Efficient Proton Exchange Membrane Research Articles

Synergistic Engineering of Dopant and Support of Ru Oxide Catalyst Enables Ultrahigh Performance for Acidic Oxygen Evolution

AbstractActive and robust electrocatalysts for acidic oxygen evolution reaction (OER) are of crucial importance for efficient proton exchange membrane water electrolyzer (PEM‐WE). Ruthenium (Ru) oxide has attracted considerable attention due to its high activity. However, the unsatisfying stability of Ru oxide in acidic OER environments hinders the application. Here, Ce‐doped RuO2 nanoparticles are designed and supported on Co─N─C material (Ce@RuO2/CoNC) for acidic OER. It is demonstrated that Ce@RuO2/CoNC delivers a super low overpotential of 150 mV and an excellent stability of 1000 h at 10 mA cm−2, outperforming most previously reported Ru‐based catalysts. The mass activity is estimated as 2365.5 AgRu−1 at 1.5 V (vs RHE), representing ≈2× advance compared to the best prior study. Furthermore, applied in a single‐cell PEM‐WE device, it can steadily operate for 1000 h at 200 mA cm−2. The studies show that Ce‐doping and Co─N─C support synergistically enhance the activity and stability of Ru oxide by optimizing the free energies of OER intermediates and suppressing the dissolution of Ru.

Characterization of Porous Transport Layers Towards the Development of Efficient Proton Exchange Membrane Water Electrolysis

Characterization of Porous Transport Layers Towards the Development of Efficient Proton Exchange Membrane Water Electrolysis

Superprotonic Conductivity by Synergistic Blending of Coordination Polymers with Organic Polymers: Fabrication of Durable and Flexible Proton Exchange Membranes.

Creation of an efficient and cost-effective proton exchange membrane (PEM) has emerged as a propitious solution to address the challenges of renewable energy development. Coordination polymers (CPs) have garnered significant interest due to their multifunctional applications and moldability, along with long-range order. To leverage the potential of CPs in fuel cells, it is essential to integrate microcrystalline CPs into organic polymers to prepare membranes and avoid grain boundary issues. In this study, we designed and synthesized CPs containing imidazole and sulfonate moieties via gel-to-crystal transformation. The integration of CPs into the PVDF-PVP matrix resulted in superprotonic conductivity in the order of 10-2 S cm-1 at room temperature (30 ºC) and 98% RH. The proton conductivity achieved with CP-integrated composite membrane was 4.69 × 10-2 S cm-1 at 80 °C and 98% RH, the highest among all CP/MOF-integrated PVDF-PVP membranes under hydrous conditions. The excellent compatibility of CPs with PVDF-PVP produced highly flexible membranes with superior mechanical, chemical, and thermal stability. About 25 times higher proton conductivity value was achieved with membrane, compared to intrinsic CPs, at RT and 98% RH. Thus, we present a cost-effective CP-integrated mixed-matrix membrane with superprotonic conductivity and long-term durability for cutting-edge fuel cell development.

High Efficiency and High Durability Proton Exchange Membrane Water Electrolyzers for Hydrogen Production with Advanced Catalyst Coated Membranes

