Study On Fabrication Method And Structure Optimization Of Membrane Electrode Assembly For PEMFC

Fuel cell is a clean and efficient way of energy utilization.At present,the technology of proton exchange membrane fuel cell(PEMFC)is developing rapidly,but its large-scale commercialization process is facing many challenges.One of them is that the cost of cathode catalyst is high.Considering this issue,this paper studied heteroatom doped non precious metal catalyst and a novel ion-mediated catalytic approach systematically.(1)Here we first build a test platform for PEMFC,optimized and developed the preparation method of membrane electrode assembly(MEA).According to different application situations,Rotary-Spray-Decal method and Catalyst-Film method were invented.Among three methods of fabrication,the peak power density of the MEA prepared by Vacuum-Heating-Spraying method can reach more than 2.0 W cm-2,and the current density can be more than 800 mA cm-2@0.8 V;the peak power density of the MEA prepared by Rotary-Spray-Decal method can be more than 1.4 W cm-2,the peak power density difference of samples is less than 5%in batch preparation,which has excellent repeatability;the developed Catalyst-Film method can quickly prepare MEA without manufacturing equipment.(2)MEA was tested by employee oxygen reduction catalyst synthesized from biomass precursor.The non precious metal nitrogen doped catalyst was prepared by hydrothermal and calcination using black fungus.The distribution of Fe,N,S and P in black fungus materials at the atomic level and the porous structure characteristics of the materials benefit the formation of oxygen reducing active sites and mass transfer.The half wave potential of the catalyst is 0.77 V and 0.91 V in acid and alkaline electrolytes,respectively.The peak power density of the catalyst made MEA can reach 255 mW cm-2 in a single cell test,and it possess a stablility for more than 32 hours.(3)To further reduce the cost of cathode catalyst of fuel cell,the traditional carbon based catalyst material was replaced by non noble metal Fe3+/Fe2+mediated ion,and a MEA of ion-mediated fuel cell was constructed.There are two states of iron ions:oxidation(Fe3+)and reduction(Fe2+,and the transition between them is fast in kinetics.The reduction reaction of Fe3+(0.77 V in equilibrium potential)is employed as the cathode reaction of fuel cell to maintain the full discharge and make it an ion-mediated fuel cell without cathode oxygen reduction catalyst.After optimization,the peak power density of the ion-mediated fuel cell reaches 330-622 mW cm-2,and can run for more than 28 hours in stability.