Observation of Potential-Induced Hydration on the Surface of Ceramic Proton Conductors Using In Situ Near-Ambient Pressure X-ray Photoelectron Spectroscopy

Abstract

Interactions of ceramic proton conductors with the environment underoperating conditions play an essential role on material properties and device performance. Itremains unclear how the chemical environment of material, as modulated by the operatingcondition, affects the proton conductivity. Combining near-ambient pressure X-rayphotoelectron spectroscopy and impedance spectroscopy, we investigate the chemicalenvironment changes of oxygen and the conductivity of BaZr0.9Y0.1O3-delta under operatingcondition. Changes in O 1s core level spectra indicate that adding water vapor pressureincreases both hydroxyl groups and active proton sites at undercoordinated oxygen. Applyingexternal potential further promotes this hydration effect, in particular, by increasing the amountof undercoordinated oxygen. The enhanced hydration is accompanied by improved protonconductivity. This work highlights the effects of undercoordinated oxygen for improving theproton conductivity in ceramics.