bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrospun Sulfonated Silica/P(VDF-TrFE)-Based Composite Membranes for PEM Fuel Cells
Authors: Yarar Kaplan Begüm , Rajabalizadeh mojarrad Naeimeh , Kırlıoğlu Ahmet Can , Alkan Gursel Selmiye
Published: February 2024

Nafion® membranes are the most widely used commercially available membranes for PEM fuel cells due to their good chemical and mechanical stability as well as high ionic conductivity at fully humidified conditions. However, their high cost and inadequate conductivity at lower humidity levels can be addressed as the main drawbacks of Nafion® membranes which needs to be overcome. In this regard new strategies such as complete replacement of these membranes with alternative cost-effective membranes or modifying their properties via synthesizing of Nafion® containing composite membranes by incorporation of some inorganic additives such as silica were extensively investigated previously [1].

In this study, we developed two types of electrospun composite membranes: in the first route: membranes were prepared with using P(VDF-TrFE) or PVDF as carrier polymers which are decorated with sulfonated silica (S-SiO2) nanoparticles, as a proton conducting additive. Here S-SiO2 nanoparticles were synthesized via hydrothermal method, then these nanoparticles were added to the electrospinning solutions to prepare the hybrid membranes. The effect of S-SiO2 amount in final properties of these membranes were investigated via preparing samples with three different S-SiO2/ carrier polymer ratios [2]. In the second approach, a combination of sol-gel and dual electrospinning methods were employed to fabricate proton conducting membranes comprising sulfonated silica network, Nafion®, and PVDF or P(VDF-TrFE) as the carrier polymers. For this purpose, the obtained S-SiO2 network via sol-gel method was incorporated into the Nafion®/carrier polymer mixed fibrous-mats during dual electrospinning process [3]. In both approaches after electrospinning all electrospun mats were transformed to compact membranes via hot-pressing process. Then fabricated mats and compact membranes, were characterized by various techniques including FTIR, XPS, SEM, TEM, ionic conductivity, ion exchange capacity (IEC), water uptake and mechanical tests. Finally, membrane-electrode-assemblies (MEAs) were prepared via composite electrospun membranes and fuel cell performance tests were performed. The results showed an enhancement in ionic conductivity for both set of membranes (102 and 132 mS/cm) compared to commercial Nafion® membranes at the same conditions. Moreover, the fuel cell test exhibited that presence of sulfonated silica in the composite membranes improved the performance at lower humidity conditions (344 mW/cm2 at 60% RH) due to enhanced water retention ability of the resultant composite membranes.

References:

[1] Shang Z., Wycisk R., Pintauro P., Energies, 14(20), 6709, (2021).

[2] Rajabalizadeh Mojarrad N., Iskandarani, B., Taşdemir, A., Yürüm, A., Gürsel, S.A., Yarar Kaplan, B., Int J Hydrogen Energy, 46(25), 13583-13593, (2021).

[3] Rajabalizadeh Mojarrad N., Kırlıoğlu A., Yarar Kaplan, B., J Solid State Ionics, 392, 116152, (2023).
(Invited) Molecular Insights into Water Structure and Proton Transfer at the Interfaces in Bipolar AEM/PEM Membranes
Authors: Paddison Stephen J.
Published: February 2024

Bipolar membranes (BPMs) are polymeric membranes composed of an acidic proton exchange membrane (PEM) and an alkaline anion exchange membrane (AEM). Bipolar membranes are operated in two different configurations, forward bias and reverse bias, based on the orientation of membranes and electrodes, when the cathode faces the PEM, it is operated in a reverse bias configuration. In reverse bias BPMs facilitates the dissociation of water at the interface of its junction. This unique feature makes it attractive to many industrial applications, including chemical industries, energy conversion and storage, environmental protection, and food processing. It was determined that the rate of water dissociation at the interface of a bipolar membrane increases with the addition of a weak acidic head group material, which acts as the catalyst for the water dissociation reaction and thus referred as the catalyst layer. BPMs have a better ion transport framework because of the amphiphilic nature of all three layers, resulting in well-connected water channels. Hence it is crucial to understand the interaction of water molecules with the functional groups at the molecular level and the morphology at mesoscale to understand the water aggregation and phase separation which helps in the asymmetric transport of proton and hydroxide ions through PEM and AEM respectively.

This talk will communicate our efforts to undertake a multiscale approach involving both electronic structure calculations and mesoscale simulations to elucidate: (1) water interaction of water with the headgroups; proton transfer, and (2) connectivity of a TMA AEM, a PFSA PEM, and a phosphonic acid-based catalyst.
Fundamentals of Gas Permeation in PEM Water Electrolyzers Operated at High Pressures
Authors: Khedekar Kaustubh , Li Kui , Gebhardt Ryan , Park Andrew , Borup Rod L. , Komini Babu Siddharth
Published: February 2024

The high cost of clean hydrogen (H2) remains a major hurdle to drive large scale adoption and achieve zero emission goals. For large scale deployment using low cost renewable electricity, polymer electrolyte membrane water electrolyzers (PEMWEs) show high potential based on their high faradaic efficiency and high operating current density. Operation of PEMWEs at high differential pressures can significantly reduce the per kilogram price of H2 and increase the overall energy efficiency while also eliminating the necessity to compress H2 during storage and transportation.1 Thinner membranes reduce the voltage losses from ohmic resistance and achieve high faradaic efficiencies. However, a higher crossover of hydrogen from the cathode through the membrane to the anode is observed for thinner membranes at high cathode operating pressures. As Ir/IrO2 (anode catalyst) is inefficient in oxidizing H2
1, this increased crossover of H2 not only reduces the PEMWE efficiency but also results in formation of an explosive gas mixture. Some initial studies also suggest critical effect of crossover H2 on durability of the anode catalyst. Addition of a gas recombination catalyst (GRC) in the membrane is a highly useful strategy to oxidize permeating H2 and prevent the formation of such explosive gas mixtures. Despite the importance, fundamentals of gas recombination reaction mechanism along with the effects of GRC and its properties on it is not well established.

