An electrochemical study of copper diffusion in non-stoichiometric copper sulphide |
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Authors: | Th Pauporté J Vedel |
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Institution: | (1) Laboratoire d'électrochimie et de Chimie Analytique, école Nationale Supérieure de Chimie, CNRS-URA 216, 11 rue Pierre et Marie Curie, 75005 Paris, France |
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Abstract: | The diffusion of copper in hexagonal chalcocite (Cu2S) is not very well-known. In this work electrochemical cells with natural polycrystalline chalcocite working electrodes have
been studied by electrochemical impedance spectroscopy (EIS) over a large frequency range at equilibrium potential. To study
this phenomenon between 120 and 160°C a solid electrolyte RbCu4Cl5 has been used. The impedance spectra present two distinct regions. At high frequencies the general shape of the diagram in
the Nyquist plane is a depleted are of a circle. Changes in electrolyte resistance, interfacial capacitance and transfer resistance
have been studied as a function of temperature. At low frequencies, a diffusion impedance is observed attributed to the mobility
of copper vacancies. Diffusion coefficients, with an activation energy of 1.7 eV, have been deduced from the impedance diagrams
(4.7·10−5cm2 s−1 at 130°C). These results are compared with those obtained with orthorhombic chalcocite between 30 and 60 °C by EIS and using
an electrochemical cell with a cupric liquid electrolyte.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 |
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