Sonication-polished anodic TiO2 nanotube array-based photoanode for efficient solar energy conversion

Abstract

In this work, the capping layer atop anodic TiO 2 nanotube arrays (NTAs), which hinders filling of other guest materials and transport of charge carriers, is discerned to be TiO 2 nanotapes. Then, it is completely removed by a novel sonication-polishing (SP) treatment, after which Sb 2 S 3 is subsequently introduced to fill the nanotubes by chemical bath deposition. The morphological, structural, and optical properties of the SP-treated TiO 2 NTAs and TiO 2 NTAs/Sb 2 S 3 heterogeneous structures are characterized systematically. The results indicate that SP treatment opens the tops of nanotubes with diameters of ∼120 nm, which endure a phase conversion from amorphous to anatase after calcination at 450°C; besides, stibnite Sb 2 S 3 with a band gap of ∼1.75 eV inside the TiO 2 networks is formed upon heat treatment at 330°C in Ar, which enhances the absorption in visible light range. The photoelectrochemical (PEC) and photovoltaic properties for the SP-treated TiO 2 NTAs are investigated. Results shows that the photoresponse of TiO 2 NTAs is improved by the SP treatment, and the photocurrent for the TiO 2 NTAs/Sb 2 S 3 electrode is substantially enhanced as compared to the bare TiO 2 one. A high efficiency of 6.28 % is achieved in a TiO 2 NTAs/Sb 2 S 3 PEC cell. In addition, charge recombination in the photoanode of dye-sensitized solar cells (DSSCs) is observed to be greatly retarded by using the SP-treated TiO 2 NTAs as compared to TiO 2 nanoparticles (NPs). Thus, the SP anodic TiO 2 NTAs are promising in applications in various PEC areas such as photocatalysis and sensitized solar cells.

Recent progress in one dimensional TiO2nanomaterials as photoanodes in dye-sensitized solar cells

“…209 It is found that efficient systems can be developed out of a combination of anodization with other synthetic methods for the fabrication of hybrid and multi-layered photoanodes. [210][211][212][213][214][215][216] Another simpler route of TiO 2 nanotube synthesis proposed by Ramakrishnan and co-workers involved the hydrothermal treatment of quasi-crystalline TiO 2 nanoparticles. 217 They were reported to have achieved hydrothermal conditions even without using an autoclave.…”

“…Apart from using individual nanotubes, designs involving nanotube arrays were made by certain research groups. 194,204,[206][207][208]210,[212][213][214][215][218][219][220] For example, a highly ordered array of TiO 2 nanotubes with a length of 360 nm was introduced in 2006 by Mor and co-workers with a PCE of 2.9%. 221 This reduction in PCE is due to the comparatively smaller thickness of the photoelectrode.…”

“…In 2016 Gu et al reported the removal of the capping layer over the TiO 2 nanotubes and subsequent enhancement of charge transport by sonication polishing treatment. 212 This sonication polishing helped the removal of flocculent substances atop TiO 2 nanotube arrays (NTAs) and also smoothened their outer surface. They have obtained an efficiency of 6.28%.…”

Synergistic Enhancement of the Photoelectrochemical Performance of TiO2 Nanorod Arrays through Embedded Plasmon and Surface Carbon Nitride Co-sensitization

“…A key figure of merit is the photocurrent density generated by the photoanode under AM1.5G 1 sun illumination (100 mW cm –2 ). Optimized, nanostructured TiO 2 photoanodes are by themselves able to generate 1.2 mA cm –2 under AM1.5G 1 sun illumination at an applied bias of <0.6 V versus NHE through utilization of ultraviolet and blue photons at high Faradaic efficiencies and internal quantum yields . Consequently, any photoanode based on doped TiO 2 or a heterojunction involving TiO 2 needs to significantly outperform the value of 1.2 mA cm –2 to merit serious consideration.…”