Surface engineering of TiO2@SrTiO3 heterojunction with Ni2S3 for efficient visible-light-driven photoelectrochemical cathodic protection

Photoelectrochemical cathodic protection (PCP) is considered a sustainable strategy against metal corrosion. Present works mainly focus on the photocarrier separation in the bulk and little attention has been paid to the photocarrier separation on the surface, which is also essential to determine the protection effectiveness. Here, a triple-junction of Ni3S2@TiO2/SrTiO3 that can simultaneously enhance the charge separation efficiency both in the bulk and on the surface was developed. Under AM 1.5 G illumination, the open circuit potential achieved ca. − 824 mV vs Ag/AgCl, which was 644 mV and 175 mV negative than the 304 SS and bare TiO2, respectively. Meanwhile, the photoinduced current reached 43 μA cm−2. The electrochemical characterization evidenced that a type II heterojunction band alignment was formed between TiO2 and SrTiO3, enabling the efficient charge separation in the bulk. Importantly, the Ni3S2 was proved to show the strong catalytic performance of oxidizing electrolytes, with the Tafel slope decreasing from 39.7 mV/dec to 33.3 mV/dec, thus resulting in a more superior PCP performance. The sample also shows excellent stability of the chemical composition, morphology, and crystalline structure after the 10 h test. This work represented a revelation of the critical function of the co-catalyst on the photoanode and guided the further design of effective photoanode systems for PCP.