Abstract
Initially reduced ≈ 100 Å diameter Rh metal particles on SiO2 are found by TEM to be dispersed into an amorphous metal film by treatment in 5% NO + 5% CO in He at 260 °C, leaving thin rings around the perimeter of the original particles. Electron diffraction shows that Rh is amorphous while XPS shows that the Rh is approximately zero valent in the dispersed state. Continued heating in this mixture resulted in irreversible volatilization of the Rh even at these low temperatures. Subsequent heating in H2 at 650 °C caused sintering and the reformation of crystalline Rh particles, but with a lower loading than observed initially. Treatment of Rh particles in 5% NO at 260 °C causes Rh particles to shrink in diameter and to form thin shells around their perimeters. The only change observed after treatment in 5% CO alone at 260 °C was slight sintering of adjacent Rh particles.
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This research was sponsored by NSF under Grant CBT-882745 and by a grant from Ford Motor Company.
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Krause, K.R., Schmidt, L.D. Catalytic disruption and volatilization of rhodium particles on silica in NO + CO. Catal Lett 14, 141–148 (1992). https://doi.org/10.1007/BF00765228
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DOI: https://doi.org/10.1007/BF00765228