Adsorption of ammonia on vanadium–antimony mixed oxides

We analyzed the adsorption of ammonia (NH3) on the VSbO4(1 1 0) catalyst surface using density functional theory (DFT) calculations. We followed the evolution of the chemical bonds between different atoms of the resulting NH3/VSbO4 system and the changes in the electronic structure of the catalyst. NH3 preferential adsorption geometries were analyzed through the crystal orbital overlap population (COOP) concept and the density of states (DOS) curves. The VSbO4(1 1 0) surface exhibits Lewis and Brønsted acid sites on which the ammonia molecule can interact. On the Lewis acid site, NH3 adsorption resulted in the interaction between the N and a surface V-isolated cation. On Brønsted acid site, N interacted with a surface H coming from the chemical dissociation of water. The COOP analysis indicate that NH3 interaction on the VSbO4(1 1 0) surface is weak. In addition, the DOS curves show more developed electronic interactions for NH3 adsorption on Lewis acid site than over Brønsted acid site.