Understanding the Aging Degradation of Doped Barium Cerate Proton Conductor in Ambient Air at Room Temperature

Friday, 31 July 2015: 15:00
Boisdale (Scottish Exhibition and Conference Centre)
N. Yan (University of Amsterdam, University of Alberta), T. Gao, W. Wang, and J. L. Luo (University of Alberta)
As a promising alternative power generation technology, solid oxide fuel cells (SOFC) have been intensively studied during the past several decades [1]. Among all the solid electrolyte candidates, proton conducting materials, e.g., BaCeO3, exhibit relatively high ionic conductivity at intermediate temperature (< 750 oC). Particularly, Zr and Y doped cerate, e.g., BaZr0.1Ce0.7Y0.2O3 (BZCY) was widely reported to have excellent conductivity as well as adequate stability in resisting concentrated CO2 up to 30 % with moisture at elevated temperatures typical for SOFC operation [2,3].

Herein, via using a combinations of various electrochemical measurements together with materials characterization techniques including XRD, TEM, SEM, XPS, TG-MS and FTIR, we firstly report that BZCY was prone to a gradual degradation in ambient air at room temperature with considerably minor CO2 (~0.04%) and humidity (<45% relative humidity). The adsorbed H2O acted as an effective catalyst that promoted the decomposition of BZCY via reaction with CO2, subsequently leading to the formation of BaCO3 nanorods as the major impurity phase, presumably following a microcrucible mechanism. Yttrium (oxy)carbonate and amorphous CeO2 and ZrO2 were also produced. It is also confirmed that the doping elements of Ce and Y caused the degradation of BZCY. During the fuel cells tests, the formed impurities on BZCY significantly hindered the electrocatalytic reactions at the electrolyte/electrode interfaces. We also proposed the regeneration and appropriate storage method of the electrolyte materials.

Figure 1. TEM microscopic analysis of: (left) HAADF-STEM image of degraded BZCY with amorphous mixed oxides microcrucible and BaCO3 nanorods: (right) elemental mapping of Ba, Ce, Zr and Y.

[1]       X. W. Zhou, N. Yan, K. T. Chuang, J. L. Luo, RSC Adv., 4(2014), 118.

[2]       N. Yan, X. Z. Fu, K. T. Chuang, J. L. Luo, J. Power Sources, 254(2014),48.

[3]       L Yang, et. al., Science 326 (2009), 126.