A TEM study on the localization of metal particles in cogelled xerogel catalysts

The localization of metal and alloy particles in monometallic Pd/SiO2 and bimetallic Pd–Ag/SiO2 sol–gel catalysts prepared by cogelation was examined by rotating transmission electron microscopy. The analysis of the resulting micrograph series provides a direct proof that the 2-to 3-nm active metal nanoparticles in those catalysts are located inside microporous silica particles or aggregates. Such localization has long been suspected but with, up to now, no direct evidence.