Structure Matters: Asymmetric CO Oxidation at Rh Steps with Different Atomic Packing
Ikusi/ Ireki
Data
2022-08Egilea
García Martínez, Fernando
Rämisch, Lisa
Ali, Khadiza
Waluyo, Iradwikanari
Castrillo Bodero, Rodrigo
Pfaff, Sebastian
Villar García, Ignacio J.
Walter, Andrew Leigh
Hunt, Adrian
Pérez Dieste, Virginia
Zetterberg, Johan
Lundgren, Edvin
Schiller, Frederik
Journal of the American Chemical Society 144(33) : 15363–15371 (2022)
Laburpena
Curved crystals are a simple but powerful approach to bridge the gap between single crystal surfaces and nanoparticle catalysts, by allowing a rational assessment of the role of active step sites in gas-surface reactions. Using a curved Rh(111) crystal, here, we investigate the effect of A-type (square geometry) and B-type (triangular geometry) atomic packing of steps on the catalytic CO oxidation on Rh at millibar pressures. Imaging the crystal during reaction ignition with laser-induced CO2 fluorescence demonstrates a two-step process, where B-steps ignite at lower temperature than A-steps. Such fundamental dissimilarity is explained in ambient pressure X-ray photoemission (AP-XPS) experiments, which reveal partial CO desorption and oxygen buildup only at B-steps. AP-XPS also proves that A-B step asymmetries extend to the active stage: at A-steps, low-active O-Rh-O trilayers buildup immediately after ignition, while highly active chemisorbed O is the dominant species on B-type steps. We conclude that B-steps are more efficient than A-steps for the CO oxidation.