High Hydroxide Conductivity Research Articles

Soluble poly(aryl piperidinium) with extended aromatic segments as anion exchange membranes for alkaline fuel cells and water electrolysis

Superacid-catalyzed polymerization of N-methyl-4-piperidone and aromatic hydrocarbons followed by quaternization is regarded as a reliable synthetic pathway to prepare anion exchange membrane (AEM) materials with superior conductivity and excellent alkaline stability, which is crucial for their application in alkaline fuel cells and alkaline water electrolysers. In this work, we design and prepare soluble p-quaterphenyl-containing poly(aryl piperidinium) (PQP-100) to increase the rigidity and hydrophobicity of aryl ether-free polymer backbones. Consequently, robust PQP-100 AEM exhibits improved microphase-separated morphology as conformed by SAXS and AFM observation. In comparison with biphenyl and p-terphenyl-based poly(aryl piperidinium), PQP-100 AEM possesses high hydroxide conductivity (118.72 mS/cm at 80 °C) and ability to be fabricated ultrathin membrane up to 4 μm without reinforcement. 75% of original conductivity is maintained for PQP-100 membrane after 1344 h of alkaline stability test in 1 M NaOH at 80 °C due to the degradation of piperidiniums via nucleophilic substitution. The practical device performance of PQP-100 membrane shows a peak power density (PPD) of 496 mW/cm2 in H2/O2 fuel cells at 60 °C and a current density of 1544 mA/cm2 at 2.0 V in alkaline water electrolysers circulating 1 M KOH at 85 °C, and the thinner membranes reduce the output of both fuel cells and electrolysers. Moreover, the durability of fuel cell and electrolyser at 200 mA/cm2 also manifest the performance loss over 85 and 402 h of operation, mainly attributed to the chemical degradation of PQP-100 membrane as evidenced by post-cell analysis using NMR technology.

Poly(arylene piperidine) Anion Exchange Membranes with Tunable N-Alicyclic Quaternary Ammonium Side Chains

To develop anion exchange membranes (AEMs) that combine high chemical stability and hydroxide conductivity, we have designed and prepared poly(arylene piperidine)s carrying tunable mono- or dicationic side chains. Poly(biphenyl piperidine) and poly(biphenyl N-methylpiperidine), respectively, were first synthesized by superacid-catalyzed polyhydroxylalkylations. Subsequently, the piperidine rings of these polymers were reacted with bromoalkylated N,N-dimethylpiperidinium (DMP) and 6-azonia-spiro[5.5]undecane (ASU) cations, respectively. This gave two series of AEMs in which the polymer backbone contained tertiary and quaternary piperidine rings, respectively, resulting in mono- and dicationic side chains in series 1 and 2, respectively. In series 1, both the piperidine rings in the backbone and the pendant cations in the side chains showed excellent alkaline stability, resulting in AEMs, which retained more than 92% of the cations after storage in 2 M NaOH at 90 °C during 30 days. In addition, these AEMs reached a hydroxide conductivity up to 131 mS cm–1 at 80 °C. Benefiting from a high local ionic concentration through the dicationic configuration, the AEMs in series 2 reached a higher conductivity, almost 170 mS cm–1 at 80 °C at moderate water uptake and swelling. Still, these AEMs were more vulnerable to hydroxide attack than the ones in series 1 because of the quaternary piperidinium groups placed in the polymer backbone. In conclusion, the AEMs in series 1 can be employed in electrochemical devices that operate under harsh alkaline conditions, while those in series 2 should be preserved for less aggressive alkaline conditions.