Water electrolyzers and fuel cells can be used to create a closed loop system for space exploration. Electrolyzers allow for reliable self-sustainable generation of hydrogen and oxygen for energy storage, followed by conversion into electrical energy in a fuel cell. A first-order safety concern for water electrolyzer operation is hydrogen crossover. Transport of hydrogen to the oxygen rich anode in proton exchange membrane (PEM) water electrolyzers poses safety concerns when the hydrogen concentration in the anode flow field approaches the hydrogen lower flammability limit (LFL). Hydrogen storage efficiency relies on high hydrogen pressure, leading to pressure-driven hydrogen crossover. Mitigation of hydrogen crossover through research and development of a platinum metal recombination layer has been demonstrated in high performing, durable PEMWEs.1-4 Ouimet4 explored the use of a novel dual recombination layer configuration to mitigate PEM water electrolyzer hydrogen crossover. In addition, the current state of the art for PEM fuel cells and water electrolyzers rely on perfluoro-sulfonated acid (PSFA) based membranes. There are significant challenges facing the use of PSFA-based membranes; namely, environmental contamination and performance limitations. The use of a hydrocarbon membrane allows for the development of a PSFA-free system that shows higher efficiency and durability. Investigation of hydrocarbon membranes pave way for developing a PEM water electrolyzer that will demonstrate improved gas permeability resistance, mechanical strength, and thermal stability.5-8 There is a need for both hydrogen crossover mitigation strategies and durability testing with hydrocarbon membranes.The research outlined in this work is focused on the development of PSFA-free PEM water electrolyzers with low hydrogen crossover. In this work, the dual recombination layer configuration will be incorporated into a hydrocarbon membrane for PEM water electrolysis. Polarization, electrochemical impedance spectroscopy, electrochemical equivalent circuits, distribution of relaxation times, and materials characterization will be used to investigate the cell performance and durability. References G. Mirshekari, R. Ouimet, Z. Zeng, H. Yu, S. Bliznakov, L. Bonville, A. Niedzwiecki, C. Capuano, K. Ayers, and R. Maric, “High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment,” international journal of hydrogen energy, vol. 46, no. 2, pp. 1526–1539, 2021.Z. Zeng, R. Ouimet, L. Bonville, A. Niedzwiecki, C. Capuano, K. Ayers, A. P. Soleymani, J. Jankovic, H. Yu, G. Mirshekari, et al., “Degradation mechanisms in advanced meas for pem water electrolyzers fabricated by reactive spray deposition technology,” Journal of The Electrochemical Society, vol. 169, no. 5, p. 054536, 2022.A. Martin, D. Abbas, P. Trinke, T. Böhm, M. Bierling, B. Bensmann, S. Thiele, and R. Hanke-Rauschenbach, “Communication—proving the importance of ptinterlayer position in pemwe membranes for the effective reduction of the anodic hydrogen content,” Journal of The Electrochemical Society, vol. 168, no. 9, p. 094509, 2021.R. J. Ouimet, “Catalyst development by a novel fabrication process for energy applications,” University of Connecticut Doctoral Dissertation, 2021.P. Trinke, P. Haug, J. Brauns, B. Bensmann, R. Hanke-Rauschenbach, and T. Turek, “Hydrogen crossover in pem and alkaline water electrolysis: mechanisms, direct comparison and mitigation strategies,” Journal of The Electrochemical Society, vol. 165, no. 7, p. F502, 2018.P. Trinke, B. Bensmann, and R. Hanke-Rauschenbach, “Current density effect on hydrogen permeation in pem water electrolyzers,” International Journal of Hydrogen Energy, vol. 42, no. 21, pp. 14355–14366, 2017.H. Q. Nguyen and B. Shabani, “Proton exchange membrane fuel cells heat recovery opportunities for combined heating/cooling and power applications,” Energy Conversion and Management, vol. 204, p. 112328, 2020.C. Klose, T. Saatkamp, A. Münchinger, L. Bohn, G. Titvinidze, M. Breitwieser, K. D. Kreuer, and S. Vierrath, “All-hydrocarbon mea for pem water electrolysis combining low hydrogen crossover and high efficiency,” Advanced Energy Materials, vol. 10, no. 14, p. 1903995, 2020.

Investigation of Iridium Catalyst Degradation in PEM Water Electrolyzers: Current Density or Cell Voltage?

