Effects of pulsed electrodeposition parameters on the properties of zinc oxide thin films to improve the photoelectrochemical and photoelectrodegradation efficiency

Abstract

Zinc oxide (ZnO) thin films were synthesized on ITO glass substrates by electrochemical deposition from a nitrate solution. The deposition potential, bath temperature and annealing temperature were fixed at −1.1 V versus SCE, 80 and 400 °C, respectively. Firstly, we prepared the ZnO thin films by two different electrochemical methods: direct (DE) and pulsed electrodeposition (PE). The results indicate that pulse electrodeposition improves the properties of ZnO thin films compared to direct electrodeposition technique. Secondly, we chose the PE method for the elaboration of ZnO thin films and we varied the time-On (ton) from 7 to 1 s. Deposited ZnO thin films were characterized using XRD, SEM, optical and photocurrent measurement. X-ray diffraction results indicate that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along the (002) plane perpendicular to the substrate. SEM analysis reveals that the electrodeposited nanosheets at time-On of 7 s are only hexagonal. A remarkable change in ZnO morphology from nanosheets to nanosheets/nanorods and decrease in gap energy is observed with the decrease in electrodeposition time-On. After optimization in electrodeposition time (ton), a significant improvement in photocurrent and Methylene Blue (MB) photoelectrocatalytical degradation were observed.