The Study On Modification Of304Stainless Steel Bipolar Plates Of Proton Exchange Membrane Fuel Cell By Coating SnO₂Film

The bipolar plate, a multi-functional component, is one of the key elements in Proton exchange membrane fuel cell (PEMFC) system, taking up about70～80% in quality and approximately40～50%in cost of PEMFC. The performance quality of the bipolar plate directly affects the output power and service life of the battery. The ideal bipolar plates have good chemical stability, high strength, low cost and excellent corrosion resistance.Stainless steel is one of the most prospective bipolar plate materials because of its good chemical stability, high strength and low cost. However, corrosion and passivation of stainless steel bipolar plates in PEMFC environments is a long-study problem. The metal ion caused by corrosion can produce pollution for membrane and catalyst, and reduce the performance quality of the fuel cell. Passivation can make bipolar plate produce a larger interface contact resistance, and lead to reduce the performance of fuel cell. Coating process is an effective method to solve the problem, has been adopted to protect the stainless steel bipolar plates. Currently, the key reseach point is improving the conductivity and corrosion resistance of the bipolar plate.In order to improve the corrosion resistance of304stainless steel bipolar plate in PEMFC environment and reduce the interface contact resistance, 304SS were modified by coating SnO2film with combing sol-gel dip-coating with alcohol thermal method in the study. And process of the surface modification, composition of film, microstructure, corrosion resistance and electrical conductivity, etc were further researched. The results show that performance of SnO2film is mainly depended by dipping tiras times, alcohol thermal reaction temperature and reaction time. Among them, dipping tiras2times, reaction at180℃for3h is the optimum one. To further reduce the contact resistance of304SS, Sb-SnO2film was used to modified304SS, the results show that Sb-SnO2film coated304SS have a quite corrosion resistance with SnO2film coated304SS, but have a smaller interface contact resistance. In simulated PEMFC environment, the current density of SnO2film modified304SS and Sb-SnO2film modified304SS decreased by about2orders of magnitude compared to that of bare304SS. The interface contact resistance of304SS, SnO2film modified304SS and Sb-SnO2film modified304SS is733mΩ·cm2,288.4mΩ·cm2and74.4mΩ·cm2at3MPa compaction forces, and the ICR of Sb-SnO2film modified304SS is14.9mΩ·cm2at1.5MPa compaction forces.In the study, we have modified304stainless steel bipolar plates by a new method, combining the sol-gel dipping coating method and alcohol thermal method. The results obtained presently have checked this modification is feasible, and has practical applications. In the future, we will research this modification furtherly so that achieving the commercial purpose, we will try our best to make this modification has a a significant role in PEMFC...