Résumé
The hydrogen production from photo-electrocatalytic water splitting attracts extensive attention as a direct way to convert solar energy into a chemical fuel. Herein, various semiconductor films have been used as photo-anode for water splitting. In particular, the nano-tree design of titanium dioxide -TiO2- films provides sufficient reactive sites on the surface and facilitates the charge and mass transfer for enhanced photocatalytic activity [1]. The presence of PEDOT on the surface of TiO2 is expected to improve the electrons transfer and photo-catalytic behaviour of TiO2 layer by improving the conductivity and the photo-excitons creation (e-/h+) [2]. The main goal of the present work is to process such PEDOT/TiO2 heterojunctions by a dry process strategy, namely oxidative and metalorganic CVD. Pure anatase, dendritic TiO2 films of variable thicknesses were obtained at 500°C by varying the deposition time. Increase of film thickness from 480 to 2500 nm results in morphologies that evolve from dense and angular structures to isolated and nanostructured tree-like columns with a concomitant decrease of the charge transfer resistance (Rct). The PEDOT/TiO2 sample with 1300 nm thick TiO2 shows the highest photocurrent (0.25 mA/cm2 at 1.8 V/RHE) response, a fast photocurrent response under illumination and highly reproducible on-off photocurrent cycles. This photocurrent level is in accordance with literature (0.27 mA/cm2 for boron/nitrogen co-doped TiO2 [3]). The photocurrent value of PEDOT/TiO2 sample with 1300 nm thick TiO2 is approximately 1.8 times higher than that of bare TiO2 film with the same thickness indicating significantly enhancement of the photo-generated electrons and holes due to PEDOT layer. Moreover, the hydrogen yield of the best PEDOT/TiO2 sample is 4.1 µmole.cm-2.h-1 under illumination of the anode at 1.8 V/RHE, which is competitive when compared to our previous study [1] related to photolysis with TiO2 (H2 yield: 0.12 µmole.cm-2.h-1). Coupling with water remediation is in progress.References[1] A. Miquelot et al., Applied Surface Science 2019, 494, 1127-1137.[2] S. Abdelnasser et al., Synthetic Metals 2019, 251, 120-126.[3] L. Yang et al., Materials Chemistry and Physics 2022, 275, 125226.