Engineering the Ionic Polymer Phase-Fluid Interface of the PEM Fuel Cell Catalyst Layer for Higher Performance

对 PEM 燃料电池催化剂层的离子聚合物相-流体界面进行工程设计，以获得更高的性能

• 批准号: 1803058
• 负责人: Trung Nguyen
• 金额: $ 30万
• 依托单位: University of Kansas Center for Research Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1803058&HistoricalAwards=false
• 关键词: Engineering; Ionic; Polymer; Phase; Fluid

A hydrogen-oxygen proton exchange membrane fuel cell (PEMFC) is a device that converts chemical energy of hydrogen reacting with oxygen into electrical power. One of the primary barriers to full-scale commercialization of PEMFCs for transport propulsion and distributed power applications is the inability to operate at high power density and high energy efficiency. Low power density keeps the system cost high, and low energy efficiency makes its operational cost high. High power density operations are currently limited because water produced in the oxygen catalyst layer wets and fills the gas pores of polymer binder in the catalyst layer of the cathode. This blocks the transport of oxygen to the catalyst reaction sites. This work will determine what controls the surface wettability of this ionic polymer binder phase, and based on this understanding, will modify the surface of this ionic polymer binder to be either hydrophilic or hydrophobic. In the case of the PEMFC application, a hydrophobic surface is preferred because it helps repel the by-product water from the pores of the catalyst layer and allow oxygen gas better access to the active sites in the catalyst layer to generate more power. If this work is successful, it will lead to large-scale commercialization of fuel cell vehicles. Moreover, discoveries in membrane/fluid interfacial property could benefit other areas such as water treatment, chemical separations, and large-scale energy storage applications, thus strengthening our scientific knowledge and technological advancement and leadership in the world and economic and national security. Finally, this work will generate the human resources needed to develop and commercialize these new technologies and sustain the scientific and technological progress.In this fundamental engineering science project, a novel process is researched to create a fuel cell catalyst layer that is optimal for two-phase (incoming gaseous oxygen reactant and outgoing liquid water product) transport. The process is based on recent discoveries with perfluorosulfonic acid (PFSA) polymers, which have shown that the surface morphology of PFSA polymers changes when varying the relative humidity (RH) of the gas in contact with the polymer. Most recently, the PI's group developed a new heat treatment process for PFSA membranes to create a permanent hydrophobic or hydrophilic surface structure. Therefore, it is hypothesized that by controlling the heat treatment conditions of the ionic polymer binder within the fuel cell catalyst layer one can engineer the polymer-gas interface inside the gas pores of the catalyst layer to be either hydrophobic or hydrophilic. Heat treating the catalyst layer such that the ionic sulfonate groups accumulate at the polymer-gas interface (under high RH in the cathode gas pores) will result in a hydrophilic polymer-gas interface. Whereas, heat treating to create a polytetrafluoroethylene (PTFE)-rich polymer-gas interface (under low RH) will lead to a hydrophobic polymer-gas interface. Subsequent cooling of the cathode catalyst layer will then crystallize the polymer's PTFE phase and lock-in the surface morphology. A hydrophilic ionic polymer-fluid interface is preferred for electrodes with liquid reactants, such as the PEM electrolyzer. A hydrophobic polymer-fluid interface is preferred for electrodes with gaseous reactants, such as the hydrogen-air PEMFC. Electrodes with hydrophobic catalyst layer, relevant to PEM fuel cells, will be fabricated, and using the PI's layer-by-layer removal method, the polymer layer morphology of their inner porous structures will be characterized by the SEM, XPS, neutron reflectometry (NR), and surface-enhanced Raman scattering (SERS). These electrodes will be tested in a PEMFC to determine the catalyst layer and electrode-membrane-assembly fabrication process conditions that will lead to the highest power density and energy efficiency performance. The effect of the solvent type used in the catalyst ink on the crystallinity of the modified polymer structure will be investigated, and the long-term durability of the polymer interfacial property will be evaluated using the water boiling and high temperature humidity cycling tests. Finally, a model of the cathode catalyst layer of a PEMFC will be developed to study the effect of the hydrophobic ionic polymer-gas interface on two-phase fluid transport in the catalyst layer gas pores, oxygen transport through the polymer layer, and fuel cell performance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

