原子尺度高熵合金纳米晶的表面结构与演变研究

高熵合金纳米催化剂表现出优异的催化活性和显著的耐久性。可控合成具有特定原子排列和表面组成的高熵合金，以及揭示高熵合金纳米催化剂的活性位点仍面临着诸多困难。在原子层次上研究高熵合金表面结构和催化反应之间的构效关系，对高熵合金纳米催化剂的应用具有重要意义。本论文通过液相化学合成的方法，合成了组成可调的高熵合金纳米材料，结合原位透射电镜、原子级三维重构技术以及谱学分析等多种表征手段，系统研究了其相结构和表面几何/电子结构的演变，探究了其表面几何结构和电子结构与催化反应之间的构效关系。
合成了PdFeCoNiCu五元高熵合金，揭示了高熵合金在氢气氛围下的相结构演变过程：体心立方固溶体合金→金属间化合物→面心立方固溶体合金。系统研究了催化剂表面元素分布，几何与电子结构同炔烃半加氢反应的构效关系，发现了高熵合金表面结构会显著影响催化剂表面吸附能，从而达到调节不同种类炔烃半加氢选择性的目的。
通过溶液法合成了组成可调的Pdx-HEAs（x=2–27%）高熵合金纳米晶，研究了由组分诱导产生的表面应力与炔烃半加氢反应之间的构效关系。研究发现，催化剂表面应力导致不同元素之间发生强的电子相互作用，催化活性中心局域电子结构发生显著变化，炔烃半加氢反应的选择性与高熵合金中钯的比例存在着“火山”型趋势。
发展原位电镜方法研究了MnFeCoNiCu五元高熵合金在氧气诱导下的形貌与结构演变，定量分析了其在演变过程中颗粒粒径和壳层厚度随时间或温度的变化关系，深入研究了不同元素在颗粒演变中的迁移过程。
本论文通过对高熵合金催化剂在不同环境下的相结构，尤其是次近表面原子结构的深入研究，明确了其与催化反应之间的构效关系。这些研究结果有望推动高熵合金在催化等领域的进一步应用。

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