A high-temperature anion-exchange membrane fuel cell with a critical raw material-free cathode

We present a first high-temperature anion-exchange membrane fuel cell (HT-AEMFC, operating at 105 °C) based on a critical raw material (CRM)-free cathode catalyst; at the same temperature, the anion-exchange membrane (AEM) has a high ex-situ hydroxide conductivity value of 201 mS cm−1. Our HT-AEMFC, containing a highly active nitrogen-doped carbon (N-doped-C) cathode catalyst, also features low polarization resistances, high catalytic activity and stability, with retention of 81% of the catalyst layer capacitance after an initial 10 h longevity test, and delivery of a peak power of 1.14 W cm−2. This is one of the highest power densities reported for an AEMFC containing a CRM-free cathode. This work shows the potential of the new field of HT-AEMFCs, opening opportunities for developing and using novel CRM-free catalysts that are highly active at these high operating temperatures.

Layered double hydroxide membrane with high hydroxide conductivity and ion selectivity for energy storage device

Membranes with fast and selective ions transport are highly demanded for energy storage devices. Layered double hydroxides (LDHs), bearing uniform interlayer galleries and abundant hydroxyl groups covalently bonded within two-dimensional (2D) host layers, make them superb candidates for high-performance membranes. However, related research on LDHs for ions separation is quite rare, especially the deep-going study on ions transport behavior in LDHs. Here, we report a LDHs-based composite membrane with fast and selective ions transport for flow battery application. The hydroxide ions transport through LDHs via vehicular (standard diffusion) & Grotthuss (proton hopping) mechanisms is uncovered. The LDHs-based membrane enables an alkaline zinc-based flow battery to operate at 200 mA cm−2, along with an energy efficiency of 82.36% for 400 cycles. This study offers an in-depth understanding of ions transport in LDHs and further inspires their applications in other energy-related devices.

Highly conductive hydroxide exchange membranes containing fluorene-units tethered with dual pairs of quaternary piperidinium cations

In the pursuit of anion exchange membranes (AEMs) with high alkaline stability and hydroxide conductivity, we have prepared and characterized a series of poly(fluorene alkylene)s in which each fluorene unit was functionalized with dual pairs of quaternary piperidinium cations on flexible alkyl spacer chains. First, ether-free precursor polymers were synthesized in superacid mediated polyhydroxyalkylations involving 2,2,2-trifluoroacetophenone, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and different amounts of 2,7-dibromo-9,9-bis(6-bromohexyl)-fluorene to regulate the degree of bromoalkylation. Subsequently, the bromoalkyl side chains were utilized to introduce bis-piperidinium (bisPip) cations via Menshutkin reactions. These materials formed transparent and mechanically strong AEMs upon casting. At 80 °C, the hydroxide conductivity of bisPip AEMs reached 85 and 150 mS cm–1 at ion-exchange capacities (IECs) of 2.0 and 2.8 mequiv g–1, respectively. Moreover, the bisPip AEMs showed high alkaline stability with an ionic loss of merely 6% following immersion in 5 M aq. NaOH solution for a period of 168 h at IEC = 2.8 mequiv g–1. Under these conditions, 1H NMR data indicated that a β-hydrogen in an alkyl spacer chain was about 8 times more susceptible to attacks by hydroxide ions than a β-hydrogen in a piperidinium ring. In comparison, corresponding AEMs with fluorene units functionalized with monoPip cations (i.e., a single pair of piperidinium cations per fluorine unit) showed lower conductivity and alkaline stability under the same conditions, demonstrating the advantage of locally concentrating the cations in the polymer structure by employing bisPip side chains.

Facilitating ionic conduction for anion exchange membrane via employing star-shaped block copolymer

Anion exchange membrane (AEM) with high ionic conductivity and good stability is of vital importance for developing high-performance alkaline anion-exchange membrane fuel cell (AEMFC). In particular, the performance of AEM largely depends on the microstructure of the basic polymer material. Herein, we have developed a novel strategy to fabricate the AEMs, featuring a star topological structure, via living anionic polymerization and the subsequent functionalization. Thanks to the introduction of well-defined amphiphilic block structure, a distinct micro-phase separation was observed in the synthesized AEMs (AEM-SCP) which were based on star-shaped block copolymers. In comparison to the AEM-LCP membranes based on linear block copolymers, the AEM-SCP membranes exhibited relatively lower water uptake and swelling ratio, but much higher hydroxide conductivity (at 80 °C, 68.1 mS cm−1 for AEM-SCP-3 vs. 38.1 mS cm−1 for AEM-LCP). This is attributed to the efficient aggregation of ionic groups via employing star-shaped block copolymers, which can result in the formation of continuous ion-conducting channels and the facilitated ionic conduction in the AEMs. Furthermore, compared with the AEM-LCP membrane, the dimensional and alkaline stability of the resultant AEM-SCPs have been significantly enhanced.

