A review on modification research of nitrogen (carbon) based composite coatings on the surface of fuel cell metallic bipolar plates

In recent years, nitrogen (carbon) based composite coatings with high corrosion resistance, high conductivity and excellent water management ability have become a hot topic in the field of hydrogen energy and fuel cells, especially their protective behavior against metal bipolar plates under extreme operation conditions. In this paper, the causes of performance degradation and corrosion failure of metal bipolar plate were analyzed. It was found that the microstructure and component distribution of the coating were the main factors affecting its long-term service, and the microstructure of the coating was determined by its deposition process. Then, the effects of deposition parameters (including deposition technology, reaction gas source, component control and matrix material) and service environment (including acid medium, potential fluctuation, multi field coupling conditions) on the corrosion resistance and conductivity of nitrogen (carbon) based composite coatings were systematically discussed. The internal mechanism of the formation of nanocrystalline/amorphous composite structure induced by the introduction of carbon phase was analyzed, and the mechanism of cooperative protection between the "sealing" effect of amorphous phase and conductive network was summarized. Finally, the problems that need to be solved and the future research trend of metal bipolar plate coating as a key modified material are pointed out.