The photochemical identification of two chemisorption states for molecular oxygen on TiO2(110)

We report the first experimental observation of two chemisorption states for molecular oxygen on a TiO2(110) surface containing anion vacancy sites. The first molecular species can be photoactivated to oxidize coadsorbed CO to CO2 (α channel) and undergoes slow photodesorption. The second molecular oxygen species only undergoes fast photodesorption (β channel). Conversion from α-O2, to β-O2 occurs upon heating the surface to above 200 K.