Electrodeposition of polypyrrole coatings doped by benzenesulfonic acid-modified graphene oxide on metallic bipolar plates

Benzenesulfonic acid (BSA)-modified graphene oxide (GO) reinforced polypyrrole (PPY) coatings were electrodeposited on metallic bipolar plates for corrosion protection. The ionization of BSA groups drove the parallel stacking of graphene oxide during the anodic deposition. Meanwhile, the doping effect of BSA groups favored the electro-polymerization of pyrrole and the π-electron delocalization of PPY. The doping level of PPY in the composite coatings increased from 15.6 % to 35.2 % when the concentration of BSA-modified GO (SGO) was increased from 1.5 mg٠mL−1 to 3 mg٠mL−1, while the surface roughness of the coatings decreased from 34.3 nm to 19.3 nm. The corrosion current density under the potentiodynamic polarization test reached 0.18 μA٠cm−2, which was an order of magnitude lower than that of the GO/PPY composite coatings. The interfacial contact resistance of the SGO/PPY coatings was 85 % lower than that of GO/PPY coatings, when the electrical conductivity was increased from 6.72 × 10−3 S٠cm−1 to 13.7 S٠cm−1. The improved performance of composite coatings was attributed to the barrier effect of parallelly stacked graphene sheets, the doping effect of BSA groups grafted on GO, and the two-dimensional template effect of SGO on PPY deposition.