Operando HERFD-XAS of La(Mn,Ni)O3 in the CO oxidation: thin films and nanoparticles

Perovskite transition metal oxides (ABO3) are cost-efficient catalysts for CO oxidation reactions. Yet, the effect of thin films and nanoparticles variation on the catalytic mechanism is not understood well. We will investigate the differences between nanoparticles and thin films. In addition, we will study the B-site doping effect in LaMnxNi1-xO3. Using high-energy resolution fluorescence detection (HERFD), we will study HERFD-XAS of La(Mn,Ni)O3 thin films (thickness: 0.4-10 nm) and nanoparticles (size: 30-50 nm) under operando conditions. The HERFD-XAS pre-edges contain 1s3d quadrupole local and 1s4p pre-edge nonlocal transitions, in which the extracted information of spin state and covalency plays a vital role in describing the activity. Moreover, we will measure the 1s2p RIXS that probes the “L2,3 XAS-like” information. We will use DFT and charge transfer multiplet calculations[3-5] in order to simulate the HERFD-XAS and the 1s2p RIXS, respectively.

钙钛矿型过渡金属氧化物（Perovskite transition metal oxides, ABO₃）是用于一氧化碳氧化反应的高性价比催化剂。然而，薄膜与纳米颗粒的结构差异对催化机制的影响尚未得到充分阐明。本研究将探究纳米颗粒与薄膜之间的差异；此外，还将研究LaMnₓNi₁₋ₓO₃中的B位掺杂效应。

本研究将采用高分辨荧光探测（high-energy resolution fluorescence detection, HERFD）技术，在原位工况下对厚度为0.4~10 nm的La(Mn,Ni)O₃薄膜与尺寸为30~50 nm的La(Mn,Ni)O₃纳米颗粒开展HERFD-X射线吸收精细结构谱（HERFD-XAS）表征。HERFD-XAS的预边峰包含1s→3d四极局域跃迁与1s→4p预边非局域跃迁两类过程，从中提取得到的自旋态与共价性信息，对阐释催化活性具有至关重要的作用。此外，本研究还将测试1s2p共振非弹性X射线散射（1s2p RIXS），该技术可探测类L₂,₃ X射线吸收精细结构谱的相关信息。

本研究将分别采用密度泛函理论（DFT）与电荷转移多重态计算（charge transfer multiplet calculations）[3-5]，对HERFD-XAS与1s2p RIXS谱进行模拟。