The effect of –NH− on quaternized polybenzimidazole anion exchange membranes for alkaline fuel cells

To investigate the effect of –NH− in polybenzimidazole (PBI) on the properties of PBI anion exchange membranes (AEMs), naphthalene based polybenzimidazole (NPBI) was partially grafted with cationic side chains to afford NPBI-QAx membrane, and then reacted with bromobutane to achieve fully grafting polymer namely NPBI-QAx-By. Surprisingly, after attaching n-butyl on the benzimidazole groups in NPBI backbones completely, the fully grafting polymer NPBI-QA55-B45 showed much higher hydroxide conductivity, achieving 31.7 mS/cm at 20 °C. This value was tenfold compared with that of NPBI-QA55 (2.96 mS/cm at 20 °C) membrane having similar IEC value without N-substitute. It was assumed that ionic interaction occurred between positively charged fixed cations and negatively charged benzimidazolide rings when the NPBI-QAx membranes were immersed in 1 M NaOH. FT-IR and XPS analysis on NPBI-QAx membranes confirmed that ionic interaction between positively charged fixed cations and negatively charged benzimidazolide rings occurred when treated in 1 M NaOH, while no obvious ionic interaction was observed when immersion in 1 M NaHCO3. However, the ionic interaction resulted in excellent stability of the membrane (NPBI-QA55) with –NH− groups, e.g. no obvious chemical structure degradation after alkaline stability test at 80 °C in 5 M NaOH for 760 h, while the NPBI-QA55-B45 membrane suffered from chemical degradations via ring opening reaction of NPBI backbones and nucleophilic substitution of pendant QA cations as confirmed by 1H NMR. Moreover, improved conductivity resulted in excellent fuel cell performance for NPBI-QA55-B45 membrane and the peak power density was about 260.1 mW/cm2. However, no fuel cell performance was obtained for the NPBI-QA55 membrane due to the formation of ionic interaction.

Facile Preparation of Highly Alkaline Stable Poly(arylene–imidazolium) Anion Exchange Membranes through an Ionized Monomer Strategy

The preparation of polyelectrolytes with excellent stability in high alkaline conditions still faces several challenges. In this study, we report a novel imidazolium-ionized monomer PhIM [PF₆], modified by the propylbenzene group on the position of N1/N3, which can be copolymerized with 1,1,1-trifluoroacetone under superacid-catalyzed conditions. The main-chain poly(arylene–imidazolium) polymers with a controllable degree of functionalization, high molecular weight, and good solubility are successfully prepared without further postfunctionalization. Two copolymers (block-like and random) can also be prepared by introducing biphenyl as a comonomer and adjusting the feed order. Due to their different microstructures, the two copolymers exhibit different ion conduction behaviors, water absorption capacities, and mechanical properties. The obtained polymer membranes exhibit high hydroxide conductivities and high chemical stability even after treatment in a 10 M NaOH solution at 80 °C. In summary, we highlight a simple, effective, and low-cost strategy to prepare highly alkaline stable poly(arylene–imidazolium) polymers.

