Phosphoric acid doped composite proton exchange membrane for hydrogen production in medium-temperature copper chloride electrolysis

A copper chloride (CuCl) electrolyzer that constitutes of composite proton exchange membrane (PEM) that functions at medium-temperature (>100 °C) is beneficial for rapid electrochemical kinetics, and better in handling fuel pollutants. A synthesized polybenzimidazole (PBI) composite membrane from the addition of ZrO₂ followed with phosphoric acid (PA) is suggested to overcome the main issues in CuCl electrolysis, including the copper diffusion and proton conductivity. PBI/ZrP properties improved significantly with enhanced proton conductivity (3 fold of pristine PBI, 50% of Nafion 117), superior thermal stability (>600 °C), good mechanical strength (85.17 MPa), reasonable Cu permeability (7.9 × 10⁻⁷) and high ionic exchange capacity (3.2 × 10⁻³ mol g⁻¹). Hydrogen produced at 0.5 A cm⁻² (115 °C) for PBI/ZrP and Nafion 117 was 3.27 cm³ min⁻¹ and 1.85 cm³ min⁻¹, respectively. The CuCl electrolyzer efficiency was ranging from 91 to 97%, thus proven that the hybrid PBI/ZrP membrane can be a promising and cheaper alternative to Nafion membrane.     

Phosphosilicate nano-network (PPSN)-Polybenzimidazole (PBI) composite electrolyte membrane for enhanced proton conductivity,durability and power generation of HT-PEMFC

Here we report a composite electrolyte membrane of Polybenzimidazole (PBI) with Phosphosilicate nano-network (PPSN) for enhanced proton conductivity, durability and power generation of high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). Solid state proton conductor three dimensional Phosphosilicate nano-network (average particle size <10 nm) is synthesized using easy and low-cost sol gel method followed by ball milling and composited with PBI at different loading employing methane sulfonic acid (MSA) as solvent. The electrolyte membrane is characterized using FESEM, XRD, FTIR, TGA; proton conductivity, ion exchange capacity, water uptake and acid doping level, chemical stability and mechanical yield strength are measured and the membrane is tested for HT-PEMFC application. Property and performance mapping reveals that with 10% PPSN loading, composite (PPSN-PBI-10) membrane offers the maximum enhancement of all properties and power generation of HT-PEMFC, while beyond a critical loading (～22%) properties and performance deteriorate below that of pristine PBI. Using optimum loading of PPSN, compared to pristine PBI, a remarkable rise in water uptake and acid doping level is achieved that facilitates proton conduction; also in spite of the presence of Phosphoric acid in the PPSN filler, the maximum 47.5% enhancement of ultimate strength is attained. The performance of HT-PEMFC using composite PPSN-PBI unveil that almost 2 times (100%) enhancement of peak power generation (～0.73 W cm^?2) is achieved using PPSN-PBI-10 at 170 °C operating temperature compared to pristine PBI. This may be attributed to the facilitated proton conduction through the extended tunnelling network offered by PPSN. Incorporation of PPSN improves the durability; over 48 h only 16% decay in voltage is noticed using PPSN-PBI-10 membrane which is remarkably lower than the 31% decay of pristine PBI membrane.     

Optimization of gas diffusion electrode for polybenzimidazole-based high temperature proton exchange membrane fuel cell: Evaluation of polymer binders in catalyst layer

Gas diffusion electrodes (GDEs) prepared with various polymer binders in their catalyst layers (CLs) were investigated to optimize the performance of phosphoric acid doped polybenzimidazole (PBI)-based high temperature proton exchange membrane fuel cells (HT-PEMFCs). The properties of these binders in the CLs were evaluated by structure characterization, electrochemical analysis, single cell polarization and durability test. The results showed that polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) are more attractive as CL binders than conventional PBI or Nafion binder. At ambient pressure and 160 °C, the maximum power density can reach ∼ 0.61 W cm⁻² (PTFE GDE), and the current density at 0.6 V is up to ca. 0.52 A cm⁻² (PVDF GDE), with H₂/air and a platinum loading of 0.5 mg cm⁻² on these electrodes. Also, both GDEs showed good stability for fuel cell operation in a short term durability test.     

