In situ Raman spectroscopy of H2 interaction with WO3 films

Abstract

It is well known that WO(3) interacts efficiently with H(2) gas in the presence of noble metals (such as Pd, Pt and Au) at elevated temperatures, changing its optical behaviors; and that its crystallinity plays an important role in these interactions. For the first time, we investigated the in situ Raman spectra changes of WO(3) films of different crystal phases, while incorporating Pd catalysts, at elevated temperatures in the presence of H(2). The Pd/WO(3) films were prepared using RF sputtering and subsequently annealed at 300, 400 and 500 °C in air in order to alter the dominant crystal phase. The films were then characterized using SEM, XRD, XPS, and both UV-VIS and Raman spectroscopy. In order to fundamentally study the process, the measurements were conducted when films were interacting with 1% H(2) in synthetic air at elevated sample temperatures (20, 60, 100 and 140 °C). We suggest that the changes of Raman spectra under such conditions to be mainly a function of the crystal phase, transforming from monoclinic to a mix phase of monoclinic and orthorhombic achieved via increasing the annealing temperature. The as-deposited sample consistently shows similar Raman spectra responses at different operating conditions upon H(2) exposure. However, increasing the annealing temperature to 500 °C tunes the optimum H(2) response operating temperature to 60 °C.

Green deposition of Pd nanoparticles on WO3 for optical, electronic and gasochromic hydrogen sensing applications

“…8) in accordance with the previous reports [18][19][20]. When the WO 3 -Pd nanocomposite is exposed to hydrogen gas ambience, the hydrogen gas gets adsorbed on the Pd surface.…”

Inkjet-printed gas sensors: metal decorated WO3 nanoparticles and their gas sensing properties

“…[65][66][67] Both platinum and palladium decorated WO 3 gas sensors were observed to be highly sensitive ($10% per ppm and $1000% per ppm, respectively) and selective towards H 2 . The Pt-decorated sensor illustrated an extremely high $10 4 -fold increase in its conductance when exposed to 640 ppm analyte (Fig.…”

Photocatalytic H2 and O2 evolution over tungsten oxide dispersed on silica

“…4 shows the UV Raman spectra of various WO 3 /SiO 2 , SiO 2 , and reference bulk WO 3 . It has been reported that Raman spectroscopy is an effective measurement in revealing information of supported tungsten oxide catalysts owing to its high sensitivity to the state of tungsten atoms [25]. The very weak band at 490 and 983 cm À1 are assigned to the silica support, and the intensities of these bands decrease upon increasing the tungsten oxide contents.…”