Preparation and performance of graphene-doped indium tin oxide coatings on titanium bipolar plate surface

Abstract

To enhance the corrosion resistance of titanium bipolar plates, indium tin oxide (ITO) coatings doped with varying quantities of graphene were fabricated using the sol-gel method. The coatings' surface morphology and microstructure were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The hydrophobicity of the coatings was evaluated using a contact angle goniometer, and their corrosion resistance in a simulated proton exchange membrane fuel cell (PEMFC) corrosion solution (0.5 mol/L H2SO4 + 2 mg/L HF) was measured using an electrochemical workstation. The findings revealed that increasing graphene doping resulted in a more uniform, smooth, and dense coating surface. The ITO coating primarily consisted of In2O3. However, with graphene doping, diffraction peaks of the InOCl phase appeared, indicating changes in the material's composition and structure. Additionally, the valence peaks of the main elements shifted, reflecting alterations in their chemical states. Graphene doping significantly enhanced the coating's hydrophobicity compared to the undoped ITO coating. The water contact angle of the ITO coating with 0.375 g/L graphene increased from 104° to 126°. Furthermore, this graphene-doped coating demonstrated superior corrosion resistance, with a corrosion current density of 0.06 μA/cm2, representing a decrease by three orders of magnitude compared to the titanium substrate. Additionally, it exhibited the largest capacitive arc radius, indicating enhanced charge transfer resistance and better overall electrochemical stability.