Effective diffusivity of protons in high-temperature proton conductors

Abstract

High-temperature proton conductors based on doped cerates and zirconates, as widely discussed by Iwahara et al., can - in principle - be used in fuel cells, hydrogen sensors, humidity sensors, hydrogen extractors etc. The chemical diffusivity in SrCe_0.95Yb_0.05O₃₋ and SrZr_0.95Yb_0.05O₃ was investigated in this work. Using the Hebb-Wagner technique a proton concentration gradient was built up in the sample. By measuring the emf across the sample the temporal decay of the proton concentration gradient was followed from which the chemical diffusivities could be extracted. The diffusion constants obtained are critically compared with those obtained in previous or independent work as presented by Matsunami et al., Kreuer et al., Hempelmann et al., Th. Matzke et al. Good agreement is seen between the sets of data in the temperature range 400–800 °C.