Design And Comprehensive Optimization Of Proton Exchange Membrane Fuel Cells

Two main categories of proton exchange membrane fuel cells,direct methanol fuel cells and oxyhydrogen fuel cells are fierce competitors in emerging energy devices in their respective fields.Fuel storage of direct methanol fuel cell is convenient,there is no technical or safety threshold for fuel replenishment,and it is suitable for various portable electronic devices.The oxyhydrogen fuel cell is the single lithium battery competitor in the field of automotive power.This paper has improved the design of many common sealing system instability problems in direct methanol fuel cell stack structure.And alleviate or even avoid these problems from the structural mechanism.The fuel cell was fabricated and tested to verify the effectiveness of the design.After solving the fuel cell structure problem,by fitting the parameters of the electrode dynamics control equation to a large number of polarization curve experimental data,a three-dimensional numerical model that was highly consistent with the experimental data was established.The 5-parameter 4-level operation parameter optimization orthogonal experiment was carried out by the 3D numerical model,and the cell performance was enhanced by 10%by using the preferred parameter combination of the orthogonal experiment.A 3135.7 hours long-term degradation test of fuel cells with 166 time of operation was carried out,and various performance loss behavior was monitored by in situ electrochemical method.Fuel cell durability varied a lot of discharge time and stage-failure phenomenon of single cell occurred in the lifetime test.During the sole operation process,continuous lifting pressure operation can realize the improvement of catalyst activity and optimization of mass transfer channel to increase fuel cell durability.The most rapid increase rate of Rohm appears at 55 oC,and lower temperature mainly caused the increase in membrane resistance.Proton recovery method and increasing operational temperature realize the effective reduction of Rohm and recovery fuel cell discharge ability.Along with the continuous discharge of a single cell,cathode "water flooding" phenomenon mainly comes out at a higher temperature,and acts as the main degradation reason,which directly results in a serious concentration polarization and sharp loss of durability.N2 purging worked as an operational method to realize the recovery of performance of fuel cell.The final catalyst deactivation caused the ultimate failure of fuel cell.Therefore,main degradation of fuel cell varies with operation time,and the relationship between operational conditions and durability is helpful to improve the real lifetime of the fuel cell.In order to solve the problem that the stability of the membrane electrode preparation is insufficient,the non-conforming product is harmful and difficult to be detected before the assembly test.The membrane electrode assembly non-destructive testing equipment was designed,and the detection scheme is demonstrated.Three of the 16 batches of the same batch of membrane electrodes were detected 100%in advance and did not have any adverse effect on the performance of the normal membrane electrode.Under the guarantee of membrane electrode nondestructive testing technology,the multi-factor life prediction scheme was studied.Through the resolution of electrochemical activation overpotential,ohmic overpotential and concentration overpotential of polarization curve data,three autonomous changes of life influencing factors were extracted,and life prediction schemes based on these three factors were studied and analyzed.Compared with the traditional average attenuation rate extrapolation method,this scheme can better reflect the hidden electrode dynamics trend in the experimental data.The prediction result for 50%performance loss lifetime is less than 4%compared with the experimental data.