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

Abstract 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 ZnIn2S4/TiO2 nanoflowerbush (NFB) photoelectrode was constructed with sufficient interfacial incorporation based on the ultrafine branched TiO2 nanobush substrate via a facile in situ hydrothermal method. This ZnIn2S4/TiO2 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 ZnIn2S4 vary with different substrates. The pure ZnIn2S4 powder is nanoflower sphere composed of a lot of thin petals; when ZnIn2S4 grow onto the FTO glass, the ZnIn2S4 petals are distributed vertically on the two-dimensional structure; when ZnIn2S4 grow on the three-dimensional ultrafine branched TiO2 nanobush substrate, a ZnIn2S4/TiO2 NFB architecture with ultrafine TiO2 branchlet cores are formed. This ZnIn2S4/TiO2 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 TiO2 and ZnIn2S4, prompting both the widened absorption of solar spectrum and high-efficiency transfer of the photogenerated electron–hole pairs. Importantly, the negative band potential of ZnIn2S4 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.