Crucial role of side-chain functionality in anion exchange membranes: Properties and alkaline fuel cell performance

Side-chain functionality is critical to achieve highly conductive and chemically stable anion exchange membrane (AEM) materials. Herein, two series of quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) having different lengths (n or m) of cationic side-chains were designed and prepared, including PPO-C-nQA with a triazole-containing linker and PPO-mQA without triazole groups in the side chains. The effect of the side-chain functionality on the properties of AEMs has been systematically investigated. Long cationic side chains in PPO-mQA membranes induced the formation of obvious microphase-separated morphology. However, PPO-C-nQA membranes with a triazole-containing linker showed a considerable higher hydroxide conductivity than that of PPO-mQA membranes, due to the developed hydrogen-bond networks between triazole and water/hydroxide. High retention of conductivity and low degree of crosslinking were observed for the AEMs with longer side-chains (PPO-C-3QA, PPO-C-4QA, PPO-6QA, and PPO-7QA) in the alkaline stability testing under 10 M NaOH at 80 °C for 250 h, indicating their excellent stability. Moreover, a single H2/O2 AEMFC with these side-chain type AEMs demonstrated that PPO-C-1QA with highest conductivity exhibited a peak power density of 141.3 mW cm−2 at a current density of 320 mA cm−2.

Mechanically robust semi-interpenetrating polymer network via thiol-ene chemistry with enhanced conductivity for anion exchange membranes

Anion exchange membranes (AEMs) have emerged as crucial functional materials in various electrochemical device, such as fuel cell. Both the mechanical property and ionic conductivity play important roles in AEMs. Herein, a series of semi-interpenetrating polymer network AEMs are prepared by introducing flexible polyvinyl alcohol to the rigid photo-crosslinked poly (2,6-dimethyl-1,4-phenylene oxide) network. Such strategy endows AEM with tunable composition and mechanical property. Among these AEMs, membrane with an IEC of 1.46 mmol/g shows the highest mechanical strength of 30.8 MPa and a relatively lower swelling ratio, as well as the highest hydroxide conductivity. Importantly, the alkaline stability of these AEMs has been improved, 66.5% of the hydroxide conductivity is maintained after treatment in 1 M NaOH at 80 °C for 1000 h. Tentative assembly of H2/O2 fuel cell at 60 °C with this AEM displays a peak power density of 78 mW/cm2. All the results demonstrate that sIPN structure is a promising way to enhance the mechanical property, ionic conductivity, and the alkaline stability of AEMs for the future application in AEMFCs.

Expeditious synthesis of aromatic-free piperidinium-functionalized polyethylene as alkaline anion exchange membranes.

Alkaline anion exchange membranes (AAEMs) with high hydroxide conductivity and good alkaline stability are essential for the development of anion exchange membrane fuel cells to generate clean energy by converting renewable fuels to electricity. Polyethylene-based AAEMs with excellent properties can be prepared via sequential ring-opening metathesis polymerization (ROMP) and hydrogenation of cyclooctene derivatives. However, one of the major limitations of this approach is the complicated multi-step synthesis of functionalized cyclooctene monomers. Herein, we report that piperidinium-functionalized cyclooctene monomers can be easily prepared via the photocatalytic hydroamination of cyclooctadiene with piperidine in a one-pot, two-step process to produce high-performance AAEMs. Possible alkaline-degradation pathways of the resultant polymers were analyzed using spectroscopic analysis and dispersion-inclusive hybrid density functional theory (DFT) calculations. Quite interestingly, our theoretical calculations indicate that local backbone morphology—which can potentially change the Hofmann elimination reaction rate constant by more than four orders of magnitude—is another important consideration in the rational design of stable high-performance AAEMs.

Construction of highly efficient ion channel within anion exchange membrane based on interpenetrating polymer network for H2/Air (CO2-free) alkaline fuel cell

Interpenetrating polymer network anion exchange membrane (IPN AEM) consists of cross-linked quaternized poly (vinylbenzyl chloride) and cross-linked poly (vinyl alcohol) is synthesized in this work. Electron microscope clearly reveals the IPN structure, and with this structural design, a highly efficient ion channel within IPN AEMs is constructed. This specially designed structure leads to high hydroxide (OH−) conductivity (e.g., 141.7 mS cm−1 at 80 °C) at a moderate ion exchange capacity (IEC) of 1.61 mmol g−1, and a remarkable peak power density of 0.64 W cm−2 with non-noble metal oxygen reduction reaction (ORR) catalyst in H2/Air (CO2-free) anion exchange membrane fuel cells (AEMFCs) test.