Influence of catalyst layer polybenzimidazole molecular weight on the polybenzimidazole-based proton exchange membrane fuel cell performance

The catalyst layer (CL) of a polybenzimidazole (PBI) membrane electrode assembly (MEA) consists of Pt–C (Pt on a carbon support), PBI, and H₃PO₄. Two series of catalyst ink solutions each containing Pt–C, N,N′-dimethyl acetamide, and PBIs comprising four different molecular weights (MWs) (i.e., M_w = 1.1 × 10⁴, 4.4 × 10⁴, 9.0 × 10⁴, and 17.4 × 10⁴ g mol⁻¹) are used to fabricate CLs. One catalyst ink solution series is mixed with LiCl, while the other solution series lacks LiCl. We demonstrate that the CL prepared using a lower MW PBI has a higher electrochemical surface area, lower charge transfer resistance, and higher fuel cell performance. The addition of LiCl enhances the dispersion of the high MW PBIs in the catalyst ink solution and acts as a foaming agent in CL, thus improving fuel cell performance. However, LiCl exerts small influence on the fuel cell performance of the MEAs fabricated using low MW PBIs.     

Multi-walled carbon nanotubes decorated by platinum catalyst for high temperature PEM fuel cell

In the literature, studies on platinum catalysts deposited on multi-walled carbon nanotube (Pt/MWCNT) have been mostly focused on low temperature fuel cell (LT-PEMFC) applications. In this study, we focus the synthesis and characterization of high temperature fuel cell (HT-PEMFC) performance of Pt/MWCNT in short and long term. The structural properties of the Pt/MWCNT electrocatalyst were analyzed by XRD, TGA, SEM and TEM measurements. The Pt/MWCNTs were also characterized by electrochemical measurements for durability estimation. Laboratory scale MEA with Pt/MWCNT was prepared by ultrasonic coating technique and has been tested in situ in single HT-PEMFC. Performance curves in dry Hydrogen/Air system were obtained that demonstrated performance comparable to commercial catalysts in that HT-PEMFC. The characterizations specified that the electrocatalytic and HT-PEMFC performance of the Pt/MWCNT catalysts are higher power density (0.360 W/cm²) than Pt/C (0.310 W/cm²) at 160 °C. The results obtained show that the synthesized catalysts are suitable for high temperature applications. In addition, the stability studies of MEAs prepared with Pt/MWCNT catalyst were performed by AST tests and compared with Pt/C based MEA.     

Performance of an HT‐PEMFC having a catalyst with graphene and multiwalled carbon nanotube support

In this study, the effect of multiwalled carbon nanotube and graphene nanoplatelet‐based catalyst supports on the performance of reformate gas‐fed polybenzimidazole (PBI)‐based high‐temperature proton exchange membrane fuel cell (HT‐PEMFC) was investigated. In addition, the effect of several microwave conditions on the performance of the Pt‐Ru/multiwalled carbon nanotube (MWCNT)–graphene nanoplatelet (GNP) catalyst was assessed. Through X‐ray diffraction, thermal gravimetric analysis, transmission electron microscopy, scanning electron microscopy, and energy dispersive spectroscopy, the catalysts' chemical structure and morphology were characterized. Cyclic voltammetry analysis was used for the electrochemical characterization of catalysts through an electrochemical cell with three electrodes connected to a potentiostat. The results showed that the best performing catalyst is the catalyst produced using 800‐W power for 40 seconds. The electrochemically active surface area values of this catalyst ranged from 54 to 45 m²/g. Single‐cell performance tests of the HT‐PEMFC were then carried out. In these tests, reformate gas mixture, consisting of H₂, CO₂, and CO, was fed to the anode side at 160°C without humidification. These tests for the best performing catalyst yielded peak power density of 0.280 W/cm² and current density (at 0.6 V) of 0.180 A/cm² in the H₂/air environment and peak power density of 0.266 W/cm² and current density (at 0.6 V) of 0.171 A/cm² in the reformate gas/air environment. As a result of the experiments, it was found that Pt‐Ru/MWCNT‐GNP hybrid material is a suitable catalyst for HT‐PEMFC.     

