The role of surface stoichiometry in the activity of doped vanadia-based catalysts for the selective catalytic reduction

Mixing dopants into oxide catalysts can improve the catalytic activity, as shown in the dramatic boost of the NH3 selective catalytic reduction (SCR) activity on vanadia catalysts upon doping by tungsten. Thus, the design and optimization of oxide catalysts require a precise understanding of the role of dopants and their influence on catalytic reactions. Here, we employ first-principles calculations to study the influence of selected dopants (Ce, Zr, Nb, Mo, and W) in tungsta-vanadia on the SCR activity in terms of dopant concentration, distribution, and species. We demonstrate how the dopants affect the stoichiometry of the catalyst and thus fine-tune the local electron distribution and polarization in the catalytic layer. In addition, we address the relation between dopant concentration and the population of the active vanadyl configuration on the surface. Finally, we propose the generalized surface stoichiometry of the doped vanadia catalysts as a descriptor for the SCR catalytic activity, which promises to be instrumental in identifying oxide catalysts with improved properties also for other important catalytic reactions.