Rhodium(III) oxide (or Rhodium sesquioxide) is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula Rh₂ O₃. It is a gray solid that is insoluble in ordinary solvents.

Structure

Rh₂O₃ has been found in two major forms. The hexagonal form adopts the corundum structure. It transforms into an orthorhombic structure when heated above 750 °C.

Production

Rhodium oxide can be produced via several routes: * Treating RhCl₃ with oxygen at high temperatures. * Rh metal powder is fused with potassium hydrogen sulfate. Adding sodium hydroxide results in hydrated rhodium oxide, which upon heating converts to Rh₂O₃. * Rhodium oxide thin films can be produced by exposing Rh layer to oxygen plasma. * Nanoparticles can be produced by the hydrothermal synthesis.

Physical properties

Rhodium oxide films behave as a fast two-color electrochromic system: Reversible yellow ↔ dark green or yellow ↔ brown-purple color changes are obtained in KOH solutions by applying voltage ~1 V. Rhodium oxide films are transparent and conductive, like indium tin oxide (ITO) - the common transparent electrode, but Rh₂O₃ has 0.2 eV lower work function than ITO. Consequently, deposition of rhodium oxide on ITO improves the carrier injection from ITO thereby improving the electrical properties of organic light-emitting diodes.

Catalytic properties

Rhodium oxides are catalysts for hydroformylation of alkenes, N₂O production from NO, and the

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...

of CO.

References

{{Oxides Transition metal oxides Rhodium(III) compounds Sesquioxides Chromism

Structure

Production

Physical properties

Catalytic properties

See also

References