Proton exchange membrane (PEM) water electrolyzers represent a cornerstone technology in the sustainable production of green hydrogen. However, their large-scale commercialization is hindered by catalyst degradation, particularly the iridium-based anode, which compromises the efficiency and durability of the stack. This study delves into the degradation mechanism(s) of the Ir-based catalyst in the anode of PEM electrolyzers, focusing on the influence of operating conditions such as current density and cell voltage. We have utilized the state-of-the-art R&D platform “PEMI” at Plug Power to construct a rainbow stack that contains several 50 cm2 membrane electrode assemblies (MEAs) with different membrane thicknesses. This innovative approach enables identical current densities across different MEAs while varying the cell voltage on the anode catalyst layer, thereby isolating the effect of cell voltage from current on catalyst degradation.Our investigation seeks to clarify the puzzle whether it is the current density or the cell voltage that determines the transition and degradation of iridium-based catalysts. Preliminary results indicate that different oxidation states of Iridium exhibit significantly different kinetics and conductivity at varied cell voltages. This is corroborated by our synchrotron-based in situ X-ray absorption spectroscopy experiments that unraveled evolution of the anode catalyst layer at elevated cell voltages. By systematically analyzing the degradation patterns of MEAs with different membrane thickness under controlled conditions, we pinpointed the operational parameter that drives catalyst degradation. The finding provides in-depth understanding of the underlying principles that govern the iridium-based catalyst durability and points to strategies mitigating the degradation. It will pave the way for more resilient and efficient PEM water electrolyzers. Acknowledgement. This research used beamline 7-BM (QAS) of the National Synchrotron Light Source II, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory Contract DE-SC0012704. Beamline operations were supported in part by the Synchrotron Catalysis Consortium Grant DE-SC0012335.Keywords: PEM water electrolyzers, catalyst degradation, iridium, current density, cell voltage, MEAs.

S-doped carbon anchoring PtCo intermetallic nanoparticles for efficient proton exchange membrane fuel cells based on molecularly engineered design

Enhanced ordered intermetallic compounds excel in catalyzing the oxygen reduction reaction (ORR). We introduce a novel synthesis strategy based on molecularly engineered to address challenges in high-temperature annealing. It involves the synthesis of carbon platforms with rich edge sites, which serve as effective anchoring points for nanoparticles. By utilizing sulfur anchoring, we synthesize ordered Pt–Co intermetallic with Pt-rich shells (o-PtCo@Pt) that exhibit remarkable ORR performance. Ordered arrangement of Pt–Co endows Pt-shell with compression stress and enhances the oxidation resistance of Pt/Co sites. O–PtCo@Pt exhibits high mass activity (MA, 0.53 A mgPt−1) and specific activity (SA, 1.17 mA cm−2). It exhibits remarkable as cathodic catalyst in proton exchange membrane fuel cells. It achieves power density of 1.14 W cm−2 at 2.0 A cm−2, with MA of 0.50 A mgPt−1 at 0.9 V. It maintains stability with only 8 % power density loss after 30,000 cycles, retaining MA of 0.35 A mgPt−1.

Efficient Proton-exchange Membrane Fuel Cell Performance of Atomic Fe Sites via p-d Hybridization with Al Dopants.

Orbital hybridization to regulate the electronic structures and surface chemisorption properties of transition metals is of great importance for boosting the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs). Herein, we developed a core-shell rambutan-like nanocarbon catalyst (FeAl-RNC) with atomically dispersed Fe-Al atom pairs from metal-organic framework (MOF) material. Experimental and theoretical results demonstrate that the strong p-d orbital hybridization between Al and Fe results in an asymmetric electron distribution with moderate adsorption strength of oxygen intermediates, rendering enhanced intrinsic ORR activity. Additionally, the core-shell rambutan-like structure of FeAl-RNC with abundant micropores and macropores can enhance the density of active sites, stability, and transport pathways in PEMFC. The FeAl-RNC-based PEMFC achieves excellent activity (68.4 mA cm-2 at 0.9 V), high peak power (1.05 W cm-2), and good stability with only 7% current loss after 100 h at 0.7 V under H2-O2 condition.

