Scanning tunneling microscopic and Auger electron spectroscopic characterization of a model catalyst: rhodium on titania(001)

Adsorption-Induced Structural Changes of Rh Supported by TiO2(110)-(1×2): An STM Study

“…The Rh coverage is expressed in monolayer equivalent (ML) which corresponds to 1.6 × 10 15 atom/cm 2 . The detailed calibration procedure was described in (42,43). High-purity gases of H 2 , CO, CO 2 , and NO were introduced into the transfer chamber for gas exposure.…”

Atomic scale characterization and surface chemistry of metal modified titanate nanotubes and nanowires

“…Rh clusters of controlled size can be prepared by physical vapor deposition (PVD) [192,306,307] and using Rh organometallic precursors [274,308] on TiO 2 (110) as well. However, STM [306,309], XPS and LEIS [192] experiments revealed that depending on the original cluster size and the evaporation temperature, the agglomeration of Rh nanoparticles can be significant even below 500 K on that surface. The relatively small cluster sizes obtained on titanate nanowires and nanotubes may indicate that the metal diffusion on these nanobjects is limited compared to that on well-ordered titania.…”

Growth of Rh nanoclusters on TiO2(1 1 0): XPS and LEIS studies

“…For this estimation the following assumptions were made: (1) the fraction of the surface covered by rhodium corresponded to the relative decrease in the titanium peak area with respect to the titanium intensity obtained for the clean oxide surface; (2) the clusters have ellipsoidal shape with circular footprint; (3) all clusters have the same diameter; (4) the aspect ratio was assumed to be 1/3, based on previous STM results [5,6]. Cluster diameters estimated this way for cluster formation at room temperature were 0.9 and 3.1 nm at 0.15 and 1.4 ML of rhodium, respectively, in reasonable agreement with previous STM studies on TiO 2 (0 0 1) [5] and TiO 2 (1 1 0)-(1 Â 2) [6]. At the same metal coverages, lowering the evaporation temperature to 160 K led to a decrease in cluster size to 0.6 and 2.3 nm, respectively.…”

“…According to STM studies, the growth mode of Rh follows the Volmer-Weber mechanism on TiO 2 (0 0 1) [5] and also on the reconstructed TiO 2 (1 1 0)-(1 Â 2) surface [6]: at room temperature three-dimensional (3D) clusters grow even at submonolayer coverages. On the non-reconstructed TiO 2 (1 1 0), the growth mode of other group VIIIA metals, such as platinum [7] and palladium [8,9] was found to be Volmer-Weber like, too, though for Pd 2D clusters were identified at very low coverages ($0.01 ML) [9].…”