bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and Activity-Durability Tradeoff of Coated Fe-N-C Catalysts for the Oxygen Reduction Reaction
Authors: Jiao Li , Sougrati Moulay-Tahar , Jaouen Frederic
Published: February 2024

Fe-based catalysts stand out for oxygen reduction reactions among the platinum group metal (PGM)-free catalysts for reducing the reliance on expensive and scarce platinum. With the endeavor of a PGM-free community, the state-of-the-art Fe-N-C catalysts have demonstrated encouraging initial activity in Proton Exchange Membrane Fuel Cell (PEMFC) 1-2. However, their long-term stability and durability remain a challenge, both in acidic liquid electrolyte cells and in single-cell PEMFCs3. Recently, a novel approach has demonstrated improved durability of Fe-N-C catalysts during ORR, which consisted of coating a pre-existing Fe-N-C with a thin carbon overlayer obtained via chemical vapor deposition of a metal-organic framework (ZIF-8), at 1100 °C4. However, the underlying mechanism for enhanced durability remains unclear. One of the keys to improved stability lies in the specific structure of the catalysts, including the coordination of the ORR-active iron atoms and the structure of the nitrogen-doped carbon matrix, especially the structure located at the top surface of catalysts. The CVD conditions that affect the structure of FeNC must be optimized, to achieve the optimal activity-durability trade-off.

This presentation will report on the structure, activity, and durability trends of a suite of FeNC catalysts coated at different CVD conditions. The key parameters have been investigated, such as deposition temperature, overlayer thickness, and iron speciation on their ORR activity and durability. The coated Fe-N-C catalysts have been evaluated for their activity/durability (in oxygenated environments) both in liquid electrolyte cells and PEMFCs. The coated Fe-N-C demonstrated inferior initial activity and improved durability (Figure 1). The correlation between the structural information derived from multiple techniques (XRD, Mossbauer spectroscopy, TEM, Raman spectroscopy, N2 sorption, etc) and their electrochemical behaviors will be discussed.

References

Jiao, L.; Li, J.; Richard, L. L.; Sun, Q.; Stracensky, T.; Liu, E.; Sougrati, M. T.; Zhao, Z.; Yang, F.; Zhong, S.; Xu, H.; Mukerjee, S.; Huang, Y.; Cullen, D. A.; Park, J. H.; Ferrandon, M.; Myers, D. J.; Jaouen, F.; Jia, Q., Nature Materials
2021, 20 (10), 1385-1391.

Mehmood, A.; Gong, M.; Jaouen, F.; Roy, A.; Zitolo, A.; Khan, A.; Sougrati, M.-T.; Primbs, M.; Bonastre, A. M.; Fongalland, D.; Drazic, G.; Strasser, P.; Kucernak, A., Nature Catalysis
2022, 5 (4), 311-323.

Martinez, U.; Komini Babu, S.; Holby, E. F.; Zelenay, P., Current Opinion in Electrochemistry
2018, 9, 224-232.

Liu, S.; Li, C.; Zachman, M. J.; Zeng, Y.; Yu, H.; Li, B.; Wang, M.; Braaten, J.; Liu, J.; Meyer, H. M.; Lucero, M.; Kropf, A. J.; Alp, E. E.; Gong, Q.; Shi, Q.; Feng, Z.; Xu, H.; Wang, G.; Myers, D. J.; Xie, J.; Cullen, D. A.; Litster, S.; Wu, G., Nature Energy
2022, 7 (7), 652-663.

Figure 1
Improving Oxygen Reduction Reaction Activity through Defect Engineering of Atomically Dispersed Iron Electrocatalysts for Proton Exchange Membrane Fuel Cells
Authors: Yi Seung Yeop , Lee Jinwoo
Published: February 2024

Atomically dispersed and nitrogen-coordinated iron catalysts(Fe-N-Cs) have the potential as an alternative to platinum-group metal catalysts for the oxygen reduction reaction (ORR). However, in the context of practical proton exchange membrane fuel cell (PEMFC) applications, the membrane electrode assembly (MEA) performances of Fe-N-Cs remain unsatisfactory. To address this issue, a defect engineering strategy has been developed to prepare high-performance PEMFC MEAs using atomically dispersed Fe-N-C catalysts. This strategy involves the use of a zeolitic imidazolate framework (ZIF)-derived nitrogen-doped carbon with additional CO2 activation to create atomically dispersed iron sites with a controlled number of defects. By adjusting the extent of defect formation in the carbon plane using CO2 activation, it is anticipated that changes in the oxidation state and spin state of the Fe center will modify the electronic structure of the Fe-N4 active sites. The Fe-N-C species with the optimal number of defect sites exhibit excellent ORR performance with a high half-wave potential of 0.83 V in 0.5 M H2SO4. Fine-tuning the number of defects can be optimized the ORR activity by adjusting the contribution of the Fe d-orbitals to the reaction intermediate binding energies. The resulting MEA based on the defect-engineered Fe-NC catalyst exhibits remarkable peak power densities in both H2/O2 and H2/air fuel cells, making it one of the most active atomically dispersed catalyst materials at the MEA level.
Carbon Corrosion Behavior of Carbon Support Materials for PGM-Based Catalysts in PEM Fuel Cells
Authors: Merzdorf Thomas , Hornberger Elisabeth , Ott Sebastian , Riebel Laurin , Guo An , Schröer Pierre , Strasser Peter
Published: February 2024

The proton exchange membrane fuel cell (PEMFC) is a promising device for the transportation sector of a fossil free society, using green hydrogen from water electrolysis as a clean and sustainable option. However, sluggish kinetics as well as durability issues limit the implementation until this day. Therefore, modifications to the platinum catalysts [1] and the carbon supports [2] are made to improve the overall performance and durability of the cathode catalyst system.

