Effect of Surface Defect Engineering on Proton Conductivity\nin Yttrium-Doped Barium Zirconate Thin Films

Abstract

Yttrium-doped\nbarium zirconate (BZY) has been considered as a potential\nelectrolyte candidate for intermediate-to-low temperature protonic\nceramic fuel cell applications. However, the transport properties\nof BZY are often limited by the formation of highly resistive space\ncharge zones at lattice discontinuities, such as lattice defects and\nsurfaces. Unlike lattice defects, how to reduce the space charge effects\nat surfaces remains less explored. In this regard, surface defect\nengineering can be a meaningful way to regulate the proton transport\nof BZY by tailoring the space charge distribution close to the surface.\nHere, the Ar and/or O₂ plasma was used to prepare BZY thin\nfilms with different levels of surface defects. The results of electrochemical\nimpedance spectroscopy and detailed structural characterization suggest\nthat the plasma treatment is effective in improving the proton conductivities\nand lowering the activation energy of BZY thin films through the generation\nof negatively charged barium vacancy defects and the enrichment of\nyttrium dopants on the surface.