Enhancing proton conduction of MOF-74(Co) by encapsulating NH3 molecules

The functional design of efficient and stable proton exchange membrane materials is an important research direction in the field of proton exchange membrane fuel cells (PEMFCs). In this work, ammonia molecules were successfully encapsulated into the one-dimensional pores of MOF-74(Co) through fumigation with ammonia vapor. Alternating current (AC) impedance tests showed that the proton conductivity of NH3 modified NH3@ MOF-74(Co) reaches an impressive value of 6.8 × 10−3 S/cm, being 10000 times that of the pristine MOF-74(Co) at 98% relative humidity (RH) and 50 °C. Various and abundant hydrogen bonds can improve the proton conduction of NH3 modified compound. This strategy provides an efficient and convenient way to construct high proton conducting porous MOFs materials by attaching NH3 molecules.

Efficient and Stable Proton Exchange Membrane Water Electrolysis Enabled by Stress Optimization.

Proton exchange membrane water electrolysis (PEMWE) is a promising solution for the conversion and storage of fluctuating renewable energy sources. Although tremendously efficient materials have been developed, commercial PEMWE products still cannot fulfill industrial demands regarding efficiency and stability. In this work, we demonstrate that the stress distribution, a purely mechanical parameter in electrolyzer assembly, plays a critical role in overall efficiency and stability. The conventional cell structure, which usually adopts a serpentine flow channel (S-FC) to deliver and distribute reactants and products, resulted in highly uneven stress distribution. Consequently, the anode catalyst layer (ACL) under the high stress region was severely deformed, whereas the low stress region was not as active due to poor electrical contact. To address these issues, we proposed a Ti mesh flow channel (TM-FC) with gradient pores to reduce the stress inhomogeneity. Consequently, the ACL with TM-FC exhibited 27 mV lower voltage initially and an 8-fold reduction in voltage degradation rate compared to that with S-FC at 2.0 A/cm2. Additionally, the applicability of the TM-FC was demonstrated in cross-scale electrolyzers up to 100 kW, showing a voltage increase of only 20 mV (accounting for less than 2% of overall voltage) after three orders of magnitude scaleup.

Poly(sulfobetaine methacrylate)-Enhanced Anode Catalyst Layer for Highly Efficient Proton Exchange Membrane Fuel Cells under Low-Humidity Conditions

Poly(sulfobetaine methacrylate)-Enhanced Anode Catalyst Layer for Highly Efficient Proton Exchange Membrane Fuel Cells under Low-Humidity Conditions

Regulating the Electronic Structure of IrO x /SnO y with NaCl for Efficient Proton Exchange Membrane Water Electrolysis

Hydrogen has been considered as a promising energy carrier because of its high gravimetric energy density. However, most hydrogen has been produced by steam methane reforming, which releases significant amounts of CO2 during the process. In contrast, water electrolysis (WE) offers the most sustainable way to produce hydrogen without carbon emissions. Especially, proton exchange membrane water electrolysis (PEMWE) technique has attracted much attention due to its high efficiency, compact design, and fast response to load fluctuations, enabling the integration of renewable energy. However, the inevitable use of precious metal (Ir, Ru) catalyst due to the sluggish kinetics of oxygen evolution reaction (OER) has hindered the practical implementation of PEMWE. In this regard, developing low-content Ir-based catalysts with high activity is critical for enhancing the cost efficiency of PEMWE. This presentation will propose a synthesis strategy for tin oxide-supported iridium oxide (IrO x /SnO y _NaCl) catalyst prepared using NaCl as a sacrificial template. This approach allows uniform dispersion of Ir particles and regulation of its valence states to favor the OER. The synthesized IrO x /SnO y _NaCl catalyst exhibited high OER activity and mass activity comparable to the state-of-the-art Ir-based OER catalysts. Electrochemical and X-ray spectroscopic analyses demonstrated that the use of NaCl template can improve the catalytic activity of IrO x by tuning the valence state ratio (Ir3+/Ir4+). Moreover, IrO x /SnO y _NaCl catalyst showed a high single-cell performance of PEMWE, achieving mass activity 2.6 times higher than commercial IrO2.

