Interface sites on vanadia-based catalysts are highly active for NO_x removal under realistic conditions

TiO₂-supported V₂O₅ catalysts are commonly used in NO_x reduction with ammonia due to their robust catalytic performance. Over these catalysts, it is generally considered that the active species are mainly derived from the vanadia species rather than the intrinsic structure of V-O-Ti entities, namely the interface sites. To reveal the role of V-O-Ti entities in NH₃-SCR, herein, we prepared TiO₂/V₂O₅ catalysts and demonstrated that V-O-Ti entities were more active for NO_x reduction under wet conditions than the V sites (V=O) working alone. On the V-O-Ti entities, kinetic measurements and first principles calculations revealed that NH₃ activation exhibited a much lower energy barrier than that on V=O sites. Under wet conditions, the V-O-Ti interface significantly inhibited the transformation of V=O to V-OH sites thus benefiting NH₃ activation. Under wet conditions, meanwhile, the migration of NH₄⁺ from Ti site neighboring the V-O-Ti interface to Ti site of the V-O-Ti interface was exothermic; thus, V-O-Ti entities together with neighboring Ti sites could serve as channels linking NH₃ pool and active centers for activation of NH₄⁺. This finding reveals that the V-O-Ti interface sites on V-based catalysts play a crucial role in NO_x removal under realistic conditions, providing a new perspective on NH₃-SCR mechanism.