In(2)S(3)@TiO(2)/In(2)S(3) Z-Scheme Heterojunction with Synergistic Effect for Enhanced Photocathodic Protection of Steel

In this work, a TiO(2)/In(2)S(3) heterojunction film was successfully synthesized using a one-step hydrothermal method and applied in the photocathodic protection (PCP) of 304SS. The octahedral In(2)S(3) and In(2)S(3)@TiO(2) nanoparticles combined and coexisted with each other, with In(2)S(3) quantum dots growing on the surface of TiO(2) to form In(2)S(3)@TiO(2) with a wrapping structure. The composite photoelectrode, which includes TiO(2) with a mixed crystalline phase and In(2)S(3), exhibited significantly enhanced PCP performance for 304SS compared with pure In(2)S(3) and TiO(2). The In(2)S(3)@TiO(2)/In(2)S(3) composites with 0.3 g of P25 titanium dioxide (P25) showed the best protection performance, resulting in a cathodic shift of its OCP coupled with 304SS to −0.664 V(AgCl). The electron transfer tracking results demonstrate that In(2)S(3)@TiO(2)/In(2)S(3) forms a Z-scheme heterojunction structure. The enhanced PCP performance could be attributed to the synergistic effect of the mixed crystalline phase and the Z-scheme heterojunction system. The mixed crystalline phase of TiO(2) provides more electrons, and these electrons are gathered at higher energy potentials in the Z-scheme system. Additionally, the built-in electric field further promotes the more effective electrons transfer from photoelectrode to the protected metals, thus, leading to enhanced photoelectrochemical cathodic protection of 304SS.