bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Exchanging Degradation for Durability: Accelerated Stress Test Protocols for Solid Oxide Fuel Cells and Electrolysers
Authors: McPhail Stephen J. , Laurencin Jérôme , Hagen Anke , Leon Aline , Van Herle Jan , Vladikova Daria , Montinaro Dario , Piccardo Paolo , Polverino Pierpaolo , Herbrig Kai
Published: May 2020

The longer lifetimes of solid oxide cells (SOC) – obtained and still required, both in fuel cell and electrolysis operation – exacerbate the need for accelerated stress tests, since neither reliable degradation models are currently available nor validated methodologies to evaluate expected stack durability in a practical timeframe. The project AD ASTRA ( “HArnessing Degradation mechanisms to prescribe Accelerated Stress Tests for the Realization of SOC lifetime prediction Algorithms”) started operations to tackle this on January 1st 2019, funded by the European Fuel Cells and Hydrogen Joint Undertaking.

Generally, a great number of operational parameters influence SOC degradation during lifetime, each contributing according to characteristic times and intensities, often in convoluted or even contrasting fashion. Aggravation of test input parameters can thus lead to non-representative accelerated degradation of a component where concurring effects are differently influenced, leading to a biased end state of the component investigate.

To systematically address, harness and accelerate the selected failure modes, a matrix was set up of degradation mechanisms, test items, test procedures and characterization methods, that was translated to protocols in such a way that consistent measurement data are generated, helping subsequent analysis and correlation of phenomena and parameters by the project’s modelling and simulation activities.

The testing approach consists of a dual-focus campaign targeting:

• macroscopic stack testing procedures, where short stacks will be operated in situ, in aggravated conditions with the objective of identifying test settings that will stress the stack in a representative way but minimizing testing time and resource expenditure

• specific component ageing tests, to reproduce (ex-situ) the degraded condition of critical stack components or interfaces in a faster time, based on analysis of the components extracted from stacks that have been field-tested.

A radical innovation of the project consists in the integration of these two methods: components specifically aged ex situ assembled into otherwise “new” stacks for in-situ testing, so that their effect on stack performance can be easily isolated from other components that in real-world conditions would also degrade. These tests allow to observe from the start (t=0) the end-of-service stack degradation, radically reducing in-situ testing time and providing powerful means to validate models simulating the long-term effects of component degradation in a stack.
A Holistic Approach to Develop Novel Processes for the Sustainable Electrochemical Synthesis of Fuels and Chemicals
Authors: Khanipour Peyman , Derleth Felix , Reichert Andreas M. , Katsounaros Ioannis
Published: May 2020

Electrochemical synthesis can become a sustainable solution for the production of fuels and fine chemicals, because (i) it can enable a revolutionary transition in chemical production away from fossil fuels if the required electricity is provided by renewables (ii) it can address the mismatch between intermittent supply and demand of energy, and (iii) it can enable the decentralized, onsite production of chemicals [1, 2]. The various promising electrochemical synthesis processes are at different levels of technological maturity, therefore, to accelerate developments in the field we need to follow holistic approaches that address all material, system or time scales.

Here, we describe a systematic methodology for the development of electrochemical process. We first screen various electrodes and potentials, utilizing an own-developed, internationally unique method for the real-time characterization of reaction products [3]. This method is based on coupling of electrochemical flow cells with delicate mass spectrometry techniques. At a second stage, promising materials are examined at selected constant potentials to quantify activity, selectivity, and durability over time. In this case, the electrochemical cell is coupled with online or offline analytical techniques for the quantification of production rates, selectivities, or faradaic efficiencies. Finally, we transfer the gained understanding from the previous two steps to design an applied electrochemical reactor that can carry out the desired process under industrially relevant conditions. The approach will be exemplified for a model oxidative electrosynthesis reaction and the individual elements of the platform will be discussed.

References

[1] R.F. Service, Renewable bonds, Science, 365 (2019) 1236-1239.

[2] K.M. Van Geem, V.V. Galvita, G.B. Marin, Making chemicals with electricity, Science, 364 (2019) 734-735.

