Direct observation of space charge induced hydrogen ion insertion in nanoscale anatase TiO2

Abstract

Space charge induced 2H+ densities up to 2H+ (0.17)TiO2 are observed directly using neutron diffraction on two different nanoscale particle sizes of anatase TiO2 immersed in sulfuric acid, and consistent with experimental evidence modelling shows that these ions show rapid self diffusion.

Proton conduction properties of nano-titania modified by sulfuric acid impregnation

“…4 decreases with increasing temperature since P H2O was fixed at 2.3 kPa [11]. It has been reported by Chan et al that the large amount of protons was inserted into TiO 2 bulk when in contact with H 2 SO 4 or CsHSO 4 due to space charge effect, and high proton conduction will occur due to protons inserted at a higher-temperature region [14,15]. In this work, increase in conductivity at high temperature region was not observed.…”

Low temperature proton conduction in bulk nanometric TiO2 prepared by high-pressure field assisted sintering

“…As previously mentioned, similar improved characteristics were also reported in the case of fully covering TiO 2 films, in comparison with zirconia and Ti 2 O 5 films with identical microstructure. Also in this case, the authors could not decide between the possibility that TiO 2 exclusively exhibits solid state proton conductivity, as suggested by other studies 17,27 or that it possesses a better proton conduction within hydrated nanopores. 16 Particularly in the case of proton migration through the solid state (grain boundary), a beneficial effect played by the excellent catalytic properties of anatase toward the breaking of water chemical bonds can have a role and cannot be a priori excluded as a factor contributing to the enhanced proton conductivity of anatase nanomaterials.…”

“…16 Investigation of the hydrogen density and transport inside TiO 2 nanoparticles immersed in sulfuric acid evidenced that H 1 and D 1 ions show rapid self-diffusion inside the anatase structure. 17 On the basis of the results described above, the possibility to investigate proton conduction in polycrystalline dense samples with grains in the low nanometric range appears to be particularly intriguing. Several studies have been devoted to the preparation of polycrystalline bulk anatase samples with grain size in the nanometric range using several different nonconventional sintering approaches, including spark plasma sintering [18][19][20][21] , hot pressing, 22 and two-stage sintering.…”

Defects in Metal Oxide Nanoparticle Powders

“…For TiO 2 nanoparticles immersed in D 2 SO 4 large deuteron intercalation values of up to 0.17 per TiO 2 unit were observed. Supported by ab initio calculations split positions inside the oxygen octahedral were identified as the sites of ion localization [117].…”