Rhodium(III) oxide

Rhodium(III) oxide
Identifiers
CAS number 12036-35-0
Properties
Molecular formula Rh2O3
Molar mass 253.8092 g/mol
Appearance dark grey odorless powder
Density 8.20 g/cm3
Melting point

1100°C (decomposes)
Solubility in water insoluble
Solubility insoluble in aqua regia
Structure
Crystal structure hexagonal (corundum)
Hazards
EU classification not listed
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Rhodium(III) oxide (or Rhodium sesquioxide) is the chemical compound with the formula Rh2O3.

Contents

Structure

Rh2O3 has been found in two major forms. The hexagonal form has the corundum structure. It transforms into an orthorhombic structure when heated above 750 °C.[1]

Production

Rhodium oxide can be produced via several routes:

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.[5]

Rhodium oxide films is a transparent, conducting material 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.[3]

Applications

The major application of rhodium oxides is in catalysts, e.g. for the conversion of CO [6] or NO gases.[7]

Safety

Conditions/substances to avoid are: extreme heat, organic solvents, hydrochloric acid, hydrosulfuric acid and ammonia.

See also

References

  1. ^ J. M. D. Coey "The crystal structure of Rh2O3" Acta Cryst. (1970). B26, 1876
  2. ^ A. Wold et al. "The Reaction of Rare Earth Oxides with a High Temperature Form of Rhodium(III) Oxide" Inorg. Chem. 2 (1963) 972
  3. ^ a b S. Y. Kim et al. "Rhodium-oxide-coated indium tin oxide for enhancement of hole injection in organic light emitting diodes" Appl. Phys. Lett. 87 (2005) 072105
  4. ^ R. S. Mulukutla "Synthesis and characterization of rhodium oxide nanoparticles in mesoporous MCM-41" Phys. Chem. Chem. Phys. 1 (1999) 2027
  5. ^ S. Gottesfeld "The Anodic Rhodium Oxide Film: A Two-Color Electrochromic System" J. Electrochem. Soc. 127 (1980) 272
  6. ^ P. R. Watson and G. A. Somorjai "The hydrogenation of carbon monoxide over rhodium oxide surfaces" Journal of Catalysis 72 (1981) 347
  7. ^ R. S. Mulukutla "Characterization of rhodium oxide nanoparticles in MCM-41 and their catalytic performances for NO–CO reactions in excess O2" Applied Catalysis A: 228 (2002) 305