AgInS2 and graphene co-sensitized TiO2 photoanodes for photocathodic protection of Q235 carbon steel under visible light.

The AgInS2 nanoparticles and graphene nanosheets co-sensitized anatase TiO2 nanotube array films were fabricated by a combination of hydrothermal reaction and electrochemical anodization method on titanium sheets. The results showed that the co-sensitization of AgInS2 nanoparticles and graphene nanosheets extended the photo response of TiO2 nanotubes into the visible light region, and improved the photogenerated charge separation and transfer capability. The photocurrent density of the AgInS2/graphene/TiO2 composites (about 4.0 mA cm-2) was 20 times that of bare TiO2 (only 0.2 mA cm-2) under visible light illumination. The potential negative shift value of AgInS2/graphene/TiO2 composites was up to 0.68 V vs. SCE. The AgInS2/graphene/TiO2 composites can provide Q235 carbon steel with highly efficient photocathodic protection under visible light illumination.