Impact of deposited Pt particles on water channel connectivity and proton conductivity in proton exchange membranes: A molecular dynamics study

Deposition of platinum ions in the proton exchange membrane significantly affects the long-term stability and proton transport capacity of the membrane electrode assembly. In this study, the impacts of deposited Pt particles on the intrinsic properties of proton exchange membranes and its mechanisms are investigated using molecular dynamics simulation method. The effect of differently sized Pt particles on water channel connectivity and proton conductivity in proton exchange membranes under dry, normal, and saturated conditions was detailly discussed. The results reveal that Pt particles reduce water channel connectivity at low hydration level while increasing it at normal and high hydration levels. However, the enhancement mechanism is different. Moreover, proton conductivity was evaluated by examining the diffusion of hydronium ions and hydrogen bond dynamics. We found that the proton conduction performance of the membranes at low hydration levels is significantly reduced by Pt particles. We believe this study can promote the design of more robust and efficient proton exchange membranes.

Integrated ultra-low PtIr catalyst coated membrane toward efficient proton exchange membrane water electrolyzers

Catalyst coated membrane (CCM) is the core component of proton exchange membrane water electrolyzers (PEMWEs) and confronts the challenge of unaffordable Ir loading of 2–4 mg cm−2, polarization loss and inferior stability closely correlated with low-activity disordered thick catalyst layers (CLs, 3–10 μm) frequently fabricated by catalyst ink painting. We report wet-chemical direct growth of semi-ordered PtIr nanoflowers array as CLs on both sides of membrane, leading to an integrated ultra-low PtIr CCM (IUCCM) with a single-side PtIr loading of 62.7 μg (1.8 μg Pt+60.9 μg Ir) cm−2 and a CL thickness of 429.1 ± 62.9 nm. Remarkably, the IUCCM exhibits 20.8 %, 34.8 % and 23.8 % attenuation of activation, ohmic and mass transfer polarization relative to a house-made CCM, respectively, and a current density of 2 A cm−2 at 1.77 V as well as the highest specific power of 21.5 kW gIr−1 at 1.6 V in the literature. The improvement of activation polarization is primarily arising from the electronic effect between Pt and Ir as evidenced by the d-band center downshift of 0.80 eV. The thin and semi-ordered CL largely accounts for the mitigation of mass transfer and ohmic polarization. Notably, the IUCCM displays a good long-term stability with a degradation rate of ca. 44.4 μV h−1 during 300 h of electrolysis at 0.5 A cm−2. The superior stability can be attributed to strong CL/membrane interfacial interaction with the CL rooted down into the membrane matrix analogous to teeth as well as structural robustness of PtIr CL.

Efficient proton exchange membranes based on bifunctional metal–organic frameworks

Efficient proton exchange membranes based on bifunctional metal–organic frameworks

Design of multi-layered gradient catalysts for efficient proton exchange membrane fuel cells

Efficient catalyst layers (CLs) in proton exchange membrane fuel cells (PEMFCs) should possess a highly active surface for electrochemical reaction and an ideal platform for simultaneous mass transfer. Efforts have been devoted to lower the widely used Pt and Nafion loading due to their high cost. However, the increase in gas transport resistance and decrease in transfer ability of protons and electrons result in a degraded fuel cell performance. Therefore, CL design with optimal efficiency is important for high performance and stability of PEMFCs. In this study, we design gradient multi-layered CLs in which the loadings of Pt–C catalyst and Nafion ionomer are set differently for each layer to increase efficiency. For ideal cell performance, the ionomer loading should be higher near the membrane layer and Pt–C loading should be higher near the gas diffusion layer. In addition, we confirm that if the loading difference between layers in the gradient CL becomes excessively large, performance can degrade due to the non-uniform Pt active surface. Thus, we compared 1-layer, 3-layer and 5-layer CLs, and designing more layers to reduce the difference in loading between layers results in higher electrochemical surface area (ECSA) and improved performance.

