Toward understanding and development of the three-dimensional atomic structures of supported metal catalysts.

Understanding of supported metal catalysts, which are indispensable for numerous practical chemical processes including chemical production, environmental purification, and power generation, has deepened alongside advances in analytical techniques. In particular, recent progress in direct atomic-scale and even three-dimensional analysis techniques has revealed that actual structures often differ significantly from conventionally assumed model structures, leading to remarkable catalysis. In this review, our recent studies on supported metal catalysts using such advanced analytical techniques, specifically high-energy-resolution fluorescence-detected X-ray absorption near edge structure (HERFD-XANES) and spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM), are reviewed. First, the complementarity of X-ray absorption fine structure spectroscopy (XAFS) and STEM in characterizing the diverse structures of supported catalysts is described. Representative examples of distinctive catalyst structures and their associated catalytic properties revealed using HERFD-XANES and Cs-STEM are then presented. Finally, the three-dimensional atomic structure of a practical supported metal nanoparticle catalyst, resolved for the first time through the application of atomic-resolution electron tomography, is discussed, and future directions in supported metal catalyst research enabled by 3D structural analysis are explored.