry of catalytic systems has long been hampered by the huge pressure difference between real-world operation and the requirement of high vacuum for electron detection. Here, the in situ growth of silver nanoparticles on a model metal-oxide catalyst support and their reactivity with a CO/H2O gas mixture has been investigated in detail. Using synchrotron X-ray photoelectron spectroscopy, near-ambient pressure X-ray photoelectron spectroscopy, and scanning tunneling microscopy, the interaction of Ag with the anatase TiO2 surface leads to metal-surface charge transfer and low mobility of Ag on the surface. Upon exposure to a 1.5 mbar CO/1.5 mbar H2O gas mixture, partial oxidation of ...
Highlights
Metal clusters supported on well-ordered metal oxide surfaces are of great interest due to their application in a wide variety of fields, including photovoltaics, photocatalysis and transition metal catalysis.[1−6] Carbon monoxide (CO), in particular, is a major air pollutant which causes serious environmental and health concerns
The catalytic oxidation of CO, to form CO2, is an important research area.[7−9] Noble metals supported on metal oxide ceramic supports have long been used for the catalytic conversion of CO to CO2, but the high cost of these metals remains a major issue
The degree of reduction of Ti is characteristic of the the clean anatase TiO2(101) surface and the maximum Ag coverage are shown in Figure 1, parts a and b, respectively
Summary
Metal clusters supported on well-ordered metal oxide surfaces are of great interest due to their application in a wide variety of fields, including photovoltaics, photocatalysis and transition metal catalysis.[1−6] Carbon monoxide (CO), in particular, is a major air pollutant which causes serious environmental and health concerns. Ag is non-toxic, catalytically active and has the highest thermal and electrical conductivity of all the noble metals.[27] In addition, Ag is not as costly as other noble metals.[9] Catalyst systems based on Ag/TiO2 have been shown to efficiently catalyze reactions at solid−gas interfaces and in aqueous solutions. They have been found to substantially enhance the photocatalytic capacity of TiO2 for renewable energy generation and degradation of environmental pollutants.[20,28] Density functional theory (DFT+U) calculations of Received: June 14, 2017 Revised: August 30, 2017 Published: September 7, 2017
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