Redox Shuttle To Improve MEA Durability

Durability of Proton exchange membrane fuel cells (PEMFC) is one of the key issues to limiting its commercialization. Studies have shown that the process of start-up and shutdown of fuel cell will produce a high voltage fluctuation (about1.4V), much higher than the dynamic corrosion potential of carbon, and thus resulting in high rate corrosion of carbon supports. The corrosion of carbon support resulting in induce the catalyst layer structure changed, and then the catalytic performance of the membrane electrode (MEA) will be seriously damaged. This paper was inspired by the lithium ion battery using redox shuttle to clamp potential at a safe position during overcharge. We tried to dope the MEA catalyst layer with redox shuttle with appropriate potential to clamping the potential fluctuation caused by the complex working condition of fuel cells to a potential below the dynamic corrosion of carbon, and then improve the durability of fuel cells.There are several models which simulate startup and shutdown working condition of fuel cell, however some of them is a little away from the real working conditions. Both of the characterization of electrochemical performance of redox shuttles and the design and anslysis of working conditions model should be proceeded. Based on the previous research of our group, we studied the electrochemical performance of several redox shuttles, and the MEA performance with o-tolidine doping was tested using designed single cell structure and working condition modulation.The experimental work are as follows:(1) The electrochemical performance of iron phenanthroline (1,10-Phenanthroline iron (Ⅱ) sulfate) and bipyridine ruthenium (Tris (2,2’-bipyridine) ruthenium (Ⅱ) chloride hexahydrate) as redox shuttles in fuel cell is characterized, including redox potential, stability and their influence on catalyst activity. The effect of phenanthroline iron on the catalytic activity is relatively small, and the redox reversibility and equilibrium potential range are in line with the basic requirements of the fuel cell redox shuttle, has and thus it is a promising fuel cell redox shuttle. Bipyridine ruthenium have certain influence on catalyst performance, but the redox potential can meet the range of potential clamping requirements. Linked Ru (bpy) showing a large current peak, indicating a rapid response and clamping for potential fluctuation during complex working conditions of fuel cells.(2) Design a simulation model was designed, and assemble into a single cell with new structure assembled to test its corrosive effects compare the corrosion effect when o-tolidine is presented and absence, respectively. The testing including single cell polarization curves, CV curves and the sectional SEM were done of the MEA to determine whether it has protective effects on the fuel cell. Its corrosive effects are tested. The battery model works well in corrosive and operation simple. Determine the corrosive effects after adding o-tolidine on single cell, including single cell polarization curves, CV curves and the sectional SEM of the MEA to determine whether it has protective effects on the fuel cell. Test results did not show the improvement of for the suppress of the carbon corrosion, indicating o-tolidine doping so in this model it can not improve the corrosion durability of carbon support during the working conditions of startup and shutdown using the modulation.(3) Select a more mature simulation model was selected and a single cell is, and assembled into a single cell to further test confirm the effect of the effect of o-tolidine doping on corrosion. The results show that when the creasing of o-tolidine the corrosive-suppress effect will be improved, however, catalytic performance of MEA will be negatively influenced.