Modelling of a Proton-Exchange Membrane Electrolysis Cell with Liquid-Fed Cathode

Conventional proton-exchange membrane (PEM) water electrolysers use much thicker membranes (>175 µm) than their PEM fuel cell counterparts (<25 µm), which reduces hydrogen crossover but also reduces electrolyzer efficiency due to the increased Ohmic resistance1. Reduction of hydrogen crossover is critical in conventional systems to avoid buildup of hydrogen in the anode above the lower explosive limit. Due to the use of liquid water at the anode in conventional systems, the anode cannot be flushed with air or an inert gas to reduce the hydrogen concentration.If the liquid water supply is moved to the cathode, the anode can be easily purged with air, reducing the safety concern related to hydrogen crossover. Proof-of-concept experiments2 have demonstrated the viability of this approach, but many open questions remain regarding the interplay between water transport, water consumption, membrane hydration, and cell performance, as well as understanding what components and properties are most important in improving the efficiency of such a device.In this work, a framework for modelling of PEM electrolysis cells will be outlined, with special attention to wet and dry anode conditions. The model will be used to provide guidance for optimizing system performance while contributing to understanding of local processes inside an electrolysis cell such as water transport, heat generation, reaction distribution, and bubble formation. We study the impact of various design and operational choices, such as membrane thicknesses, PTL structure, air feed humidity, and differential pressure operation, on the rate of water transport from cathode to anode and on overall cell polarization performance. Using these results, we provide design recommendations for PEM electrolysers with liquid-fed cathodes. Finally, progress towards an open-source implementation of this model will be discussed.This work has been performed within the HOPE (Revolutionizing Green Hydrogen Production with Next Generation PEM Water Electrolyser Electrodes) and HYSTACK (Low cost, high efficiency PEM electrolyser stack) projects financially supported by the Research Council of Norway under project numbers 325873 and 321466, respectively. Ayers, K. et al. Perspectives on Low-Temperature Electrolysis and Potential for Renewable Hydrogen at Scale. Annu. Rev. Chem. Biomol. Eng. 10, 219–239 (2019).Barnett, A. O. & Thomassen, M. S. Method for producing hydrogen in a PEM water electrolyser system, PEM water electrolyser cell, stack and system. Patent No.: WO 2019/009732. EP3649276B1. US11408081B2.

Fabrication of Cellulose Acetate-Based Proton Exchange Membrane with Sulfonated SiO2 and Plasticizers for Microbial Fuel Cell Applications.

Developing a hybrid composite polymer membrane with desired functional and intrinsic properties has gained significant consideration in the fabrication of proton exchange membranes for microbial fuel cell applications. Among the different polymers, a naturally derived cellulose biopolymer has excellent benefits over synthetic polymers derived from petrochemical byproducts. However, the inferior physicochemical, thermal, and mechanical properties of biopolymers limit their benefits. In this study, we developed a new hybrid polymer composite of a semi-synthetic cellulose acetate (CA) polymer derivate incorporated with inorganic silica (SiO2) nanoparticles, with or without a sulfonation (-SO3H) functional group (sSiO2). The excellent composite membrane formation was further improved by adding a plasticizer (glycerol (G)) and optimized by varying the SiO2 concentration in the polymer membrane matrix. The composite membrane's effectively improved physicochemical properties (water uptake, swelling ratio, proton conductivity, and ion exchange capacity) were identified because of the intramolecular bonding between the cellulose acetate, SiO2, and plasticizer. The proton (H+) transfer properties were exhibited in the composite membrane by incorporating sSiO2. The composite CAG-2% sSiO2 membrane exhibited a higher proton conductivity (6.4 mS/cm) than the pristine CA membrane. The homogeneous incorporation of SiO2 inorganic additives in the polymer matrix provided excellent mechanical properties. Due to the enhancement of the physicochemical, thermal, and mechanical properties, CAG-sSiO2 can effectively be considered an eco-friendly, low-cost, and efficient proton exchange membrane for enhancing MFC performance.

