Carbon nitride interlayer-enhanced TiO2/WO3 nanorods with surface oxygen vacancies for durable photocathodic performance on 304 stainless steel in simulated seawater

To achieve a long-term photocathodic protective effect on metals in the marine environment, efficient charge mobility and electron storage are essential. Herein, we develop an oxygen vacancy (VO)-involved TiO2-wrapped WO3 nanorod composite by PPy-derived carbon nitride interlayer (TiO2/CNx/WO3) for the photoelectrochemical cathodic protection of 304SS in 3.5 % NaCl solution. The introduced CNx can serve not only as an electron channel to accelerate carrier migration but also as an efficient reductant to generate VO at the interfaces of TiO2 and WO3 during crystallization. The incorporated VO tunes the electronic structure and produces the mid-gap states, which lower the energy barrier for electron-hole separation. Meanwhile, WO3 nanorods as an electron self-storage pool make the photocathodic protection functional in darkness. Consequently, the as-prepared TiO2/CNx/WO3 photoanode yields a photocurrent density of 18.23 μA·cm−2 and a photoinduced cathodic polarization potential of −306 mV in simulated seawater. Even in the absence of light illustration, it can polarize 304SS to approximately −200 mV and continuously to 300 mV after 12 h. This work will offer a universal strategy for the rational design and fabrication of highly efficient semiconductor composite materials in the field of photocathodic anticorrosion.