In this study, effect of the GRC and its properties (loading, particle size, distribution, and location) on H2 permeation will be elucidated using a high pressure (up to 30 bar) electrolyzer setup coupled with online gas chromatography (Figure 1). The role of H2 and O2 partial pressures and operating current densities (simulated by varying the flow rates) will also be closely examined. Effects caused by the addition of anode and cathode catalyst layers on H2 permeation will also be presented in addition to long-term membrane durability results.

Figure 1. Decreased H2 permeation rate observed with GRC (Membrane A) at different cathode (H2) operating pressures at 80 °C using ex-situ electrolyzer setup. Deactivation of the GRC reaction is observed when switching the anode gas from O2 to N2.

Figure 1
PGM Recovery: Maximizing PGM Dissolution through Minimizing Ostwald Ripening
Authors: Andersen Shuang Ma , Sharma Raghunandan
Published: February 2024

Efficient recovery of platinum group metals (PGMs) through electrochemical means using mild conditions is of significant impact from both the industrial and the environmental points of view. Owing to their large surface-to-volume ratio, fast dissolution of PGM nanoparticles is possible through potential cycling between oxidizing and reducing potentials, leading to formation and dissolution of surface-oxide layer (transient dissolution). However, at reducing potentials, reduction of the dissolved metal species on the source nanoparticles leads to enhance the Ostwald ripening process1 and hence to decrease the overall dissolution efficiency significantly. In this talk, we present strategies to accelerate dissolution of PGM nanoparticles by limiting Ostwald ripening through (1) use of surface switching species (SSS), which selectively block the PGM surface to inhibit redeposition induced particle growth at reducing condition and expose the PGM surface to facilitate dissolution at oxidation condition, respectively2. (2) use of an auxiliary deposition system to continuously remove the dissolved PGM species through reaction kinetic manipulation3. Such surface relegation property to depress unwanted process and assist desired reaction documents an alternative and efficient approach for precious metal electrochemical recovery.

References

Sharma, R.; Andersen, S. M., Quantification on Degradation Mechanisms of Polymer Electrolyte Membrane Fuel Cell Catalyst Layers during an Accelerated Stress Test. ACS Catal.
2018,
8 (4), 3424-3434.

Sharma, R.; Simonsen, S. B.; Morgen, P.; Andersen, S. M., Inhibition of Ostwald ripening through surface switching species during potentiodynamic dissolution of platinum nanoparticles as an efficient strategy for platinum group metal (PGM) recovery. Electrochim. Acta
2019,
321, 11.

Sharma, R.; Gyergyek, S.; Andersen, S. M., Environmentally and Industrially Friendly Recycling of Platinum Nanoparticles Through Electrochemical Dissolution-Electrodeposition in Acid-Free/Dilute Acidic Electrolytes. ChemSusChem
2018,
11 (21), 3742-3750.
Pt-Ta-Co Electrocatalysts for Polymer Electrolyte Fuel Cells
Authors: Miyamoto Ryo , Ogawa Taichi , Nishiizumi Ryosuke , Yasutake Masahiro , Noda Zhiyun , Nishihara Masamichi , Hayashi Akari , Matsuda Junko , Sasaki Kazunari
Published: February 2024

Introduction

Electrocatalysts with both high catalytic activity and high potential cycling durability are required for polymer electrolyte fuel cells. It is of technological interest to develop electrocatalysts using mesoporous carbon as a support framework and Pt-Ta-Co as a catalyst. Fuel cells using this novel electrocatalyst have to be prepared to evaluate their electrochemical performance. Here in this study, we aim to examine polymer electrolyte fuel cells using these new electrocatalysts by evaluating the current-voltage characteristics and various overvoltages under different electrocatalyst layer preparation conditions such as ionomer and solid contents.

Experimental

A novel electrocatalyst (Pt0.7Ta0.2Co0.1/MC) was prepared by loading Pt-Ta-Co catalyst onto mesoporous carbon as a support framework by the acac method [1]. MEAs with Pt/C (TEC10E50E, Tanaka Kikinzoku Kogyo, Japan) as the anode electrocatalyst layer and a new electrocatalyst as the cathode electrocatalyst layer were prepared by spray printing. The cathode electrocatalyst layer was deposited with various ionomer and solid contents, and fabrication conditions of other cells were based on previous conditions [2]. The MEAs prepared were subjected to performance tests and overvoltage separation. Their cell performance was analyzed by subsequent microstructural observation using field emission scanning electron microscopy (FE-SEM).

Results and discussion

Figure 1 shows cell voltage of MEAs with the new electrocatalyst with various ionomer contents under operating conditions of 80°C and 100% relative humidity. In the preparation of the cathode electrocatalyst layer using the new electrocatalyst, it was found that relatively high performance was obtained at the solid content of 3.5 wt.% and ionomer content of 35 wt.%. The solid content of 3.5 wt.% was found to exhibit higher performance than that of 5 wt.%. Although the new electrocatalyst was highly active on the half-cell level, its electrochemical performance in a single cell has still lower than that of the cell fabricated using the standard Pt/C (TEC10E50E) for both electrodes. The concentration overvoltage was particularly high, as shown in Fig. 2, and microstructural observations revealed issues related to the microstructure of the electrocatalyst layer. Further improvement of cell performance has to be made through detailed analysis and optimization of the microstructure of the electrocatalyst layers such as their porosity.

