Development Of Proton Exchange Membranes Research Articles

A novel ‘3D + digital twin + 3D’ upscaling strategy for predicting the detailed multi-physics distributions in a commercial-size proton exchange membrane fuel cell stack

With the rapid development of proton exchange membrane fuel cell (PEMFC) commercialization, a comprehensive knowledge of multi-physics fields in large-scale PEMFC stacks has become ever more critical. Although conventional three-dimensional computational fluid dynamic (CFD) models have achieved great success, the application in the commercial-size stack-scale simulation remains inapplicable due to enormous computational resource requirements. Herein, based on the latest 3D CFD model, multi-physics digital twin (DT) technology and 3D stack flow distribution prediction model, a novel multi-scale upscaling prediction model is proposed. The voltage, water and thermal management characteristics of a 164-cell PEMFC stack with an active electrode area of 292.5 cm2 are studied and analyzed in details. For the analysis of commercial-size PEMFC stacks, the most comprehensive multi-physics fields are covered in this paper to date. And the results suggest that by introducing the DT technology, the time requirement of the multi-physics field prediction for unit scale prediction can be reduced by hundreds of thousands of times with a maximum global relative deviation of 1% under 10 groups of random test conditions, giving a solution from the cell scale to stack scale performance prediction, design, heat and thermal management in the PEMFC research and application.

Study on the Performance Degradation of Membrane Electrode Assembly in Proton Exchange Membrane Fuel Cell Caused by Freeze–Thaw Cycles

ABSTRACTDurability of membrane electrode assembly (MEA) is a serious problem to be overcome in the commercial development of proton exchange membrane fuel cell (PEMFC). The change in volume due to water–ice conversion has an irreversible effect on the MEA, which affects the performance of PEMFC. For investigating the optimal initial water content of MEA that minimizes the impact on PEMFC performance after freeze–thaw (F/T) cycles, this study first measured the high‐frequency resistance to determine the water content of MEA, and then subjected five MEAs with different water contents to 60 F/T cycles at −20°C to 30°C. The fuel cell output performance of five MEAs was found to be inconsistently degraded by polarization curve tests, with the cells of the two MEAs with the lowest and highest water contents exhibiting the worst output performance. Electrochemical impedance spectroscopy curves proved that the difference in resistance change after F/T cycles is one reason why the cell output performance is degraded differently. Finally, the degradation of cell performance was further explained by cyclic voltammetry. These results indicate that MEA has the best output performance for F/T cycles at an initial water content of 3.0.

A model with high-precision on proton exchange membrane fuel cell performance degradation prediction based on temporal convolutional network-long short-term memory

Prediction with high-precision of the performance degradation is crucial for the development of proton exchange membrane fuel cells (PEMFCs) with long lifetime. In this work, a new hybrid neural network model on fuel cell performance degradation prediction (TCN-LSTM) is developed by incorporating the advantages of temporal convolutional network (TCN) and long short-term memory (LSTM). The innovation of TCN-LSTM is that LSTM captures the long-term correlation of data from the high-level features of the original data extracted by TCN. On the available PEMFC datasets (IEEE 2014 PHM Data Challenge), the TCN-LSTM reduces the root mean square error (RMSE) by up to 94% compared with other state-of-the-art algorithms. In addition, the TCN-LSTM is also assessed on 2673 h self-tested fuel cell voltage degradation dataset recorded under dynamic cyclic load conditions with complicated decay mechanism. The RMSE is only 0.00205 even under the 50% training length, which further verifies the excellent prediction performance of TCN-LSTM. It can be concluded that the TCN-LSTM will be a promising fuel cell performance degradation prediction model.

Molten-Salt Electrochemical-Assisted Synthesis of the CeO2-OV@GC Composite-Supported Pt Clusters with a Pt-O-Ce Structure for the Oxygen Reduction Reaction.