[3] P. Khanipour, M. Löffler, A.M. Reichert, F.T. Haase, K.J.J. Mayrhofer, I. Katsounaros, Electrochemical Real-Time Mass Spectrometry (EC-RTMS): Monitoring Electrochemical Reaction Products in Real Time, Angew. Chem. Int. Ed., 58 (2019) 7273-7277.
Highly Selective and Scalable Electrolysis for Gaseous CO2 Reduction in the Zero-Gap Electrolyzer
Authors: Lee Woong Hee , Hwang Yun Jeong , Min Byoung Koun , Oh Hyung-Suk
Published: May 2020

The electroreduction of carbon dioxide (CO2) to chemicals represents a promising pathway for the storage of renewable electricity and toward low-carbon-footprint chemicals production. Prior study on CO2RR have focused on the catalytic properties of various materials in liquid condition. However, the current density for CO2RR is restricted under 30 mA cm–2 due to the mass transfer limit and low solubility of CO2 in the aqueous solution. To increase the current density, the gas fed CO2 electrolysis system was investigated using a gas-diffusion layer (GDL) system. Masel et al. reported about new zero-gap CO2 electrolysis device that uses an anion exchange membrane (AEM, SustainionTM) with humidified CO2 flow in the cathode and shows a current density of 200 mA cm-2 with steady FECO of over 90% using Ag catalyst.

Herein, we developed a convenient Ag-based and Cu-based electrode with high selectivity and high current density for electrochemical conversion of CO2 to CO and ethylene in a zero-gap electrolyzer, respectively. We tested the electrochemical properties of the prepared Ag-based electrode in the gaseous CO2-fed electrolyzer and H-type electrochemical cell with respect to CO2RR. Ag coral electrode achieves CO partial current density of 312 mA cm–2 with FECO > 95%. Cu-KOH electrode demonstrate 260 mA cm–2 current density with 60.5 % C2H4 faraday efficiency at 10 cm2 electrode area. Moreover, the prepared electrode was analyzed the change of electronic structure using in-situ/operando X-ray absorption spectroscopy (XAFS) at real gas fed zero-gap electrolyzer condition. Based on these results, we could give insights about the scalable electrolyzer system for electrochemical conversion of CO2 with high catalytic activity and selectivity.
Engineered Electrolyte-Electrocatalyst Nanocomposites for Enhanced CO2 Electroreduction
Authors: Elgammal Ramez A. , Zawodzinski Thomas A.
Published: May 2020

The development of a viable approach to capture, store, and convert carbon dioxide into fuels and chemicals may offer a means to mitigate climate change while also creating value added commodity chemicals. Critical bottlenecks in existing technologies that have impeded commercialization of CO2 electrosynthesis include catalysts with high overpotentials and limited selectivities. Furthermore, current approaches often employ PEM-based electrolyzers that suffer from low CO2 solubility in acidic aqueous solutions, limiting mass transport and reaction rates, or AEM-based systems which have much higher CO2 solubilites in alkaline electrolytes, but have the added problem of membrane poisoning by bicarbonate and carbonate.

We have recently developed an electrochemical reactor that overcomes many of the shortcomings that have limited the above technologies. Our preliminary results suggest that onset potentials for CO2 reduction are more than 200 mV lower than with current densities in excess of 150 mA/cm2 at -1 V vs RHE. The selectivities for CO are in excess of 90% and the electrocatalysts. We have examined several cathode electrocatalysts and some of the most promising include a series of nanostructured mixed and/or doped transition metal and main group metal oxides that also suppress the hydrogen evolution reaction. We will present detailed electrochemical and structural studies and will comment on possible reaction mechanisms as well as the key features of the reactor that enable the enhanced kinetics.
Techno-Economic Perspectives on Upgrading Carbon Dioxide into Higher-Value Chemicals
Authors: Pritchard Tyler Lynn , Sullivan Neal P , Braun Robert J.
Published: May 2020

We present our early stage techno-economic analyses on electrochemical upgrading of sequestered carbon dioxide into higher-value chemicals. The technology seeks harness intermittent, renewable electricity to drive electrochemical processes that convert CO2 into fuels. Through our techno-economic study, we explore the cost functions and value propositions of this energy-storage technology.

With the deployment of intermittent renewable energy resources into the utilities sector, research into fast and efficient forms of energy storage has become critical to address the temporal variation associated with these renewable resources. Our efforts seek to convert this renewable-but-intermittent electricity into chemical energy that is more-easily stored. This power-to-chemicals conversion utilizes water vapor and carbon dioxide feedstocks to form methane and higher-value chemicals. The approach has the potential to decrease CO2 emissions while providing storage for intermittent renewables.