Acknowledgments

This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

References

A. Hayashi, H. Notsu, K. Kimijima, J. Miyamoto, and I. Yagi, Electrochim. Acta, 53, 6117–6125 (2008).

T. Ogawa, Y. Inoue, K. Yamamoto, M. Yasutake, Z. Noda, S. M. Lyth, J. Matsuda, M. Nishihara,

Hayashi, and K. Sasaki, ECS Trans.,
109 (9), 241 (2022).

Figure 1
Electrochemical Top-Down Synthesis of Nanostructured Electrocatalysts for Polymer Electrolyte Membrane Fuel Cells
Authors: Schneider Peter Maximilian , Sarpey Theophilus Kobina , Fichtner Johannes , Garlyyev Batyr , Bandarenka Aliaksandr S.
Published: February 2024

Nanostructured catalysts are a promising class of materials to meet the requirements for the energy transition away from fossil fuels towards alternative, carbon-free, energy carriers, such as hydrogen. These catalyst materials boost the efficiency of energy conversion devices, such as fuel cells or electrolyzers, by accelerating their fundamental electrochemical reactions. Bottom-up synthetic routes for nanostructured materials often involve multiple synthesis steps and the use of surfactants, reducing agents or stabilizers. This results in complex and extensive synthesis protocols.[1] In recent years, a novel top-down synthesis approach to form metal nanoparticles has been established, in which bulk metal wires are immersed in an electrolyte and subsequently subjected to a high alternating potential. This leads to the generation of nanoparticles dispersed in the electrolyte.[2] There is no need for reducing agents, surfactants, or precursor solutions. The complete synthesis can be performed in one pot involving one main step with consequent washing and drying of the nanoparticles.

In this study, we synthesized Pt-based nanoparticles supported on Vulcan® carbon support (Pt/C) and tested their electrochemical activity towards the oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells (PEMFCs). Firstly, we elucidated the influence of synthesis parameters such as potential amplitude, frequency, electrolyte composition, and concentration on the size and shape of Pt nanoparticles.[3] We continued with the synthesis of more complex nanostructures, such as Pt alloy nanoparticles. This introduces strain and ligand effects at the surface of the nanoparticles, which increases the electrocatalytic activity for the ORR. We demonstrated the facile, simple, and surfactant-free synthesis of highly active PtxPr/C[4] and PtxCu/C, as two examples for Pt alloy catalysts for the ORR, and give an outlook on other systems, such as PtxGd/C.

References:

[1] Chen et. al., Chem. Rev. 2010, 110, 3767-3804

[2] Yanson et. al., Angew. Chem. Int. Ed. 2011, 50, 6346-6350

[3] Garlyyev et. al., Nano Res. 2021, 14(8), 2762-2769

[4] Fichtner et. al., ACS Appl. Mater. Interfaces 2019, 11, 5, 5129–5135

Figure 1
Optimization of PdCu Alloys as Efficient and Durable HOR Electrocatalysts in Anion Exchange Membrane Fuel Cells
Authors: Pagliaro Maria Vincenza , Miller Hamish Andrew , Evangelisti Claudio , Bartoli Francesco , Bellini Marco , Berretti Enrico , Castello Carolina , Poggini Lorenzo , Vizza Francesco
Published: February 2024

Anion-exchange membrane fuel cells (AEMFCs) allow for the use of Pt-free or precious group metal (PGM-free) catalysts and for a wider choice of cell and stack materials. Currently, there are still development challenges, such as the need to improve the efficiency of anode catalysts, due to the sluggish hydrogen oxidation reaction (HOR) in alkaline electrolytes. It has been demonstrated that the HOR rate can be improved using bifunctional materials, which have both an optimized hydrogen binding energy (HBE) and a favorable OHads binding energy (OHBE) [1,2]. In literature, experimental and theoretical studies demonstrate that HOR electrochemical activity of PdCu alloys strongly depends on their crystalline structure, which can be tuned through thermal treatment (300-600°C) modifying the Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC) phase ratio [3-5]. On this basis, a FCC-phased PdCu(1:1) alloy supported on Vulcan XC-72 was synthesized via a metal-vapor method (MVS) and furtherly modified through thermal annealing (5 hours under N2 atmosphere) in order to obtain the appearance of an ordered BCC structure. The HOR performance and stability of these materials were tested for first time in a complete in AEMFC. The use of PdCu allows us to lower the effective Pd loading on the electrode to about 0.16 mg cm-2, obtaining in the case of PdCu/C-500°C (where FCC-BCC phases coexist) a maximum power density of 941 mW/cm2. The increased activity and stability of the PdCu/C-500°C was demonstrated through long stability test, where it exhibits an average of 685 mW/cm2 of power density over 15 hours of testing during 3 days in AEMFC fixed at a constant potential of 0.4 V and 80°C (H2 0.5 L/min, O2 1 L/min), 10% more of the FCC-phased PdCu. Moreover, acquiring a final scan of potential at the end of the experiments, it is clear that PdCu/C 500°C suffers of a minor drop of performances (only of 19%), respect with disordered FCC-phased PdCu which efficiency in terms of maximum power density drops of 30% (Figure 1).

