Photoelectrochemical Activity of TiO₂/MWCNT Thin-Film Electrodes with Different Film Structures Prepared by Combining Electrophoretic Deposition and Sol–Gel Method (Supporting Information)

Photoelectrodes have attracted significant attention in green hydrogen production via water electrolysis. Among others, titanium oxide (TiO₂) is a representative photoelectrode for the conversion of solar energy in the ultravisible region into electrical and chemical energies. However, the poor solar adsorption of this material and the low anode reaction rate have limited the efficiency of hydrogen production via water electrolysis. In addition, there is an urgent need for more ecofriendly hydrogen production systems. The composite films of TiO₂ and electronically conductive materials with various structures have been investigated to improve the photoelectrochemical activity of TiO₂ by increasing the effective surface area of TiO₂ and electronic conductivity of the films, which suppress the electron–hole pair combination. Herein, TiO₂ and multiwalled carbon nanotube (MWCNT) composite films with various structures are prepared using the sol–gel method and electrophoretic deposition simultaneously, i.e., sol–gel electrophoresis deposition, under different solution conditions. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS) results reveals that additives and the mixing ratio of TiO₂ sol and MWCNT dispersion solution in the electrophoresis bath affect film structure. Thin-film electrodes with different structures show different photoelectrochemical activities. Most as-fabricated TiO₂/MWCNT composite thin-film electrodes outperform pristine TiO₂ thin-film electrodes. TiO₂ deposition on the MWCNT network surface with an antenna-like shape yields the best photoelectrochemical activity, achieving a low film resistance and ∼80 % anatase/rutile ratio.