Time-resolved observation of VO/TiO in NH-SCR reveals the equivalence of Brønsted and Lewis acid sites.

The involvement of Lewis and Brønsted acid sites on VO/TiO catalyst in the selective catalytic reduction of NO with NH (NH-SCR) is under debate. Here, a Li doping strategy is applied to selectively block Brønsted sites, which aims to prepare model catalysts with the same V loading but different ratios of the two acid sites. Time-resolved in situ DRIFTS observation demonstrates that the surface ammonia species pre-adsorbed on Lewis and Brønsted sites can participate equally in the reaction. Consideration of site redistribution in the early stages of the transient reaction is key to accurate measurement of the ammonia consumption rate.