Polybenzimidazole-modified carbon nanotubes as a support material for platinum-based high-temperature proton exchange membrane fuel cell electrocatalysts

We fabricate polybenzimidazole (PBI) wrapped carbon nanotubes (MWCNTs) as support material for platinum-based fuel cell electrocatalyst. With the aid of microwave-assisted polyol reduction, we obtain very fine platinum (Pt) nanoparticles on PBI/MWCNT support while reducing the amount of Pt waste during synthesis. Cyclic voltammetry (CV) concludes that Pt-PBI/MWCNT has 43.0 m² g⁻¹ of electrochemically active surface area (ECSA) to catalyze hydrogen oxidation. Furthermore, after the 1000th cycle, Pt-PBI/MWCNT preserves almost 80% of its maximum ECSA, meaning that Pt-PBI/MWCNT is much more durable than the Pt/MWCNT and commercial Pt/C. High-temperature proton exchange membrane fuel cell (HT-PEMFC) performance tests are conducted under H₂/Air conditions at the temperatures ranging from 150 °C to 180 °C. Nevertheless, tests conclude that the maximum power density values of the Pt-PBI/MWCNT are found inferior to the Pt/C at all temperatures (e.g., 47 vs. 62 mW cm⁻² at 180 °C), suggesting that some balance between durability and performance has to be taken into consideration.     

Improving the performance of high-temperature PEM fuel cells based on PBI electrolyte

This paper describes the testing of the gas-diffusion electrodes for polymer electrolyte membrane fuel cells utilizing phosphoric acid doped polybenzimidazole (PBI) electrolyte, which allows for an operating temperature as high as 200 °C. In order to determine the optimum structure of our anodes and cathodes, the platinum content in the Pt/C catalyst and catalyst loading were varied, as well as the loading of the PBI electrolyte dispersed in the catalyst layer. The different MEAs were tested in terms of their performance by recording polarization curves using pure oxygen and hydrogen. It was found that a high platinum content and a thin catalyst layer on both anode and cathode, gave the overall best performance. This was attributed to the different catalyst surface areas, the location of the catalyst in relation to the electrolyte membrane and particularly the amount of PBI dispersed in the catalyst layer. Scanning electron microscopy (SEM) was used in order to examine the cross-section of the MEAs and measure the thickness of the catalyst layers. With this information, it was possible to give an estimate of the porosity of the catalyst layer.     

Effects of hot pressing conditions on the performance of Nafion membranes coated by ink-jet printing of Pt/MWCNTs electrocatalyst for PEMFCs

In our previous work, a hydrothermal method was employed to prepare Pt/MWCNTs nanocomposites with 20 wt.% Pt, a low mean Pt nanoparticles size (2.8 nm) and a specific surface area of 99 m² g⁻¹. In this work, the membrane electrode assemblies (MEAs) with hydrothermally synthesized Pt/MWCNTs nanocatalysts were fabricated by catalyst-coated membrane (CCM) method. For this purpose, a commercial HP inkjet printer was used to deposit Pt/MWCNTs ink (as catalyst ink) directly on to the substrate (Nafion membrane or decal substrate) with a loading of 0.2 mg cm⁻² Pt for both the anode and cathode. The effects of hot-pressing conditions on the performance of MEAs were investigated through Taguchi design of experiments method using temperature (100 and 130 °C), pressure (800 and 1000 psi) and time (3 and 5 min) as effective experimental parameters. The compression ratios of MEAs were determined by testing the thicknesses before and after hot-pressing process. The performance of MEAs was characterized by the polarization curves and cyclic voltammetry (CV) and the surface morphologies of the electrodes were observed by scanning electron microscopy (SEM). The results showed that the most appropriate hot-pressing conditions were 800 psi, 100 °C, and 3 min. Electrochemical analysis and physical property examination revealed that the MEA fabricated by CCM method has a better performance compared to the one prepared by conventional decal transfer (DT) method.     

The effect of functionalised multi-walled carbon nanotubes in the hydrogen electrooxidation reaction in reactive currents impurified with CO

The present article investigates the tolerant effect exerted by a functionalised multi-walled carbon nanotube (MWCNT) support compared with the Vulcan XC-72 support for a nanoparticulate Pt catalyst. The negative effect produced in the hydrogen oxidation reaction (HOR) by the presence of a Pt contaminated with high CO coverage was analysed. This investigation was conducted using a rotating disk electrode (RDE) and a single cell with membrane electrode assemblies (MEAs) with loads of 0.3 mg Pt/cm² for the anode and 0.6 mg Pt/cm² for the cathode at various poisoning times. To this end, polarisation curves were performed, and electrochemical impedance spectroscopy (EIS) measurements were analysed. In addition, the recovery of the poisoning/de-poisoning process was studied. The –OH groups anchored to the MWCNT support exert a protective effect on the Pt nanoparticles, making the catalyst more efficient in a PEMFC fed with H₂ + CO.     

