Manipulating the charge state of Au clusters on rutile TiO2(110) single crystal surfaces through molecular reactions probed by infrared spectroscopy. Issue 26 (16th June 2016) - Cao, Yunjun
Abstract : The charge state of Au clusters on TiO2 (110) is manipulated through (NO)2 → N2 O + Oa reactions: (1) interfacial Au atoms by intensely direct charge transfer; (2) top Au atoms by weakly indirect charge transfer. Abstract : The charge state of Au clusters deposited on rutile TiO2 (110) single crystal surfaces was studied by UHV-FTIRS using CO as a probe. The as-deposited Au clusters on oxidized TiO2 (110) surfaces are electrically neutral and are identified by the 2105–2112 cm −1 vibrational frequency of adsorbed CO depending on Au coverage. Annealing Au/TiO2 (110) in a moderate O2 atmosphere at 400 K blue shifts the CO vibrational frequency by only 2–3 cm −1 both on bare TiO2 (110) surfaces and on Au clusters. However, NO exposure blue shifts the CO vibrational frequency by 16–26 cm −1 for CO adsorbed on Au atoms near the interface and by 3–4 cm −1 for CO adsorbed on top of Au clusters. As the acceptors of the intense charge transfer from Au, the Oa atoms generated through (NO)2 → N2 O + Oa reactions on the small fraction of the bare TiO2 (110) surface reside around the Au/TiO2 (110) interface perimeter, causing the neutral Au 0 to be cationic Au δ+ states. This is a new approach to manipulate the charge state of Au clusters on oxide surfaces, which may be helpful in regulating the catalytic redox reactions on oxide supported metal systems.