Chemisorbed Oxygen Species over the (110) Face of SnO2

The electronic states of chemisorbed oxygen species on the (110) face of SnO₂ and their variations caused by heat treatments and/or O₂ exposure have been investigated. The reactivities of the chemisorbed oxygen species for methane oxidations were also examined.Four different chemisorbed oxygen species (O₂ ^2-, O_2-, O^-, O_b) were observed, in addition to the lattice oxygen (O^2-), on the surface of the stabilized (110) surface of SnO₂ after O₂ exposure. The O_b species was assumed to be the bridging oxygen at the topmost layer of the SnO₂ (110) surface having no neighboring oxygen vacancies. The electronic state of O_b was converted to O^- upon CH₄ exposure at 473 K by coupling with newly produced vacancies at the bridging site of the SnO₂ (110) surface.