TiO2负载的V2O5催化剂由于其强大的催化性能而通常用于用氨还原NOx。在这些催化剂上,通常认为活性物种主要来自钒物种,而不是V-O-Ti实体的固有结构,即接口站点。为了揭示V-O-Ti实体在NH3-SCR中的作用,在这里,我们制备了TiO2/V2O5催化剂,并证明了V-O-Ti实体在潮湿条件下比单独工作的V位点(V=O)对NOx还原更具活性。在V-O-Ti实体上,动力学测量和第一性原理计算表明,NH3活化表现出比V=O位点低得多的能垒。在潮湿条件下,V-O-Ti界面显着抑制了V=O向V-OH位点的转化,从而有利于NH3活化。在潮湿条件下,同时,NH4+从V-O-Ti界面附近的Ti位点向V-O-Ti界面的Ti位点的迁移是放热的;因此,V-O-Ti实体与相邻的Ti位点一起可以用作连接NH3池和活化NH4的活性中心的通道。这一发现表明,在实际条件下,V基催化剂上的V-O-Ti界面位点在NOx去除中起着至关重要的作用。为NH3-SCR机理提供了新的视角。
TiO2-supported V2O5 catalysts are commonly used in NOx 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 NOx 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 NOx removal under realistic conditions, providing a new perspective on NH3-SCR mechanism.