Adsorption of ammonia on vanadium-antimony mixed oxides

► The N atom is oriented toward surface, while interacts using its N(2pz) orbital. ► The main orbital interaction occurs between N and V (for the Lewis acid site), and between N and H4 (for the Brønsted acid site). ► On Lewis acid sites, the surface V atom interacts with the N(2pz) orbital, using its V(3dz2) orbital. ► There is no other N-surface interactions both on Lewis or Brønsted sites and from the point of view of bonding, the NH3 adsorption is weak.