Investigation of the effect of graphitized carbon nanotube catalyst support for high temperature PEM fuel cells

In this study, it is aimed to investigate the graphitization effect on the performance of the multi walled carbon nanotube catalyst support for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. Microwave synthesis method was selected to load Pt nanoparticles on both CNT materials. Prepared catalyst was analyzed thermal analysis (TGA), Transmission Electron Microscopy (TEM) and corrosion tests. TEM analysis proved that a distribution of Pt nanoparticles with a size range of 2.8–3.1 nm was loaded on the Pt/CNT and Pt/GCNT catalysts. Gas diffusion electrodes (GDE) were manufactured by an ultrasonic spray method with synthesized catalyst. Polybenzimidazole (PBI) membrane based Membrane Electrode Assembly (MEA) was prepared for observe the performance of the prepared catalysts. The synthesized catalysts were also tested in a HT-PEMFC environment with a 5 cm² active area at 160 °C without humidification. This study demonstrates the feasibility of using the microwave synthesis method as a fast and effective method for preparing high performance Pt/CNT and Pt/GCNT catalyst for HT-PEMFC. The HT-PEMFC performance evaluation shows current densities of 0.36 A/cm²0.30 A/cm² and 0.20 A/cm² for the MEAs prepared with Pt/GCNT, Pt/CNT and Pt/C catalysts @ 0.6 V operating voltage, respectively. AST (Accelerated Stress Test) analyzes of MEAs prepared with Pt/GCNT and Pt/CNT catalysts were also performed and compared with Pt/C catalyst. According to current density @ 0.6 V after 10,000 potential cycles, Pt/GCNT, Pt/CNT and Pt/C catalysts can retain 61%, 67% and 60% of their performance, respectively.     

Electroreduction of oxygen on sputter-deposited Pd nanolayers on multi-walled carbon nanotubes

The electrochemical reduction of oxygen on Pd nanoparticle/multi-walled carbon nanotube (PdNP/MWCNT) catalysts was studied in acid and alkaline solutions using the rotating disk electrode (RDE) method. The PdNP/MWCNT nanocomposites were prepared by sputter-deposition of palladium onto the surface of MWCNTs. The surface morphology of the PdNP/MWCNT composites was characterised by scanning electron microscopy (SEM). The SEM images showed the formation of Pd nanolayers around MWCNTs. The RDE results revealed a high electrocatalytic activity of PdNP/MWCNT catalysts towards the oxygen reduction reaction (ORR) in alkaline media. Two Tafel regions with different slope can be distinguished. At low overpotentials the Tafel slope is close to −60 mV dec⁻¹ and at higher current densities the slope is approximately −100 mV dec⁻¹. The PdNP/MWCNT composite is a promising material to be used as a cathode catalyst for alkaline membrane fuel cells.     

Study of the influence of Nafion/C composition on electrochemical performance of PEM single cells with ultra-low platinum load

The electrochemical performance of membrane electrode assemblies (MEAs) with ultra-low platinum load (0.02 mg_Pt cm^?2) and different compositions of Nafion/C in the catalytic layer have been investigated. The electrodes were fabricated depositing the catalytic ink, prepared with commercial catalyst (HiSPEC 2000), onto the gas diffusion layers by wet powder spraying. The MEAs were electrochemically tested using current-voltage curves and electrochemical impedance spectroscopy measurements. The experiments were carried out at 70 °C in H₂/O₂ and H₂/air as reactant gases at 1 and 2 bar pressure and 100% of relative humidity. For all MEAs tested, power density increases when the gasses pressure is increased from 1 to 2 bar. On the other hand, power density also increased when oxygen is used instead of air as oxidant gas in cathode. The lower power density (34 mW cm^?2) and power per Pt loading (0.86 kW g_Pt^?1) corresponds to the MEA prepared without Nafion in anode and cathode catalytic layers working with hydrogen and air at 1 bar pressure as reactants gas. The MEA with 30% wt Nafion/C reached the highest power density (422 mW cm^?2) and power per Pt loading (10.60 kW g_Pt^?1) using hydrogen and oxygen at 2 bar pressure. Finally, electrode surface microstructure and cross sections of MEAs were analyzed by Scanning Electron Microscopy (SEM). Examination of the electrodes, revealed that the most uniform ionomer network surface corresponds to the electrode with 40 wt% Nafion/C, and MEA ionomer-free catalytic layer shows delamination, it leads to low electrochemical performance.     

