Hydrogen on In2O3: Reducibility, Bonding, Defect Formation, and Reactivity

The adsorption, bonding, defect formation, and reactivity of hydrogen on different In2O3 powder samples were studied by a combination of volumetric adsorption, thermal desorption, diffraction, and spectroscopic techniques. Surface reduction was observed in dry hydrogen up to 400 K, followed by reduction of surface-near regions. Above 500 K hulk reduction, along with the formation of metallic In, sets in. Raman spectra indicate a considerable reordering of the In2O3 structure in this temperature regime. Despite their TPD proven presence, the related adsorbed H-containing species were not detectable by Fourier transform infrared spectroscopy and/or Raman spectroscopy, in strong contrast to related experiments on beta-Ga2O3. Hydrogen-induced oxygen vacancies were found to be easily replenished by traces of water in the gas feed.