The Research On Durability And Cell Reversal For PEM Fuel Cells

Proton exchange membrane fuel cells(PEM fuel cell)have entered the precommercial stage since 2015,but durability,cost,and performance are still three major obstacles to its further development.In terms of durability,the current life of fuel cells has not yet reached the commercial use requirements,and durability is still a hot and complicated issue.In our study,the theory of polarization curve fitting was studied to investigate the durability of single PEM fuel cells and stacks;meanwhile electrochemical and structural analysis methods are conducted to study the durability of single cell membrane electrodes.Moreover,we also investigate the influence of cell reversal on durability of fuel cells.Conclusions can be reached that:1.A reasonable polarization curve fitting formula was given.Based on this formula,the overpotential,ohmic overpotential,and mass transfer overpotential can be separately analyzed.2.Furthermore,polarization curve fitting method was used to study the durability ofthe single cell under high back pressure and the short stack working in urban drive cycles.It was found that under these two conditions,the increase of mass transport overpotential were both the major cause of performance degradation.3.The study also found that after a 1600-hour durability test,there had a significantdrop in performance for the short stack,and the performance of the first unit cell decreased most significantly.Moreover,the open circuit voltage(OCV)of the stack had a significant drop(about 22 m V).This may be due to the high proportion of idle duty in the operating conditions,which accelerates the degradation of the proton exchange membrane,thereby reducing the open circuit voltage(OCV).4.We used a single cell to simulate the cell reversal phenomenon caused by the lack ofhydrogen in the stack.The study has found that:(1)The performance deteriorated significantly due to cell reversal.Typically,theoutput voltage of the cell was significantly reduced at the same current density,and the internal resistance of the cell was significantly increased;(2)Carbon corrosion is the main contributor to the decay of performance after cellreversal,which the rate of carbon corrosion reaction is extremely dependent on the potential,and the lower the termination voltage is,the greater the damage to the cell is.(3)The addition of the water electrolysis catalyst(OER)Ir O2 to the anode catalystlayer can significantly extend the water electrolysis platform time.This is of extremely important practical value.(4)Unfortunately,the stability of Ir O2 does not seem to be reliable,and the waterelectrolysis platform time is not significantly longer than that without Ir O2 addition in the second cell reversal experiment.