Highly active and robust Pt-based electrocatalysts for an oxygen reduction reaction (ORR) are of crucial significance for the development of proton exchange membrane fuel cells (PEMFCs). Herein, the high-loading and well-dispersive Pt clusters on graphitic carbon-supported CeO2 with abundant oxygen vacancies (PtAC/CeO2-OV@GC) were successfully fabricated by a molten-salt electrochemical-assisted method. The bonding of Pt with the highly electronegative O induces charge redistribution through the Pt-O-Ce structure, thus reducing the adsorption energies of oxygen-containing species. Such a PtAC/CeO2-OV@GC electrocatalyst exhibits a greatly enhanced ORR performance with a mass activity of 0.41 ± 0.02 A·mg-1Pt at 0.9 V versus a reversible hydrogen electrode, which is 2.7 times the value of a commercial Pt/C catalyst and shows negligible activity decay after 20000 cycles of accelerated degradation tests. It is anticipated that this work will provide enlightening guidance on the controllable synthesis and rational design of high-performance Pt-based electrocatalysts for PEMFCs.

Strategies for Achieving Ultra-Long ORR Durability-Rh Activates Interatomic Interactions in Alloys.

The stability of platinum-based alloy catalysts is crucial for the future development of proton exchange membrane fuel cells, considering the potential dissolution of transition metals under complex operating conditions. Here, we report on a Rh-doped Pt3Co alloy that exhibits strong interatomic interactions, thereby enhancing the durability of fuel cells. The Rh-Pt3Co/C catalyst demonstrates exceptional catalytic activity for oxygen reduction reactions (ORR) (1.31 A mgPt -1 at 0.9 V vs. the reversible hydrogen electrode (RHE) and maintaining 92 % of its mass activity after 170,000 potential cycles). Long-term testing has shown direct inhibition of Co dissolution in Rh-Pt3Co/C. Furthermore, tests on proton exchange membrane fuel cells (PEMFC) have shown excellent performance and long-term durability with low Pt loading. After 50,000 cycles, there was no voltage loss at 0.8 A cm-2 for Rh-Pt3Co/C, while Pt3Co/C experienced a loss of 200 mV. Theoretical calculations suggest that introducing transition metal atoms through doping creates a stronger compressive strain, which in turn leads to increased catalytic activity. Additionally, Rh doping increases the energy barrier for Co diffusion in the bulk phase, while also raising the vacancy formation energy of the surface Pt. This ensures the long-term stability of the alloy over the course of the cycle.

Strategies for Achieving Ultra‐Long ORR Durability—Rh Activates Interatomic Interactions in Alloys

AbstractThe stability of platinum‐based alloy catalysts is crucial for the future development of proton exchange membrane fuel cells, considering the potential dissolution of transition metals under complex operating conditions. Here, we report on a Rh‐doped Pt3Co alloy that exhibits strong interatomic interactions, thereby enhancing the durability of fuel cells. The Rh−Pt3Co/C catalyst demonstrates exceptional catalytic activity for oxygen reduction reactions (ORR) (1.31 A mgPt−1 at 0.9 V vs. the reversible hydrogen electrode (RHE) and maintaining 92 % of its mass activity after 170,000 potential cycles). Long‐term testing has shown direct inhibition of Co dissolution in Rh−Pt3Co/C. Furthermore, tests on proton exchange membrane fuel cells (PEMFC) have shown excellent performance and long‐term durability with low Pt loading. After 50,000 cycles, there was no voltage loss at 0.8 A cm−2 for Rh−Pt3Co/C, while Pt3Co/C experienced a loss of 200 mV. Theoretical calculations suggest that introducing transition metal atoms through doping creates a stronger compressive strain, which in turn leads to increased catalytic activity. Additionally, Rh doping increases the energy barrier for Co diffusion in the bulk phase, while also raising the vacancy formation energy of the surface Pt. This ensures the long‐term stability of the alloy over the course of the cycle.

Acidic Oxygen Evolution Reaction: Fundamental Understanding and Electrocatalysts Design.

