Improved strontium segregation suppression of lanthanum strontium cobalt oxide cathode via chemical etching and atomic layer deposition

Abstract

This study was conducted to improve the stability of a high-performance cathode, which plays a crucial role in lowering the operating temperature of solid oxide fuel cells (SOFCs) to below 600 C while retaining its performance. Lanthanum strontium cobalt oxide (LSC) is a representative SOFC cathode material used in the intermediate temperature (IT) region (500 C-600 C). When segregation occurs on the cathode surface during high-temperature fabrication, the initial performance degrades to a certain extent, followed by continuous performance degradation. Herein, we aimed to overcome this degradation through surface modification. Accordingly, an ideal LSC surface composition was achieved by removing the segregated Sr through wet chemical etching of the cathode surface. Further, an atomic layer deposition (ALD) process of less than 1 nm thickness was introduced to prevent further Sr separation and minimize performance degradation. The peak power density of the cell with the modified surface (M-LSC) at 550 C was 509 mW cm À2 , whereas that of the cell with bare LSC was 483 mW cm À2 . Based on the 70-h short-term stability test, the bare LSC showed a degradation of 70 mV, while the M-LSC remained stable with no degradation.

A Self-Assembled Multiphasic Thin Film as an Oxygen Electrode for Enhanced Durability in Reversible Solid Oxide Cells

“…Comparison of the power output in SOFC mode (c) or electrolysis current in SOEC mode (d) per critical raw materials mass units of the cell in this work with state-of-the-art cells 33,[61][62][63][64][65][66][67][68][69] .…”

A Self-Assembled Multiphasic Thin Film as an Oxygen Electrode for Enhanced Durability in Reversible Solid Oxide Cells

“…A comparison with cells using PLDdeposited thin films is also reported. 68,69 Similarly, the electrolysis current per unit mass (cf. Figure 6d) is up to 1.5 orders of magnitude higher than that in SoA cells.…”

“…showed LSC stability on a full cell only for 70 h at 550 °C, 68 while Shin et al implemented a 3-μm thick LSC layer on a large-area cell operating for longer time at 500 °C but without proofs of long-term performances in electrolysis mode. 69 At the end of the test, the LSC−SDC layer maintains full density and conformality throughout the whole cross-section with no specific alteration (Figure 5).…”

An Ideal Surface Reveals How Active It Is and Why It Degrades: Atomically Flat SrTi0.5Fe0.5O3-δ Model Thin Film – a Case Study

“…However, without careful control, PLD can also cause surface Sr non-stoichiometry and second-phase particle formation because high temperatures (> 600°C) are required during depositions 29,39,40 . Other strategies, such as etching using acid 14,41 or water 22,32 have also been attempted to remove the excess Sr on the thin lm, and porous bulk samples, respectively. These methods have not yielded well-controlled model systems featuring both stoichiometric compositions and atomic-level atness.…”