First observation of surface protonics on SrZrO 3 perovskite under a H 2 atmosphere.

This is the first direct observation that surface proton hopping occurs on SrZrO ₃ perovskite even under a H ₂ (i.e. dry) atmosphere. Understanding proton conduction mechanisms on ceramic surfaces under a H ₂ atmosphere is necessary to investigate the role of proton hopping on the surface of heterogeneous catalysts in an electric field. In this work, surface protonics was investigated using electrochemical impedance spectroscopy (EIS). To extract the surface proton conduction, two pellets of different relative densities were prepared: a porous sample (R.D. = 60%) and a dense sample (R.D. = 90%). Comparison of conductivities with and without H ₂ revealed that only the porous sample showed a decrease in the apparent activation energy of conductivity by supplying H ₂ . H/D isotope exchange tests revealed that the surface proton is the dominant conductive species over the porous sample with H ₂ supply. Such identification of a dominant conductive carrier facilitates consideration of the role of surface protonics in chemical reactions.