ELECTRON-PARAMAGNETIC-RES STUDY OF THE SURFACE REACTIVITY AND REDUCIBILITY UNDER VACUUM OF A RHCL3/SRTIO3 CATALYST PRECURSOR

The effect of oxygen adsorption and uv irradiation on a RhCl//3/SrTiO//3 catalyst precursor previously outgassed at different temperatures has been studied by EPR. The results indicate that the presence of rhodium does not influence substantially the nature of the radical species formed on the support, suggesting a lower degree of metal-oxide electron transfer than in Rh/TiO//2, and show the formation of two types of Rh(II)-dioxygen complexes, whose dependence on the pre-outgassing temperature indicates a stronger stabilization of cationic Rh than on TiO//2, due probably to the more basic character of the SiTiO//3 surface, but a smaller stabilization of isolated Rh(O), which agglormerates easily into metal particles.