Herein, we present the investigation of the carbon corrosion behavior of different carbon support materials in PEMFCs using online nondispersive infrared (NDIR).The different carbon supports used for this study are commercial materials such as Vulcan, Ketjenblack EC-300J and Ketjenblack EC-600JD as well as self-synthesized mesoporous carbon nanodendrites (MCND). [3] The MCND support material is a highly porous high surface area carbon, which makes it a suitable candidate for fuel cell applications. Onto the support materials, Pt nanoparticles were deposited using a customized fluidized bed reduction reactor [4], resulting in similar Pt particle size and distribution onto the support material, thus making a comparison between different supports possible. Beginning of life (BOL) measurements in a single cell setup, as shown in Figure 1, show promising performance of the platinum catalyst supported on MCND (Pt/CMCND) compared to the platinum catalysts on commercial supports. Furthermore, we will present the investigated carbon corrosion behavior of the different support materials conducted by accelerated stress tests (AST) based on the DOE support degradation protocol. The online quantification of the evolved CO and CO2 from the cathode catalyst layer is measured using our online NDIR giving insight in the carbon corrosion resistivity of the different support materials. Together with the performance measurements, we develop a better understanding of the impact of the carbon support material on the performance and durability of the cathode catalyst layer.

Literature:

[1] Strasser, P; Kühl, S. Nano Energy
2016, 29, 166.

[2] Ott, S. et. al., Nat. Mater.
2020, 19 (1), 77-85.

[3] Numao, S. et al., Carbon
2009, 47, 306-312.

[4] Hornberger, E. et. Al. J. Electrochem. Soc. 2020, 167, 114509.

Figure 1: Air polarization curves of the four different catalysts under the following conditions: 80° C, 100% RH, 150 kPaabs backpressure, stoich.: 1.5 (H2) and 2 (air), min. flow: 50 ml/min (H2) and 800 ml/min (air).

Figure 1
Revealing the Synthesis and Degradation Mechanisms of Pt-Rare Earth Metal Alloy Catalysts by Multiple in-Situ Techniques
Authors: Hu Yang , Liu Pei , Gellrich Florian , Jensen Jens Oluf , Li Qingfeng
Published: February 2024

In comparison to conventional Pt alloys with late transition metals such as nickel and cobalt, Pt-rare earth metal alloys (Pt-RE) such as Pt-Ce, Pt-La, and Pt-Nd could have much-improved stability for the oxygen reduction reaction (ORR) in acidic media. However, this promise has only been demonstrated with polycrystalline electrodes rather than the more industrially relevant form of nanoparticles. A major challenge lies in the synthesis of Pt-RE alloy particles with well-defined shapes, sizes, and crystalline structures. We recently invented a solid-state chemical process for the synthesis of Pt-Re alloy nanoparticles. Here, we report our recent findings on the understanding of synthesis mechanisms and structural changes of Pt-RE alloy particles under operating ORR conditions, which are based on the results obtained from multiple in-situ techniques including in-situ transmission electron microscope, X-ray diffraction, and thermal-gravimetric mass spectrometry, etc. We aim to answer two questions through the studies, that is, 1) how do the alloy crystals come into formation during the synthesis? and 2) how do the structures of the alloy particles change during operating ORR conditions?
Enhancing the Hydrogen-Air Fuel Cell Performance of Octahedral Ptni Nanoalloys with Rational Design of Dopants, Layering and Support in the PEM Fuel Cells
Authors: Pan Lujin , Parnière Alice , Dunseath Olivia , Weber Cesar , Lu Jiasheng , Ronovský Michal , Klingenhof Malte , Arinchtein Aleks , Oh Hyung-Suk , Blanchard Pierre-Yves , Cavaliere Sara , Heggen Marc , Dunin-Borkowski Rafal E. , M. Bonastre Alejandro , Dionigi Fabio , Sharman Jonathan , Jones Deborah J. , Strasser Peter
Published: February 2024

This study focuses on the scale-up synthesis of carbon-supported octahedral PtNiX nanoparticles to improve their oxygen reduction reaction electrocatalytic activity, stability, and high current density for fuel cell applications. Octahedral PtNiX nanoparticles doped with different elements such as Rh or Ir and with high Pt loading on carbon supports were synthesized, characterized by physio-chemical methods and tested in single MEA-based fuel cells after rotating disk electrode (RDE) pre-screening measurements. Different carbon supports were compared, including N-doped carbon. We investigated the sensitivity of the I/C ratio for the ink on the performance of the nanoparticles in RDE, and show that it is an important parameter to consider during synthesis. Our study shows that the sensitivity of the I/C ratio is more pronounced for PtNi alloy octahedra than for pure Pt catalyst. Moreover, we also use in-situ measurement techniques, such as X-ray Absorption Spectroscopy (XAS) in a liquid cell, to study the impact of the dopants during the operation. In the MEA, we achieve a state-of-the-art current density of around 1500 mA/cm2 at 0.6V for octahedral PtNiX nanoparticles in fuel cell applications. This high current density is attributed to the superior electrocatalytic activity and stability of the doped nanoparticles, as well as their high loading of Pt. Overall, our results demonstrate the potential of octahedral PtNiX nanoparticles as highly efficient electrocatalysts for fuel cell applications. The study highlights the importance of considering the I/C ratio during catalyst ink preparation, and the use of in-situ measurement techniques to improve the fundamental understanding of catalyst structure-activity and -stability for the design of future electrocatalysts.
Mesoporous Carbon Supported Catalyst for Heavy Duty Fuel Cells
Authors: Komini Babu Siddharth , Mckinney Samuel , Wang Xiaojing , Yu Haoran , Li Kui , Mccool Geoff , Zulevi Barr , Park Andrew , Cullen David A. , Borup Rod L.
Published: February 2024