The renewable electricity is used to drive solid-oxide electrolysis cells that feature novel proton-conducting ceramics. As shown in the figure, the protonic-ceramic electrolyzers split the water-vapor feedstock at the steam electrode into protons and molecular oxygen. The protons (H+) are transported across the dense protonic-ceramic membrane to the fuel electrode, while the molecular oxygen simply exhausts from the electrolyzer. At the fuel electrode, the protons serve to hydrogenate the CO2 into higher-value chemicals, such as methane. If successful, such a device could be harnessed to convert renewable electricity into a drop-in fuel for our nation’s natural gas infrastructure.

We are developing a techno-economic analysis (TEA) of an protonic-ceramic electrolysis cells (PCECs) to determine the value proposition of CO2-to-methane synthesis,. Our TEA draws from previously established models of more-common solid-oxide electrolysis cells (SOECs). To date, our TEA was built around a single-cell PCEC model in MATLAB that was later migrated to Aspen HYSYS for integration with larger thermofluid systems. The preliminary MATLAB model utilized a straightforward current-density-dependent voltage model for the SOEC, similar to the equation commonly used to model SOFCs. The TEA looked specifically at the cost associated with production of methane from a PCEC sized to consume three tons of coal feedstock CO2 equivalent per day.

Projected costs vary with the assumed performance point: peak flow efficiency, peak stoichiometric efficiency, or peak methane production rate. Continued iterations of this model will lend more insight into how these cost projections change with scale, and provide insight on cost drivers.

Figure 1
Mass-Manufacturing of Sub-Micron Coated Metal Coils for Scaling-up the Production of Electrochemical Devices
Authors: Bernuy-Lopez Carlos , Proch Sebastian Karl , Bexell Ulf , Westlinder Jörgen
Published: May 2020

Sandvik Surface Technology is a production unit within AB Sandvik Materials Technology (SMT). The business area SMT belongs to the Sandvik group and is a world-leading manufacturer of advanced stainless steels and special alloys for the most demanding industries. Sandvik Surface Technology offers a portfolio of cost-effective coated metal strip for applications such as batteries, fuel cells and electrolyzers.

Metal coils are coated with sub-micron metal coatings according to customer specifications regarding composition and thickness of both the substrate and the coating in a Physical Vapour Deposition process through the roll-to-roll coating lines developed by Sandvik (Figure 1). This pre-coated solution reduces some of the handling that comes with batch coating of individual components and provides an outstanding opportunity for the cost-effective industrial mass production of electrochemical devices.

Figure 1. Image of one of the coating lines developed by Sandvik in Sandviken (Sweden). The final coated metal coils are also shown.

The Surface Research group at SMT Strategic Research provides vital knowledge and understanding of such a complex coating process which facilitates the development of the above-mentioned products. Scientific questions such as the development of the adequate coating and substrate composition for every electrochemical device, the influence of nanometric defects on the performance of the electrochemical device or the formation of stable and protective layers against corrosion after more than 20,000 h of operation are addressed and will be shown in this work.

Figure 1
Water Oxidation in Acidic Solutions: Beyond Noble Metals
Authors: Chatti Manjunath , Gardiner James L , Du Hoang Long , Tammer Darcy Simondson , MacFarlane Douglas R. , Simonov Alexandr N
Published: May 2020

Water oxidation, a kinetically demanding half-reaction, plays a vital role in hydrogen production through electrochemical water-splitting. Thus, the development of efficient and stable oxygen evolution reaction electrocatalysts has become a central theme for basic research in the field of renewable energy. Substantial progress has been made in developing robust and inexpensive noble metal-free heterogeneous electrocatalysts for water oxidation operating under alkaline and neutral pH conditions. There is, however, a scarcity of active and stable electrocatalysts for acidic water oxidation, which is an ideal pH condition for high purity hydrogen production and offers several other technological advantages. Low performance and poor stability of existing water oxidation electrocatalysts based on non-noble metals are mainly attributed to the dissolution of respective elements in acidic solution. Considering these challenging aspects, we constructed the water oxidations catalysts based on thermodynamically and acid-stable oxides, which are incorporated with catalytically active species (transition metal-based water oxidation catalysts). Specifically, the highly-disordered mixed metal oxide, based on cobalt, iron, and lead, produced in situ exhibits excellent OER performance with unprecedented stability, through self-healing mechanism, under harsh operating conditions of pH 0 and temperature 80 °C. Importantly, the Cobalt-iron-lead oxide demonstrates the capability of operating at industrially relevant rates of 0.5 A cm-2 at low OER overpotentials of 0.7 V. These findings highlight the new strategy to design highly active and acid-stable, noble metal-free, OER electrocatalysts that can essentially operate indefinitely. Our most recent developments focused on replacement of lead with alternative, less toxic components. The presentation will also highlight these new systems, some of which demonstrate outstanding stability even without a self-healing mechanism.
(Invited) Earth Abundant Electrocatalysts for Alkaline Water Electrolysis
Authors: Zhao Chuan
Published: May 2020

