Preparation and characterization of the semiconductor CuMnO2 by sol-gel route

Nano crystallites of the crednerite CuMnO2 are prepared by sol-gel method with two-step annealing process. The powder heated at 450 degrees C under air flow shows a mixture of CuO, Mn2O3 and CuxMn3-xO4. However, when calcined at 900 degrees C under N-2 atmosphere, the crednerite CuMnO2 with a monoclinic structure (space group: C2/m) is obtained. The Raman spectrum shows a single peak at 679 cm(-1) assigned to A(lg) mode whereas the infrared analysis confirms the linearity of CuO23- units. The optical transition at 1.70 eV, determined from the diffuse reflectance is attributed to the inter-band d-d transition of Cu+ ion. The oxide exhibits semiconducting properties with an activation energy of 0.21 eV. The photo-electrochemical measurement shows p-type conduction due to O2- insertion in the two dimensional lattice. The flat band potential (+0.12 V-SCE), indicates a cationic character of both valence and conduction bands deriving from Cu+: 3d orbital. (C) 2016 Published by Elsevier Ltd.