The interaction between the catalyst and the carbon support is crucial to both the performance and durability of the membrane electrode assembly (MEA) in a polymer electrolyte membrane fuel cell. Local oxygen transport resistance (RO2) has shown to be a significant contributor to the overpotential loss in the catalyst layer.1 Utilizing mesoporous carbon supports has shown to reduce RO2 compared to high surface area carbon and prevent ionomer poisoning of Pt inside the pores.2 Engineered catalyst supports (ECS) synthesized through templated organic precursor provides improved control of resulting carbon morphology.3 This work presents a detailed study of the performance and durability of the ECS supported catalyst. Effect of Pt weight percentage on the carbon support, ionomer loading, and the ionomer type on the catalyst performance and durability is presented. Figure 1 shows the performance at beginning of life (BOL) and end of life (EOL) after 90000 cycles, using US DOE’s electrocatalyst protocol, for MEAs with different ionomer loadings. Polarization curve, Pt accessibility through CO stripping, and RO2 from limiting current will be presented are measured at different intervals between BOL and EOL. Characterization of the Pt particle and catalyst layer structure performed at BOL and EOL will also be presented. This study highlights the value of the morphological and electrochemical evaluation to provide detailed insights into the catalyst and mesoporous carbon support interaction.

Acknowledgement

This research is supported by Technology Readiness Gross Receipts Tax Credit through New Mexico Legislature. This research is supported by U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office, through the Million Mile Fuel Cell Truck Consortium (M2FCT).

References

1 Kongkanand, A. et al. Journal of Physical Chemistry Letters, 7, (7), 1127-1137, 2016.

2 Ramaswamy, N. et al. Journal of The Electrochemical Society, 167, (6), 064515, 2020.

3 Ramaswamy, N. US DOE Hydrogen and Fuel Cells Program: 2020 Annual Merit Review and Peer Evaluation Report, 2020.

Figure 1
CVD Growth Graphene Foam Functionalized with Platinum for Fuel Cells Applications
Authors: Ion-Ebrasu Daniela , Andei Radu Dorin , Negrila Constantin Catalin , Boerasu Iulian , Carcadea Elena , Marinoiu Adriana , Vasile Bogdan Stefan
Published: February 2024

The development of catalysts with high activity for the ORR is essential to proton exchange membrane fuel cells (PEMFCs), since the majority of activation losses occur at the cathode and it turns into an interesting research area. In the present study, it is investigated the hydrothermal platinum functionalization of the CVD grown three-dimensional graphene foam (3D-GrFoam) using three concentrations of dihydrogen hexachloroplatinate (IV) hydrate [1]. The platinum functionalized graphene foam determined from XPS was 0.2at %, 0.3 at % and 0.4 at %, respectively.The catalytic activity towards ORR was analyzed from linear sweep voltammetry (LSV) plots recorded with a scan rate of 5 mV s-1 in oxygen saturated 0.5 M H2SO4. From the LSV curves and the Koutecky-Levich (K-L) plots for 0.4PtGrFoam as current density (mA-1 cm2
geo) vs. w-1/2 (rad s-1)-1/2), for various rotation speeds (among 250–1500 rpm) and different potentials (0.1 V-0.8 V). From the fitted K-L plots it is noticed a fair linear relationship at all potentials, that confirms the electroreduction of platinum. The number of transferred electrons is between 3.22 to 3.59 indicating the preponderance of the four-electron transfer mechanism in the ORR corresponding to the directly reduction of O2 to H2O.

1. Ion-Ebrasu, R.D. Andrei, S. Enache, S. Caprarescu, C. C. Negrila, C. Jianu, A. Enache, I. Boerasu, E. Carcadea, M. Varlam, B. S. Vasile, J. Ren, Materials 2021, 14, 4952.
(Invited) The Stability of Nanomaterials in Electrochemical Energy Conversion, Illustrated on Selected Examples
Authors: Ledendecker Marc
Published: February 2024

Energy is the most valuable resource for human activity and the foundation for all human progress. Thereby, electrochemical processes are considered a crucial technology for our future society's energy landscape. Catalysts are fundamental components of these processes, and the ability to control their structure and composition during synthesis is essential for obtaining high-performance and stable catalysts while preserving critical resources. The stability of materials that can endure reaction conditions over extended periods is of immense significance. In nanoparticle systems, typical deactivation mechanisms include catalyst agglomeration, dissolution, coalescence, Ostwald ripening, support corrosion, or poisoning.[1] In this conference contribution, I will discuss the prerequisites for stable electrocatalysts using selected examples. I will demonstrate how the catalyst's environment and support material can prevent degradation based on our recent observations.[2-5]

[1] Y. Shao-Horn, W. C. Sheng, S. Chen, P. J. Ferreira, E. F. Holby, D. Morgan, Top. Catal., 46, 285-305, 2007, J. C. Meier, I. Katsounaros, C. Galeano, H. J. Bongard, A. A. Topalov, A. Kostka, A. Karschin, F. Schüth, K. J. J. Mayrhofer, Energy & Environmental Science 2012, 5, 9319-9330.

