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

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