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Sulfation occurs when commercial vanadia SCR catalysts are exposed to SO₂-laden coal combustion flue gases. Effects of sulfation on the surface chemistry of vanadia/titania catalysts and SCR activity have not been adequately addressed in previously published work. In this work, in situ FTIR spectroscopy and post situ XPS investigations were performed during vanadia/titania catalyst sulfation under simulated coal combustion flue gas conditions. In situ FTIR spectroscopy combined with XPS analyses on fresh and sulfated TiO₂, 2% and 5% V₂O₅/TiO₂ indicate that sulfate does not form on vanadia sites but rather on titania sites. FTIR spectroscopy data show that sulfation inhibits NO adsorption in the presence of oxygen, but greatly enhances NH₃ adsorption by generating additional Brønsted acid sites while reducing the concentration of Lewis acid sites. Observed increases in the intrinsic NO reduction activity of …