Self-healing protective coating with dual reversible bonds triggered by photothermal responsive Co9S8@Bi2S3 hollow core-shell nanofillers

Herein, we develop a novel composite coating with excellent self-healing and anticorrosion properties activated by photothermal responsive hollow core-shell nanofillers. A photothermal heterojunction Co 9 S 8 @Bi 2 S 3 was prepared and integrated into polyurethane containing disulfide bonds. It is found that the heterojunction has enhanced the light absorption capacity and has increased the number and lifetime of photogenerated electron-hole pairs, making more photogenerated charges pass through the heterojunction interface by reducing interface transfer resistance and releasing heat as well. Under 808 nm near-infrared light irradiation, the photothermal effect of Co 9 S 8 @Bi 2 S 3 can trigger the reconstruction of dynamic disulfide bonds and reversible hydrogen bonds simultaneously to heal coating scratches. The surface characterization and electrochemical test results manifest that the coating containing 2 wt% 10 %-Co 9 S 8 @Bi 2 S 3 nanofillers displayed excellent self-healing and anti-corrosive capabilities. The self-healing efficiency of nearly 90 % was achieved after five-time cutting-healing cycles on the coating. The protection performance of the initial immersion stage could be restored by nearly 100 % after five-time self-healing, and the low-frequency impedance modulus was above 10 8  Ω cm 2 even after 60 days of immersion. This work would provide a new tactic for developing multi-cycle self-healing coatings triggered by photothermal effects.