Improvement of photoelectrochemical water splitting performance by electrochemical synthesis of Cu-doped ZnO nanotubes decorated with silver nanoparticles

Cu-doped ZnO nanotube arrays decorated with silver nanoparticles (ZnO NTs: Cu/Ag) were synthesized on fluorine-doped tin oxide (FTO) substrates by electrodeposition technique and used as photoanodes to investigate photoelectrochemical (PEC) water splitting efficiency under visible light irradiation. The prepared photoanodes were characterized by field emission scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction and UV-Visible absorption spectroscopy. Linear sweep voltammetry, electrochemical impedance spectroscopy and Mott-Schottky analysis were used to evaluate PEC efficiency. The ZnO NT: Cu/Ag photoanode exhibits a significant photocurrent density of about180 µA/cm2 at 1.6 V vs. RHE compared to other films. Also, the results show that the charge transfer density increases to 1.03×1022cm-3 and the charge transfer resistance decreases to 17.6 Ω. The improved PEC performance of ZnO NTs: Cu/Ag is attributed to the localized surface plasmon resonance (LSPR) effect of Ag nanoparticles, the ability of Cu to absorb visible light, efficient separation and transfer charge carriers.