Preparation of polybenzimidazole/ZIF-8 and polybenzimidazole/UiO-66 composite membranes with enhanced proton conductivity

Metal-organic frameworks (MOFs) are considered emerging materials as they further improve the various properties of polymer membranes used in energy applications, ranging from electrochemical storage and purification of hydrogen to proton exchange membrane fuel cells. Herein, we fabricate composite membranes consisting of polybenzimidazole (PBI) polymer as a matrix and MOFs as filler. Synthesis of ZIF-8 and UiO-66 MOFs are conducted through a typical solvothermal method, and composite membranes are fabricated with different MOF compositions (e.g., 2.5, 5.0, 7.5, and 10.0 wt %). We report a significant improvement in proton conductivity compared with the pristine PBI; for example, more than a three-fold increase in conductivity is observed when the PBI-UiO66 (10.0 wt %) and PBI-ZIF8 (10.0 wt %) membranes are tested at 160 °C. Proton conductivities of the composite membranes vary between 0.225 and 0.316 S cm^?1 at 140 and 160 °C. For the comparison, pure PBI exhibits 0.060 S cm^?1 at 140 °C and 0.083 S cm^?1 at 160 °C. However, we also report a decrease in permeability and mechanical stability with the composite membranes.     

Non-platinum cathode catalysts for alkaline membrane fuel cells

Hydrogen–oxygen fuel cells using an alkaline anion exchange membrane were prepared and evaluated. Various non-platinum catalyst materials were investigated by fabricating membrane-electrode assemblies (MEAs) using Tokuyama membrane (# A201) and compared with commercial noble metal catalysts. Co and Fe phthalocyanine catalyst materials were synthesized using multi-walled carbon nanotubes (MWCNTs) as support materials. X-ray photoelectron spectroscopic study was conducted in order to examine the surface composition. The electroreduction of oxygen has been investigated on Fe phthalocyanine/MWCNT, Co phthalocyanine/MWCNT and commercial Pt/C catalysts. The oxygen reduction reaction kinetics on these catalyst materials were evaluated using rotating disk electrodes in 0.1 M KOH solution and the current density values were consistently higher for Co phthalocyanine based electrodes compared to Fe phthalocyanine. The fuel cell performance of the MEAs with Co and Fe phthalocyanines and Tanaka Kikinzoku Kogyo Pt/C cathode catalysts were 100, 60 and 120 mW cm⁻² using H₂ and O₂ gases.     

Gel combustion synthesized NiMoO4 anchored polymer nanocomposites as a flexible electrode material for solid state asymmetric supercapacitors

Recent research has focused on the search for new electrode materials to improve the specific capacitance of supercapacitors. Conductive polymers and metal oxides have been extensively tested as electrode materials for supercapacitors. Incorporating both conductive polymers and metal oxides into a composite provides excellent results for the electrochemical performance of supercapacitors. In this present work, we have fabricated the nanoscale α-NiMoO₄ particles that enwrapped on electronically conducting polymer nanocomposites (PNCs) based on Polyvinyl alcohol (PVA)/Poly(vinyl) pyrrolidone (PVP) for supercapacitor applications. The different concentrations of PVA/PVP with α-NiMoO₄ loaded polymer nanocomposites were developed by using a solution casting method. All the polymer nanocomposites have been subjected to Scanning Electron Microscopy (SEM), Fourier Transforms Infrared (FTIR), X-ray diffraction (XRD), and electrochemical studies. The prepared PNCs surface morphology has been acquired as a non-uniform rod-like structure. The electrochemical performances of the prepared PNCs have been investigated and the resultant value of the maximum specific capacitance is 15.56 F g⁻¹ for 1 wt % of α-NiMoO₄ nanoparticles(NPs) loaded polymer blended electrode at a scan rate of 5 mVs⁻¹. The prepared PNCs exhibit 97.12% of columbic efficiency studied by using two electrode systems at room temperature in an aqueous electrolyte solution of 3 M KOH. From these investigation, it has been revealed that the PVA/PVP/α-NiMoO₄ composites could be portable and flexible electrodes for energy storage applications.     