[2] D. Göhl, H. Rueß, A. M. Mingers, K. J. J. Mayrhofer, J. M. Schneider, M. Ledendecker, J. Electrochem. Soc., 169, 011502, 2022

[3] D. Göhl, A. Garg, P. Paciok, K. J. Mayrhofer, M. Heggen, Y. Shao-Horn, R. E. Dunin-Borkowski, Y. Román-Leshkov, M. Ledendecker, Nat. Mater., 19, 287-291, 2020

[4] D. Göhl, H. Rueß, M. Pander, A. R. Zeradjanin, K. J. Mayrhofer, J. M. Schneider, A. Erbe, M. Ledendecker, J. Electrochem. Soc., 167, 021501, 2020

[5] M. Ledendecker, S. Krick Calderón, C. Papp, H. P. Steinrück, M. Antonietti, M. Shalom, Angew. Chem. Int. Ed., 54, 12361-12365, 2015
Strong Coupling Effects between Single Metal Site-Rich Carbon and PtCo Intermetallic Catalysts for Heavy-Duty Meas
Authors: Zeng Yachao , Chenzhao Li , Kariuki Nancy N. , Cullen David A. , Myers Deborah J. , Xie Jian , Wu Gang
Published: February 2024

Developing active and durable low-platinum group metal (PGM) oxygen reduction reaction (ORR) catalysts for proton-exchange membrane fuel cells (PEMFCs) remains a critical challenge for heavy-duty vehicle (HDV) applications. This work comprehensively studies synergistic catalysts, composed of Pt-based nanoparticles and supports with atomically dispersed M-N-C sites (MnSA-NC), using a suite of experimental techniques and DFT calculations. DFT calculations predicted that the presence of Mn-N4 sites could induce a strong coupling effect between Pt and support, which can strongly bind with Pt to immobilize the Pt clusters and weaken the adsorption of oxygen on the Pt surface to enhance intrinsic activity. In addition to the favorable MnN4 dopants, the MnSA-NC support is optimal support with sufficient surface areas, porosities, and adequate graphitization degree. Subsequently, well-dispersed Pt and ordered L12-Pt3Co nanoparticles with an average diameter of 2.1 nm and 3.3 nm were deposited on the MnSA-N-C support, which was comprehensively studied as the ORR cathode catalyst for PEMFCs, presenting remarkable performance and durability. In particular, the Pt@MnSA-NC catalyst achieved a mass activity (MA) of 0.70 A mgPt
−1 at 0.9 V
iR

-free and maintained 86 % of its initial performance after a 30,000-cycle accelerated stress test (AST). The L12-Pt3Co@MnSA-NC catalyst achieved much higher performance, with MA of 0.91 A mgPt
−1 and current density of 1.63 A cm−2 at 0.7 V in an H2-air fuel cell at 150 kPaabs with 0.10 mgPt cm−2 on the cathode. Furthermore, under HDV operating conditions (250 kPaabs and 0.20 mgPt cm-2), the L12-Pt3Co@MnSA-NC catalyst delivered an impressive current density of 1.80 A cm−2 at 0.7 V, with only 13 % performance loss after the 30,000 cycles AST, showing great potential to meet the DOE target set for HDVs.
Effect of Cerium Oxide Nanoparticle Morphology on the Performance and Durability of Hydrogen/Air Fuel Cell Electrodes
Authors: Yarar Kaplan Begum , Iskandarani Bilal , Zabara Mohammed Ahmed , Yurum Alp , Alkan Gursel Selmiye
Published: February 2024

There has been considerable research on ceria (CeO2) in catalytic applications due to its excellent redox property, providing the ability to easily shift Ce4+ to Ce3+ [1]. This leads to a change in oxidation states and the number of oxygen vacancy defects by minimal activation energy. The catalytic property of CeO2 is directly related to its oxygen storage capacity (OSC) which stands for the quantity of oxygen vacancies that a crystal structure is capable to host. In our previous study, utilization of CeO2 as an additive provided excellent oxygen storage capacity and enhancement in the performance and durability for the cathode of the PEM fuel cell [2]. In the present study, CeO2-based additives with different morphologies including cubic (c-CeO2), rod (r-CeO2), and octahedral (o-CeO2) incorporated into the cathode and their impact on the ORR, performance, and durability of the electrode for hydrogen/air fuel cell was explored. As the first step, CeO2 additives were successfully synthesized via a hydrothermal method and characterized physical techniques such as BET, XRD, and SEM. In the prepared electrodes, the Pt/C and Nafion® loadings were kept constant while varying the CeO2/(Pt/C) loadings. The results have shown an overall enhancement in fuel cell performance (up to 31.8% increase in maximum power density) for cubic-CeO2 loadings reaching only 0.075 mg.cm-2 (20% CeO2). In addition, a fixed additive amount (20%) was employed for different morphologies as well. It was determined that all morphologies exhibited an enhancement in the overall performance compared to Pt/C-based electrode.

References:

[1] Campbell, T.C. and Peden, C.H.F. Science
,

309
(5735), 713-714, (2005).

[2] Taşdemir, A., Iskandarani, B., Yürüm, A., Gürsel, S.A., Yarar Kaplan, B. Int J Hydrogen Energy, 46(63), 32250-32260, (2021).
Improved Activity and Durability of Carbon-Coated Pd and PdNi Anode Catalysts in AEMFC
Authors: Sgarbi Ricardo , Doan Huong , Bibent Nicolas , Amigues Simon , Jaouen Frederic , Chatenet Marian
Published: February 2024

Anion exchange membrane fuel cells (AEMFC) have received growing attention due to the strategic potential of using low content (or absence) of PGM catalysts in the electrodes.[1] Completely PGM-free cathode catalysts are well established in those conditions,[2] while the anode ones remain critical in terms of the beginning-of-life activity and long-term performance.[3] The widely Pt- and Pd-based catalysts degrade mainly by nanoparticles detachment and agglomeration in alkaline conditions.[4] These degradations may be slowed down by wrapping the nanoparticles in some carbon layers (called carbon-coated), that prevent also metal oxidation and leaching into the electrolyte in the RDE setup.[5] However, the performance in AEMFC of carbon-coated nanoparticle catalysts is still unclear.

