Revised Pourbaix Diagrams for Copper at 25 to 300°C

Abstract

The Pourbaix diagrams (potential-pH diagrams) for copper at 25 to 300°C have been revised. Extrapolation of thermochemical data to elevated temperatures has been performed with the revised model of Helgeson-Kirkham-Flowers, which also allows uncharged aqueous complexes, such as CuOH(aq) and Cu(OH)2(aq), to be handled. Calculated high temperature thermodynamic data have been fitted against experimental data at elevated temperature. The hydrolysis of copper(I) and (II) is included with two and four hydroxide complexes, respectively. The Pourbaix diagrams show that the oxides (Cu20(cr) and CuO(cr)) are stable at 25 to 200°C at 106 mol kg_L of dissolved species, and at 300°C only CuO is stable. The oxides are stable at 25°C at i0-mol kg', but at 100 to 300°C no solid compound is stable.

Electrochemical Study of Bulk and Monolayer Copper in Alkaline Solution

“…However, based on the thermodynamic data provided by Beverskog et al, 9 the formation of Cu(OH) − 2 by reaction 1 seems unlikely as the standard electrochemical potential for the above reaction is much higher compared to the appearance of the shoulder in the cyclic voltammetry. We suspect that the formation of Cu(OH) − 2 is not due to direct oxidation of copper as given in reaction 1, but by oxidation of Cu to Cu 2 O initially (reaction 2) and its subsequent dissolution via the reaction 3.…”

Potential-pH Diagrams for Oxidation-State Control of Nanoparticles Synthesized via Chemical Reduction

“…In this procedure, the equilibrium activities of Cu 2+ aquo ion was set to be 7.5 x 10 -11 considering the following copper species; Cu 2+ , CuO, Cu 2 O, and Cu. Oxyanions of copper, HCuO 2 − and CuO 2 2− , or hydroxyanions of copper, Cu(OH) 3 − and Cu(OH) 4 2− (Beverskog, 1997), are not considered for simplicity. In order to include such ions, one should consider all the additional possible equilibrium relationships.…”

Exploring monovalent copper compounds with oxygen and hydrogen

“…At ambient conditions, the most stable compounds of copper with oxygen and hydrogen are copper(II) oxide CuO (stable) and copper(II) hydroxide CuðOHÞ 2 (metastable) (1,2). Among the compounds of monovalent copper with oxygen and hydrogen, cuprous oxide Cu 2 O is known to be the only stable and therefore best-studied compound (1)(2)(3)(4)(5). Cu 2 O has the cuprite crystal structure (Fig.…”