A g-C3N4/PANI S-scheme heterojunction with face-to-face structure to improve the anticorrosion property on Q235 steel and enhanced mechanism study

In photocatalytic anticorrosion perspective, the migration rate of excited electrons from surface layers to substrate steels restricted the performance of g-C 3 N 4 due to the high resistance between interface of g-C 3 N 4 layers and adhesive layers. Herein, an S-scheme g-C 3 N 4 /polyaniline (PANI) heterojunction with face-to-face structure was established by a secondary calcining method. The as-prepared heterojunctions were applied to protect Q235 carbon steel, and the results showed that the anticorrosion performance of S-scheme g-C 3 N 4 /PANI heterojunction is much higher than that of g-C 3 N 4 and PANI coating layers according to salt spray test. Photocurrent intensity indicated that the optimum amounts of g-C 3 N 4 and PANI were 0.06 and 0.09 mL/cm 2 , which are benefit for the transport of excited electrons due to the optimum thickness of coating layers. Furthermore, the S-scheme g-C 3 N 4 /PANI heterojunction can promote the separation rate of charge carriers and suppress the recombination rate at the same time, which are inferred from photocurrent intensity, electrochemical impedance spectra, super-depth-of-field microscope, and photoluminescence investigation. In the last, the enhanced anticorrosion performance of S-scheme g-C 3 N 4 /PANI heterojunction with face-to-face structure was deduced according to mentioned characterization.