Crosslinked Pore-Filling Anion Exchange Membrane Using the Cylindrical Centrifugal Force for Anion Exchange Membrane Fuel Cell System.

In this study, novel crosslinked pore-filling membranes were fabricated by using a centrifugal force from the cylindrical centrifugal machine. For preparing these crosslinked pore-filling membranes, the poly(phenylene oxide) containing long side chains to improve the water management (hydrophilic), porous polyethylene support (hydrophobic) and crosslinker based on the diamine were used. The resulting membranes showed a uniform thickness, flexible and transparent because it is well filled. Among them, PF-XAc-PPO70_25 showed good mechanical properties (56.1 MPa of tensile strength and 781.0 MPa of Young’s modulus) and dimensional stability due to the support. In addition, it has a high hydroxide conductivity (87.1 mS/cm at 80 °C) and low area specific resistance (0.040 Ω·cm2), at the same time showing stable alkaline stability. These data outperformed the commercial FAA-3-50 membrane sold by Fumatech in Germany. Based on the optimized properties, membrane electrode assembly using XAc-PPO70_25 revealed excellent cell performance (maximum power density: 239 mW/cm2 at 0.49 V) than those of commercial FAA-3-50 Fumatech anion exchange membrane (maximum power density: 212 mW/cm2 at 0.54 V) under the operating condition of 60 °C and 100% RH as well. It was expected that PF-XAc-PPO70_25 could be an excellent candidate based on the results superior to those of commercial membranes in these essential characteristics of fuel cells.

Investigating the Influences of Polystyrene-Based Hydroxide Ion Conducting Ionomer on Electrode in Anion Exchange Membrane Fuel Cells

Alkaline anion exchange membrane fuel cells (AEMFCs) are an attractive alternative to proton exchange membrane fuel cells because they have the advantage of cost savings due to the use of non-noble metal catalysts. Since AEMFCs has a charge carrier of hydroxide ions, anion exchange membranes having various cationic groups substituted on the hydrocarbon polymer backbone have been actively studied for high hydroxide conductivity, mechanical properties and durability. In addition, the electrode ionomer of the core material of the membrane electrode assembly acts as a binder for uniformly dispersing the catalyst and fixing the catalyst layer and anion exchange membrane. It also serves as a transport pathway for hydroxide ions produced from the cathode to the anode. In particular, it is important that the electrode ionomer greatly affects the catalyst layer type and fuel cell performance.Herein, polystyrene-based copolymers with variable molecular weight are prepared by radical polymerization of styrene, grafted with bromo-alkyl chains of different length (C3 or C6) through Friedel-Crafts acylation, and quaternized to afford a series of hydroxide ion–conducting ionomers. The performance of anion-exchange membrane fuel cells (AEMFCs) constructed using the prepared electrode ionomers is affected by several ionomer properties, and a maximal power density of 407 mW cm−2 and a durability exceeding that of a reference cell with a commercially available ionomer are achieved under optimal conditions. Thus, the developed approach is concluded to be well suited for the fabrication of next-generation electrode ionomers for high-performance AEMFCs.

Block copolymer anion exchange membrane containing polymer of intrinsic microporosity for fuel cell application

