Study On The Performance Of PEMFC In The Operating Mode Of Dead-ended Anode

As a new type of clean energy device,proton exchange membrane fuel cell(PEMFC)has attracted much attention because of its high fuel efficiency,low noise,pollution-free and rapid start-up at room temperature.The dead-ended anode(DEA)is an operating mode of PEMFC.In this mode,the PEMFC system have a simpler structure,smaller in size,lighter in weight,minimal additional power loss,and higher fuel efficiency.Therefore,the PEMFC with DEA has become an optimal choice among the various operating modes of PEMFC.The performance of the PEMFC with DEA is studied in depth,and the mechanism of performance degradation of PEMFC caused by the DEA working mode is explored in this paper,so as to improve the working performance,material durability and fuel utilization efficiency of the PEMFC with DEA.A two-dimensional theoretical model of PEMFC with DEA is established,which is combined with experiments to study the influence of different cathode operating parameters on the working performance of PEMFC with DEA,and to reveal the mechanism of the change in the working performance of PEMFC with DEA caused by different cathode operating parameters.It is found that the DEA working time of PEMFC with DEA is prolonged with the decrease of cathode gas humidification and working pressure,and the effect of changing the gas stoichiometric ratio of cathode on the transient working time of PEMFC with DEA is not significant.Compared with the cathode stoichiometric ratio,the effect of changing the humidification and working pressure of the cathode on the transient voltage of the PEMFC with DEA is more significant.Based on the visualized fuel cell and printed circuit board(PCB)segmented measurement,the influence mechanism of the flow channel orientation in gravity environment on the performance of PEMFC with DEA is investigated,and the evolution and cumulative distribution of water in the anode flow channel are revealed.It is found that the orientation of the flow channel under the action of gravity has significant effect on the cumulative content and distribution of water in the anode flow channel,as well as the uniformity of local current density distribution.In addition,the time of opening the anode outlet for purging also has a significant effect on the local current density distribution of the PEMFC with DEA.The effects of different cathode gas supply modes on the performance of PEMFC with DEA are studied.It is found that compared with the same flow supply reaction gas,the reverse flow supply reaction gas could significantly prolong the DEA working time of the PEMFC with DEA,and eliminate the accumulation of water in the anode flow channel.However,the uniformity of the local current density distribution of the PEMFC with DEA could not be improved by using the reverse flow supply reaction gas.Furthermore,the DEA working time of the PEMFC with DEA is significantly prolonged with the decrease of the humidification time of the cathode reaction gas,whether the reaction gas is supplied by the same flow or by the reverse flow.A new method for the preparation of hydrophobic carbon paper by ultrasonic dispersion is proposed,which provides an efficient and convenient basis for the preparation of hydrophobic carbon paper with different PTFE content.The effect of carbon paper with different PTFE content on the working performance of PEMFC with DEA is investigated,and the general rule of the influence of carbon paper with different PTFE content on the performance of PEMFC with DEA is revealed.It is found that the DEA working time of the PEMFC with DEA mainly shows a decreasing trend with the increase of the PTFE content in the anode carbon paper when the PTFE content in the cathode carbon paper is equal,and the DEA working time of the PEMFC with DEA increases with the increase of the PTFE content in the cathode carbon paper when the bare carbon paper is used in the anode.Moreover,the PTFE content in the carbon paper also has an important effect on the uniformity of the local current density distribution of the PEMFC with DEA.The effects of different anode outlet purge frequencies on the performance of PEMFC with DEA are studied,and the performance degradation mechanism of PEMFC in the DEA operating mode is revealed.It is found that with the increase of the purge frequency of the anode outlet,the degradation of the working performance of the PEMFC becomes more and more serious.The attenuation of the electrochemical active area of the catalyst layer is determined by electrochemical characterization method,which is the main cause of the degradation of the PEMFC performance.According to the characterization results after the accelerated experimental tests,it is shown that the catalyst layer of the cathode and anode of the membrane electrode assembly(MEA)is obviously thinned,which led to the serious attenuation of the electrochemical active area of the catalyst layer of cathode and anode.Which also indicates that the periodic gas purge action at the anode outlet of the PEMFC with DEA would indeed affect the performance of the PEMFC,and lead to irreversible degradation of the working performance of PEMFC with DEA.