Non-Stoichiometry in Oxide Thin Films Operating Under Anodic Conditions: A Chemical Capacitance Study of the Praseodymium-Cerium Oxide System

摘要

Pr_xCe_(1-x)O_(2-δ) can potentially serve as both cathode and anode in solid oxide fuel cells given that it exhibits significant mixed ionic-electronic conductivity (MIEC) under both cathodic and anodic conditions. While MIEC depends strongly on oxygen nonstoichiometry 5, there have been few ways to extract this information reliably and in situ, particularly for thin films. In this work, this is achieved by analysis of chemical capacitance values extracted from impedance spectroscopy data obtained on electrochemical cells of the form Pr_(0.1)Ce_(0.9)O_(2-δ)/Y_(0.16)Zr_(0.84)O_(1.92) / Pr_(0.1)Ce_(0.9)O_(2-δ) operating at temperatures between 500 to 700 °C and over the pO_2 range of 10~(-31)-10~(-16) atm. The enthalpy of reduction for the Pr_(0.1)Ce_(0.9)O_(2-δ) thin film is derived.