Seed-assisted hydrothermal synthesis of aligned single-crystalline anatase nanorods on FTO: synthesis and application
Anatase TiO2 nanorod arrays (NRAs) are difficult to grow on transparent conductive fluorine-doped tin oxide (FTO) substrates via hydrothermal synthesis. Published hydrothermal products are either rutile NRAs or anatase nanorods dispersions. In this study, single-crystalline anatase NRAs have been grown on FTO by hydrothermal synthesis in tetramethylammonium solution (TMAOH). The introduction of anatase seed layer on FTO before growth plays a key role. Experimental parameters such as growth time, reaction temperature and reactant concentration were investigated to control the morphology of the nanorods. X-ray diffraction reveals that the prepared nanorods are well crystallized anatase. The enhanced (0 0 4) peak in XRD patterns and SEM images indicates the nanorods grow vertically aligned on FTO. HRTEM and SAED patterns confirm that a single nanorod is approximately 50 nm in diameter and is single-crystalline. A growth mechanism controlled by a seed decomposition-growth process has been proposed. Furthermore, photocatalytic properties and dye-sensitized solar cells performances of the synthesized NRAs were measured. Variations in cell-performances resulting from varying the thickness of anatase NRAs were studied. The power conversion efficiency (PCE) of prepared anatase NRAs photoanode is higher than that of the P25 photoanode with the similar thickness. A PCE of 2.1% was obtained with only 2.25 µm thick NRAs.