| Proton exchange membrane fuel cell（PEMFC）has broad application prospects due to their high energy conversion efficiency and specific power.However,the commercialization of PEMFC is severely limited by issues such as high cost and short lifespan.The membrane electrode assembly（MEA）is the core component of PEMFC where electrochemical reactions occur and energy conversion takes place.The thirdgeneration ordered MEA can obtain higher discharge performance and longer durability in fuel cells by designing an ordered structure at the interface of the proton exchange membrane/catalyst layer/gas diffusion layer.Currently,most of the research on ordered MEA is still in the laboratory stage,focusing mainly on the design and construction of ordered structures with a single structure or a single conductor function.In addition,the preparation process of the ordered MEA is generally complex and energy-consuming,which is not conducive to its mass production and commercial application.Based on this,this paper focuses on the structural regulation of ordered membrane electrodes in proton exchange membrane fuel cells to improve their performance and lifespan.Meanwhile,It explores the structural design and optimization of the proton exchange membrane（PEM）surface,the optimization of the proton exchange membrane/catalyst layer（PEM/CL）contact interface,and the surface boundary issues in the batch production of structured proton exchange membranes.Thus,the preparation cost of ordered membrane electrode is greatly reduced and its further commercial application is promoted.The details are as follows:1.Using the multi-level structure of natural lotus leaves as the original template,and after structural imprinting,hot pressing and plasma etching steps,a multi-scale structure PEM with micro-scale pillar structure and nano-scale needle-like structure was successfully constructed.Compared with the flat PEM,this multi-scale structured PEM has thinner thickness（～7.9%）,a surface roughness 71 times higher and a hydrophobic contact angle（141°）.The ordered multi-scale structure,which inherits the multi-level structure and hydrophobic characteristics of lotus leaves,it can provide smooth channels for the transmission of protons,gases,and water in the catalyst layer at the PEM/CL interface.As a result,this structure can greatly improve the performance of the MEA in the fuel cell（1.96 times）and an effectively improvement water management.2.The preparation of ordered structure PEM with dual-function electronic and proton conductivity is achieved by filling a Nafion emulsion containing doped single walled carbon nanotube（SWCNT）into an ordered nanostructured anodic aluminum oxide（AAO）template.After solidifying it,the conical ordered structure was transferred onto a commercial flat membrane through hot pressing.Introducing SWCNTs into the ordered proton conductor array can effectively increase the roughness（～2 times）and specific surface area（～5 times）of the PEM surface,thereby providing more active sites for catalytic reactions at the PEM/CL interface.This integrated transport structure consisting of ordered proton（Nafion）,electron（SWCNT）and material（ordered array structure）built on the surface of a PEM,can effectively optimize the three-phase reaction interface at the interface between the PEM and the catalytic layer.As a result,it enables a significant improvement in catalyst utilization efficiency at a lower catalyst loading(30 μg cm-2 on the cathode side).The integrated array PEM achieved higher cell performance(62 mW cm-2).The fuel cell performance of the dual-function structure membrane is twice that of the pure Nafion array membrane(30.8 mW cm-2),and four times that of the unstructured flat membrane(16.4 mW cm-2).3.By constructing an ordered Nafion array structure at the PEM/CL interface and accelerating stress testing,the aging behavior of this interface was studied to investigate the effects of the structured array layer on the power density and durability of PEMFC.Compared to traditional flat membrane MEA,after aging for 5000 cycles,the ordered proton conductor array membrane MEA showed a 21.0%increase in peak power density（Pmax）and a 16.8%increase in electrochemical surface area（ECSA）at 0.65 V.After aging for 30000 cycles,the loss rates of Pmax and ECSA at 0.65 V were only 12.7%and 11.7%,respectively,much lower than those of traditional flat membrane MEAs at 22.0%and 22.6%.It can be attributed to the ordered array structure reduces H2 permeation current during voltage cycling,increases the number of catalytic active sites,reduces Co loss during catalyst degradation,maintains close contact on PEM/CL interface and reduces the proton transfer resistance of the interface.4.A nanoimprinting method was developed for the efficient batch preparation of ordered proton array structure PEM by solving the surface interface problem in the demolding process.This method can construct large area（up to 1800 cm2）ordered Nafion array structures at the contact interface between the PEM and the catalyst layer（CL）in less than 1 minute.This universally applicable method can prepare ordered proton conductor array structures of various sizes on multi-kinds commercial PEM surfaces.The resulting ordered Nafion array structure can effectively optimize the PEM/CL interface,resulting in a 1.6-folds increase in Pmax of MEA and a one-tenth hydrogen permeation rate of MEA compared to commercial PEM.The proposed method employs water as a pollution-free demoulding agent,and the water infiltration can significantly reduce the interfacial adhesion between the ordered Nafion conductor array and the AAO template.Therefore,the AAO template can be reused for at least 50 times,which avoids the high cost and complicated preparation process associated with the commonly used sacrificial AAO template method for the construction of ordered proton conductor array structures. |
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