Here, two groups (previously characterized in RDE, XRD, IL-TEM, XPS and ICP-MS techniques[5]) of carbon-coated catalysts were investigated in 5 cm2 AEMFC: monometallic Pd (Pd@C/C) and bimetallic PdNi (PdNi@C/C) nanoparticles supported on carbon, and compared them to unprotected ones (Pd/C and PdNi/C). The four different anode catalysts were compared for a fixed Pd anode loading of 0.27 mgPd cm-2, and were combined with a ZIF-8 derived Fe-N-C cathode catalyst (previously developed Fe0.5-NH3). The Pd@C/C and PdNi@C/C reached superior initial performances (700 and 1300 mA cm-2) than the Pd/C and PdNi/C references (300 and 390 mA cm-2) at 0.6 V and Tcell
= 60 °C. This translates into an initial activity trend of PdNi@C/C > PdNi/C > Pd@C/C > Pd/C. After 12 h durability test at a cell voltage of 0.3 V, the AEMFC with the PdNi@C/C based anode exhibits a dramatically higher retention of performance (95%) than the cells with Pd/C (55%) and PdNi/C (70%) anodes. These results evidence the robustness of bimetallic carbon-coated nanoparticle catalysts for AEMFC anodes.

Figure 1
The Oxygen Reduction Reaction on Pt and Ag Catalysts in Alkaline Media in Rrde and Half-Cell Setups
Authors: Rampf Alexander , Braig Michael , Passerini Stefano , Zeis Roswitha
Published: February 2024

Understanding the Oxygen Reduction Reaction (ORR) in alkaline media is essential to optimize alkaline fuel cells or metal-air batteries. The catalytic activity of various ORR catalysts has usually been evaluated via Rotating (Ring) Disk Electrode (R(R)DE) measurements. However, using an electrolyte with dissolved oxygen at low KOH concentrations measured in a microampere regime at room temperature does not reflect the real cell conditions.1 Yet, RRDE is still a valuable tool for probing the reaction pathway of catalysts in alkaline media. Our study combined traditional RRDE with Gas Diffusion Electrodes (GDEs) half-cell measurements using Pt and Ag catalysts.

The polarization curve of Pt-GDE exhibits a kink near 0.8 V vs. RHE leading to a significant potential drop. This specific feature can be explained by the RRDE results, which display an increased peroxide formation in that potential region due to the adsorption/desorption of hydroxyl adsorbates.2 However, Ag does not exhibit such behavior since the peroxide formation is below typical operating potentials. Depending on the operating conditions, Ag can catalyze the ORR more effectively than Pt in alkaline conditions while significantly reducing production costs. Furthermore, our study presents a general approach for evaluating ORR catalysts under experimentally challenging conditions such as elevated temperature and high KOH molarity.

References:

(1) Ehelebe, K.; Schmitt, N.; Sievers, G.; Jensen, A. W.; Hrnjić, A.; Collantes Jiménez, P.; Kaiser, P.; Geuß, M.; Ku, Y.-P.; Jovanovič, P.; et al. Benchmarking Fuel Cell Electrocatalysts Using Gas Diffusion Electrodes: Inter-lab Comparison and Best Practices. ACS Energy Lett.
2022, 7, 816–826.

(2) Ramaswamy, N.; Mukerjee, S. Fundamental Mechanistic Understanding of Electrocatalysis of Oxygen Reduction on Pt and Non-Pt Surfaces: Acid versus Alkaline Media. Advances in Physical Chemistry
2012, 2012, 1–17.

Figure 1
Performance and Durability of Poly(norbornene) Anion-Conducting Membranes and Ionomers
Authors: Kohl Paul , Park Habin , Shah Parin
Published: February 2024

Low-temperature, polymer-based water electrolyzers using anion conductive polymers have several potential advantages over acid-based polymer electrolyzers. However, the long-term durability of the anion conducting polymer membrane and ionomer remains to be demonstrated.

In this study, a family of norbornene-based copolymers and terpolymers have been used in fuel cells and electrolyzers to provide high conductivity (>200 mS/cm at 80oC) and superior mechanical properties. The factors affecting the voltage and durability of alkaline electrolyzers will be reported.
Low Loading and High Utilization Ratio of Iridium Catalyst Coated Smoltek Carbon Nanofibers Used as Anode Material for PEM Water Electrolyzers
Authors: Wen Xin , Penninckx Bastien , Sanchez Jaime Sanchez , Ehrnberg Ellinor , Li Qi , Wenger Fabian
Published: February 2024

Proton exchange membrane water electrolyzers (PEMWE) are a core technology for the future green hydrogen production market. The installed power for PEMWE is estimated to be 40 GW by 2030 [1]. The oxygen evolution reaction (OER) catalyst on the anode side is dominated by Iridium (Ir)-based materials, one of the rarest noble metals in the crust of Earth. It is critical to lower the loading of Ir-based catalyst to ≈ 0.1 mg Ir/cm2 without compromising the overall performance to enable the mass manufacturing targets. It is a big challenge due to the poor electrical contact between the resulting catalyst layers and the anode substrate [2-3]. To reach this goal, Smoltek invented an advanced porous transport electrode (PTE) concept using its proprietary carbon nanofiber (CNF) technology [4] and unique Ir coating technology. An anode porous transport layer (PTL) is first modified by vertically aligned CNFs to increase surface area, followed by coating a corrosion-resistant and conductive layer (e.g. Platinum) and a subsequent OER catalyst layer (Fig. 1a). Cathodic electrodeposition in a three-electrode static cell was performed for Ir-based catalyst deposition. We demonstrate that with this method, the morphology and deposition process of Ir are controllable at very low loading amounts (≥ 0.1 mg Ir/cm2). An Ir coating layer can be formed on the highly structured CNF-based surface. The electrodeposited Ir has strong adhesion with the CNF PTEs, resulting in a high electrical conductivity [5].