The increasing demands for clean energy have triggered tremendous research interests on electrochemical energy conversion and storage systems with minimum environmental impact. Hydrogen holds the promise as energy carriers for global scale storage of renewable energy, e.g., solar and wind, enabling the continuous usage of these diffusive and intermittent energy sources when used together with fuel cells.Nevertheless, the widespread application of hydrogen technology has been severely constrained by the use of precious metal catalysts, such as oxides of ruthenium and iridium for the oxygen evolution reaction (OER), and platinum for the hydrogen evolution reaction (HER) and oxygen reduction reactions (ORR). Furthermore, electrochemical CO2 reduction reactions (CRR) and nitrogen reduction (NRR) provide alternative pathways for hydrogen storage and transport. These emerging technologies also call for highly efficient and selective catalysts to promote their industrial viabilities.

This presentation shows our efforts in developing non-precious metal-based electrocatalysts for alkaline water electrolysis, as well as our strategies for enhancing these catalysts to a level comparable to that of precious metal catalysts. The commercialisation of some our catalysts in hydrogen industry also will be highlighted.
Tuning Fundamental Properties of Ir-Based Materials to Enhance Their Electrocatalytic Performance in the Oxygen Evolution Reaction
Authors: Kasian Olga , Schweinar Kevin , Li Tong , Mayrhofer Karl J. J. , Gault Baptiste
Published: May 2020

The oxygen evolution reaction (OER) underpins electrochemical technologies for hydrogen generation [1]. The sluggish kinetics of the OER and the instability of most of the anode materials hinder widespread application of proton exchange membrane water electrolyzers (PEMWE). Up to now, only iridium-based catalysts meet the necessary requirements and are currently employed in PEMWE [2]. Despite the scarcity and high cost of iridium, its relatively high reactivity and superior stability make it irreplaceable to optimize the durability of the electrolyzer. Understanding what governs the electrocatalytic activity as well as the long-term stability of iridium is crucial for the development of novel catalysts that will enable efficient energy conversion and storage technologies. Gaining this knowledge requires establishing the correlation between the atomic-scale structure of the catalysts, their electronic properties and the mechanisms of the OER and other side reactions that lead to the material’s degradation.

In this presentation, I give an overview of our recent results, with a special focus on the mechanisms of the reactions ongoing at the surface of an array of iridium-based anodes during the OER [2-4]. The mechanistic insights are obtained from combination of X-ray photoelectron spectroscopy, online electrochemical mass spectrometry, electron microscopy and atom probe tomography. During the presentation, specific structural and compositional features that we recently revealed are responsible for high reactivity and/or instability of catalytic systems will be discussed in detail [4]. In addition several approaches to improve both the reactivity and the stability will be proposed, and can serve as guiding principles for the development of materials with superior electrocatalytic performance towards the OER.

[1] V. R. Stamenkovic, D. Strmcnik, P. P. Lopes and N. M. Markovic, Nat. Mater., 16 (2017) 57.

[2] T. Li, O. Kasian, S. Cherevko, et al., Nat. Catalysis 1 (2018) 300.

[3] O. Kasian, J.-P. Grote, S. Geiger, S. Cherevko, K. J. J. Mayrhofer, Angew. Chem., Int. Ed., 57 (2018) 2488.

