In this work, we aim to describe the energetics associated with the formation of ammonia from N2 interacting with doped hydroxylated rutile TiO2(110) surfaces with the vacant O2c site, following the reaction N2 + 3H2O → 2NH3 + 3/2O2. The water molecules interact with the surface, creating exposed Ti-OH groups that can transfer hydrogen to the adsorbed N2 molecule. Two metal dopants are evaluated: Mo and Ta. For both metals, calculations show a dramatic decrease in the energy of most intermediates during the entire mechanism, leading to more favorable reaction mechanisms. Nonetheless, it is worth noting that when the Ti6c site of the vacant site is doped with either Mo or Ta, there is a stronger effect on the energetics than doping on the exposed Ti5c sites. The effect of increasing the concentration of metal dopants on the vacant site was also investigated. In this case, calculations indicate that a higher percentage of the dopant on the surface results in a more substantial decrease in the energy of most intermediates, suggesting that increasing the dopant content could be beneficial for the catalytic process.
Núñez-Zarur et al. (Tue,) studied this question.