CdSe/ZnO Composite via Galvanic Displacement Followed by Photocathodic Deposition: Hybrid Electrosynthesis and Characterization

This study focuses on the preparation of CdSe/ZnO composite by combining three techniques, namely, electrodeposition, galvanic displacement, and photocathodic deposition. Thus ZnO nanowire array was first electrodeposited on Sn-doped indium oxide (ITO) or polycrystalline Au electrode; then, the metallic zinc codeposited with ZnO was galvanically replaced with Se from a Se4+ containing aqueous solution, which resulted in a Se/ZnO composite nanowire array. Finally, the Se component in Se/ZnO was photoelectrochemically reduced to Se2– by irradiation. The Se species reacted with Cd2+ in the electrolyte phase to produce CdSe/ZnO composite in situ. The deposition details were elucidated in situ by a combination of stripping voltammetry and electrochemical quartz crystal microgravimetry. The composite sample was subsequently characterized by scanning electron microscopy, X-ray powder diffraction, energy-dispersive X-ray analyses, and photoelectrochemical (PEC) measurements. The PEC experiments revealed that the electrodeposited ZnO nanowire array behaved as an n-type semiconductor, which changed to p-type after deposition of Se. The ZnO/CdSe composite showed anodic photocurrents upon light illumination, again consistent with the n-type nature of both the composite components.