Confinement assembly of a novel Nb2O5&ZnIn2S4 photoanode and its highly efficient and sensitive photoelectrochemical cathodic protection performance

Constructing a metal-oxides based type Ⅱ heterojunction owning both controllable topography and well matched energy band remains urgent for photoelectrochemical cathodic protection technology. In this work, we designed a desert flower-like Nb2O5&ZnIn2S4 photoanode via a synergistic confinement assembly strategy (structural confinement and electronic confinement) for in situ photoelectrochemical cathodic protection of carbon steel in marine environments. Metal oxides with spherical morphologies were obtained by tuning the crystal plane orientation and nuclei growth, which defines the structural region for the in situ assembly of ZnIn2S4. Compared with TiO2&ZnIn2S4 system, the Nb2O5&ZnIn2S4 system exhibits stronger photoelectric conversion efficiency and photoelectron reduction ability due to its more matched energy bands. The structural confinement facilitates the exposure of reactive sites, and electronic confinement significantly improves the redox activity of type Ⅱ heterojunction, thereby realizing a high efficiency (protection potential is as low as −0.69 V) and high sensitivity (performance retention rate after 200 cycles is as high as 92%) photoelectrochemical cathodic protection for carbon steel in marine environment (without hole scavenging agent).