Increasing PEM fuel cell performance via fuzzy-logic controlled cascaded DC-DC boost converter

The voltage level produced by Proton Exchange Membrane (PEM) fuel cell (FC), which is one of the clean energy sources, is low for many industrial applications. For this reason, for many industrial applications such as electric vehicles, it is necessary to use a boost type DC-DC power electronic circuit at the output of PEM FC. In this case, in addition to the PEM FC performance, the dynamic performance and efficiency of the DC-DC converter to be used affect the performance and efficiency of the total system. In this study, a single-switch cascaded DC-DC boost converter, which has both higher voltage gain and more efficiency compared to conventional cascade converter and other boost type converters, is proposed for PEM FC. Since the proposed single-switch cascaded DC-DC boost converter includes only one controlled-switch, it is efficient as well as smaller in size and less costly compared to the other types. In addition, the proposed single-switch cascaded DC-DC boost converter is tested with the traditional PID and fuzzy-logic control methods to observe the dynamic performance of PEM FC. When the fuzzy logic controller is compared with the PID controller, it is clearly seen that it gives 21% more successful results as per rise time, 71% settling time, 97% overshoot, and 26% RMSE (Root Mean Square Error) error rate. As a result, when the proposed single-switch cascaded DC-DC boost converter is regulated via fuzzy control method, a more efficient PEM FC system which has better dynamic performance can be designed.

Coaly Graphite as an Eco-Friendly Material in the Microporous Layer of Proton Exchange Membrane Fuel Cells

Proton exchange membrane (PEM) fuel cells, which can directly convert chemical energy to electricity, are promising as the next-generation energy harvesting method. Among all of the components, the microporous layer (MPL) controls the water and gas transport between the gas diffusion layer and the catalysis layer, where carbon black is one of the traditional materials for fabrication. However, owing to its energy-intensive preparation method, high capitalized cost, and low water transport rate features, the realization of carbon black on a large scale still faces obstacles. Here, we demonstrate a combination of three carbon materials for synthesizing the MPL using carbon black (CB), coaly graphite (CG), and graphene oxide (GO), whose synergistic effect ensures a high output in PEM fuel cells. CB is partially replaced by CG, which reduces the carbon and toxic gas footprint while still maintaining a high power density. This work for designing membrane structures for the MPL opens opportunities for developing highly efficient PEM fuel cells.

Enhanced Proton Transfer in Proton-Exchange Membranes with Interconnected and Zwitterion-Functionalized Covalent Porous Material Structures.

Excellent proton-conductive accelerators are indispensable for efficient proton-exchange membranes (PEMs). Covalent porous materials (CPMs), with adjustable functionalities and well-ordered porosities, show much promise as effective proton-conductive accelerators. In this study, an interconnected and zwitterion-functionalized CPM structure based on carbon nanotubes and a Schiff-base network (CNT@ZSNW-1) is constructed as a highly efficient proton-conducting accelerator by in situ growth of SNW-1 onto carbon nanotubes (CNTs) and subsequent zwitterion functionalization. A composite PEM with enhanced proton conduction is acquired by integrating CNT@ZSNW-1 with Nafion. Zwitterion functionalization offers additional proton-conducting sites and promotes the water retention capacity. Moreover, the interconnected structure of CNT@ZSNW-1 induces a more consecutive arrangement of ionic clusters, which significantly relieves the proton transfer barrier of the composite PEM and increases its proton conductivity to 0.287 S cm-1 under 95 % RH at 90 °C (about 2.2 times that of the recast Nafion, 0.131 S cm-1 ). Furthermore, the composite PEM displays a peak power density of 39.6 mW cm-2 in a direct methanol fuel cell, which is significantly higher than that of the recast Nafion (19.9 mW cm-2 ). This study affords a potential reference for devising and preparing functionalized CPMs with optimized structures to expedite proton transfer in PEMs.