Fig. 2: Evidence for the electronic communications between active sites on the metallic particles.
From: Electronic communications between active sites on individual metallic nanoparticles in catalysis
a CO conversions as a function of temperature over Rhmet/Al2O3 and Rhnon/Al2O3. b Average Ea values with the error bars of CO oxidation over Rhmet/Al2O3 and Rhnon/Al2O3. c O2-TPD profiles of Rhmet/Al2O3 and Rhnon/Al2O3 after O2 saturation adsorption at 50 oC. DO2 represents the desorption amount of O2. The red shade stands for the low-temperature desorption peak of O2 from Rhmet/Al2O3. d Intensity contours of in situ DRIFT spectra of Rhnon/Al2O3. The bands at ~2090 and 2018 cm-1 are assigned to symmetric (vs) and asymmetric (vas) stretching vibration modes of the adsorbed CO molecules on the edge Rh atoms, respectively. The band appearing at ~2116 cm−1 is due to O2−-Rh2+-CO species. Inset: adsorption model on individual Rh atom, and the purple, black, and red balls represent Rh, C, and O atoms, respectively. e CO-TPD profiles of Rhmet/Al2O3 after CO saturation adsorption at 50 oC. DCO represents the desorption amount of CO. Inset: a Wulff model of one Rh nanoparticle. The gold, purple, and green balls represent Rh atoms at vertex sites, edge sites, and on the nanofacets, respectively. f, Intensity contours of in situ DRIFT spectra of Rhmet/Al2O3. g Excess electronic charge of CO (δQCO) and the oxidation state (n+) of Rh (Rhn+) as a function of square adsorbed CO vibration frequency (ν2). These data are taken from the refs. 33,37. h CO DRIFT spectra on Rhmet/Al2O3. The spectrum is collected at 30 oC after CO saturation adsorption in a flow of He, and then the sample is heated to 150 oC in a flow of O2/He to collect the spectrum.
