Sulfidation of Single-Phase Oxide on Copper and as Powder Studied Using Soft X-Ray Spectroscopy
2015 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, no 14, C785-C791 p.Article in journal (Refereed) PublishedText
The high corrosion resistance of copper is a key feature in the design of copper-lined canisters that will be utilized to protect people and the environment from dangers of spent nuclear fuel far into the future. Our present study sheds light on the effects that sulfide ions in otherwise relatively benign anoxic groundwater may have on the copper of the container material. Using soft X-ray spectroscopy, we have studied the chemistry of the transformation of single-phase copper oxide cover layers (cuprite, tenorite, paratacamite) as well as single-phase oxide powders (paratacamite and malachite) when exposed to aqueous sulfide solutions. While X-ray diffraction shows that the main bulk of the oxides are nearly unaffected, Cu L-edge absorption spectroscopy shows that a cover layer of about 100 nm thickness on the metal substrate is transformed from Cu(II)- to Cu(I)-species. By contrast, paratacamite and malachite powders exposed to the same kind of aqueous sulfide solutions show much less transformation to Cu(I)-species. We conclude that the main mechanism for reduction of Cu(II) on copper is the comproportionation reaction between divalent copper ions from the covering oxide and the underlying metallic copper atoms to form monovalent copper ions. By contrast, the absence of metallic copper inhibits this mechanism in the powders.
Place, publisher, year, edition, pages
2015. Vol. 162, no 14, C785-C791 p.
IdentifiersURN: urn:nbn:se:uu:diva-272429DOI: 10.1149/2.0801514jesISI: 000366069300069OAI: oai:DiVA.org:uu-272429DiVA: diva2:894564