Figure 1
Unlocking Bifunctional Electrocatalytic Performance of Co-MOF-Derived Catalysts for ORR and OER
Authors: Yusibova Gulnara , Kongi Nadezda , Karpichev Yevgen
Published: February 2024

As the world is rapidly moving towards renewable energy technologies, the demand for efficient and cost-effective bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is increasing. Metal-organic framework (MOF)-based catalysts possess tunable and hierarchical porous structures with high surface area, making them superior to noble metal catalysts for energy storage technologies due to their high catalytic activity and stability.

In this study, we report a novel Co-N-C bifunctional oxygen electrocatalyst synthesized by carbonizing single metal Co-MOF precursor TAL-2. The optimized Co-N-C material demonstrated superior ORR/OER bifunctional catalytic activity compared to the commercial Pt/C and RuO2. The outcomes of this study highlight the considerable potential of utilizing a single metal Co-N-C catalyst as a facile precursor for the development of highly efficient electrocatalyst materials.
Rationalizing the Effect of the Redox-Inactive Metals on the Activity of Oxides in Oxygen Electrocatalysis
Authors: Kuznetsov Denis A. , Wu Yi-Hsuan , Müller Christoph R.
Published: February 2024

The large-scale implementation of renewable energy conversion and storage technologies is a key challenge to transition to a sustainable society. One of the most critical elements towards this goal is the discovery of active, stable and inexpensive catalysts for electrochemical energy conversion processes, such as the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are central for the efficiency of water-splitting electrolyzers, fuel cells and metal–air batteries.1 Manganese-based spinels, MxMn3-xO4, and ruthenium pyrochlores, M2Ru2O7
−
δ, are known as active catalysts for the ORR and OER, respectively, and were studied here as model systems to rationalize the effect of the incorporation (doping) of redox-inactive elements (M) into the structure on the catalytic performance of complex oxides in oxygen electrocatalysis.

We found a direct correlation between the ORR/OER activity of Mn3O4:M spinels (M = Mn, Cu, Zn, Mg, Ca, Sr),2 and Y1.8M0.2Ru2O7
−
δ pyrochlores (M = Y, Fe, Co, Ni, Cu),3 the lattice oxygen binding strength/lability and the formation enthalpy of the binary MO
x
oxides. We found experimentally that the activity of Mn3O4:M and Y1.8M0.2Ru2O7
−
δ in, respectively, ORR and OER, varies significantly depending on the nature of M. We observed that metals M with higher enthalpies of formation for the respective oxide weaken the oxygen binding on the surface of the complex oxide that correlates in turn with changes in ORR/OER activity. DFT studies captured changes in the electronic structure upon M substitution and allowed to correlate trends in the electronic band structure and the oxygen vacancies formation energies with the ORR/OER performance of the Mn3O4:M/Y1.8M0.2Ru2O7
−
δ catalysts. These activity trends are subsequently discussed in the framework of theoretically established correlations between the electrocatalytic activity and adsorption energies of catalytic intermediates. We demonstrated that the introduction of redox-inactive metal substituents/dopants into the host structure of a metal oxide is a highly versatile approach to tune the binding strength of reaction intermediates (determining the position of the catalyst on the ORR/OER activity volcano), and in turn improve the ORR/OER activity and also selectivity. This approach is a general concept that is transferrable to a broad selection of materials and processes associated with adsorption and redox reactions involving oxygen species.

References

(1) Seh, Z. W.; Kibsgaard, J.; Dickens, C. F.; Chorkendorff, I.; Nørskov, J. K.; Jaramillo, T. F. Science
2017,
355, eaad4998.

(2) Wu, Y.-H.; Mehta, H.; Willinger, E.; Yuwono, J. A.; Kumar, P. V.; Abdala, P. M.; Wach, A.; Kierzkowska, A.; Donat, F.; Kuznetsov, D. A.; Müller, C. R. Angew. Chem. Int. Ed.
2023,
62, e202217186.

(3) Kuznetsov, D. A.; Naeem, M. A.; Kumar, P. V.; Abdala, P. M.; Fedorov, A.; Müller, C. R. J. Am. Chem. Soc.
2020,
142, 7883-7888.
Investigating the Effects on Replacing Platinum by Molybdenum as Cathode Electrocatalysts in Proton Exchange Membrane Water Electrolysis
Authors: Piñeiro Alexis , Perivoliotis Dimitrios , Wu Xiuyu , Gracia-Espino Eduardo
Published: February 2024

Water electrolysis coupled to renewable energy sources has become in a crucial technique for the green hydrogen production. Hydrogen economy is currently in the spotlight to solve energy demands due to its advantages such as clean, sustainable, low footprint, as well as high-power density which is 3 times above gasoline and diesel. To produce large quantities of hydrogen, proton exchange membrane water electrolysis (PEMWE) has arisen as a promising system to solve hydrogen demands. The heart of the PEMWE consists in a membrane electrode assembly (MEA), where two gas diffusion layers (GDLs), hosting the respective catalysts, are sandwiched between an ionomer membrane. Commonly, noble metals are needed as catalyst in the anode (Ir, Ru) and cathode (Pt) to reach high current densities maintaining low cell voltages. The large content of noble metals, their high cost, and accelerated corrosion rates at high cell voltages are some drawbacks that limit the industrialization and commercialization of PEMWE technology. Replacing, decreasing, or simply extending the operational lifetime of these noble metals have a positive impact on the hydrogen economy. Molybdenum is an earth-abundant metal with low-cost which has been already used to produce highly active electrocatalysts, that can potentially replace Pt. However, most electrocatalytic studies are restricted to three-electrode cells with different operational conditions than those employed in PEM cells. The latter makes a complicated task to predict the performance of the catalyst and stability under relevant instrial applications. Here, we investigated the viability of using three selected Mo-based nanomaterials (1T’-MoS2, Co-MoS2, and ß-Mo2C) as potential electrocatalysts to replace Pt in PEMWE systems. We investigated the effects of replacing Pt in the catalyst loading, charge transfer resistance, kinetics, operational stability, and hydrogen production efficiency during PEMWE operation. Furthermore, we developed a methodology to identify the effects of tuning the cathode catalyst while keeping the anode catalyst in the overall kinetics of PEMWE system. Our results point that electrochemical performance in traditional open cell might not strictly predict the performance that could be seen in PEMWE cells due to differences in interfaces, contact between the components and porosity of the macroscopic catalyst layers. Among the catalyst studied, 1T’-MoS2 exhibited low overpotential associated to low charge transfer resistance while reaching 1 A cm-2 at 1.9 V. Our study highlights the importance to continue developing efficient electrocatalysts to replace noble metals suitable for PEMWE systems.

