Marshak Lectureship (2021): Tuning the morphology, charge and activity of nanocatalysts by support doping

Precious metal nanoparticles deposited oxide supports are known to be good catalysts for several commercially important chemical reactions. The catalytic activity of such nanocatalysts is known to be highly sensitive to their morphology and charge. It is known that differently charged metal nanocatalysts are to be preferred for different chemical reactions; it is also generally believed that two-dimensional planar nanoparticles would be better catalysts than three-dimensional ones. Among the various ways that have been suggested to gain control over the nanoparticle morphology and charge, possibly one of the simplest is to dope the oxide support with an electron donor or acceptor. Using density functional theory calculations, we have shown that doping with an electron donor can switch the morphology of small deposited gold nanoparticles from upright or clumped-up shapes to wetting geometries, due to a charge transfer from the dopant atoms to the nanocatalyst. We have identified two possible descriptors for the efficacy of doping; one of these depends on the electronegativities and atomic sizes of the dopant atoms and the cation/anion in the host support. Another descriptor, that correlates well with both the morphology and charge of the nanocatalyst, is the work function of the bare support. Depending upon the type of dopant, one can make the deposited Au nanoparticles positively or negatively charged. We have also investigated the effect of support doping on adsorption energies and activation barriers for simple reactions.