Transition metals (Co, Cu) as additives on hydrothermally treated TiO2 for gas sensing

Titania-supported Cu or Co nanoparticles have been prepared with loading of 0.5 wt.% and have been tested for the detection of CO. Characterization with XRD showed that Cu and Co did not change appreciably the titania grain size. However, the anatase-to-rutile phase transformation was promoted. XPS results manifested a conspicuous coating of the additives on the TiO2 surface, and suggested chemical states of values 0 and +2 for Cu at 600 and 800 degrees C respectively, and +2 for Co at both calcination temperatures. The evaluation of the gas sensing properties highlighted an adequate n-type response to CO for the Cu-TiO2 and Co-TiO2 materials calcined at 600 degrees C, while the response of the same materials calcined at 800 degrees C was diminished and exhibited a p-type characteristic, which could be related to the formation of a inversion layer localized in the surface. (c) 2005 Elsevier B.V. All rights reserved.