This unique Ir-electrodeposited CNF PTEs structure maximizes the anode surface area and paves a new way to increase the utilization ratio of catalyst surface at a low loading amount, which makes it a competitive anode material in today’s PEMWE market.

References

Stiber et al. Adv. Energy Mater., 2021, 11, 2100630.

Möckl et al. J. Electrochem. Soc., 2022, 169, 064505.

Bernt et al. Chem. Ing. Tech., 2020, 92, 31-39.

https://www.smoltek.com/applications/electrolyzers/

Krivina et al. Adv.Mater., 2022, 34, 2203033.

Figure 1
Investigating the Stability of Electrodeposited NiMo Alloy for Hydrogen Evolution Reaction in Alkaline Media
Authors: Majeed Abdul , Etzold Bastian J.M.
Published: February 2024

A lot of efforts have been devoted to develop highly active noble-metal-free catalysts for hydrogen production by water electrolysis.1,2 Nevertheless, the stability of such catalysts, yet equally important, is rarely touched. NiMo alloy is an emerging catalyst for hydrogen evolution reaction (HER) in alkaline media.3 In the present work, we studied the stability of NiMo alloy for HER under alkaline (1M KOH, Fe-free) conditions as a model catalyst. Using electrodeposition at room temperature, we deposited NiMo alloy onto nickel foam substrates. A long-term (20h) stability test at a fixed current density of -100 mA cm-2 was carried out using chronopotentiometry. Electrochemical active surface area (ECSA) and HER polarization curves were determined prior and after this stability test. Here, obvious activity loss is observed. The ECSA of NiMo catalyst after chronopotentiometry test increases by 10%. Thus, an obvious increase in the overpotential is observed upon normalizing the catalytic current with ECSA (Figure 1a). As further stability test 100 CV cycles at a scan rate of 100 mV s-1 from 0 to –350 mV vs. RHE were carried out, the catalysts then hold for 30 min at open circuit potential and again 100 CV cycles carried out. A clear drop in activity during the second 100 cycles is also observed here and especially at the higher current density of 60 mA cm-2 (Figure 1b). In summary, we found that NiMo, though active initially, loses its activity with time under HER conditions in alkaline media.

References

Vesborg, P. C. K.; Seger, B.; Chorkendorff, I. Phys. Chem. Lett.
2015, 6, 951– 957.

Zou, X. X.; Zhang, Y. Soc. Rev.
2015, 44, 5148– 5180.

Kuznetsov, V. V.; Gamburg, Y. D.; Zhulikov, V. V.; Krutskikh, V. M.; Filatova, E. A.; Trigub, A. L.; Belyakova, O. A. Electrochim. Acta
2020, 354, 136610.

Figure 1
Visualization of Bubble Behaviors in Flow Fields of PEM Water Electrolyzer
Authors: WU Lizhen , Pan Zhefei , LIU Yun
Published: February 2024

Proton exchange membrane water electrolyzer (PEMWE) has been considered to be a promising technology for green hydrogen production, primarily because of its significant advantages in terms of high efficiency, high purity and fast dynamic response [1]. During its operation, hydrogen/oxygen evolves from the catalyst layer (CL), transports through the diffusion layer (DL) and then releases to the flow channel, forming various two-phase flow regimes, including bubbly, slug, annular, etc [2]. The presence of bubbles not only covers the electrode surface, but also blocks the water delivery, creating a large mass transfer resistance and even terminating the cell operation [3]. Another issue associated with bubble management is that the conventional parallel and serpentine flow-field configurations showed a poor self-pumping effect, exhibiting a mismatch between bubble evolution and removal rates [4]. To address this issue, therefore, some novel flow field designs have also been proposed in recent years, but the underlying mechanism how two-phase flow regime in flow-filed channels affects the electrolyzer performance is still not clear.

In this work, we investigate the effect of two-phase behavior on the electrolyzer performance via a visualization approach, as illustrated in Figure 1. Our preliminary results have shown that an increase of water supply flow rate has insignificant effect on the electrolyzer performance even at high current densities. It is observed that with increasing the water supply rate, many bubbles are still covering the electrode surface, meaning that water cannot be effectively supplied to the CL. To address this issue, a degassing layer, with a thinner rib and a wider channel, is introduced to the flow field design, which is able to promote the self-pumping effect of gas bubbles. This novel design can facilitate the rapid detachment of bubbles from the electrode surface, providing more paths for the water penetration into the CL.

Acknowledgement

This work was fully supported by a grant from the National Natural Science Foundation of China (Project No. 52022003).

References

Razmjooei, T. Morawietz, E. Taghizadeh, et al, Increasing the performance of an anion-exchange membrane electrolyzer operating in pure water with a nickel-based microporous layer, Joule, 5(7) (2021) 1776-1799.

Rakousky, U. Reimer, K. Wippermann, et al, An analysis of degradation phenomena in polymer electrolyte membrane water electrolysis, J. Power Sources, 326 (2016) 120-128.

Villagra, P. Millet, An analysis of PEM water electrolysis cells operating at elevated current densities, Int. J. Hydrog. Energy, 44(20) (2019) 9708-9717.

