Effects of various metal additives on the gas sensing performances of TiO2 nanocrystals obtained from hydrothermal treatments

Nanocrystalline titanium dioxide after hydrothermal treatment was loaded singly or doubly with various metals or metal oxides (Au, Ag, Pt, Pd, Cu, Co, Nb, V). Hydrothermally treated TiO2 exhibited enhanced thermal stability: resistance to grain growth and phase transformation. Incorporation of metal additives further decreased the grain size of titania, while the phase transition was generally promoted, except in the case of Au and Pd, which maintained predominant anatase phase at 800 °C. Among the different additives tested, Au was found to be the most attractive promoter for the CO sensing properties. Therefore, studies were extended to several Au concentrations on TiO2 and, in addition, to simultaneous loads of Au and Nb or V. Doubly modified Au– and Nb–TiO2 presented the highest Au content on surface, as inferred from XPS measurements, and exhibited the largest and fastest sensor response to CO at high operating temperatures.