Novel ZnO/BiOI nanorod photoanode with interface p-n heterojunction and excellent photoelectric conversion efficiency for photocathodic protection of stainless steel

Bismuth oxyhalide nanoheterojunctions with high photovoltaic conversion efficiency by constructing internal electric field have received extensive attention for photocathode protection (PCP) applications. In this work, BiOI/ZnO nanorod composites (BiOI/ZnO NRs) were synthesized by spin coating and hydrothermal method. The BiOI nanoparticles were found uniformly anchored on the surface of hexagonal wurtzite ZnO nanorods. Morphology and Mott Schottky plots analysis confirm the structure of the p-n heterojunctions at the interface of BiOI and ZnO. Loading of BiOI on the ZnO surface results in the negative shift of the Fermi level of ZnO. The BiOI/ZnO NRs expanded the absorption region of solar light and constructed an internal electric field in p-n heterojunction, which more efficiently accelerated the migration of electrons, inhibited the carrier’s recombination and improved the photoelectric conversion efficiency of BiOI/ZnO. The Open circuit potential (OCP) of BiOI/ZnO NRs photoanode coupled with the 304 stainless steel negatively shifted to −0.757 mV (vs.SCE), and it could protect stainless steel steadily in 4000 s intermittent illumination, showing the high stability of BiOI/ZnO photoanode. The synergistic effects of p-n heterojunction enable BiOI/ZnO NRs photoanode to exhibit an excellent photocathode protection performance.