Water electrolysis driven by "green electricity" is an ideal technology to realize energy conversion and store renewable energy into hydrogen. With the development of proton exchange membrane (PEM), water electrolysis in acidic media suitable for many situations with an outstanding advantage of high gas purity has attracted significant attention. Compared with hydrogen evolution reaction (HER) in water electrolysis, oxygen evolution reaction (OER) is a kinetic sluggish process that needs a higher overpotential. Especially in acidic media, OER process poses higher requirements for the electrocatalysts, such as high efficiency, high stability and low costs. This review focuses on the acidic OER electrocatalysis, reaction mechanisms, and critical parameters used to evaluate performance. Especially the modification strategies applied in the design and construction of new-type electrocatalysts are also summarized. The characteristics of traditional noble metal-based electrocatalysts and the noble metal-free electrocatalysts developed in recent decades are compared and discussed. Finally, the current challenges for the most promising acidic OER electrocatalysts are presented, together with a perspective for future water electrolysis.

Manipulation of Electronic States of Pt Sites via d-Band Center Tuning for Enhanced Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells.

Expediting the torpid kinetics of the oxygen reduction reaction (ORR) at the cathode with minimal amounts of Pt under acidic conditions plays a significant role in the development of proton exchange membrane fuel cells (PEMFCs). Herein, a novel Pt-N-C system consisting of Pt single atoms and nanoparticles anchored onto the defective carbon nanofibers is proposed as a highly active ORR catalyst (denoted as Pt-N-C). Detailed characterizations together with theoretical simulations illustrate that the strong coupling effect between different Pt sites can enrich the electron density of Pt sites, modify the d-band electronic environments, and optimize the oxygen intermediate adsorption energies, ultimately leading to significantly enhanced ORR performance. Specifically, the as-designed Pt-N-C demonstrates exceptional ORR properties with a high half-wave potential of 0.84 V. Moreover, the mass activity of Pt-N-C reaches 193.8 mA gPt-1 at 0.9 V versus RHE, which is 8-fold greater than that of Pt/C, highlighting the enormously improved electrochemical properties. More impressively, when integrated into a membrane electrode assembly as cathode in an air-fed PEMFC, Pt-N-C achieved a higher maximum power density (655.1 mW cm-2) as compared to Pt/C-based batteries (376.25 mW cm-2), hinting at the practical application of Pt-N-C in PEMFCs.

In-field experimental study and multivariable analysis on a PEMFC combined heat and power cogeneration for climate-adaptive buildings with taguchi method

Due to overwhelming advantages in high power density, stability in long-term storage and clear by-product water, application of hydrogen energy in buildings has attracted global interests for sustainable and low-carbon transformation, especially with the fast technology development of proton exchange membrane fuel cell (PEMFC) combined heat and power (CHP) cogeneration system. However, the cost-effective operating control of PEMFC CHP cogeneration system has not been investigated, comprehensively considering intermittence and stochasticity of building energy demands in different climate regions under extreme climates. In this study, in-field experimental study following the orthogonal method is conducted for underlying mechanism analysis of operating parameters on electric power, total power, and electric/thermal (E/T) power ratio of a PEMFC stack, considering energy losses by convection, radiation and exhausted reactant gas flow. Sensitivity analysis of operating parameters on PEMFC output performances is conducted based on Taguchi Method. For climate-adaptive applications of PEMFC CHP cogeneration systems in Guangzhou (cooling-dominated area) and Beijing (heating-dominated area), two operating strategies with electricity- and heat-dominated outputs have been proposed and compared. Results indicate that, the PEMFC output performances are influenced by internal factors, including reaction rate, substance transportation, membrane hydration level and energy losses. Electric power and total power are mainly dependent on coolant inlet temperature, inlet gas pressure and coolant flux, while E/T power ratio is mainly controlled by inlet coolant temperature, inlet gas pressure and cathode stoichiometric ratio. Furthermore, based on the proposed cost-effective operating control (the electricity-dominated output control strategy under extreme hot weather in Guangzhou and heat-dominated output control strategy under extreme cold weather in Beijing), the PEMFC could save 0.246 kg hydrogen with 2.137 × 103 kJ surplus thermal energy one day in Guangzhou, and save 2.763 kg hydrogen with 3.527 × 103 kJ surplus electric energy one day in Beijing. This study could provide a guideline for operating parameter selections of PEMFC CHP cogeneration system in variable climate areas.

