Deconvoluting charge-transfer, mass transfer, and ohmic resistances in phosphonic acid–sulfonic acid ionomer binders used in electrochemical hydrogen pumps
Deconvoluting charge-transfer, mass transfer, and ohmic resistances in phosphonic acid–sulfonic acid ionomer binders used in electrochemical hydrogen pumps
复制标题
对电化学氢泵中使用的膦酸-磺酸离聚物粘合剂中的电荷转移、传质和欧姆电阻进行解卷积
DOI：
10.1039/d3ee01776a
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发表时间：
2023
影响因子：
32.5
通讯作者：
Arges, Christopher G.
中科院分区：
文献类型：
--
作者：
Arunagiri, Karthik;Wong, Andrew Jark-Wah;Briceno-Mena, Luis;Elsayed, Hania Mohamed;Romagnoli, José A.;Janik, Michael J.;Arges, Christopher G.
离子对高温聚合物电解质膜（HT-PEM）与膦酸离聚物电极粘合剂配对，显着提高了 HT-PEM 电化学氢泵（EHP）和燃料电池的性能。将聚（五氟苯乙烯-共-四氟苯乙烯膦酸）（PTFSPA）与 Nafion™ 混合，并使用该混合物作为电极粘合剂，改善了电极层中的质子电导率，从而使燃料电池在 240 °C 时达到 2 W cm−2 峰值功率密度（HT-PEM 燃料电池记录）。然而，关于膦酸离聚物与全氟磺酸材料混合如何影响多孔电极中的电极动力学和气体传输尚不清楚。在这项工作中，我们研究了 3 种膦酸离聚物（聚（乙烯基膦酸）、聚（乙烯基苄基膦酸）和 PTFSPA）本身以及与 Aquivion®（一种全氟磺酸材料）混合时的质子电导率、电极动力学和气体传输阻力。这些研究是使用 EHP 平台进行的。对于所有磷酸离聚物类型，Aquivion® 的添加可提高离子电导率、氢氧化/析出反应动力学 (HOR/HER) 和氢气渗透性。固态 31P NMR 显示，Aquivion® 的添加消除或显着减少了磷酸离聚物中磷酸酯的形成，这在增强离聚物共混物电导率方面发挥着至关重要的作用。使用最佳混合变体 PTFSPA-Aquivion®，在 T = 200 °C、0.4 V 下获得了 5.1 A cm−2 的 EHP 性能。密度泛函理论（DFT）计算表明，具有吸电子部分的膦酸降低了膦酸吸附在铂电催化剂表面上的倾向。 DFT 中各种膦酸离聚物的相对吸附亲和力与实验确定的电荷转移电阻一致。电压损失击穿模型表明，添加 Aquivion® 可降低 EHP 中的活化和浓度过电势。总体而言，系统的实验和建模方法进一步深入了解全氟磺酸离聚物与磷酸离聚物混合如何影响 EHP 平台中的离子电导率、反应动力学和气体渗透率。
Ion-pair high-temperature polymer electrolyte membranes (HT-PEMs) paired with phosphonic acid ionomer electrode binders have substantially improved the performance of HT-PEM electrochemical hydrogen pumps (EHPs) and fuel cells. Blending poly(pentafluorstyrene-co-tetrafluorostyrene phosphonic acid) (PTFSPA) with Nafion™, and using this blend as an electrode binder, improved proton conductivity in the electrode layer resulting in a 2 W cm−2 peak power density of fuel cells at 240 °C (a HT-PEM fuel cell record). However, much is unknown about how phosphonic acid ionomers blended with perfluorosulfonic acid materials affect electrode kinetics and gas transport in porous electrodes. In this work, we studied the proton conductivity, electrode kinetics, and gas transport resistances of 3 types of phosphonic acid ionomers, poly(vinyl phosphonic acid), poly(vinyl benzyl phosphonic acid), and PTFSPA by themselves and when blended with Aquivion® (a perfluorosulfonic acid material). These studies were performed using EHP platforms. For all phosphoric acid ionomer types, the addition of Aquivion® promoted ionic conductivity, hydrogen oxidation/evolution reaction kinetics (HOR/HER), and hydrogen gas permeability. Solid-state 31P NMR revealed that the addition of Aquivion® eliminated or significantly reduced phosphate ester formation in phosphoric acid ionomers and this plays a vital role in enhancing ionomer blend conductivity. Using the best blend variant, PTFSPA-Aquivion®, an EHP performance of 5.1 A cm−2 at 0.4 V at T = 200 °C was attained. Density functional theory (DFT) calculations identified that phosphonic acids with electron-withdrawing moieties reduced the propensity of the phosphonic acid to adsorb on platinum electrocatalyst surfaces. The relative adsorption affinity of the various phosphonic acid ionomers from DFT is consistent with experimentally determined charge transfer resistance. A voltage loss breakdown model revealed that the addition of Aquivion® reduced activation and concentration overpotentials in EHPs. Overall, a systematic experimental and modeling approach provided further insight as to how perfluorosulfonic acid ionomers blended with phosphoric acid ionomers affect ionic conductivity, reaction kinetics, and gas permeability in EHP platforms.