Rhodium(III) oxide (or Rhodium sesquioxide) is the inorganic compound 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 Potassium bisulfate/ Potassium Sulphate is an inorganic compound with the chemical formula KHSO4 and is the potassium acid salt of sulfuric acid. It is a white, water-soluble solid. Preparation More than 1 million tons were produced in 1985 as t ...

. Adding sodium hydroxide results in hydrated rhodium oxide, which upon heating converts to Rh₂O₃. * Rhodium oxide

thin film A thin film is a layer of material ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...

s can be produced by exposing Rh layer to oxygen plasma. *

Nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 10 ...

s can be produced by the hydrothermal synthesis.

Physical properties

Rhodium oxide films behave as a fast two-color

electrochromic Electrochromism is a phenomenon in which a material displays changes in color or opacity in response to an electrical stimulus. In this way, a smart window made of an electrochromic material can block specific wavelengths of ultraviolet, vis ...

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 Indium tin oxide (ITO) is a ternary composition of indium, tin and oxygen in varying proportions. Depending on the oxygen content, it can be described as either a ceramic or an alloy. Indium tin oxide is typically encountered as an oxygen-saturated ...

(ITO) - the common transparent electrode, but Rh₂O₃ has 0.2 eV lower

work function In solid-state physics, the work function (sometimes spelt workfunction) is the minimum thermodynamic work (i.e., energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface. Here "immediately" ...

than ITO. Consequently, deposition of rhodium oxide on ITO improves the carrier injection from ITO thereby improving the electrical properties of

organic light-emitting diode An organic light-emitting diode (OLED or organic LED), also known as organic electroluminescent (organic EL) diode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light i ...

Catalytic properties

Rhodium oxides are

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

s for

hydroformylation Hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes from alkenes. This chemical reaction entails the net addition of a formyl group (CHO) and a hydrogen atom to a carbon-carbon d ...

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 reduce or saturate organ ...

of CO.

References

{{DEFAULTSORT:Rhodium(Iii) Oxide Transition metal oxides Rhodium(III) compounds Sesquioxides Chromism

Structure

Production

Physical properties

Catalytic properties

See also

References