Micro-beam XAFS reveals in-situ 3D exsolution of transition metal nanoparticles in accelerating hydrogen separation

<p>Perovskite-based membranes for hydrogen separation have garnered significant attention due to their exceptional capability in efficiently segregating and refining hydrogen. A successful strategy for enhancing the electronic conductivity and catalytic properties of perovskite-based membranes involves anchoring transition metal particles onto carriers composed of perovskite oxides at elevated temperatures. This study involved doping Fe, Co, and Ni elements into the B-site of the BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ perovskite structure. We effectively demonstrated the exsolution of transition metal elements by combining X-ray absorption fine structure (XAFS) spectroscopy and electron microscopy. Furthermore, micro-beam XAFS analysis reveals that the exsolution of transition metals occurs not only at the surface but also within the bulk phase. This highlights the capability of micro-beam XAFS technique in elucidating changes in valence states of elements within bulk regions. Consequently, we have extended the concept of "nanoparticles for electronic conduction and catalysis" from two-dimensional surfaces to three-dimensional bulk phase structures for the first time.</p>