[4] O. Kasian, S. Geiger, T. Li, J-P. Grote, K. Schweinar, S. Zhang, C. Scheu, D. Raabe, S. Cherevko, B. Gault, K. Mayrhofer, Energy & Environmental Science (2019), DOI: 10.1039/C9EE01872G.
Nano-Structured Transition Metal Phosphides As an Efficient Electrocatalysts for Oxygen Evolution Reaction
Authors: Poureshghi Fatemeh , Seland Frode , Sunde Svein
Published: May 2020

Although the catalytic activity of transition metal phosphide compounds, such as dinickel phosphide (Ni2P), have been known for over half a century. they have only recently been investigated for heterogeneous (electro)catalysis. In 1995, it was shown that the performance of electrodeposited amorphous Ni–P electrodes (ca. 3 wt% phosphorous content) toward the HER in alkaline conditions can be orders of magnitude higher than that of Ni electrodes [1]. Detailed structural analysis of these transition metal phosphide materials had not been discussed in such early works. it was only very recently realized that the transition metal phosphides have reemerged as one of the most promising classes of earth-abundant inorganic electrocatalysts.

Depending on the P:Ni molar ratio and the reaction temperature, different phases have been reported for Ni-phosphide compounds. Among all NixPy phases, Ni12P5 nanoparticles shows high electrocatalytical activity toward OER due to its unique crystallite structure and the higher concentration of nickel in this phase. which enables the formation of an amorphous NiOOH/Ni(OH)2 shell on a modified multiphase with a disordered phosphide/phosphite core [2]. However, the synthesis of Ni12P5 is quite challenging and a small deviation in the P:Ni molar ratio will result in Ni2P phase.

In this study, pure phase of Ni12P5 and Ni0.9Fe0.1P colloidal nanoparticles have been synthesized by the reaction of [Ni(acac)2] with oleylamine (OA) and trioctylphosphine (TOP) reactants. OA is the reducing agent and thus controls the nucleation rate and TOP acts a source of phosphorus and also provides surface stabilization for tuning particles size. This synthesis results in monodisperse nanoparticles of diameter approximately 12nm [3]. These Ni12P5 and Ni0.9Fe0.1P nanoparticles show enhanced electrocatalytical activity toward OER in 0.1M KOH electrolyte, resulting in a current density of 10 mA cm−2 with overpotentials at 0.304 V and 0.20 V respectively.

References:

[1] Yu, F., Zhou, H., Huang, Y., Sun, J., Qin, F., Bao, J., ... Ren, Z. (n.d.). metal phosphide catalyst for overall water splitting, (2018), 1–9.

[2] Menezes, P. W., Indra, A., Das, C., Walter, C., Göbel, C., Gutkin, V., ... Driess, M. (2017). Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splitting. ACS Catalysis, 7(1), 103–109.

[3] Muthuswamy, E., Savithra, G. H. L., & Brock, S. L. (2011). Control of Phase, Size, and Morphology in Nickel Phosphide Nanoparticles, (3), 2402–2411.
Microwave-Assisted Hydrothermal Synthesis of Transition Metal Doped ZnO Nanoparticles and Their Electrocatalytic Activity for Water Oxidation
Authors: Nishiumi Nobuyuki , Harada Yuya , Sun He , Shiroishi Hidenobu , Matsushima Yuta , Stadler Philipp , Yoshida Tsukasa
Published: May 2020

Among various metal oxides previously tested, Co3O4 is known to be one of the best catalysts for oxygen evolution reaction (OER). In this study, doping of Co ions into nanocrystals of zinc oxide (ZnO) has been achieved by microwave (MW) assisted hydrothermal reaction to form catalytic surface sites for OER combined with highly conductive and stable ZnO for flexible catalyst design and potential enhancement of the catalytic activity.

MW-assisted hydrothermal reaction has successfully achieved synthesis of Co-doped ZnO nanocrystals at a low reaction temperature of 160ºC and in a short reaction time of 30 min. Partial replacement of 4-coordinated Zn(II) ions of ZnO with Co(II) ions up to about 10at% has been suggested from evaluation of the products by UV-Vis absorption spectra, morphological observations and X-ray diffraction. The higher addition of Co resulted in its phase-separated precipitation as Co(OH)2. While mesoporous electrode processed from ZnO nanocrystals was totally inactive for water oxidation, that of Co-doped ZnO exhibited a good catalytic activity to achieve about 1 mA cm-2 current of OER with an overvoltage of 0.545 V in a neutral aqueous KCl solution, which in fact was far superior to a Co3O4 electrode known to suffer from its limited conductivity. The doped Co ions are only expected to act as reaction centers for charge transfer on the very surface in contact with the electrolyte, while ZnO acts as a highly conductive and chemically stable host matrix to support the catalyst.
Simple Deposition of Metal Salts on Graphene Oxide As Novel Water Oxidation Catalysts
Authors: Fruehwald Holly M , Moghaddam Reza B. , Zenkina Olena V , Easton E. Bradley
Published: May 2020

