Carbon nanotube films as current collectors in TiO2 photoanodes

Commercial methods for the production of green hydrogen are based on alkaline or proton exchange membrane (PEM) electrolysis. Several alternatives are being investigated, including photo-electrochemical water splitting. At a laboratory scale, working electrodes are tipically assembled on ITO of FTO transparent conducting films. Those substrates could be substituted by cheaper more abundant materials. Therefore, we fabricated opaque films of carbon nanotubes (CNTs) to be probed as supports for a photo-active semiconductive oxide, namely nanoparticulate TiO2. Aqueous dispersions of single-walled and multi-walled CNTs were prepared by sonication or stirring in a surfactant (SDBS). The inks were utilized to fabricate conducting electrodes by ultrasounds-assisted spraycoating on glass substrates. Nanoparticulate TiO2 (Aeroxide P25) was deposited on the CNT films by spray-coating of isopropanol suspensions. The TiO2/CNT electrodes were tested in a transient photocurrent experiment in 0.1M Na2SO4 at 0.4V vs. Ag/AgCl. A large capacitance contribution was detected because of CNTs. However, it was clearly demonstrated that an anodic photocurrent is generated under irradiation with a solar simulator (~300 mW·cm-2). While the obtained photocurrents were small ( a few µA·cm-2), the way is open to optimize new architectures for PEC hydrogen generation.