Synthesis and characterization of ZnO micro- and nanostructures grown from recovered ZnO from spent alkaline batteries

Abstract ZnO powders were obtained via thermal decomposition of Zn 5 (CO 3 ) 2 (OH) 6 precursor, resulting from the ammoniacal leaching of the black mass produced during recycling of spent alkaline batteries. Zn 5 (CO 3 ) 2 (OH) 6 powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and then calcined under oxidizing conditions resulting in ZnO powders. Transmission electron microscopy (TEM), XRD and Raman spectroscopy of the obtained ZnO indicated wurtzite crystal structure with lattice parameter a value of 0.331 nm, in agreement with the reported value. Photoluminescence (PL) measurements in the visible range showed two main bands centred at 3.01 eV (412 nm) and 2.35 eV (527 nm) and the red range PL spectra showed two bands centred at 1.87 eV (660 nm) and 1.63 eV (760 nm). These emission bands are characteristic of ZnO and normally ascribed to intrinsic defects, related to the stoichiometry of the crystal. Several morphological kinds of ZnO micro- and nanostructures such as micro- and nanorods, nanocombs, nanowires and microfibers were grown by the vapor-solid method (VS). Structures were characterized by SEM, energy-dispersive X-ray spectroscopy (EDS), cathodoluminescence (CL) and Raman spectroscopy.