Y. Son, N. Tacconi, K. Rajeshwar
Feb 15, 1993
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26
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Journal
Journal of Electroanalytical Chemistry
Abstract
Abstract The formation of cuprous thiocyanate films on polycrystalline copper electrodes in acidic KSCN solutions was studied at controlled potentials and at open circuit using a combination of voltammetry, chronoamperometry, Raman spectroelectrochemistry and photoelectrochemistry techniques. A restricted potential domain was used to avoid incipient oxide formation at the copper surface. Cyclic photovoltammetry, coupling white light illumination and voltammetric scanning between −0.80 V and −0.20 V (vs. Ag/ AgCl) of the working Cu electrode, showed the formation of a p-type semiconductor film at the Cu surface. Film formation was accompanied by the evolution of a Raman band at 2172 cm−1 in the cyanide stretching region. These observations, coupled with other Raman and IR spectral data, enabled the chemical identification of the photoactive film as α-CuSCN. However, the films formed at open circuit (−0.41 V) manifested another Raman band at 2120 cm−1. This band also appeared and “peaked” in intensity during the electroreduction of α-CuSCN. A mechanism involving (CuSCN)x aggregates is proposed. The evolution of the interphasial chemistry at the Cu electrode surface from adsorbed SCN− to aggregate formation, finally culminating in the α-CuSCN phase, is reminiscent of the “sliding scale” observed by previous authors for the Ag + SCN system. However, this study further shows that this scale is dependent on the film growth history.