Location of deuterium sites at operating temperature from neutron diffraction of BaIn_0.6Ti_0.2Yb_0.2O_2.6−n(OH)_2n, an electrolyte for proton-solid oxide fuel cells

Abstract

A fundamental understanding of the doping effect on the hydration mechanism and related proton diffusion pathways are keys to the progress of Proton-Solid Oxide Fuel Cell (H(+)-SOFC) technologies. Here, we elucidate the possible interplay between the crystal structure upon hydration and the conductivity properties in a promising perovskite type H(+)-SOFC electrolyte, BaIn0.6Yb0.2Ti0.2O2.6-n(OH)2n. Thermal X-ray and neutron diffractions, neutron time-of-flight scattering along with thermal gravimetric analysis reveal the structural features of BaIn0.6Ti0.2Yb0.2O2.6-n(OH)2n at fuel cell operating temperatures. Between 400-600 °C, BaIn0.6Yb0.2Ti0.2O2.6-n(OD)2n (n < 0.042) remains in a disordered perovskite structure with high anisotropies in the form of oblate spheroids for oxygen. At 400 °C, the presence of oxygen and proton static disorder is clearly established. Yet, the insertion of mobile protons in 24k sites does not induce long-range structural distortion while facilitating both inter- and intra-octahedral proton transfers via quasi-linear O-DO bonds, strong hydrogen bonding, and octahedral tilting. This experimental evidence reveals that the co-doping approach on Ba2In2O5 enhances greatly protonic conductivity levels by enabling a continuous proton diffusion pathway through BaIn0.6Yb0.2Ti0.2O2.6-n(OH)2n. These new insights into the doping effect on the proton-transfer mechanism offer new perspectives for the development of H(+)-SOFC electrolyte materials.

Assessing Substitution Effects on Surface Chemistry by in Situ Ambient Pressure X-ray Photoelectron Spectroscopy on Perovskite Thin Films, BaCexZr0.9–xY0.1O2.95 (x = 0; 0.2; 0.9)

“…Encouraging results toward establishing the interplay between surface oxide chemistry, proton conduction, and degradation mechanisms have been reported. ,, However, because of low concentration of protons, surface gas sensitivity, and high operating temperatures, the understanding of the surface processes at relevant conditions remains limited. Available knowledge relies mostly on a combination of ex situ surface [X-ray photoelectron spectroscopy (XPS), low-energy ion scattering, electron energy loss spectroscopy, scanning electron microscopy] ,,− and in situ bulk [X-ray diffraction (XRD), neutron powder diffraction, Raman] , techniques at low temperature and computational studies. − Because of these shortcomings, these studies provide limited information on surface and bulk states at the same time in operating conditions.…”

Photocatalytic CO2 reduction by Cr-substituted Ba2(In2-Cr )O5·(H2O) (0.04 ≤ x ≤ 0.60)

“…Ba 2 In 2 O 5 has drawn increasing research interest regarding fast oxide ion and proton conduction due to its unique crystal structure [1][2][3][4][5][6]. Partial cationic and/or anionic substitution in Ba 2 In 2 O 5 brings marked changes in crystal structure, defect structure, and electronic structure resulting in a number of materials properties, which are interesting for various technical applications [2,[7][8][9][10][11][12][13][14][15][16][17][18][19]. For example, gallium or zirconium substituted Ba 2 In 2 O 5 for solid oxide fuel cells (SOFC) with an intermediate operating temperature range of 823 -1023 K was a research focus in recent years [13,[20][21][22].…”