Cadmium- and indium-doped zinc oxide by combustion synthesis using dopant chloride precursors

Cadmium-doped ZnO was prepared for the first time by combustion synthesis using CdCl₂ as a dopant precursor, with zinc nitrate and urea as the combustion mixture. Unlike previous studies of combustion synthesis of ZnO in the presence of an indium nitrate precursor, which resulted in (ZnO)_mIn₂O₃ (m = 3 or 4) compound formation, In-doped ZnO was prepared by combustion synthesis in this study using an InCl₃ precursor. The doped samples were compared and contrasted with undoped ZnO using scanning electron microscopy, x-ray powder diffraction, energy-dispersive x-ray analyses, and x-ray photoelectron spectroscopy. Diffuse reflectance spectroscopy showed the optical band gap of ZnO to shrink from 3.14 to 3.07 eV and 3.02 eV on Cd and In doping, respectively. Finally, the doped samples showed an improved photoelectrochemical response relative to undoped ZnO over the wavelength range from ∼300 to ∼450 nm.