氢 - 氧质子交换膜燃料电池（PEMFC）是一种将与氧气反应的氢的化学能转化为电力。 PEMFC用于运输推进和分布式功率应用的全尺度商业化的主要障碍之一是无法以高功率密度和高能效率运行。低功率密度使系统成本高，低能效率使其运营成本高。目前，高功率密度的操作受到限制，因为在氧气催化剂层中产生的水并填充了阴极催化剂层中聚合物粘合剂的气孔。 这阻断了氧气向催化剂反应位点的转运。 这项工作将确定是什么控制该离子聚合物粘合剂阶段的表面润湿性，并基于这种理解，将改变该离子聚合物粘合剂的表面为亲水或疏水。 在PEMFC应用的情况下，首选疏水表面，因为它有助于从催化剂层的孔中排除副产物水，并让氧气更好地进入催化剂层中的活性位点以产生更多的功率。 如果这项工作成功，它将导致燃料电池车的大规模商业化。此外，膜/液体界面财产中的发现可能使水处理，化学分离和大规模的能源存储应用等其他领域受益，从而增强我们在世界上的科学知识，技术进步以及领导力以及经济和国家安全。最后，这项工作将产生开发和商业化这些新技术并维持科学和技术进步所需的人力资源。在这项基本工程科学项目中，研究了一个新颖的过程，可以创建一个燃料电池催化剂层，最适合两相（传入的气体氧反应剂和出现的液体水产品）运输。该过程是基于全氟磺酸（PFSA）聚合物的最新发现，这些发现表明，当与聚合物接触的气体相对湿度（RH）变化时，PFSA聚合物的表面形态会发生变化。最近，PI组为PFSA膜开发了一种新的热处理过程，以创建永久性疏水或亲水性表面结构。因此，假设通过控制燃料电池催化剂层中离子聚合物粘合剂的热处理条件，可以设计催化剂层内的聚合物气体界面，使其具有疏水性或嗜水。热处理催化剂层的热使离子磺酸基团积聚在聚合物气体界面（在阴极气体孔中的高RH下）将导致亲水性聚合物燃气界面。而热处理以产生聚氟乙烯（PTFE） - 富含聚合物气体界面（在低RH下）将导致疏水聚合物气体界面。然后，随后的阴极催化剂层冷却将使聚合物的PTFE相结晶并锁定表面形态。对于具有液体反应剂（例如PEM电解质）的电极，优选的亲水离子聚合物 - 流体界面是优选的。对于具有气态反应物（例如氢气PEMFC）的电极，优选疏水聚合物 - 流体界面。将制造具有与PEM燃料电池相关的疏水催化剂层的电极，并使用PI的逐层去除方法，其内部多孔结构的聚合物层形态将以SEM，XPS，XPS，中子反射仪（NR）和表面增强的拉曼散射（SER）来表征。这些电极将在PEMFC中进行测试，以确定催化剂层和电极膜组装工艺条件，这将导致最高的功率密度和能效性能。将研究催化剂墨水中使用的溶剂类型对改性聚合物结构结晶度的影响，并将使用水沸腾和高温湿度循环测试评估聚合物界面特性的长期耐用性。 Finally, a model of the cathode catalyst layer of a PEMFC will be developed to study the effect of the hydrophobic ionic polymer-gas interface on two-phase fluid transport in the catalyst layer gas pores, oxygen transport through the polymer layer, and fuel cell performance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review 标准。

项目成果

Controlling the ionic polymer/gas interface property of a PEM fuel cell catalyst layer during membrane electrode assembly fabrication

在膜电极组件制造过程中控制 PEM 燃料电池催化剂层的离子聚合物/气体界面特性

• DOI: 10.1007/s10800-020-01453-w
• 发表时间: 2020
• 期刊: Journal of Applied Electrochemistry
• 影响因子: 2.9
• 作者: Dowd, Regis P.;Li, Yuanchao;Van Nguyen, Trung
• 通讯作者: Van Nguyen, Trung

Modification of Nafion's nanostructure for the water management of PEM fuel cells

• DOI: 10.1002/pol.20220774
• 发表时间: 2023-03
• 期刊: Journal of Polymer Science
• 影响因子: 3.4
• 作者: Yuanchao Li;Natalie L. Schwab;R. Briber;J. Dura;T. Nguyen

A One-Dimensional Model of a PEM Fuel Cell with the Cathode Catalyst Layer Hydrophobically Treated for Water Management

具有用于水管理的经过疏水处理的阴极催化剂层的 PEM 燃料电池的一维模型

• DOI: 10.1149/1945-7111/ac9bdf
• 发表时间: 2022
• 期刊: Journal of The Electrochemical Society
• 影响因子: 3.9
• 作者: Li, Yuanchao;Van Nguyen, Trung
• 通讯作者: Van Nguyen, Trung