High hydroxide conductivity and good stability of anion exchange membranes (AEMs) is the guarantee that anion exchange membrane fuel cells (AEMFCs) yield high power output for a long time. Balanced conductivity and stability can be better guaranteed by adopting a relatively low ion exchange capacity (IEC) while reducing the ion transport resistance Herein, a novel block copolymer AEM was designed and synthesized, which contains hydrophobic polymer of intrinsic microporosity (PIM) blocks and hydrophilic, quaternized polysulfone (PSF) blocks. The PIM block imparts high free volume to the membrane so that the resistance of hydroxide ion transport can be reduced; meanwhile, the hydrophilic block can self-assemble more easily to produce a better developed hydrophilic microphase, which may function as efficient channels for hydroxide ion transport. Both transmission electron microscopy images and small-angle X-ray scattering patterns suggested that the resulting AEM possessed a microphase separated morphology. The membrane showed a conductivity of 52.6 mS cm-l at 80 °C with a relatively low IEC of 0.91 mmol g−1. It also exhibited a good dimensional stability, swelling ratio maintained almost constant (ca. 17%) at 25 to 80 °C. The assembled H2/O2 fuel cell yielded a peak power density of 270 mW cm−2 at 560 mA cm−2. Our work demonstrates that incorporation of PIM in an AEM by means of block polymerization is an efficient way of promoting microphase separation and facilitating ion transport.

Anion exchange membranes based on ionic polybenzimidazoles crosslinked by thiol-ene reaction

In this study, we report the synthesis and properties of new anion exchange membranes using m-polybenzimidazole (m-PBI) as polymer backbone attached with quaternary ammonium group and alkene group as side chains. These ionic m-PBIs were crosslinked by thermal thiol-ene reaction. The ion exchange capacity (IEC) values and crosslinking degrees were controlled independently by the amount of attached quaternary ammonium groups and alkene groups, respectively. m-PBI based AEMs with IEC from 1.51 to 2.50 mmol/g exhibit hydroxide conductivity of 14 to 58 mS/cm at 80 °C. With similar IEC values, crosslinked membranes absorb less water but show similar hydroxide conductivity and better dimension stability than uncrosslinked membranes. A crosslinked membrane with an IEC value of 2.46 mmol/g can retain 84% of its pristine hydroxide conductivity after being immersed in 1.0 M sodium hydroxide solution at 60 °C after 720 h. These membranes in hydrated condition also show mechanical robustness with tensile strength of 10.8 to 14.6 MPa. From the high hydroxide conductivity, enhanced alkaline stability and good mechanical properties, crosslinked ionic m-PBIs are promising candidate as anion exchange membranes for fuel cell application.

A high-temperature anion-exchange membrane fuel cell

In the past few years, developments in anion exchange membranes (AEMs) have led to a significant increase in hydroxide conductivities, ultimately yielding striking improvements in the performance of anion exchange membrane fuel cells (AEMFCs) at low operating temperatures, usually at 40–80 °C. Aside from these remarkable achievements, the literature is void of any work on AEMFCs operated at temperatures above 100 °C, despite the consensus from various models remarking that working at higher cell temperatures may lead to many significant advantages. In this work, we present the first high-temperature AEMFC (HT-AEMFC) tested at 110 °C. The HT-AEMFC exhibits high performance, with a peak power density of 2.1 W cm −2 and a current density of as high as 574 mA cm −2 measured at 0.8 V. This initial work represents a significant landmark for the research and development of the fuel cell technology, opening a wide door for a new field of research we call hereafter, HT-AEMFCs . • For the first time, AEMFC performance was evaluated at high-temperature of 110 °C. • At 110 °C the AEM showed a record high hydroxide conductivity of ca. 300 mS cm −1 . • Excellent cell performance achieved – 2.1 W cm −2 peak and 574 mA cm −2 at 0.8 V. • The AEMFC showed good stability measured for 50 h at 110 °C. • This first test opens the doors for a new research field we call “HT-AEMFCs”.