O. Majasan, J.I.S. Cho, I. Dedigama, et al, Two-phase flow behaviour and performance of polymer electrolyte membrane electrolysers: Electrochemical and optical characterization, Int. J. Hydrog. Energy, 43(33) (2018) 15659-15672.

Figure 1
Elucidating the Role of Flow Fields in Bubble Removal from Porous Transport Layers
Authors: Zhu Lijun , Tugirumubano Alexandre , Bazylak Aimy
Published: February 2024

Accelerating bubble removal from the porous transport layer (PTL) will be the key to reaching high current densities and cell efficiencies for polymer electrolyte membrane (PEM) water electrolyzers by improving catalyst utilization through reduced bubble accumulation for enhanced water transport to reach reaction sites 1,2. Previous studies have reported non-uniform bubble distributions within the PTL, where bubble saturation under the flow field lands was higher than that under the channel 3–5. This bubble distribution heterogeneity was attributed to the PTL/flow field interface and PTL/catalyst layer interface, which caused non-uniform outlet and non-uniform inlet conditions for bubble transport within the PTL, respectively. As such, determining the impact of the interfacial conditions on bubble removal from the PTL is critical for optimizing designs for next generation PTLs that need to exhibit low reactant mass transport resistances for PEM water electrolyzers.

In this study, we elucidated the effects of the PTL/flow field interface on bubble transport in the PTL and specified the role of flow fields in bubble removal from the PTL. First, X-ray computed tomography (CT) was employed to reconstruct the microstructure of a titanium fibre-based PTL. Pore network modelling was then implemented to simulate and analyze the multiphase flow behaviour within the PTL under two kinds of outlet boundary conditions, i.e., with and without a flow field. We showed a dramatic non-uniform bubble distribution within the PTL when using an outlet condition with a flow field, while a uniform bubble distribution occurred in the PTL when using an outlet condition without a flow field. We attributed this to the existence of flow fields that lead to longer gas transport pathways through the PTL regions under the flow field lands. This study demonstrates the effects of flow fields on hindering bubble transport within the PTL and informs the need of tailored designs of the PTL/flow field interface for accelerating bubble transport in the PTL.

References

J. K. Lee and A. Bazylak, Joule, 5, 19–21 (2021).

S. Yuan et al., Prog. Energy Combust. Sci., 96, 101075 (2023).

J. K. Lee et al., Cell Reports Phys. Sci., 1, 100147 (2020).

C. H. Lee et al., J. Power Sources, 446, 227312 (2020).

S. De Angelis et al., J. Mater.
Chem. A, 9, 22102–22113 (2021).
Operando Identification of Temperature-Dependent Pore-Scale Gas Saturations in PEM Water Electrolyzers
Authors: Ham Chaeyoung Tina , Shrestha Pranay , Lytle Spencer , Bazylak Aimy
Published: February 2024

Polymer electrolyte membrane (PEM) water electrolysis is a promising solution for the chemical storage of intermittent renewable energy in the form of clean hydrogen (1). For the widespread adoption of this technology, the efficiency of PEM electrolyzers must be improved through informed material design and tailored operating conditions to compete with incumbent carbon-emitting technologies (2). A main source of inefficiency is related to mass transport losses, where oxygen gas, a by-product of the anode reaction, accumulates in the anode porous transport layer (PTL) and hinders reactant liquid water delivery to reaction sites (3). Although extensive studies have explored this two-phase flow phenomenon, the consideration of operating temperature on gas accumulation in the PTL adds further complexity. A duality in temperature effects has been reported in the literature where increasing the operating temperature may encourage gas coverage which obstructs liquid water transport, but it may also enhance liquid water delivery due to favorable fluid property changes in viscosity and surface tension (4). Efforts have been made previously to reconcile these competing observations using 2D visualization methods (5), however a closer investigation using 3D visualization techniques will provide valuable pore-scale insights in the comprehensive understanding of the impact of operating temperature on gas transport in the PTL, and subsequently mass transport losses in the PEM electrolyzer.

In this work, we employed operando X-ray computed tomography (CT) to visualize three-dimensional (3D) pore-scale gas saturations in the PTL at various industrially relevant operating conditions. Specifically, a custom in-house electrolyzer was imaged with synchrotron CT at five different temperatures (40°C, 50°C, 60°C, 70°C, 80°C) and current densities ranging from 0.5 A/cm² to 4.0 A/cm² with 0.5 A/cm² incremental steps. Electrochemical impedance spectroscopy and Tafel measurements were also acquired to characterize the relationship between gas distributions and corresponding mass transport overpotentials. Considering X-ray transparency, a model PTL made of carbon fibers was used to achieve sufficient contrast to quantify water and gas in the obtained images. Using precise volume registration and subtraction methods, pore-scale gas distributions in the PTL were quantified to reveal changes in bubble accumulation and coverage area at different operating temperatures and over operation time. The novel insights from this work will aid in our understanding of the complex relationship between operating temperature and multiphase flow phenomena in the PTL, which is vital for tailoring operating conditions of PEM electrolyzers to curtail the costs of green hydrogen production.
Utilization of 3-D Volume of Fluid Simulations to Understand Oxygen Evolution through Multilayer Porous Transport Layers for PEMWE Improvement
Authors: Sepe Mitchell , Cho Hyunseok , Shimpalee Sirivatch
Published: February 2024

In this work, direct numerical modeling techniques were applied to 3-D generated porous transport layers (PTL), with the addition of a microporous layer (MPL), to understand the effect pore structure has on oxygen evolution. Proton Exchange Membrane Water Electrolyzers rely on PTLs to remove oxygen from the catalyst layer. Traditionally, an MPL is added to the PTL surface in contact with the catalyst layer. This creates a bilayer PTL, which is believed to improve oxygen removal, while maintaining liquid saturation. Two questions arise when creating a PTL sample for PEMWE application. First, how thick should the MPL be to achieve adequate oxygen removal? Second, is a bilayer PTL sufficient, or does a multilayer PTL result in improved oxygen removal?

