Preparation of PbS and CdS cosensitized graphene/TiO2 nanosheets for photoelectrochemical protection of 304 stainless steels

TiO2 nanosheets with highly reactive {0 0 1} facet exposed were prepared and modified with graphene and PbS/CdS quantum dots (GT/PbS/CdS) by a facile two-step hydrothermal method and a sonication-assisted successive ionic layer adsorption and reaction (S-SILAR) process. The GT/PbS/CdS composites exhibit superior photoelectrochemical performance for the enhanced photocurrent density, corrosion potential and corrosion morphology of the connected 304 stainless steel. The light harvesting feature of the composites is improved for the narrow band gap quantum dots deposition and the interband transition of the photoexcited electrons in the heterostructure. The p-n junction electric field formed in the TiO2/PbS interface and the CdS/PbS interface promotes the separation of electrons and holes in the hybrid semiconductor. The increased inner electric field intensity in the semiconductor/electrolyte interface and the Schottky barrier in the semiconductor/metal interface boost the photogenerated electron transfer from the semiconductor to the connected metal, leading to enhancement of the photoelectrochemical protection performance. Furthermore, the electrochemical oxidation and reduction of the PbS is expected to prolong the protection in dark.