As populations grow world-wide, there is an ever increasing need for more sustainable and renewable energy sources to keep up with the high demand of energy needed. One promising high energy source is the water splitting reaction where water is split into hydrogen and oxygen gas. However, the materials usually required to facilitate this reaction are often rare and expensive earth metals such as iridium. Thus, the focus has been on using Ir-free materials as a cost-efficient alternative. One such metal is ruthenium, Ru is ideal as it has many oxidation states to help facilitate the water splitting reaction, to aid in reducing the over potentials[1]. Yet, ruthenium-based materials have problems such as being prone to stability issues in acidic media, high over potentials and slow kinetics, so improvements should be made on catalyst design to lower over potentials and improve stability. On the other hand, Ru can also be considered a somewhat rare metal, thus further inexpensive and non-precious metals should be used in the future designs of these materials to lower cost without sacrificing activity.

In this work we synthesized graphene oxide electrochemically from a graphite rod source, using a simple, low cost method[2]. Graphene was chosen to stabilize the nanoparticles and enhance the conductivity of the resulting materials. Metal nanoparticles from either a Ru(III) or Ru(VII) salt precursor were deposited on the surface of the graphene oxide using a facile method of preparation to afford a ca. 3% metal loading on the graphene oxide. The materials were examined electrochemically in acidic media for the water oxidation reaction, where we observed low over potentials for the reaction and high stability during prolonged testing[3]. Now, we are comparing the activity of these metals and other non-precious metals for their water oxidation activity in basic electrolyte. These novel metal nanoparticles stabilized on a graphene could aid in the development of cost efficient and sustainable materials for the future of renewable energy technologies.

[1] Kamdar, J.M.; Grotjahn, D.B. Molecules
2019, 24, 494.

[2] Liu, J.; Poh C. K.; Zhan, D.; Lai, L; Lim, S. H.; Wang, L.; Liu, X.; Sahoo, N. G.; Li, C.;

Shen, Z.; Lin, J. Nano Energy. 2013, 3, 377-386

[3] Fruehwald, H. M.; Moghaddam, R. B.; Zekina, O. V.; Easton, E. B., Cat. Sci. Technol.
2019, 9, 6547-6551
Efficient Light Responsive (UCNPs)-Pt@MOF/Au Composites for Photocatalytic Hydrogen Evolution By Harvesting from Extended UV to Near-Infrared
Authors: Paul Subir , Choi Sang-June , Kim Hee Jin
Published: May 2020

Photocatalytic water splitting by utilizing broadband spectral response from UV to near-infrared (NIR) region is a big challenge and yet a prime target. 50% of the solar spectrum constituted by NIR light and in this work, our target is to increase absorption range from UV-visible to NIR by using (UCNPs)-Pt@MOF/Au composites. In this context, lanthanide-doped upconversion nanoparticles (UCNPs) are able to convert NIR to UV and visible, which are then harvested by metal-organic framework (MOF) and Au. MOF and plasmonic Au nanoparticles (NPs) broaden the absorption of UV light to a visible region as well as speed up the transfer of charges considerably. For this experiment, we used MIL-125 as a MOF because it is a wide-bandgap semiconductor. The spatial separation of Pt and Au particles by the MOF further steers the charge migration and also provides access to active Pt sites for the catalytic product as a result, the optimized composite exhibits high photocatalytic H2 production rate under UV, visible and NIR regions.
Electrospun Ruthenium-Cobalt Mixed Oxide Nanotubes As a Highly Active and Stable Electrocatalyst for Oxygen Evolution Reaction
Authors: Yu Areum , Lee Chongmok , Kim M. H. , Lee Youngmi
Published: May 2020

Proton exchange membrane (PEM) water electrolysis using acidic electrolytes has many positive aspects of high operating current densities, gases with high purity, and high efficiency. However, it has disadvantages such as noble electrocatalysts required. Metal oxides (RuO2, IrO2) known as efficient electrocatalysts for anodic oxygen evolution reaction (OER) are scarce and expensive. Therefore, a substantial research effort has been devoted to the development of economical electrocatalysts with high performance and durability.