Deciphering the Roles of Chemistry and Structure in Iridium Oxide Oxygen Evolution Catalysts through the Study of Annealed Iridium Oxide Nanoparticles

The development of proton exchange membrane (PEM) water electrolysis, which enables the production of de-carbonized hydrogen, is hindered by the low efficiency of the oxygen evolution reaction (OER). This is especially true in acidic environment where only noble metals (mainly Ru and Ir) can be used as electrocatalysts. Iridium oxide nanocatalysts (IrOx) are promising due to their high OER activity and good resistance to acidic and oxidative conditions. However, finding a compromise between their electrocatalytic activity and stability remains challenging. Moreover, it is not yet clear which parameter (the material structure1 or the initial iridium oxidation state2) controls these two properties.To address these challenges, we synthesized IrOx nanoparticles (NPs) supported on carbon (IrOx/C), through a modified polyol process, and annealed them under air, at temperatures ranging from 200◦C to 850◦C. This allows us to deconvolute the effects of the oxidation state, the structure and the size of IrOx NPs and to tune their activity and stability3. To analyze the structure, morphology, and oxidation state of Ir in these catalysts, we used transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and both laboratory-based and synchrotron-based X-ray diffraction (XRD) techniques.We observed in situ the crystallization of IrOx NPs, leading to crystallite size growth and change in Ir electronic state (see Figure 1a). Additionally, we investigated the morphological changes of IrOx NPs with respect to annealing temperature (refer to Figure 1b-f). We assessed their electrocatalytic activity towards the OER and determined their stability number4 (S-number) using inductively coupled plasma mass spectrometry and electrochemistry. We observed that increasing the annealing temperature led to an increase in particle size and degree of crystallinity, but did not result in significant changes in the iridium oxidation state (refer to Figure 1g). We observed the evolution of the electrochemical activity of the nanoparticles with the annealing temperature (see Figure 1h). Our results show a correlation between the changes in electronic structure, morphology, and size, and the evolution of OER activity and stability of the IrOx NPs. Specifically, we identified certain conditions that achieved an optimal balance between activity and stability.(1) Elmaalouf, M.; Odziomek, M.; Duran, S.; Gayrard, M.; Bahri, M.; Tard, C.; Zitolo, A.; Lassalle-Kaiser, B.; Piquemal, J.-Y.; Ersen, O.; Boissière, C.; Sanchez, C.; Giraud, M.; Faustini, M.; Peron, J. Nat. Commun. 2021, 12 (1), 3935. https://doi.org/10.1038/s41467-021-24181-x.(2) Claudel, F.; Dubau, L.; Berthomé, G.; Sola-Hernandez, L.; Beauger, C.; Piccolo, L.; Maillard, F. ACS Catal. 2019, 9 (5), 4688–4698. https://doi.org/10.1021/acscatal.9b00280.(3) Geiger, S.; Kasian, O.; Shrestha, B. R.; Mingers, A. M.; Mayrhofer, K. J. J.; Cherevko, S. J. Electrochem. Soc. 2016, 163 (11), F3132. https://doi.org/10.1149/2.0181611jes.(4) Geiger, S.; Kasian, O.; Ledendecker, M.; Pizzutilo, E.; Mingers, A. M.; Fu, W. T.; Diaz-Morales, O.; Li, Z.; Oellers, T.; Fruchter, L.; Ludwig, A.; Mayrhofer, K. J. J.; Koper, M. T. M.; Cherevko, S. Nat. Catal. 2018, 1 (7), 508–515. https://doi.org/10.1038/s41929-018-0085-6.Acknowledgments: This work was supported by the French National Research Agency in the frame of the MATHYLDE project (grant number n° ANR-22-PEHY-0001).Figure 1 – a. X-ray diffractograms obtained on IrOx/C annealed at 290, 340, 380, 420, 470, 520, 570, 620, 670 and 850°C under air. Each measurement lasted 13 minutes. The hashes correspond to tetragonal IrO2 (PDF card 00-043-1019) and the stars to metallic Ir (PDF card 00-006-0598). b-f. TEM images of IrOx/C NPs as-synthesized and calcined at 290, 380, 420, 570 and 850 °C. g. X-ray photoelectron spectra showing the Ir 4f levels of IrOx/C NPs as-synthesized and calcined at 380, 420, 520 and 850 °C. The dotted lines indicates the theoretical position of the peaks for Ir(IV) and Ir(III). h. Cyclic voltammograms measured in 0.1 M HClO4 at 50 mV s−1 indicating the change in electrochemical properties of IrOx/C NPs with annealing temperature. Figure 1

