Copper(I) and Copper(II) Coordination Structure under Hydrothermal Conditions at 325 degrees C: An X-ray Absorption Fine Structure and Molecular Dynamics Study

December 14, 2000

Journal Article

Copper(I) and Copper(II) Coordination Structure under Hydrothermal Conditions at 325 degrees C: An X-ray Absorption Fine Structure and Molecular Dynamics Study

Abstract

X-ray absorption fine structure (XAFS) spectroscopy was used to measure the coordination structure about Cu2+, Cu1+ and Br- in water at temperatures up to 325°C. The hexaaqua Cu2+ species maintains its distorted octahedral structure up to 325°C whereas at higher temperatures, dehydration reactions occur producing CuO. Under reducing conditions, the dibromo Cu1+ species [CuBr2]-, is predominant at 200°C and above for systems having excess Br-. Even for a very high salt concentration of 2.0 m NaBr, only the dibromo Cu1+ species, [CuBr2]-, is observed with no evidence of higher Br- coordination. For this dibromo-species there are no tightly-bound hydration waters in the first shell. In the absence of excess Br-, a monoaqua monobrmo Cu1+ species, [Cu(H2O)Br] is observed.

Revised: January 29, 2001 | Published: December 14, 2000

Citation

Fulton J.L., M.M. Hoffmann, J.G. Darab, B.J. Palmer, and E.A. Stern. 2000. Copper(I) and Copper(II) Coordination Structure under Hydrothermal Conditions at 325 degrees C: An X-ray Absorption Fine Structure and Molecular Dynamics Study. Journal of Physical Chemistry A 104, no. 49:11651-11663. PNNL-SA-33219.