Triple conducting perovskite Ba0.95La0.05Fe0.8Zn0.2O3?δ as oxygen electrode for reversible protonic ceramic cells

摘要

? 2022 Hydrogen Energy Publications LLCReversible protonic ceramic cells (R-PCCs) have drawn much attention as energy conversion devices. However, the performance of R-PCCs is limited by the lack of highly active oxygen electrodes under operating conditions. Herein, crystal structure, oxygen non-stoichiometry, and conductivity of a triple-conducting perovskite Ba0.95La0.05Fe0.8Zn0.2O3?δ (BLFZ) are investigated. High oxygen vacancy concentration of BLFZ (δ = 0.575–0.705) is observed at a temperature range of 400–700 °C, as confirmed by combining thermo-gravimetric and iodometric titration results. The electrochemical reaction process of BLFZ-BaZr0.1Ce0.7Y0.1Yb0.1O3?δ (BZCYYb) electrode for symmetrical cells is elucidated by the distribution relaxation time (DRT) analysis. Oxygen dissociation is the rate-limiting step for protonic ceramic fuel cell (PCFC). At 650 °C, a single cell with BLFZ-BZCYYb oxygen electrode demonstrates the current density of 1070 mA cm?2 at 1.5 V in protonic ceramic electrolysis cell (PCEC) mode under wet H2 and 10% H2O-air atmospheres, achieving no apparent degradation of a cycling test for 200 h in dual modes of PCFC and PCEC. This research suggests that the triple-conducting perovskite BLFZ is a promising candidate for R-PCCs electrodes.