The Role of Space Charge at Metal/Oxide Interfaces in Proton Ceramic Electrochemical Cells

Abstract

The contact potential and the resulting charge accumulation or depletion at the electrode/electrolyte interface are investigated for Ni and Cu group metals in contact with the stateof-the-art proton conductor acceptor-doped BaZrO 3 by firstprinciples calculations and thermodynamic modeling. The contact potential depends on the metal's work function and the defect chemical properties of the oxide, rendering it strongly temperature and atmosphere dependent. Above 900 K, most metals yield negative contact potentials and enrichment of protonic charge carriers at the electrode/electrolyte interface, facilitating charge transfer. Below 600 K, the contact potentials vary from positive to negative depending on the metal's work function. As such, higher work function metals lead to a space-charge contribution to the electrode impedance at lower temperatures. The prospects of exploiting charge accumulation (or depletion) characteristics of such interfaces are furthermore discussed with a focus on nanocomposite electrodes and solid-state electrochemical capacitors.

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

“…Later on, Chen et al systematically explored the impact of space charge on hydration kinetics and electrode kinetics at the Pt/BZY interface. They found that the protons generated from the hydrogen oxidation reaction can be depleted at the Pt/BZY interface similar to the proton depletion at the grain boundary, further deteriorating the surface hydration and subsequently the proton migration of BZY. , The aim of this work is to put forward possible solutions for manipulating the surface space charge of BZY by investigating the influence of surface defects on the proton transport properties of BZY. Specifically, the plasma treatment, which is commonly used to modify nanomaterials for the applications of renewable energy in a clean and efficient way, was originally applied in this work to prepare BZY thin films with various surface defects.…”