effect of thickness on photoconversion efficiency of al2tio5/tio2/al2o3 nanocomposite films in water splitting

This report represents an experimental development and investigation of nanostructured aluminum titanate-based composite films with controlled thickness. tio2 is a well-known metal oxide material in photoelectrochemical (pec) water splitting applications. but there are a few studies on optoelectronical properties of aluminum titanate phase. there are several parameters affecting the pec behavior of a thick film-based metal oxide photoanode such as thickness which must be chosen with care due to its effect on the efficiency of the device. in this research, the effect of thickness on the photoelectrochemical performance of al2tio5-based nanocomposite layers as a photoanode was investigated under the sunlight simulator respectively. the al2tio5/tio2/al2o3 nanocomposite was initially synthesized utilizing the citrate sol-gel technique and after the calcination, it was deposited on the fto substrate by the dr. blade method and the thickness of deposited layers was controlled by changing the adhesive tape layers. the photoelectrochemical performance of samples was studied in a standard three-electrode system consisting of the bulk film as the working electrode, the platinum wire as a counter electrode, and finally the silver/silver chloride (ag/agcl) electrode as the reference electrode under the irradiation by simulated sunlight in aqueous 1m naoh electrolyte. it was seen that, the ability of semiconductor film to carry the electronic charges, was affected by the photoanode layer thickness significantly and eventually the slightly different photoelectrochemical behavior was recorded by the samples. according to the results obtained by linear sweep voltammetry (lsv) measurements, it was seen that the achieved photoconversion efficiency of the aluminum titanate-based sample with the optimum film thickness of ∼ 5 μm under the illumination intensity of 100 mw cm-2 was 2 times higher than the resulted value for the tio2 p25 sample in the same situation at 1.23 v vs. rhe, while the observed overpotential for water splitting was as low as 0.2 v at these photoanodes. the diffuse transmittance (dts) spectroscopic technique was employed to investigate the optical properties of specimens. the estimated optical bandgap energy (eg) using the kubelka-munk model in analyzing the dts plots was about 2.9 ev for al2tio5/tio2/al2o3 nanocomposite. the field-emission scanning electron microscopy (fe-sem) images represent the partially spherical morphology of nps in tio2/al2o3/al2tio5 nanocomposite films with particle size distribution ranging from 30 nm to 100 nm while the thickness of the deposited films varied from 2 to 10 nm. the x-ray diffraction analysis exhibited the presence of the tialite phase besides the anatase, rutile, and corundum phases.