In this presentation, bimetallic RuCo mixed oxide nanotubes with various relative compositions are synthesized by electrospinning and calcination in expectation of the synergistic effect and cost cutting. The hollow morphologies, compositions and atomic distribution of the prepared RuCo mixed oxide nanotubes are characterized by field-emission scanning electron microscopy (FE-SEM) equipped with an energy disperse X-ray spectrometer (EDS) and transmission electron microscopy (TEM). Through X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis, the sizes of unit cell of RuO2 rutile structure and Co3O4 cubic structure are found to be changed due to the mutual substitution. Electrochemical acitivities of diverse RuCo mixed oxide nanotubes for OER are studied with rotating disk electrode (RDE) voltammetry in 1 M HClO4 aqueous solution. Tafel slopes are obtained from the corresponding voltammetric curves for OER to comprehensively elucidate the kinetics of OER. The onset potential of RuCo mixed oxide nanotubes is determined precisely using scanning electrochemical microscopy (SECM). This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science, ICT and Future Planning (NRF-2017R1A2A2A14001137).
Enhanced Performance and Durability of Low Pt- and Ir-Loading PEM Water Electrolysis
Authors: Fujita Mitsuharu , Konaka Saki , Goto Hiroki , Arima Ikkei , Tada Tomoyuki
Published: May 2020

In recent years, water electrolysis for hydrogen production is considered as a key technology to greenhouse gases reduction. In particular, PEM water electrolysis has the advantages of high efficiency, high current density and responsiveness to renewable energies. On the other hand, since a large amount of Pt and Ir metals are used in the PEM electrolyzer, it is necessary to reduce the amount of Pt and Ir metal used for the growth market in the future.

In this study, we focused on the low Pt and Ir loading CCM with SA100(Ir catalyst) and TEC10E50E(Pt catalyst). CCMs were prepared by splay method, the SEM images of cross-section are shown in Figure. CCMs with different configurations for catalysts, ink process, and catalysts loadings were studied using particle size distribution analyzer, polarization curves, durability, and other electrochemical methods. Ir Oxide should behave two roles in the catalyst layer: conductor and catalyst. In the case of CCMs with controlled ink particle size, the cross-section images and IV performance were improved. Catalyst loading reduction partially improved the polarization curves, it had a negative effect on durability.

Figure 1
Fused Hybrid Linkers for Metal–Organic Frameworks-Derived Bifunctional Oxygen Electrocatalysts
Authors: Alam Mahboob , Ping Kefeng , Bhadoria Rohit , Mikli V. , Mere Arvo , Aruväli Jaan , Paiste Päärn , Kook Mati , Rähn Mihkel , Sammelselg Väino , Tammeveski Kaido , Kongi Nadezda , Starkov Pavel
Published: May 2020

Noble metal free M-N-C oxygen electrocatalysts are generaly synthesized using inorganic salts, organometallic precursors, nanostructured carbon nanotubes, several dopants and carbonization under modifying environments such as NH3 or H2. Reducing synthesis steps or bringing versatility in post product is quite rare. We have introduced a series of metal-organic frameworks using iron/benzimidazole as the only primary precursor to obtain a uniform material. By merging catechol and imidazole units together, we prepared efficient bifunctional oxygen electrocatalyst. The proposed material outperforms the Pt-based materials with respect to electrocatalytic properties in alkaline media (ORR: Eon = 1.01 V, E1/2 = 0.87 V vs. RHE in 0.1 M KOH; OER: 1.60 V @10 mA cm–2 in 0.1 M KOH; ΔE = 0.73 V). It was also established that fine-tuning of organic linker can help to modulate the electrochemical properties of the single precursor based electro-catalyst material.
High Performance and Durable Membrane Electrode Assemblies with Binder-Free Plasma Sprayed Electrodes and Nanocomposite Membranes for Anion Exchange Membrane Electrolyzer
Authors: Razmjooei Fatemeh , Kaur Jasneet , Zarrin Hadis , Gago Aldo Saul , Ansar Syed-asif , Friedrich Andreas K
Published: May 2020

