Chemical identification of point defects and adsorbates on a metal oxide surface by atomic force microscopy

Lauritsen JV, Foster AS, Olesen GH, et al. Chemical identification of point defects and adsorbates on a metal oxide surface by atomic force microscopy. Nanotechnology. 2006;17(14):3436-3441.Atomic force microscopy in the non-contact mode (nc-AFM) can provide atom-resolved images of the surface of, in principle, any material independent of its conductivity. Due to the complex mechanisms involved in the contrast formation in nc-AFM imaging, it is, however, far from trivial to identify individual surface atoms or adsorbates from AFM images. In this work, we successfully demonstrate how to extract detailed information about defects and the chemical identity of adsorbates on a metal oxide surface from nc-AFM images. We make use of the observation that the apex of the AFM tip can be altered to expose either a positive or negative tip termination. The complementary set of images recorded with the two tip terminations unambiguously define the ionic sub-lattices and reveal the exact positions of oxygen vacancies and hydroxyl (OH) defects on a TiO2 surface. Chemical specificity is extracted by comparing the characteristic contrast patterns of the defects with results from comprehensive AFM simulations. Our methodology of analysis is generally applicable and may be pivotal for uncovering surface defects and adsorbates on other transition metal oxides designed for heterogeneous catalysis, photo-electrolysis or biocompatibility

Concepts in syngas manufacture

This book provides a general overview of syngas technologies as well as an in-depth analysis of the steam reforming process. Syngas is a mixture of hydrogen and carbon oxides which can be made from hydrocarbons, coal and biomass. It is an important intermediate in the chemical industry for manufacture of ammonia, methanol and other petrochemicals as well as hydrogen for refineries and fuel cells. Syngas is playing a growing role in the energy sector, because it can be converted into a number of important energy carriers and fuels. Syngas catalysis creates new options and flexibility in the co