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==Structure==
==Structure==
Rh<sub>2</sub>O<sub>3</sub> has been found in two major forms. The hexagonal form has the [[corundum]] structure. It transforms into an [[orthorhombic]] structure when heated above 750&nbsp;°C.<ref>J. M. D. Coey "The crystal structure of Rh2O3" [http://dx.doi.org/10.1107/S0567740870005022 Acta Crystallogr. (1970). B26, 1876]</ref>
Rh<sub>2</sub>O<sub>3</sub> has been found in two major forms. The hexagonal form has the [[corundum]] structure. It transforms into an [[orthorhombic]] structure when heated above 750&nbsp;°C.<ref>J. M. D. Coey "The crystal structure of Rh2O3" [https://dx.doi.org/10.1107/S0567740870005022 Acta Crystallogr. (1970). B26, 1876]</ref>


==Production==
==Production==
Rhodium oxide can be produced via several routes:
Rhodium oxide can be produced via several routes:


* Rh metal powder is fused with [[potassium hydrogen sulfate]]. Adding [[sodium hydroxide]] results in [[hydrate]]d rhodium oxide, which upon heating converts to Rh<sub>2</sub>O<sub>3</sub>.<ref name=wold>A. Wold et al. "The Reaction of Rare Earth Oxides with a High Temperature Form of Rhodium(III) Oxide" [http://dx.doi.org/10.1021/ic50009a023 Inorg. Chem. 2 (1963) 972]</ref>
* Rh metal powder is fused with [[potassium hydrogen sulfate]]. Adding [[sodium hydroxide]] results in [[hydrate]]d rhodium oxide, which upon heating converts to Rh<sub>2</sub>O<sub>3</sub>.<ref name=wold>A. Wold et al. "The Reaction of Rare Earth Oxides with a High Temperature Form of Rhodium(III) Oxide" [https://dx.doi.org/10.1021/ic50009a023 Inorg. Chem. 2 (1963) 972]</ref>
* Rhodium oxide [[thin film]]s can be produced by exposing Rh layer to oxygen plasma.<ref name=apl/>
* Rhodium oxide [[thin film]]s can be produced by exposing Rh layer to oxygen plasma.<ref name=apl/>
* [[Nanoparticle]]s can be produced by the [[hydrothermal synthesis]].<ref>R. S. Mulukutla "Synthesis and characterization of rhodium oxide nanoparticles in
* [[Nanoparticle]]s can be produced by the [[hydrothermal synthesis]].<ref>R. S. Mulukutla "Synthesis and characterization of rhodium oxide nanoparticles in
mesoporous MCM-41" [http://dx.doi.org/10.1039/a900588i Phys. Chem. Chem. Phys. 1 (1999) 2027]</ref>
mesoporous MCM-41" [https://dx.doi.org/10.1039/a900588i Phys. Chem. Chem. Phys. 1 (1999) 2027]</ref>


==Physical properties==
==Physical properties==
Line 57: Line 57:


==Applications==
==Applications==
The major application of rhodium oxides is in [[catalyst]]s (e.g. [[hydroformylation]] reactions,<ref>{{cite journal|last1=Pino|first1=P.|last2=Botteghi|first2=C.|title=Aldehydes from olefins: cyclohexanecarboxaldehyde|journal=Organic Syntheses|date=1977|volume=57|page=11|doi=10.15227/orgsyn.057.0011}}</ref> [[nitrous oxide|N<sub>2</sub>O]] production from [[nitric oxide|NO]],<ref>R. S. Mulukutla "Characterization of rhodium oxide nanoparticles in MCM-41 and their catalytic performances for NO–CO reactions in excess O2" [http://dx.doi.org/10.1016/S0926-860X(01)00992-9 Applied Catalysis A: 228 (2002) 305]</ref> or the [[hydrogenation]] of [[carbon monoxide|CO]]).<ref>P. R. Watson and G. A. Somorjai "The hydrogenation of carbon monoxide over rhodium oxide surfaces" [http://dx.doi.org/10.1016/0021-9517(81)90018-X Journal of Catalysis 72 (1981) 347]</ref>
The major application of rhodium oxides is in [[catalyst]]s (e.g. [[hydroformylation]] reactions,<ref>{{cite journal|last1=Pino|first1=P.|last2=Botteghi|first2=C.|title=Aldehydes from olefins: cyclohexanecarboxaldehyde|journal=Organic Syntheses|date=1977|volume=57|page=11|doi=10.15227/orgsyn.057.0011}}</ref> [[nitrous oxide|N<sub>2</sub>O]] production from [[nitric oxide|NO]],<ref>R. S. Mulukutla "Characterization of rhodium oxide nanoparticles in MCM-41 and their catalytic performances for NO–CO reactions in excess O2" [https://dx.doi.org/10.1016/S0926-860X(01)00992-9 Applied Catalysis A: 228 (2002) 305]</ref> or the [[hydrogenation]] of [[carbon monoxide|CO]]).<ref>P. R. Watson and G. A. Somorjai "The hydrogenation of carbon monoxide over rhodium oxide surfaces" [https://dx.doi.org/10.1016/0021-9517(81)90018-X Journal of Catalysis 72 (1981) 347]</ref>


==Safety==
==Safety==

Revision as of 17:39, 10 September 2017

Rhodium(III) oxide
Rhodium(III) oxide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.666 Edit this at Wikidata
EC Number
  • 234-846-9
  • InChI=1S/3O.2Rh/q3*-2;2*+3
  • [O-2].[O-2].[O-2].[Rh+3].[Rh+3]
Properties
Rh2O3
Molar mass 253.8092 g/mol
Appearance dark grey odorless powder
Density 8.20 g/cm3
Melting point 1,100 °C (2,010 °F; 1,370 K) (decomposes)
insoluble
Solubility insoluble in aqua regia
+104.0·10−6 cm3/mol
Structure
hexagonal (corundum)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Rhodium(III) oxide (or Rhodium sesquioxide) is the chemical compound with the formula Rh2O3.

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 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.[3]

Applications

The major application of rhodium oxides is in catalysts (e.g. hydroformylation reactions,[6] N2O production from NO,[7] or the hydrogenation of CO).[8]

Safety

Conditions/substances to avoid when using Rhodium(III) oxide include: extreme heat,[9] hydrochloric acid, hydrosulfuric acid and ammonia.[10]

See also

References

  1. ^ J. M. D. Coey "The crystal structure of Rh2O3" Acta Crystallogr. (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. ^ Pino, P.; Botteghi, C. (1977). "Aldehydes from olefins: cyclohexanecarboxaldehyde". Organic Syntheses. 57: 11. doi:10.15227/orgsyn.057.0011.
  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
  8. ^ P. R. Watson and G. A. Somorjai "The hydrogenation of carbon monoxide over rhodium oxide surfaces" Journal of Catalysis 72 (1981) 347
  9. ^ David C. Sassani "Solubility and transport of platinum-group elements in supercritical fluids: summary and estimates of thermodynamic properties for ruthenium, rhodium, palladium, and platinum solids, aqueous ions, and complexes to 1000°C and 5 kbar" [1]
  10. ^ Chemistry of the Elements (Second Edition) "26 – Cobalt, Rhodium and Iridium" [2]
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