Figure 1
Trapped Platinum Single-Site Catalysts for the Hydrogen Evolution Reaction
Authors: Huang Po-Yuan , Tang Peng , Swallow Jack E. N. , Gianolio Diego , Weatherup Robert S , Pasta Mauro
Published: February 2024

Trapped platinum single-site catalysts (Pt-SSCs) in defective carbon substrates are of particular interest for polymer-electrolyte membrane (PEM) water electrolysers due to their high Pt atom utilization for the hydrogen evolution reaction (HER). However, their intrinsic catalytic activity compared with metallic Pt nanoparticles remains a topic of debate in the field with opposing results reported. [1, 2] A detailed investigation of the bonding environment of Pt and its evolution at HER working conditions is therefore warranted in order to corelate the Pt single-site structure to its catalytic activity and stability.

Here, we present a detailed analysis on trapped Pt-SSC prepared by pyrolysing H2PtCl6 adsorbed on a polyaniline substrate. [3] We used in-situ heated scanning transmission electron microscopy, temperature-dependent X-ray photoelectron spectroscopy and operando X-ray absorption spectroscopy to follow the evolution of Pt’s bonding environment during pyrolysis and HER. We demonstrate that the trapped Pt-SSC is stable under HER potentials but with lower catalytic activity relative to commercial Pt nanoparticles. We also perform first principles calculations to elucidate the origin of the inferior activity.

Our results promote the understanding of the relationship between the structure of trapped Pt-SSC and its HER performance, and calls for a techno-economic analysis to assess the practicality of using Pt-SSCs in commercial PEM water electrolyzers.

References

Q. Yang, H. Liu, P. Yuan, Y. Jia, L. Zhuang, H. Zhang, X. Yan, G. Liu,Y. Zhao, J. Liu, S. Wei, L. Song, Q. Wu, B. Ge, L. Zhang, K. Wang, X. Wang, C.-R. Chang, and X. Yao, J. Am. Chem. Soc., 144, 2171 (2022).

J. Wang, H. Y. Tan, T. R. Kuo, S. C. Lin, C. S. Hsu, Y. Zhu, Y. C. Chu, T. L. Chen, J. F. Lee, and H. M. Chen, Small, 17, 2005713 (2021).

P. Tang, P.-Y. Huang, J. E. N. Swallow, C. Wang, D. Gianolio, H. Guo, J. H. Warner, R. S. Weatherup and M. Pasta, “Structure- property relationship of defect-trapped Pt single-site electrocatalysts for the hydrogen evolution reaction” Reasearch Square (2023), doi: 10.21203/rs.3.rs-2397818/v1.
Polymer Design Strategies for Alkaline Membrane Water Electrolysis
Authors: Park Eun Joo , Arges Christopher , Xu Hui , Bae Chulsung , Fujimoto Cy , Matanovic Ivana , Kim Yu Seung
Published: February 2024

Water electrolysis is a carbon-free hydrogen production technology, making it a promising candidate to mitigate aggravating climate change. Ion exchange membranes are an essential component of membrane-based water electrolysis, enabling high hydrogen production efficiency through a zero-gap configuration. The recent research efforts to develop anion exchange membranes and electrode ionomers have made significant improvement in durability of alkaline membrane water electrolyzers without sacrificing performance and efficiency. Still, there are several factors related to polymer electrolytes that contribute to the voltage loss for water splitting in the alkaline condition including electrode local pH, the interface between membrane and electrodes, and electrochemical oxidation of ionomers at high potentials. This presentation will provide the state-of-the-art performance of alkaline membrane water electrolyzers with respect to the structure of anion exchange membranes and ionomers. The material design strategies and future directions to develop advanced polymer electrolytes will be discussed for this green hydrogen production technology.

Reference:

Park, E.J., Arges, C.G., Xu, H., Kim, Y.S. ACS Energy Lett.
2022
, 7, 10, 3447–3457

Motz, A.R., Li, D., Keane, A., Manriquez, L.D., Park, E.J., Maurya, S., Chung, H., Fujimoto, C., Jeon, J., Pagels, M.K., Bae, C., Ayers, K.E., Kim, Y.S. Mater. Chem. A
2021
, 9, 22670-22683

Matanovic, I., Kim, Y.S. Current Opinion in Electrochemistry
2023
, 38, 101218

Leonard, D.P., Lehmann, M., Klein, J.M., Matanovic, I., Fujimoto, C., Saito, T., Kim, Y.S. Advanced Energy Materials
2023
, 13, 2203488
Water Transport and Salt Precipitation in Anion-Exchange Membrane Electrolyzers
Authors: Koch Susanne , Disch Joey , Kilian Sophia K. , Metzler Lukas , Vierrath Severin
Published: February 2024

The hydrophilic nature of hydrocarbon ionomers and membranes presents a major challenge in anion-exchange membrane (AEM) electrolysis, despite improved stability from reinforcements and modified polymer chemistry. Durability and performance are still highly influenced by the operation mode and water management within the membrane-electrode-assembly (MEA).