Lung-inspired hybrid flow field to enhance PEMFC performance: A case of dual optimization by response surface and artificial intelligence

The design and optimization of flow field play a crucial role in the development of proton exchange membrane fuel cells (PEMFC). This study presents a modular tri-layer lung-inspired hybrid flow field (LHFF) design that incorporates 2D and 3D flow field advantages. The key structural parameters of LHFF mainly encompass G, D, and S of reactant distribution layer and A of directional transport layer. The LHFFs with different G have been investigated, and the G = 2 LHFF exhibits a 16.55% enhancement in maximum net power density compared to conventional parallel flow field. Then the response surface methodology (RSM) and artificial intelligence methodology (AIM) have been employed to optimize the D, S, and A structure parameters of LHFF to determine the optimal inlet position of water removal layer. The LHFFs optimized by RSM and AIM show a further increase in maximum net power density by 3.58% and 4.10%, respectively. The optimized LHFFs achieve a trade-off among species distribution, water management, and pressure drop, with high consistency between numerical and experimental results. It demonstrates the reliability of artificial intelligence in optimizing PEMFC flow field. Therefore, the optimization strategies presented here hold a promising solution to improve the flow fields in other electrochemical systems.

Development of proton exchange membrane fuel cell flow plate geometry design

The advancement of bipolar plate technology can potentially make hydrogen fuel cells more viable as a part of renewable energy system. Two new bipolar plate designs were developed and compared with a reference channel in this study. Compared to the reference channel, the rectangular and hexagonal baffle designs performed significantly better. The rectangular design demonstrated better reactant distribution and fewer dead zones than the hexagonal design, resulting in higher current and power densities. The rectangular baffle design's operating conditions were improved by increasing pressure, temperature, humidity, and adding cooling channels to the anode and cathode. Power and current output were significantly increased as a result of this optimization.

Immobilized hindered amine radical scavenger for durability enhancement of perfluorosulfonic acid membrane in PEMFCs

Membrane durability is one of the crucial considerations that restrict the development of proton exchange membrane fuel cells (PEMFCs). The widely used and inexpensive stabilizer hindered amine 4-amino-2,2,6,6-tetramethylpiperidine (TEMP) was selected as the free radical scavenger and tethered onto the skeleton of carboxyl-functionalized metal-organic frameworks for addressing its migration problem. The resulted inorganic-organic hybrid dopant (UIO-66-TEMP) was then incorporated into the Nafion matrix to alleviate the attacks of free radicals on the membrane in the fuel cell working circumstances. Besides the improved mechanical strength and oxidative stability, and restricted water swelling and hydrogen crossover, the resulted hybrid membranes also possess excellent proton conductivity up to 176 mS cm−1, endowing them with high power density up to 612.78 mW cm−2, 1.5 times higher than recast Nafion. After accelerated durability testing for 120 h, the OCV decay rate of the hybrid membranes decreased to 0.74 mV h−1, only 40% of recast Nafion (1.89 mV h−1). Meanwhile, the optimized hybrid membrane still maintained a high peak power density of 463.62 mW cm−2 and a low hydrogen crossover density of 4.44 mA cm−2, which were superior to recast Nafion after OCV durability tests. Hindered amines can be “regenerated” by the “Denisov cycle” to ensure that they can be used sustainably in the fuel cell. The results demonstrate that the novel UIO-66-TEMP decorated with hindered amine radical scavengers are promising nanofillers for mitigating the membrane degradation and improving the proton conductivity, thereby significantly enhancing the performance and durability of PEMFCs.