The objectives of this work are to observe the influence that the MPL has on oxygen transport, the effect of the MPL on oxygen removal when compared to a single layer PTL, determine an ideal MPL to PTL ratio, and identify if multilayer PTLs aid in oxygen removal. Each sample is created through an improved image processing technique that eliminates the need for interface communication when meshing. This process allows for multilayer PTL structures to be created as one geometry. Due to the improved imaging technique, meshing of these complex structures is possible. The Finite Volume Method combined with a volume of fluid model was used to simulate two phase flow, liquid water and gaseous oxygen, through all PTL samples. Each PTL/MPL combination has three different MPL thickness, which corresponds to a PTL/MPL ratio of 90:10, 80:20, and 70:30. Bilayer, trilayer, and quadlayer PTL samples were also studied. Oxygen bubble evolution, growth, and surface interaction through all sample microstructures was observed. In-plane and through-plane permeability, liquid saturation, and liquid/gas interfacial area were calculated from simulation results. Findings from this work will provide insight into ideal MPL thickness and number of MPL layers for improved oxygen removal inside PEMWEs.
The Business Model of an Emerging Hydrogen Market in the Swedish Transportation Sector – outlook towards 2050
Authors: Särnbratt Mirjam , Fransson Nathalie , Hansson Herman , Sernhed Kerstin , Lygnerud Kristina , Andersson Martin
Published: February 2024

With the rapid growth of hydrogen and associated initiatives, there is a need to review the state of knowledge on hydrogen business models, and to specifically understand efficient production and distribution to the transport sector. Previous studies have focused on specific parts of business models, such as revenue streams, price models or profitability, but have failed to take a holistic approach to business models that also includes analyzes of value proposition, customer segments, relationships and channels as well as partnerships, resources and activities required to achieve the value proposition. This study adopts a holistic view of business models and conducts a review of the current state of business models in hydrogen followed by an analysis of the future boundary conditions that hydrogen actors need to account for in 2050. Investor perspectives on the industry are also adressed Based on these insights, two future-oriented business models are proposed and validated with stakeholders and investors in hydrogen.
Novel Strategies for Efficient Water Electrolysis
Authors: Wågberg Thomas , Gracia-Espino Eduardo , Hu Guangzhi
Published: February 2024

A growing global population in parallel with an increased prosperity seen from a global perspective have raised the need for energy and raw material resources exponentially. These increased needs have led to a number of negative consequences such as pollution, raw material shortages, increasing carbon dioxide levels in the atmosphere, and not least a threatening global warming. Renewable energy will be essential to break the dependence of fossil fuels, but due to the intermittency of renewables a storable non-fossil alternative is needed. Hydrogen represents one of very few sustainable options to store renewable energy on large scale and for seasonal variations. Here, we present novel strategies on water electrolysis driven by photovoltaics, with a focus on the development of state-of the art electrocatalysts based on earth-abundant transition metals, doped with sulphur and phosphor [1]. We show that by tuning parameters such as adsorption energy, morphology and conductance of the electrocatalysts we can achieve solar-to hydrogen efficiency approaching 20 % [2]. We discuss on strategies, mechanisms and challenges in the field of PV-driven electrolysis.

[1] Ekspong, J; Larsen, C; Stenberg, J;, Kwong, WL; Wang, J; Zhang, J; Johansson, EM; Messinger, J; Edman, L; Wagberg T, Solar-Driven Water Splitting at 13.8% Solar-to-Hydrogen Efficiency by an Earth-Abundant Electrolyzer, ACS Sustainable Chemistry & Engineering, sc-2021-03565f (acssuschemeng.1c03565). (2021)

[2] H Zhang, A Aierke, Y Zhou, Z Ni, L Feng, A Chen, T Wågberg, G Hu, A high‐performance transition‐metal phosphide electrocatalyst for converting solar energy into hydrogen at 19.6% STH efficiency, Carbon Energy, 5 (1), e217 (2022)
(ECS Carl Wagner Memorial Award) Free Electrons to Molecular Bonds and Back - The Dark Side of Solar Fuels and Chemicals
Authors: Strasser Peter
Published: February 2024

The rising share of renewable electricity in power generation is testament to the increasing importance of solar/wind-electric routes to harvest sun light in form of free electrons. While some electricity will always be used directly or stored short-term in batteries, an increasing portion of it calls for direct conversion into valuable molecular solar e-fuels and e-chemicals, possibly followed by a later re-conversion into power. These “dark” e-conversion processes are made possible by electrocatalysis at electrified solid-liquid interfaces, coupled to mass and charge transport in the electrolyte bulk. New catalyst and ion conducting materials along with an understanding of the origin of reaction kinetic and transport barriers are needed for the design of ever more efficient, electrochemical interfaces in galvanic and electrolytic devices for the production and use of fuels and chemicals.

This presentation reports on a few examples of advances in our design and understanding of electrocatalytic materials, interfaces and mechanisms relevant to the conversion of electricity into energy or value-added molecular compounds. Experimental approaches covered range from in-situ/operando spectroscopic, microscopic, scattering and spectrometric techniques at the microscale to new diagnostic tools and analyses of mass transport at the macroscopic device level. Examples include generation and use of green hydrogen and the conversion of CO2.

Figure 1