Direct observation of tunable surface structure and reactivity in TiO2 nanopowders

摘要

Surface structure and reactivity is of primary importance in numerous metal oxide applications. Nanopowders can offer advantages both in ease of preparation and in total surface area relative to mono crystals. Although monocrystal surfaces have been characterized using a variety of spectroscopy and microscopy techniques, key features of these surfaces may not translate to nanopowders. In previous studies of alumina and zirconia, we employed nuclear reaction analysis coupled with density functional calculations to show that the atomic and electronic structures of these nanopowder surfaces are distinct from those predicted thermodynamically for macroscopic crystals. Here, we report similar findings for the technologically important metal oxide TiO2. For the first time, we extend our studies to characterize these nanopowders' surface reactivity with oxygen and hydrogen. We observe reactivity indicative of surface states with metallic character distinct from the stoichiometric oxide. This notable behavior holds crucial implications for use of these powders as catalysts and catalyst supports. (C) 2017 Elsevier B.V. All rights reserved.