Polyphenol synergistic cerium oxide surface engineering constructed core-shell nanostructures as antioxidants for durable and high-performance proton exchange membrane fuel cells

The chemical degradation of proton exchange membranes (PEMs) suffering from radical attack is a crucial issue in the development of proton exchange membrane fuel cells (PEMFCs), while incorporating cerium oxide (CeO2) nanoparticles (NPs) with regenerative redox properties to eliminate radicals could effectively alleviate degradation. However, the low stability and restricted activity of CeO2 in the PEMFC operating condition and the poor compatibility with PEM due to CeO2 agglomeration stimulate the urgency for structural modulation of CeO2. Achieving a balance of membrane performance and oxidation resistance through a rational surface modification strategy of CeO2 is important for expanding PEMFC applications. Herein, polyphenols surface functionalized CeO2 core-shell structure (CeO2@TP) were constructed via assembling oxidation-induced coupling tea polyphenols (TP) on CeO2 NPs. The TP oligomeric shell as a protective layer enhances the stability of CeO2, mitigating radical scavenging activity degradation and improving compatibility with PEMs. Physicochemical characterisation shows that the overall performance of the nanocomposite membrane is improved due to the interaction of CeO2@TP nanoparticles with the polymer matrix. Gratifyingly, the phenolic hydroxyl-rich reductive TP oligomeric shell accelerates the regeneration of Ce(IV) to Ce(III), increasing the proportion of Ce(III) and oxygen vacancies on the CeO2 surface, thus boosting antioxidation efficiency. As a result, the CeO2@TP-based PEMs exhibited an OCV decay rate of 0.22 mV h−1, a maximum power density of 1.06 W cm−2, an H2 crossover value of 2.18 mA cm−2, thickness retention (91.1%), and negligible Ce migration after 404 h of accelerated degradation testing. It is proven that the desired consequences of doping antioxidants in PFSA matrix can be intensified by surface modulation of the physicochemical properties of CeO2.

Finely Adjusted Intrinsically Microporous Copolyimide Electrolyte Membranes for Fuel Cells Operating in a Wide Temperature Range

The development of proton exchange membrane fuel cells (PEMFCs) that operate over a wide temperature range without additional humidification systems remains challenging. In this work, wide-temperature-range proton exchange membranes (PEMs) were constructed from novel Tröger’s base (TB)-based intrinsically microporous copolyimides (co-PIs) finely adjusted by incorporating crown ether units into chain backbones. Owing to the strong siphoning effect of existing microporosity and hydrogen bonds or the acid–base interactions of crown ether and TB units with phosphoric acid (PA) and/or H2O, the PA-doped co-PI membrane electrode assemblies (MEAs) can easily operate stably from 30 to 160 °C under H2/air conditions even without any external humidifiers. Regarding its single-cell performance, PI-TB-N30C achieved maximum power densities of 250 and 361 mW cm–2 at 80 and 160 °C, respectively, under anhydrous conditions. In addition, PA-doped co-PI MEA can accomplish long-term stable operation under low or high temperatures for 120 h. The structural architectures for PEMs based on finely adjusted microporous co-PIs extend beyond the current capabilities of existing PEMFCs.

