Effect of electrolyte agitation on anodic titanium dioxide (ATO) growth and its photoelectrochemical properties

Nanoporous anodic titanium dioxide (ATO) layers were synthesized at 20 °C by a three-step anodization carried out at the constant voltage of 30 V in the electrolyte based on an ethylene glycol containing fluoride ions. The effect of stirring speed on the growth of anodic TiO2 layers was investigated in the range of 0–500 rpm. It was found that the thickness of grown oxide layer, and consequently, the rate of oxide formation depend directly on the stirring speed. The morphological characterizations – porosity, cell density, cell size, oxide thickness, percentage of defective cells and their arrangement in ATO layers were correlated with different electrolyte stirring speeds. The influence of ultrasound irradiation during ATO formation and extended time of third anodization on photoelectrochemical response of ATO electrodes was studied. Photoelectrochemical properties of received anodic oxide layers were measured in a 0.1 M KNO3 aqueous solution under the applied potentials of 0–1000 mV vs. SCE. The generated photocurrents were studied at the wavelength range of 300–400 nm. The highest values of generated photocurrents were observed at 350 nm. For all studied stirring speeds, photoconversion efficiencies, determined as incident photon-to-current efficiency (IPCE), were calculated.