Preparation and nitrobenzene reaction kinetics of microcrystalline tungsten bronze thin films with or without transition metal (silver, titanium, chromium, manganese, iron, cobalt, nickel and copper) coatings

Microcrystalline tungsten bronze (HxWO3 ) thin films are prepared using wet chemical techniques from tungsten oxide thin films. The oxide films are obtained by thermal oxidation of a sputter deposited tungsten metal film on a quartz substrate. X-ray photoelectron and visible spectroscopy results confirm that these films are indistinguishable from conventionally prepared tungsten bronze powders. The use of a quartz support allows the total amount of incorporated hydrogen in the film to be quantified by monitoring the absorbance at 900 nm. Once formed, the reduction kinetics of nitrobenzene and the concomitant oxidation of the tungsten bronze film are studied by measuring the absorption of 900 nm light as a function of time. By measuring the reaction rates on tungsten bronze films of various thicknesses a lower bound of 2 × 10-13 cm2/sec is obtained for the hydrogen diffusion constant within the film. (Abstract shortened by UMI.).