Physical and photoelectrochemical characterization of CuCrO2 single crystal

CuCrO2 single crystal, elaborated by the flux method, is a narrow-band-gap semiconductor crystallizing in the delafossite structure with an indirect optical transition at 2.12 eV. The relatively longer Cu-Cu is consistent with the semi-conducting behavior. The conductivity in the (001) plans is thermally activated and occurs predominantly by small polaron hopping through mixed-valence states Cu+/2+ in conformity with a classical dielectric behavior. The activation energy (0.05 eV) gave an effective mass of 9 m (o), indicating that the levels in the vicinity of the Fermi level E (f) are strongly localized. The oxide shows an excellent chemical stability over the whole pH range; the semi-logarithmic plot gave an exchange current density of 0.7 mA cm(-2) and a corrosion potential of 0.18 V-/SCE in KOH (0.5 M) electrolyte. The electrochemical study is confined in (001) plans, and reversible oxygen intercalation is evidenced from the cyclic voltammetry. The Mott-Schottky plot (C-2-V) is characteristic of p type conduction and exhibits a linear plot from which a flat band potential of +0.21 V-/SCE and a holes density N (A) of 5.06 x 10(14) cm(-3) were obtained. The photocurrent is due to Cu+: d -> aEuro parts per thousand d transition and the valence band is positioned at 5.34 eV below vacuum.