Boosted photoinduced cathodic protection performance of ZnIn2S4/TiO2 nanoflowerbush with efficient photoelectric conversion in NaCl solution

Boosting the photoinduced cathodic protection (CP) for metals in NaCl solution is crucial for achieving the application of photoelectrochemical conversion in marine corrosion protection. An environmentally friendly three-dimensional ZnIn 2 S 4 /TiO 2 nanoflowerbush (NFB) photoelectrode was constructed with sufficient interfacial incorporation based on the ultrafine branched TiO 2 nanobush substrate via a facile in situ hydrothermal method . This ZnIn 2 S 4 /TiO 2 NFB nanoheterojunction composite behaves excellent photoinduced CP performance for metallic materials. This is owing to the optimized construction of photoelectrode with relatively negative band potential, wide solar spectrum response, effective generation and collection of photoinduced electrons. The morphology, distribution and performance of ZnIn 2 S 4 vary with different substrates. The pure ZnIn 2 S 4 powder is nanoflower sphere composed of a lot of thin petals; when ZnIn 2 S 4 grow onto the FTO glass, the ZnIn 2 S 4 petals are distributed vertically on the two-dimensional structure; when ZnIn 2 S 4 grow on the three-dimensional ultrafine branched TiO 2 nanobush substrate, a ZnIn 2 S 4 /TiO 2 NFB architecture with ultrafine TiO 2 branchlet cores are formed. This ZnIn 2 S 4 /TiO 2 NFB photoelectrode can achieve efficient photoinduced CP performance for pure copper and low alloy steels with different negative self-corrosion potentials, such as Cu (−0.18 V), E40 (−0.45 V), Q345 (−0.55 V) and Q235 carbon steel (−0.65 V) under simulated sunlight irradiation in NaCl solution without additional hole scavengers, and the photoinduced CP current densities reach as high as 170, 72, 63 and 44   μA   cm −2 , respectively. The high-efficiency photoinduced CP performance is closely related to the band structure gradient matching between the TiO 2 and ZnIn 2 S 4 , prompting both the widened absorption of solar spectrum and high-efficiency transfer of the photogenerated electron–hole pairs. Importantly, the negative band potential of ZnIn 2 S 4 endues a lower surface work function which benefits the electron transport to the under-protected metallic materials to achieve photoinduced CP. This photoelectrode exhibits huge photoinduced CP application potential in marine environments.