| TiO2is often used as a photoanode material in photocathodic protection because of its excellent photoelectric properties,good stability and low cost.However,TiO2has problems such as low utilization of visible light,poor photoelectric conversion performance and inability to provide effective cathodic protection in the dark state.To address the above problems,in this paper,three TiO2nanocomposites including Ag In S2/graphene/TiO2,Sn In4S8/TiO2and Cd In2S4/TiO2were prepared by modifying TiO2using semiconductor compounding and graphene sensitization.The prepared composites were characterized and tested for the electrochemical properties to investigate the photocathodic protection performance and protection mechanism for Q235 carbon steel.The following is the main content of this paper:（1）TiO2nanotubes were prepared by electrochemical anodic oxidation,and then Ag In S2/graphene/TiO2composites were prepared by depositing graphene nanosheets and Ag In S2nanoparticles on the surface of TiO2nanotubes successively by two hydrothermal methods.It was found that the Ag In S2/graphene/TiO2composites could provide stronger photocathodic protection for Q235 carbon steel than pure TiO2.Under visible light irradiation,the open circuit potential of Q235 carbon steel coupled with Ag In S2/graphene/TiO2composites was significantly negatively shifted with a potential drop of 0.68 V vs.SCE,and the photocurrent density of Ag In S2/graphene/TiO2composites was 4.0 m A cm–2,which was 20 times higher than that of pure TiO2.The co-sensitization of Ag In S2nanoparticles and graphene nanosheets enhanced visible light responsiveness of TiO2nanotubes and accelerated the separation and transfer efficiency of photogenerated charges.（2）Sn In4S8/TiO2composites were prepared by depositing Sn In4S8nanosheets on the surface of TiO2nanotubes by the solvent thermal method,and the effect of solvent thermal reaction time on the photocathodic protection effect of the composites was investigated.It was found that under visible light irradiation,the Q235 carbon steel coupled with 6 h Sn In4S8/TiO2composite had the most obvious negative shift of open circuit potential and had the best photocathodic protection performance.The photocurrent density of 6 h Sn In4S8/TiO2composite coupled with the carbon steel could reach 100μA cm–2,which was 8 times higher than that of pure TiO2.This is due to the narrowing of the band gap of the composite after depositing Sn In4S8,which enhanced the response of the composite to visible light and in turn improved its photocathodic protection performance.（3）Cd In2S4/TiO2composites were prepared deposition of flower cluster-like Cd In2S4on the surface of TiO2nanotubes by hydrothermal method,and the effect of the concentration of the hydrothermal precursor solution on the photocathodic protection performance of the composites was investigated.It was found that under visible light irradiation,when the amount of Cd source in the precursor solution was 0.2 mmol,Q235carbon steel coupled with Cd In2S4/TiO2composites showed the most significant negative shift of the open circuit potential with a potential drop of 0.54 V vs.SCE.This is due to the significant negative shift of the Fermi energy level of TiO2after depositing Cd In2S4,which significantly improved the photoelectric conversion efficiency,thus improving its photocathodic protection effect. |
