Interaction of Zinc Oxide Nanoparticles with Water: Implications for Catalytic Activity

Novel technological applications in catalysis and bactericidal formulation have emerged for Zinc oxide (ZnO) nanoparticles owing to their ability to generate reactive oxygen species by fostering H2O dissociation. Rational improvement of those properties requires a mechanistic understanding of ZnO nanoparticle reactivity, which is currently lacking. Here, we determine the structural and electronic properties of nanometer-sized ZnO, determine the binding energetics of H2O adsorption and compare to an extended macroscopic surface. We show that the electronic density of states of ZnO nanoparticles is size-dependent, exhibiting a decreasing bandgap with the increase of nanoparticle diameter. The electronic states near the Fermi energy dominantly arise from O 2p states, which are spatially localized on “reactive” surface O atoms on the nanoparticle edges that are doubly coordinated. The frontier electronic states localized at the low coordinated atoms, induce a spontaneous dissociation of H2O at the nanoparticl...