Dry cathode operation in AEM water electrolysis, where only the anode is supplied with liquid electrolyte (KOH), offers increased hydrogen purity but poses challenges for non-fluorinated anion-exchange polymers that are sensitive to water content. In-situ neutron imaging with high resolution (~6 µm effective resolution) revealed that adjusting the anion-exchange capacity of the cathode binder ionomer can retain membrane humidification (Fig. 1)1.

In the electrochemical reduction of CO2 using AEM, water management and salt precipitation are significant challenges. High-resolution neutron imaging of a zero-gap CO2 electrolyzer operating at 200 mA cm-² and 2.8 V showed salt precipitates penetrating the cathode gas diffusion layer, leading to blocked CO2 gas transport and a decay in Faraday efficiency. Salt accumulation was higher under the cathode channel of the flow field than the land2.

Both studies demonstrate the substantial impact of water management and salt precipitation on the operation of AEM-based electrolyzers and how neutron imaging can assist in addressing these challenges.

References

(1) Koch, S.; Disch, J.; Kilian, S. K.; Han, Y.; Metzler, L.; Tengattini, A.; Helfen, L.; Schulz, M.; Breitwieser, M.; Vierrath, S. Water management in anion-exchange membrane water electrolyzers under dry cathode operation. RSC Adv
2022, 12, 20778–20784.

(2) Disch, J.; Bohn, L.; Koch, S.; Schulz, M.; Han, Y.; Tengattini, A.; Helfen, L.; Breitwieser, M.; Vierrath, S.; High-resolution neutron imaging of salt precipitation and water transport in zero-gap CO2 electrolysis. Nat Commun
2022, 13, 6099.

Figure 1
Iridium-Cobalt Oxide from Modified Adam’s Fusion Synthesis Method as Electrocatalyst for Oxygen Evolution Reaction
Authors: Labata Marc Francis , Li Guangfu , Chuang Po-Ya
Published: February 2024

Green hydrogen from water electrolysis is one of the leading energy carriers towards energy sustainability; however, cost reduction is necessary to make this technology more commercially viable. One of the most expensive components in an electrolysis cell are the iridium-based catalysts. To reduce cost, we propose to minimize iridium loading through alloying with a less-expensive cobalt (Co) metal. Here, we synthesized iridium-cobalt oxide (IrCo) using a surfactant-assisted Adam’s fusion synthesis technique as a scalable method. The in-house IrCo catalyst demonstrates improved performance than the commercial iridium oxide (IrOx_C) in both acidic and alkaline media. Further activity enhancement was achieved through acid etching (IrCo_ae), preferentially removing Co to generate more active sites. XPS and ICP-MS results reveal that the Ir:Co atomic ratio is increased from 1.0 to 5.5 after acid etching. The elemental distribution is also supported by EDX mapping. The effects of Ir/Co molar ratio, the use of surfactant and their interaction with the acid etching process were also investigated. The dependence of Ir valency on Ir/Co ratio and the possible influence of Ir3+ surface concentration to achieve high OER activity, especially in the acidic media, are highlighted in the study. In the absence of surfactant, the segregation of Ir and Co is much stronger forming a Co core and an Ir shell, and the OER activity is lower compared to its surfactant-assisted counterpart. The results confirm that surfactant improves the interaction of Ir and Co, leading to a better OER performance. This study proves an effective Ir utilization with the proposed synthesis method and could be tailored and enhanced to improve the catalyst stability for green hydrogen production.
Oxygen Evolution Reaction Activity of Iridium Oxide with Strange Structure, Its Toward PEM Water Electrolysis
Authors: Ishida Takanobu , Takeda Yuko , Watanabe Yuta , Aoki Naoya
Published: February 2024

Water electrolysis is a promising approach of hydrogen mass production.PEM water electrolysis has advantages such as high current density operation and quick response against input electricity.From these advantages, PEM water electrolysis is adequate to the hydrogen mass production system adopted the renewable energy.Iridium oxide shows good oxygen evolution reaction(OER) activity and durability for PEM water electrolysis anode catalyst, but there are material supply and cost issues as it is precious metal.To solve these issues, a number of studies have been conducted to improve OER activity of Iridium oxide.

In this work, the crystal structure of iridium oxide is focused in order to improve OER activity.As a result of several synthesis survey, we have synthesized iridium oxide with unique structure and it shows more than four times OER activity compared to commercial catalysts in RDE.The mechanism for the high OER activity would be discussed based on the results of electrochemical properties, spectroscopy, and structural analysis.
Towards Low Iridium Loading in Proton-Exchange Membrane Water Electrolysis: Scalable Synthesis of IrOx@TiO2 Core-Shell Particles
Authors: Hoffmeister Darius , Finger Selina , Fiedler Lena , Körner Andreas , Zlatar Matej , Thiele Simon , Hutzler Andreas , Pham Chuyen
Published: February 2024