Effect of platinum amount in carbon supported platinum catalyst on performance of polymer electrolyte membrane fuel cell

The performance of polymer electrolyte membrane fuel cells fabricated with different catalyst loadings (20, 40 and 60 wt.% on a carbon support) was examined. The membrane electrode assembly (MEA) of the catalyst coated membrane (CCM) type was fabricated without a hot-pressing process using a spray coating method with a Pt loading of 0.2 mg cm⁻². The surface was examined using scanning electron microscopy. The catalysts with different loadings were characterized by X-ray diffraction and cyclic voltammetry. The single cell performance with the fabricated MEAs was evaluated and electrochemical impedance spectroscopy was used to characterize the fuel cell. The best performance of 742 mA cm⁻² at a cell voltage of 0.6 V was obtained using 40 wt.% Pt/C in both the anode and cathode.     

Photocured PEO-based solid polymer electrolyte and its application to lithium–polymer batteries

A solid polymer electrolyte (SPE) based on polyethylene oxide (PEO) is prepared by photocuring of polyethylene glycol acrylates. The conductivity is greatly enhanced by adding low molecular weight poly(ethylene glycol) dimethylether (PEGDME). The maximum conducticity is 5.1×10⁻⁴ S cm⁻¹ at 30°C. These electrolytes display oxidation stability up to 4.5 V against a lithium reference electrode. Reversible electrochemical plating/stripping of lithium is observed on a stainless steel electrode. Li/SPE/LiMn₂O₄ as well as C(Li)/SPE/LiCoO₂ cells have been fabricated and tested to demonstrate the applicability of the resulting polymer electrolytes in lithium–polymer batteries.     

Optimal catalyst layer structure of polymer electrolyte membrane fuel cell

In a membrane electrode assembly (MEA) of polymer electrolyte membrane fuel cells, the structure and morphology of catalyst layers are important to reduce electrochemical resistance and thus obtain high single cell performance. In this study, the catalyst layers fabricated by two catalyst coating methods, spraying method and screen printing method, were characterized by the microscopic images of catalyst layer surface, pore distributions, and electrochemical performances to study the effective MEA fabrication process. For this purpose, a micro-porous layer (MPL) was applied to two different coating methods intending to increase single cell performances by enhancing mass transport. Here, the morphology and structure of catalyst layers were controlled by different catalyst coating methods without varying the ionomer ratio. In particular, MEA fabricated by a screen printing method in a catalyst coated substrate showed uniformly dispersed pores for maximum mass transport. This catalyst layer on micro porous layer resulted in lower ohmic resistance of 0.087 Ω cm² and low mass transport resistance because of enhanced adhesion between catalyst layers and a membrane and improved mass transport of fuel and vapors. Consequently, higher electrochemical performance of current density of 1000 mA cm^-2 at 0.6 V and 1600 mAcm⁻² under 0.5 V came from these low electrochemical resistances comparing the catalyst layer fabricated by a spraying method on membranes because adhesion between catalyst layers and a membrane was much enhanced by screen printing method.     

Demonstration of a 20 W class high-temperature polymer electrolyte fuel cell stack with novel fabrication of a membrane electrode assembly

Acid-doped polybenzimidazole (PBI) membrane and polytetrafluoroethylene (PTFE)-based electrodes are used for the membrane electrode assembly (MEA) in high-temperature polymer electrolyte fuel cells (HTPEFCs). To find the optimum PTFE content for the catalyst layer, the PTFE ratio in the electrodes is varied from 25 to 50 wt%. To improve the performance of the electrodes, PBI is added to the catalyst layer. With a weight ratio of PTFE to Pt/C of 45:55 (45 wt% PTFE in the catalyst layer), the fuel cell shows good performance at 150 °C under non-humidified conditions. When 5 wt% PBI is added to the electrodes, performance is further improved (250 mA cm⁻² at 0.6 V). Our 20 W class HTPEFC stack is fabricated with a novel MEA. This MEA consists of 8 layers (1 phosphoric acid-doped PBI membrane, 2 electrodes, 1 sub-gasket, 2 gas-diffusion media, 2 gas-sealing gaskets). The sub-gasket mitigates the destruction of a highly acid-doped PBI membrane and provides long-term durability to the fuel cell stack. The stack operates for 1200 h without noticeable cell degradation.