Obtenção de hidrogênio verde via fotoeletrocatálise utilizando eletrodos de dióxido de titânio sensibilizados com pontos quânticos

Abstract

In this work, photoanodes composed of hierarchical structures of titanium dioxide (TiO2) sensitized with quantum dots (QDs) of bismuth sulfide (Bi2S3) were applied in the photoelectrochemical water splitting reaction. Thin films were produced on a conductive glass substrate through deposition, heat treatment, and formation of compact and mesoporous layers. Initially, a compact layer of TiO2 was deposited by adding a titanium diisopropoxide (TDBA) solution in 1-butanol, followed by heat treatment at 500 °C/60 min. Next, the mesoporous layer was prepared, which in the first experiments was studied depending on the TiO2:EtOH ratio under conditions 1:2, 1:3, 1:4, and 1:5. Based on the evaluation of the photoelectrochemical gains associated with the film thickness and paste concentration, the mesoporous layer was optimized in terms of the number of layers. After receiving the mesoporous layer, the electrode is heat treated at 450 °C/30 min. The photoelectrochemical performance of the electrodes exhibited a dependence on the thickness of the films, reaching an efficiency of 0.34 mA.cm-2 with a thickness of 4.453 ± 0.096 μm after the deposition of 4 layers in a ratio of 1:4, which obtained the best performance. To improve the absorption of TiO2, Bi2S3 quantum dots were applied as sensitizers. After sensitization, carried out by chemical adsorption for 24 h, the electrodes presented a photocurrent density of approximately 1.3 mA.cm-2, approximately 382 % higher than pure TiO2. Optimization of photoelectrochemical performance was achieved by sensitizing mesoporous TiO2 films with nanocrystalline semiconductors, resulting in hydrogen production of 0.12 mL.cm-2 (TiO2) and 3.81 mL.cm-2 (TiO2@Bi2S3).