Proton-exchange membrane water electrolysis (PEMWE) is a promising technology for producing hydrogen from renewable energy sources. However, the high demand for noble metals hinders the widespread adoption of this technology. Especially the anodic catalyst layer is usually manufactured with high loadings of the scarce element iridium, typically ~2 mgIr·cm-2. As an active and stable noble-metal-free alternative to iridium catalysts has yet to be developed, the most viable strategy for the near future development of PEMWE is to reduce iridium loadings as much as possible. Lowering the iridium loading to values below 0.5 mgIr·cm-2, however, often leads to inhomogeneous catalyst layers resulting in disconnected catalyst islands.1, 2 In two related contributions, we report a novel anodic catalyst for PEMWE that can overcome this limitation by forming homogeneous layers even at lower loadings, thus exhibiting high full cell performance. In this first contribution, we synthesized catalysts with less than 50 wt% iridium content to obtain low iridium loadings while maintaining electrical conductivity. The catalyst is based on the IrO2@TiO2 core-shell microparticles introduced in our previous work,3 which we optimized towards their structural and electrochemical properties. The structural properties of these novel catalysts are analyzed by scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Furthermore, the catalytic activity is evaluated by rotating disk electrode (RDE) measurements, and the electrochemical stability is assessed in a scanning flow cell setup combined with an inductively coupled plasma mass spectrometer (SFC-ICP-MS). Our catalysts outperform state-of-the-art materials in terms of mass activity in RDE measurements, while a comparable dissolution stability is achieved, as evidenced by SFC-ICP-MS measurements. In our second contribution, we show a high performance of this novel catalyst in catalyst-coated membrane (CCM) configuration with iridium loadings below the above mentioned threshold of 0.5 mgIr·cm-2. This proves that our novel IrOx@TiO2 particles with low iridium contents enable a significant reduction of iridium for the anode in PEMWE.

References:

M. Bernt, A. Siebel and H. A. Gasteiger, J. Electrochem. Soc.,
165(5), F305-F314 (2018).

C. Rozain, E. Mayousse, N. Guillet and P. Millet, Applied Catalysis B: Environmental,
182, 123–131 (2016).

C. van Pham, M. Bühler, J. Knöppel, M. Bierling, D. Seeberger, D. Escalera-López, K. J. Mayrhofer, S. Cherevko and S. Thiele, Applied Catalysis B: Environmental,
269, 118762 (2020).

Figure 1
Supported-Ir Catalysts: The Impact of the Supports' Chemical Composition on the Oxygen Evolution Reaction
Authors: Blanco Redondo Lucinda , Lobko Yevheniia , Rodriguez Miquel , Dinhová Thu Ngan , Hrbek Tomas , Matolínová Iva
Published: February 2024

In water electrolyzer cells, the anode electrode is one of the most important components, where the oxygen evolution reaction (OER) takes place. In this process, the water molecules split into oxygen ions, protons, and electrons, and the oxygen gas is produced on the anode surface [1]. The most suitable materials that catalyze OER are ruthenium, iridium, and their oxides, but their cost and scarcity require reduction and enhancement of their utilization [2]. One morphological strategy consists of the dispersion of the active nanoparticles in supportive nanoparticles made of less expensive materials to increase their mass activity. In addition, due to the high potential reached during operating conditions for water splitting, supportive materials have to possess a high corrosion resistance. Titanium oxides are good candidates because of their high thermal and chemical stability, low cost, and commercial availability [3]. But their poor electric conductivity (∼10−6 S cm−1) makes the design of an active and stable catalyst a complex task. In this work, Ir nanoparticles have been synthesized on the surface of several Ti-based nanoparticles and a complete analysis of their physicochemical properties have been carried out (
Fig. 1a-b
). In addition, electrochemical behaviour has been tested ex-situ in a half cell by the rotating disk electrode technique and after, the catalysts have been deposited in a polymer membrane for testing in-situ in a single cell proton exchange membrane water electrolyzer. The results show a successful performance of the supported Ir/TiO2 nanoparticles comparable to the pure Ir black nanoparticles but with an active metal loading five times lower. Differently, even though TiC showed excellent electrical conductivity during the ex-situ characterization, Ir/TiC nanoparticles had a poor activity after just one day of performance in the WE due to the complete oxidation of the TiC into TiO2 (
Fig. 1c-d
). Finally, Ir/TiB2 showed a balanced result in terms of activity and stability, showing promising properties as a catalyst for PEM-WE.

Sadhasivam T., Ho-Young J. Chapter 3 - Nanostructured bifunctional electrocatalyst support materials for unitized regenerative fuel cells// Nanostructured, Functional, and Flexible Materials for Energy Conversion and Storage Systems- 2020.- 69-103.

Antolini E. Iridium as Catalyst and Cocatalyst for Oxygen Evolution /Reduction in Acidic Polymer Electrolyte Membrane Electrolyzers and Fuel Cells // ACS Catal. - 2014.- 4, N 5.- P. 1426-1440.

Van Pham C., Bühler M. IrO2 coated TiO2 core-shell microparticles advance performance of low loading proton exchange membrane water electrolyzers// Applied Catalysis B: Environmental-2020.- P 269.- P. 118762.

Figure 1. TEM image of Ir/TIO2 (a), EDX mapping of Ir/TiO2(b), linear sweep voltammetry of catalysts (c), the current density at given potential 1.80 V (d).

