Synthesis of phase pure high entropy perovskites with unique electrocatalytic and oxygen transport properties

该项目专注于合成相纯、无铬、高熵的钙钛矿，这些钙钛矿有望表现出优异的性能，如提高温度和化学稳定性，改善催化和氧气传输性能。因此，具有高构型熵的化合物在高温下是相纯的，而快速冷却会在室温下产生相纯的假设正在被检验。为此，选择雾化喷雾热解作为合成方法，使其能够快速冷却，从而使在高温下通过熵效应稳定的亚稳态相在室温下也能保留下来。除了冷却外，使用雾化喷雾热解进行整体合成也比其他合成方法更省时。在合成了无铬高熵钙钛矿粉末后，用X射线衍射和扫描电子显微镜对其进行了结构分析。因此，可以通过迭代循环来优化工艺参数和元素组成，直到获得产品的物相纯度，进而确定晶体结构、形貌和颗粒尺寸。由于潜在的环境和安全问题，应从成分中省略铬。如果等摩尔阳离子组成的钙钛矿粉的合成成功，则应改变组成中镍的比例。这可能会导致镍的出溶，这将对粉末的催化性能产生积极的影响。为了对生成的颗粒进行结构分类，除了前面提到的方法外，还使用了透射电子显微镜和电子能量损失谱，从而提供了关于颗粒大小和结构的更准确的信息。然后通过压制和烧结将粉末加工成膜。在迭代循环中调整参数，结合结构分析，应该能够在烧结所需的高温下保持相纯度。研究了膜的导电性和透氧性。此外，还对粉末和膜的电催化性能进行了分析。从而得到了可用于各种多相催化过程的电催化输氧膜。

This project focuses on the synthesis of phase-pure, chromium-free, high-entropy perovskites that are expected to exhibit exceptional properties, such as enhanced temperature and chemical stability and improved catalytic and oxygen transport performances. Therefore, the hypothesis that compounds with high configurational entropy are phase pure at high temperatures and that rapid cooling leads to phase purity at room temperature is being tested. For this reason, nebulized spray pyrolysis is chosen as the synthesis method that enables rapid cooling so that the metastable phase stabilized at high temperatures by entropic effects is also retained at room temperature. In addition to cooling, overall synthesis using nebulized spray pyrolysis is also more time efficient than other synthesis methods. After the chromium-free high-entropy perovskite powders have been synthesized, they are next analysed structurally using X-ray diffraction and scanning electron microscopy. The process parameters and elemental compositions can thus be optimized via iteration loops until phase purity of the product is achieved, for which additionally crystal structure, morphology and particle size are determined. Chromium should be omitted from the composition due to potential environmental and safety issues. If the synthesis of the perovskite powders with an equimolar composition of cations is successful, the nickel proportion of the composition should be varied. This could result in an exsolution of nickel, which would have positive effects on the catalytic properties of the powder. In order to classify the resulting particles structurally, transmission electron microscopy and electron energy-loss spectroscopy are used in addition to the methods already mentioned, which provides more precise information on particle size and structure. The powders are then processed into membranes by pressing and sintering. Iteration loops in which the parameters are adjusted, in combination with structural analysis, should enable the phase purity to be maintained despite the high temperatures required for sintering. The electrical conductivity and oxygen permeation of the membranes are investigated. In addition, the electrocatalytic properties of the powders and the membranes are analyzed. Electrocatalytic oxygen-transporting membranes are thus obtained, which can be used in various heterogeneous catalytic processes.