Portal de Periódicos da CAPES

Formation and stability of the platinum and rhodium oxides at high oxygen pressures and the structures of Pt3O4, β-PtO2 and RhO2

1968; Elsevier BV; Volume: 16; Issue: 2 Linguagem: Inglês

10.1016/0022-5088(68)90070-2

1878-2728

Olaf Müller, Rustum Roy,

Catalysis and Oxidation Reactions

The systems Pt-O and Rh-O have been investigated at high oxygen pressures (up to 3500 atm) and temperatures ranging from 400 ° to nearly 900 °C. Three platinum oxide phases were found: the hexagonal α-PtO2, already described in the literature, a new phase, β-PtO2 (CaCl2 structure), and Pt3O4 (NaxPt3O4 structure). β-PtO2 andPt3O4 are black, highly insoluble solids, which can be easily synthesized in bulk at high oxygen pressures. The tetragonal PtO phase reported by MooreandPauling was not encountered in this study and neither was the b.c.c. Pt3O4 found by GalloniandRoffo. In the system Rh-O we found (besides the already-known, two Rh2O3 polymorphs) a new RhO2 phase with the rutile structure. RhO2 is a black, easily synthesized solid, which is highly insoluble even in hot aqua regia. "Goldschmidt radii" were derived for Pt4+ and Rh4+ and found to be 0.66 Å and 0.64 Å, respectively.