What is the true nature of conducting proton in perovskite ceramic membrane: hydroxyl ion or interstitial proton ?

摘要

The proton conducting perovskites are widely investigated due to their high potential as electrolyte membranes of fuel cells, water steam electrolysers and CO_2/syngas converters. Our comprehensive spectroscopic (Raman, 1R, neutron), thermogravimetric, elastic and quasi-elastic neutron diffusion as well as conductivity studies performed on Ln/RE- modified zirconate ceramics with controlled densification (90-99% of theoretical density) reveal the important differences between the surface and bulk protonic species. The results clearly show that trivial ization of the protonation process complexity can favorite the adsorption of the surface protonic species (hydroxide, hydrocarbonates, etc), prohibit the incorporation of bulk protons, i.e. species responsible for the proton conduction and confuse the understanding of fundamental aspects concerning the proton conductors such as the true nature of conducting species. Our studies reveal that OH~- ions are located at the surface of poor densified ceramic and the bulk conducting protons exhibit an ionic, free of covalent-bonded nature.