Figure 1
Comparative Study of Degradation Features in Proton Exchange Membrane Water Electrolysis: Irregular Renewable Energy Vs Regular Steady-State/Dynamic Loads
Authors: Voronova Anastasiia , Kim Sol , Park Hee-Young , Jang Jong Hyun , Seo Bora
Published: February 2024

Green hydrogen production is currently on the rise, and it is reshaping the future of the energy sector. Numerous hydrogen roadmaps and projects are scaling up this technology in various target sectors, which necessitates cost reduction for green hydrogen implementation. Proton exchange membrane water electrolysis coupled with the renewable energy source (PEMWE-ReS) is a promising technology that offers notable advantages to decrease the electricity cost by using wind generation and solar photovoltaic system. However, to meet the growth of green hydrogen technology, accurate lifetime assessment and subsequent development of durable materials should be considered. In this regard, this presentation will discuss a comparative analysis of stability test results based on various load-ranges. In particular, to consider the PEMWE-ReS coupling, a realistic solar profile was simulated and applied for PEMWE cell measurement. The results were then compared to previous steady-state and dynamic loads to gain insight into the differences in degradation patterns at field and laboratory scale. For this purpose, the degradation features were systematically analyzed with electrochemical, microscopic, and spectrochemical analyses to see the dynamic of overpotential changes, membrane chemical degradation, catalyst dissolution/migration/diffusion, and Ti porous transport layer passivation. Notably, a realistic solar profile that simulates PEMWE-ReS conditions is featured by the increased fluoride release rate due to cycling to low load, and Pt dissolution/diffusion to the anode. Given the degradation features of the realistic solar operation, it was determined that a combined pattern of specific steady-state and dynamic cycling loads can induce the degradation features of solar operation the most. The findings can provide useful insights for establishing accelerated stress test to diagnose system durability and for setting design guidance for durable materials.
Impact of Low Catalyst Loading and Incorporation of Additives on Structure and Performance of PEM Electrolyzer Catalyst Layers
Authors: Zaccarine Sarah , Alia Shaun M , Foster Jayson , Pivovar Bryan S. , Pylypenko Svitlana
Published: February 2024

Polymer electrolyte membrane water electrolyzers (PEMWEs) are an important technology that can produce renewable hydrogen on demand, although with challenges posed by the slow kinetics of the anodic oxygen evolution reaction (OER) and degradation issues. The degradation of membrane electrode assemblies (MEAs) prepared with Ir-based catalysts is not well understood, especially with lower-loading catalyst layers and intermittent load inputs. This work investigates low-loading IrO2 catalyst layers made with different carbon-based additives, including high-surface-area carbon (HSC), graphitized HSC (gHSC), Vulcan, graphitic carbon nanofibers (gCNFs), graphitic nanoplatelets (gNPs), nitrogen-doped carbon spheres (NCs), Ti carbide (TiC) and Ti carbonitride (TiCN). While carbon-based supports have issues with corrosion at high oxidizing potentials, these materials provide a range of variations in morphology, shape, size, surface area, graphitization, and composition, allowing exploration of the impact of these parameters on catalyst layer structure to identify promising routes to improve catalyst layer structures. Catalyst layers were characterized with electron microscopy and x-ray spectroscopy to assess the distribution of catalyst, carbon additive, and ionomer. This information was correlated with electrochemical performance measurements to elucidate the impact on kinetic site access and mass transport. Selected samples were also subjected to more extended operation to investigate how the initial structures and their performance evolved.
Impact of Position and Platinum Loading of Recombination Interlayers in Proton Exchange Membranes on the Anodic Hydrogen Content in Water Electrolysis
Authors: Abbas Dunia , Martin Agate , Trinke Patrick , Bierling Markus , Bensmann Boris , Thiele Simon , Hanke-Rauschenbach Richard , Boehm Thomas
Published: February 2024

Hydrogen crossover through the membrane is a significant safety concern in proton exchange membrane water electrolyzers (PEMWEs). This issue is predominant at low loads, which contradicts the application of PEMWEs in conjunction with fluctuating renewable energy sources that require the electrolyzer to switch between low- and high-load operation. The risk of flammable or explosive oxygen-hydrogen mixtures on the anode side of the electrolyzer prevents the application of membranes as thin as in fuel cells, which results in relatively large Ohmic losses. A means to mitigate the accumulation of hydrogen in the oxygen compartment is the integration of platinum nanoparticles as a recombination catalyst interlayer within the membrane that catalyzes the recombination of hydrogen and oxygen to water. It was shown that such an interlayer effectively minimizes the hydrogen concentration on the anode side without reducing the cell performance.1 Thus, this technology can pave the way toward thinner membranes and more efficient electrolyzers.

However, the interlayer should not increase the costs of the membrane electrode assembly by excessive Pt loading. Hence, we investigated the ideal position of this recombination interlayer within the membrane,2 and we performed a parameter study on the minimum required catalyst loading for an effective hydrogen-in-oxygen reduction.3 We find that the best position for the interlayer is close to the anode due to the lower oxygen permeability of the membrane. Also, a loading of 10 µg per cm² of platinum nanoparticles is sufficient to reduce the anodic hydrogen content from more than 2.5 vol.% (without interlayer) to approx. 0.5 vol.% when operating a PEMWE cell with a 110 µm thick membrane at 0.5 A/cm² and a differential pressure of 10 barc/1 bara. In summary, we are able to show that low platinum loadings within the membrane are sufficient to reduce the anodic hydrogen content in PEMWEs to safe values without impairing the electrochemical performance of the cell.

References

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165(16), F1271-F1277 (2018).

A. Martin, D. Abbas, P. Trinke, T. Böhm, M. Bierling, B. Bensmann, S. Thiele and R. Hanke-Rauschenbach, J. Electrochem. Soc.,
168(9), 94509 (2021).

D. Abbas, A. Martin, P. Trinke, M. Bierling, B. Bensmann, S. Thiele, R. Hanke-Rauschenbach and T. Böhm, J. Electrochem.
Soc.,
169(12), 124514 (2022).