Electrode with a Carbon Nanotube Array for a Proton Exchange Membrane Fuel Cell

One of the most important problems in the development of proton exchange membrane fuel cells remains the selection of an efficient electrocatalyst support capable of providing a low loading of active metal with minimal changes in the electrochemical surface, electronic conductivity, and activity. In this work, carbon nanotube arrays (CNTAs) grown directly on commercial gas diffusion layers (GDLs) are used to form electrodes of a new type. The CNTAs are used in the electrode as a microporous layer. The catalytic layer is formed in the microporous layer by a method that does not destroy the carbon support structure and consists of the controlled impregnation of CNTAs with the Pt-precursor with subsequent reduction in platinum particles in the surface volume of the layer. The resulting electrode was studied by scanning/transmission electron microscopy and Raman spectroscopy. This electrode provides increased electrical conductivity of the layer and can also improve stability and longer service life due to the enhanced adhesion of carbon materials to the GDL.

The advances development of proton exchange membrane with high proton conductivity and balanced stability in fuel cells

AbstractIn the proton exchange membrane fuel cell, proton exchange membrane (PEM) serves as both the main conductor of protons and the fuel‐blocking membrane. Thus, high proton conductivity and excellent stability are expected for PEMs at the same time. According to chemical structure, this review divides PEM into three groups. Recently, high‐performance PEM has been made possible by controlling chemical structure, organic–inorganic hybrid composite membranes, and nanofiber composite membranes. One of them, nanofiber composite membranes, is distinguished by long‐range order and is capable of achieving both strong proton conductivity with exceptional stability. The high‐performance PEM has been accomplished by the presence of an acid‐rich layer, acid–base interaction, and proton transport channel in PEMs are also summarized in this paper. We believe that our discussion will help the researcher create high‐performance PEM and pave the way for further developments in the field of energy materials as a whole.

Structurally Ordered PtNi Intermetallic Nanoparticles as Efficient and Stable Cathode Catalysts for Proton Exchange Membrane Fuel Cells.

Exploring oxygen reduction reaction (ORR) catalysts with superior electrochemical performance and long-term stability is crucial to the development of proton exchange membrane fuel cells (PEMFCs). In this work, graphited carbon with high specific surface area was obtained under relatively low temperature using Ni catalyst, then ordered nanoparticles (NPs) PtNi catalysts attaching to graphited carbon were synthesized via polyol reduction and thermal treatment. Benefiting from graphitized carbon support and appropriate order degree, PtNi/GC-700 NPs catalyst exhibits excellent electrocatalytic ORR performance with specific and mass activities as high as 2.8-fold and 3.7-fold of the commercial Pt/C catalyst, respectively. Besides, the as-prepared PtNi/GC-700 catalyst exhibits superior stability with negligible degradation after 10000 potential cycles, due to its ordered chemical structure. The work described herein highlights the potential of structurally ordered electrocatalysts for efficient and durable fuel cell cathodic catalysts.

Mixed matrix composite PEM with super proton conductivity developed from ionic liquid modified silica nanoparticle and polybenzimidazole

Phosphoric acid (PA) leaching, low proton conductivity and weak mechanical strength of the polybenzimidazole (PBI) membrane need to be improved considerably for the development of proton exchange membrane (PEM). We have addressed these issues by preparing a mixed matrix composite (MMC) membrane comprising of oxy-polybenzimidazole (OPBI) and imidazole ionic liquid modified silica (ImILSi). Imidazolium based ionic liquid was synthesized and grafted to the surface of the silica nanoparticles (SiNP) to obtain ImILSi which further blended with OPBI to obtain OPBI@ImILSi. The uniform dispersion nature of the ImILSi in the OPBI matrix and the strong H-bonded interfacial interactions between nanofillers and polymers are found to be primary reason for significant improvement of various physical properties of the MMC. TGA, DMA and stress-strain studies exhibited significant enhancement in the thermal and mechanical properties of the MMC membranes. Most importantly, due to the loading of hydrophilic ImILSi, the MMC membranes resulted higher PA loading (∼3-fold increase) which enabled the formation of facial proton transport nanochannels for their superior proton conduction under anhydrous environment and elevated temperature. For example, the OPBI@ImILSi-3% membrane showed proton conductivity value of 0.219 S cm−1 at 160 °C which is a ∼4-fold increase compared to OPBI membrane.

