Enhancing photocathodic protection of Q235 carbon steel by co-sensitizing TiO2 nanotubes with CdIn2S4 nanogranules and WO3 nanoplates

In order to improve the photocathodic protection (PCP) performance of TiO2 and its continuous protection ability in the dark, we designed and prepared CdIn2S4/WO3/TiO2 (C/W/T) photoanodes through sequentially depositing WO3 nanoplates (NPs) and CdIn2S4 nanogranules (NGs) on TiO2 nanotubes (NTs) by simple hydrothermal method. The effect of hydrothermal time on the PCP performances of C/W/T for Q235 carbon steel (CS) was studied. The PCP performance of C/W/T was compared with that of pure TiO2, CdIn2S4/TiO2 (C/T) and WO3/TiO2 (W/T). When the hydrothermal time for preparing WO3 NPS and CdIn2S4 NGs was both 6 h, the prepared C/W/T possessed the optimal PCP performance. The photogenerated potential drop of C/W/T could reach 490 mV vs. SCE. The C/W/T exhibited higher photocurrent density (633 μA·cm−2) and lower charge transfer resistance (11.34 Ω·cm2) than bare TiO2, C/T and W/T. The electron storage capacity of C/W/T was 2.88 times that of C/T, which may be attributed to the electronic storage properties of WO3 NPs. In addition, C/W/T can provide continuous protection for Q235 CS for up to 10 h in the dark. This work provides a new idea for designing energy storage photoanode materials with good PCP properties. [Display omitted] •The optimal hydrothermal time of preparing WO3 NPs and CdIn2S4 NGs was both 6 h.•C/W/T showed better PCP for Q235 CS than C/T, W/T, and TiO2.•C/W/T had higher electron storage and continuous protection capacity than C/T.•DFT calculations proved the formation of an intrinsic electric field in the C/W/T.