The low temperature proton conductivity in nanostructured ceria (NC) is crucial in determining electrochemistry and transport phenomena in a number of applications such as catalytic devices and sensors. However, a range of operational conditions is inaccessible by classical electrochemical techniques. In this report, we use a combination of sample design and novel and well-established characterization methods to study the effects of surface roughness, grain size and crystallographic orientation on the electrochemical reactivity and proton conductivity of NC thin films from 25 °C to 200 °C, as a function of humidity and temperature. It is found that surface morphology determines the water splitting rate and proton conductivity at 25 °C and wet conditions, where protons are mainly generated and transported within surface physisorbed water layers. However, at higher temperature (i.e., ≥125 °C) and dry conditions, when physisorbed water evaporates, grain size and crystallographic orientation become significant factors. Specifically, the proton generation rate is negatively correlated with the grain size, whereas proton diffusivity is facilitated by surface 111} planes and additional conduction pathways offered by cracks and open pores connected to the surface.
, Strelcov, E.
and Bassiri-Gharb, N.
Effects of Microstructure on Electrochemical Reactivity and Conductivity in Nanostructured Ceria Thin Films, Journal of the American Ceramic Society, [online], https://doi.org/10.1111/jace.15183, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=923019
(Accessed June 2, 2023)