Operando High Energy Resolution Fluorescence Detected (HERFD) X-Ray Absorption Spectroscopic Study of Toyota Mirai Gen.1 Catalysts

The development of proton exchange membrane fuel cells (PEMFCs) have received increasing attention for its potential to get rid of dependence on fossil fuels and curb carbon emissions. However, the application of PEMFC has been limited by the consumption of platinum due to the sluggish kinetics of the cathode reaction and limiting platinum resources. It is well-known that the oxygen species generated on the Pt surface hiders ORR reaction at high potential region. Therefore, it is very important to evaluate the interaction between the oxygen species and the catalyst based on the electronic structure. However, the differences in XAFS spectra due to the presence of oxygen species are relatively small, and conventional detection methods, such as transmittance and total fluorescence yield, have difficulty distinguishing differences in electronic structure because the fine structure of the spectra is filled in by the lifetime width of the Pt 2p 3/2 core hole. In contrast, the new high-energy-resolution fluorescence-detection X-ray absorption spectroscopy (HERFD-XAS) monochromatized fluorescence lines (e.g., Pt Lα1), which are broadened only by Pt 3d 5/2 (~2.4 eV) rather than by Pt 2p 3/2 (~5.2 eV) core hole lifetime, are used to monitor core High-resolution X-ray absorption spectra with extended hole lifetimes can now be extracted. The present study covers conventional platinum catalysts supported on Vulcan carbon and TOYOTA MIRAI Gen.1 catalysts. The HERFD-XAS method was applied to elucidate the cause of the superior electrochemical properties of the TOYOTA MIRAI Gen.1 catalyst. o perando Pt LIII edge HERFD-XAS measurements were performed on Pt/C and TOYOTA MIRAI Gen.1 catalysts under oxygen reduction conditions, and the high energy resolution revealed the interaction of oxygen species with the Pt surface.Pt/C (29.1 wt %; TEC10V30E, average particle size of 3 nm, observed by TEM) catalyst was purchased from TKK Co. Ltd., Japan. The Pt/C catalyst ink contained water and 2-propanol in a 3:2 ratio (99.99%, FUJIFILM Wako Pure Chemical Corporation, Japan), and the amount of Pt/C was adjusted to form a 20 μg carbon cm–2 catalyst layer after dropping 10 μL on a glassy carbon RDE (GC RDE, HOKUTO DENKO, Japan; 0.196 cm2 area). TOYOTA MIRAI Gen.1 catalyst was also prepared by the above-mentioned preparation method. operando XAS measurements for Pt LΙΙΙ-edge of the catalysts were carried out at BL39XU of SPring-8, Hyogo, Japan. Prior to the experiments, the samples were electrochemically cleaned by CV in the range 0.0–1.1 V (vs. RHE). The electrode potential was swept cathodically from 0.5 to 1.1 V (vs. RHE).Figure 1 shows the results for in situ HERFD-XAS spectra of Pt and MIRAI Gen.1 catalyst. For both samples, the white line intensity changes depending on the adsorption conditions. The obtained HERFD-XAS spectra were decomposed into oxidized (Pt-OH) and reduced (Pt metal) components. The ratio of the peak area intensity of the two components is proportional to the surface coverage assuming similar charge transfer among the catalysts. It is noted that enhancement of oxidation is significantly suppressed on MIRAI Gen.1 catalysts. Figure 1. operando HERFD-XAS spectra for (a) TOYOTA MIRAI Gen.1 catalyst. (b) Pt/C (TEC10V30E) Acknowledgement This work was supported by a NEDO FC-Platform project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1