Infrared Spectroscopy Investigation of Fe-Promoted Rh Catalysts Supported on Titania and Ceria for CO Hydrogenation

Joseph W. Mageea, Robert M. Palominoa, Michael G. Whitea,b*

a.Department of Chemistry, Stony Brook University, Stony Brook, NY

b.Chemistry Department, Brookhaven National Laboratory, Upton, NY

HR-TEM image of Rh/CeO2prepared via wet impregnation 2

STEM image of Rh/TiO2 prepared via wet impregnation 3


Microstructural characterization by HRTEM was performed at 200 kV in a JEOL 2010F microscope equipped with a field emission source. The point-to-point resolution of the electron microscope was 0.19 nm, and the resolution between lines was 0.14 nm. The magnification was calibrated against a Si standard. Samples were deposited from alcohol suspensions onto holey-carbon Cu grids.

Figure S1: HRTEM

Figure S1shows a HRTEM image of Rh/CeO2. The area enclosed in the white square is shown in the insets of the figure. The inset at the top corresponds to a filtered image obtained from the Fourier Transform image by masking the spots of the ceria crystallite support, which allows to identify the ceria lattice of the ceria nanoparticles oriented along the [110] crystallographic direction. The inset at the bottom corresponds to the raw image after subtraction of the information contained in the spots corresponding to the ceria crystallite support, which allows for highlighting other features not related to the ceria nanoparticle support. In this image, the resulting dark features can be attributed to Rh entities. In particular, the distance between several atomic rows at 2.2 Å corresponds well to the (111) planes of Rh metal. Therefore, Rh appears to be extremely well dispersed over the ceria support, likely as clusters of several atoms only

The Rh/TiO2 catalysts is dispersed into an ethanol suspension, then drop casted onto an ultrathin carbon filmed 3.0 mm Cu TEM grid. High-Angle Annular Dark-Field (HAADF) Scanning Transmission Electron Microscopy (STEM) imaging is performed on a JEOL 2100F high resolution microscope operating at 200 kV accelerating voltage with a 0.19 nm point-to-point resolution. Size distribution measurements are averaged over 60 particles.

Figure S2

Figure S2 shows a STEM image of Rh/TiO2. The inset shows the size distribution of Rh particles. Average particle size was measured to be ~2-2.5nm over 60 particles, but as is seen from the distribution and the STEM image, Rh particle sizes >5nm were also present.