Tuning the effects of N1 substituents on the 2-methylimidazolium functionalized polynorbornene alkaline anion exchange membranes

The N1-substituted (methyl, isopropyl, butyl, benzyl or dodecyl) 2-methylimidazolium functionalized polynorbornene (rPNB-RMIm-30) AEMs are prepared and the effects of substituents are studied. The N1-butyl or isopropyl-substituted 2-methylimidzolium (rPNB-BuMIm-30 or rPNB-iPrMIm-30) anion exchange membrane (AEM) reveals much better alkaline durability than that of methyl, benzyl and dodecyl-substituted 2-methylimidazolium-based AEMs, reflected by the almost unaltered FT-IR spectra and TGA curves after being subjected to 1 M NaOH for 720 h at 60 °C, with a conductivity degradation of 17% and 14% respectively. Furthermore, a highest hydroxide conductivity (51.5 mS cm−1, 80 °C) is achieved of the rPNB-BuMIm-30 AEM, attributing to its well-defined phase-separated structure, as evidenced by results of atomic force microscope (AFM) and X-ray scattering (SAXS). Membrane electrode assembly (MEA) with rPNB-BuMIm-30 AEM exhibits a peak power density of 205 mWcm−2 at 60 °C. This study paves the way of N1-Substituented 2-methylimidazolium-based AEM for fuel cells practical application.

Water Layering Affects Hydroxide Diffusion in Functionalized Nanoconfined Environments.

In functionalized nanoconfined environments of the type employed in the study of anion exchange membranes (AEMs), a unique set of water layers forms as a result of the presence of cations and the proximity of the waters to the edges of the confining volume. In this work, we employ fully atomistic ab initio molecular dynamics in order to provide a clear picture of the solvation patterns and diffusion mechanisms of the hydroxide ion within each water layer. We find that each water layer supports a particular dominant coordination pattern for the hydroxide ion and that these solvation complexes differ among the layers. As these solvation structures affect the rate of hydroxide diffusion, it is suggested that different water layers can either promote or suppress diffusion. We believe the results presented in this work elucidate water layer features that influence hydroxide transport and can provide a guide for engineering AEMs with high hydroxide conductivity.

Effect of N-cyclic cationic groups in poly(phenylene oxide)-based catalyst ionomer membranes for anion exchange membrane fuel cells

Herein, as a binder (or catalyst ionomer) for AEMFCs, we investigated the effect of two different cationic copolymers based on poly(phenylene oxide) (PPO) with N-cyclic quaternary ammonium (QA) groups, including six-membered dimethyl piperidinium (DMP) and bis-six-membered azonia-spiro undecane (ASU). An earlier report on the same polymers for membranes in AEMFCs indicated the better electrochemical performance of PPO-ASU compared with PPO-DMP. Therefore, we would like to investigate these two polymers for catalyst ionomers. The outcome in this study using these two copolymers as catalyst ionomers indicates the opposite result; the electrochemical performance of the PPO-DMP ionomer is much better than the PPO-ASU ionomer. The commercial Fumion ionomer was used for the qualitative comparison. The density functional theory (DFT) calculation of the adsorption energy according to different orientations of the cationic groups on the catalyst surface shows that there is no difference between the adsorption energy of DMP and ASU cations, in compliance with the orientations of the cations. Although the PPO-ASU ionomer membrane has the highest hydroxide conductivity at 60 °C in liquid water, the hydrogen oxidation/reduction (HOR) activity of PPO-DMP and PPO-ASU showed similar values with the Fumion ionomer. While the PPO-DMP ionomer membrane shows relatively large fuel gas (hydrogen) permeability in dry and wet conditions, due to the chain flexibility and the presence of two methyl groups compared to the single methyl groups and lower flexibility of the PPO-ASU and Fumion ionomers. The electrochemical performance of a membrane electrode assembly (MEA) using the PPO-DMP ionomer exhibited an exceptional peak power density of 335 mW cm−2 compared to lower peak power densities the of PPO-ASU and Fumion ionomers under 60 °C and a fully humidified condition (H2/O2). The SEM images of MEAs after testing supports the conclusion that the PPO-DMP ionomer forms a uniform catalyst interface that is very well bound between the electrode and membrane, unlike the PPO-ASU and Fumion ionomers. The PPO-DMP ionomer membrane also showed better tensile strength and elongation at break than the PPO-ASU ionomer membrane. Therefore, we conclude that the well-prepared three-phase boundary structure played a critical role for the catalyst ionomer in each electrode, overcoming one of the critical performance-limiting factors.