Role of TiO₂ surface hydration on NO oxidation photo-activity

The paper highlights the role of TiO2 surface hydration in the conversion of nitric oxide, NO, under irradiation of UVA light. H2O desorption thermokinetics of TiO2 surface is studied to characterise the state of water on TiO2 and identify criteria for potential thermal dehydration. Hydrated and dehydrated surfaces are then studied for their ability to oxidise gaseous NO and emphasise the overall role of H2Oads and OHads groups and the differences between initial and transient regimes before reaching steady state. A model based on a rapid initial NO reactive photoodsorption is used to interpret the high initial removal of NO which develops in a lower NO conversion transient regime. The development of NO and NO2 profiles as a function of time coupled with the total NOx balance in the gas phase, also offer ways to understand deactivation phenomena at the catalyst surface. (C) 2011 Elsevier B.V. All rights reserved.