Surface Protonic Conduction on Oxide Ceramics: Mechanism, Materials, and Method for Characterization

Abstract

Surface protonic conduction originates from a common phenomenon of surface adsorption of water, which occurs almost everywhere when the temperature and humidity are properly controlled. Different from the volume transport of protons inside the oxide ceramics, which exhibits an Arrhenius relationship with the temperature and asks for at least 500 °C to activate sufficiently high proton conductivity, the surface protonic conduction exhibits an anti-Arrhenius behavior, enabling to achieve high surface proton conductivity at much lower temperature (e.g., close to room temperature). Therefore, the surface protonic conduction is attracting increasing attention due to its promising application in the areas of low temperature catalysis and solid-state electrochemical devices. This review paper summarizes recent progress on the mechanism, materials, influential factors, and characterization methods of the protonic conduction on the surface of oxide ceramics, and discusses present problems and future perspectives.