Abstract Perovskite oxides displaying mixed ionic and electronic conductivity have attracted a lot of interest for application in oxygen separation membranes. Such membranes could be used for a range of processes, including the conversion of natural gas to hydrogen or syngas. A major limitation of these materials is their tendency to segregate into simpler oxides under operating conditions, reacting with sulphur-based species often found in natural gas and leading to irreversible membrane degradation over time. Here we aim to delay or prevent this process by coating La0.6Sr0.4Co0.2Fe0.8O3-δ membranes with Alumina (Al2O3) layers of 1–100 nm thickness by using atomic layer deposition. We show that coatings of about 30 nm have negligible negative effect on O2 transport flux across the membrane and display good flux recovery when H2S is removed from the stream. Coatings thinner than this critical value provide little protection against irreversible poisoning while thicker coatings dramatically decrease overall O2 permeation fluxes. We also show that the irreversible sulphur poisoning under O2 permeation conditions is linked to microstructural and composition changes at the membrane surface caused predominantly by the formation of SrSO4 particles at the perovskite grain boundaries.

中文翻译：

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硫中毒对纳米氧化铝涂层钙钛矿膜微观结构、组成和氧传输性能的影响

摘要 显示混合离子和电子导电性的钙钛矿氧化物在氧分离膜中的应用引起了很多兴趣。这种膜可用于一系列过程，包括将天然气转化为氢气或合成气。这些材料的一个主要限制是它们在操作条件下倾向于分离成更简单的氧化物，与天然气中常见的硫基物质发生反应，并随着时间的推移导致不可逆的膜降解。在这里，我们的目标是通过使用原子层沉积在 La0.6Sr0.4Co0.2Fe0.8O3-δ 膜上涂覆厚度为 1-100 nm 的氧化铝 (Al2O3) 层来延迟或防止该过程。我们表明，约 30 nm 的涂层对 O2 跨膜传输通量的负面影响可以忽略不计，并且当 H2S 从流中去除时显示出良好的通量恢复。比这个临界值更薄的涂层几乎不能防止不可逆中毒，而更厚的涂层会显着降低整体 O2 渗透通量。我们还表明，在 O2 渗透条件下不可逆的硫中毒与膜表面的微观结构和成分变化有关，主要是由钙钛矿晶界处 SrSO4 颗粒的形成引起的。