Influence of the Shape of Deposited Area on Photoelectrochemical Activity of TiO₂–Multiwalled Carbon Nanotube Film Electrode Prepared Via Sol–Gel Electrophoresis Deposition

As environmental concerns have become increasingly pressing, photocatalytic water splitting for hydrogen production has attracted significant attention to reduce carbon dioxide emissions. However, the improvement in photocatalytic activity is still a critical focus. Among various photocatalysts, titanium dioxide (TiO₂) composited with a highly conductive material is promising for hydrogen energy generation.<br/>In our previous study, TiO₂ was successfully composited with highly conductive multiwalled carbon nanotubes (MWCNT) by combining the sol–gel method and electrophoretic deposition (EPD), namely sol–gel EPD, to enhance the photoelectrochemical activity of TiO₂. Recently, we reported the effect of the TiO₂ sol/MWCNT ratio and additives in the bath [1] and the effect of the solvent in the bath [2] on the morphology and composition of the film, crystal structure of TiO₂, and other physicochemical properties influencing the photoelectrochemical activity.<br/>In this study, the effect of the immersion geometry (i.e., triangles and rectangles with identical surface areas) of the ITO substrate during EPD on the photoelectrochemical activities of thin-film electrodes was investigated by focusing on the inner stress of the thin films. As a result, rectangular films with more stress within the film show an increased film thickness, large crystallite size, and clacking in the film, resulting in superior photoelectrochemical activity than the film on the triangular area, which enables energy savings in achieving the same film thickness or volume of H₂emission.<br/>[1] Matsunaga, M.; Yu, Y.; Takahashi, K. Photoelectrochemical activity of TiO₂/MWCNT thin-film electrodes with different film structures prepared by combining electrophoretic deposition and sol–gel method. <i>Electrochemistry</i> <b>2024</b>, <i>92 (4)</i>, 047004. DOI: 10.5796/electrochemistry.24-00014.<br/>[2] Yu, Y.; Matsunaga, M. Fabrication and evaluation of TiO₂/multiwalled carbon nanotube composite thin-film photoelectrodes via sol–gel electrophoretic deposition using mixed solvents. <i>J Appl Electrochem</i><b> 2024</b>. DOI: 10.1007/s10800-024-02173-1.