The selective reduction of NO with NH 3 catalyzed by isolated VO, species grafted onto TiO 2 (anatase) is studied by means of periodic density functional calculations. NH 3 is adsorbed molecularly by the bare support both as a Lewis-bonded complex at (101) 5-fold coordinated Ti sites, and as a H-bonded complex at (001) Ti-OH sites. Analogous interactions are predicted for stable submonolayer VO x species, which provide V 5+ Lewis acid sites and V-OH sites. Neither Ti-OH nor submonolayer V-OH groups act as Brønsted acids toward NH 3. Reaction pathways where both Lewis-bonded and H-bonded NH 3 complexes yield a NH 2NO intermediate are found. In the former case, a (rate-determining) deprotonation step of NH 3 is required, whereas, in the latter, NH 2NO is formed directly through a concerted mechanism. This suggests mat many channels may contribute to the NO reduction process.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry