Effect of the Modification Method of TiO2 Nanotubes with Cu2O on Their Activity in Photoelectrochemical Water Splitting

Electrodes based on TiO₂ nanotube arrays for the photoelectrochemical process of water splitting were modified with Cu₂O, a p-type semiconductor (p-Cu₂O). Cyclic voltammetry (CV) was used for the deposition of p-Cu₂O nanoparticles to achieve a more uniform distribution of the particles over the inner and outer surfaces of TiO₂ nanotubes. The measurements of incident photon-to-current conversion efficiency (IPCE) in the range of 365–660 nm demonstrated that the proposed method significantly enhanced photoactivity in the visible light region compared to the potentiostatic deposition method. The IPCE value was 0.18% at a wavelength of 523 nm, which was 7 and 45 times higher than those for the potentiostatically modified and pristine samples, respectively. Under continuous illumination with visible light at a wavelength of 523 nm and a potential of 0.2 V (Ag/AgCl_(sat.)), a transition from Cu₂O to CuO was observed for 5 h, which was accompanied by a decrease in the photocurrent density.