Synthesis, physical and photo-electrochemical properties of Gd2CuO4

Abstract Gadolinium cuprate Gd2CuO4 was synthesized by nitrate route and its physical and electrochemical properties were investigated for the first time. The cuprate was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The Diffuse reflectance infrared Fourier transform (DRIFT) spectrum confirms the characteristic peaks of Gd2CuO4 while the Brunauer-Emmett-Teller (BET) measurement gave a specific surface area of 20.45 m2 g−1. An optical gap of 1.41 eV was obtained from the diffuse reflectance (DR) and the transition is directly allowed. The electrical conductivity indicated semiconducting behavior with activation energy of 0.1 eV that correlates with the formal valence of copper. Indeed, the insertion of oxygen into the layered crystal lattice induces p-conductivity with mixed valences Cu3+/2+ and mechanism conduction by small polaron hopping. The carrier density (1.17 1019 cm−3) and flat potential (Efb = −0.33 VSCE) were determined from the (capacitance−2 – potential) characteristic. The conduction band (−1.64 VSCE), positioned at 3.11 eV below vacuum, is made up of Gd3+: (5d, 6s) hybridized orbital while the valence band (−0.23 VSCE/4.52 eV) derives mostly from Cu2+: 3d orbital.