Abstract
The activation mechanism of NH₃ in the selective catalytic reduction of NO by NH₃ on a V₂O₇H₄ cluster was investigated using a complete active space self-consistent field method. Because of the easy bond dissociation of NH₄⁺ adsorbed on Brønsted acid sites of the V₂O₅ configuration, the radical species NH₃⁺ can occur with an activation energy of only 26.7 kcal/mol. The highly active intermediate NH₃⁺ is stabilized by forming a very strong hydrogen bond of approximately 29.2 kcal/mol to the vanadyl oxygen. This stabilization mechanism is very similar to the low-barrier hydrogen bond in the transition state, or in an unstable intermediate state, which has been reported for some enzymatic reactions.