Hydrogen production via water electrolysis using electricity from renewable power sources is a promising method for storing energy in a large scale. Anion exchange membrane (AEM) electrolyzers have the potential for decreasing the hydrogen cost produced by renewables due to use of non-noble materials and inexpensive components for the membrane electrode assembly (MEA). This work demonstrates a highly active and durable MEA for AEM electrolysis using binder-free atmospheric plasma sprayed (APS) RANEY®-type nickel and RANEY®-type nickel-molybdenum electrodes,[1,2] as anode and cathode, respectively in combination with robust two-dimensional hexagonal boron nitride (h-BN)-based anion exchange membranes, nanocomposed with either polyvinylidene fluoride (PVDF) or polyvinyl alcohol (PVA). In this present work, various AEMs with different ionic conductivity and thickness, M1: High-loaded h-BN nanocomposite with PVDF or HL-BN-PVDF (0.23 Scm-1 and 125 mμ), M2: low-loaded h-BN nanocomposite with PVDF or LL-BN-PVDF (0.19 Scm-1 and 80 mμ) and M3: high-loaded h-BN nanocomposite with PVA or HL-BN-PVA (0.36 Scm-1 and 45 mμ) have been used. Three MEAs were fabricated using three membranes of HL-BN-PVDF, LL-BN-PVDF and HL-BN-PVA placed between two APS electrodes denoted as The MEA1, MEA2 and MEA3, respectively, and tested in single AEM electrolyzer cells. The tests are carried out in 1M KOH at 60 °C. As expected, the highest current, 2.6 Acm-2, at 2 V is achieved with MEA3, while MEA2 and MEA1 reached 2.95 and 3 A cm-2, respectively. The performance of AEM water electrolysis with the MEA3 is found to be slightly better than the MEA with the same electrode package but commercial membrane from Fumasep (2.71 Acm-2 at 2.0 V). The stability of the cell with MEA3 is tested under the constant load of 0.5 A cm-2 for 250 h showing negligible degradation. This can be attributed to the high mechanical and chemical stability of the membrane and low dissolution of anodic electrode. Furthermore, the lack of binders or ionomers in the APS electrodes avoids irreversible oxidation reactions of the polymer that can lead to voltage loss over time [3]. Thus, APS electrodes combined with stable nanocomposed (h-BN)-based membranes can potentially lower the cost of the hydrogen produced by water electrolysis.

1. Razmjooei, R. Reißner, A. S. Gago, and A. Ansar, ECS Transactions, 92 (8) 689-702 (2019).

2. Wang, T. Weissbach, R. Reißner, A. Ansar, A. S. Gago, S. Holdcroft, K. A. Friedrich, ACS
Appl. Energy Mater. DOI: 10.1021/acsaem.9b01392 (2019).

3. Li, I. Matanovic, A. S. Lee, E. J. Park, C. Fujimoto, H. T. Chung, and Y. S. Kim, ACS Appl. Mater. Interfaces, 11 (10) 9696-9701 (2019).
Fiber-like Structure on the Proton Exchange Membrane Created By Simultaneous Magnetron Sputtering and Plasma Etching in Role of a Catalyst Support in Water Electrolyzers
Authors: Kúš Peter , Hrbek Tomáš , Yakovlev Yurii , Novakova Jaroslava , Matolin Vladimír , Matolínová Iva
Published: May 2020

The increasing amount of installed power capacity from wind and solar power plants puts high demand on reliable and scalable system, capable of storing the energy during the overproduction and releasing it in times of deficit. The concept of hydrogen economy seems to be an interesting alternative in this regard. It is built around the conversion of electricity into H2 in times of energy overproduction and its subsequent utilization in various different ways, such as converting back to electricity on-site via fuel cells, injecting into the existing natural gas network, processing as a commodity or dispatching as an energy vector. Regardless of which pathway for H2 is ultimately chosen, the key inseparable technology necessary for the concept of hydrogen economy to function remains the water electrolysis. Proton exchange membrane water electrolyzers (PEM-WE) are arguably the most suitable for industrial scale-up. Still there are challenges that need to be solved, should the technology enter the mass production. One of the most crucial aspects is the need of lowering the amount of iridium on the anode of PEM-WE. It is currently the only sufficiently active catalyst which withstands the aggressive conditions during the oxygen evolution reaction (OER). Reducing Ir loading through its dispersion over the catalyst support, a method adopted from fuel cell industry, is not trivial since it is hard to find inexpensive, corrosion-resistant and conductive material in form of nanoparticles.

In this work, we present and discuss an innovative, yet very straightforward and industrially adaptable approach on how to circumvent the above mentioned problem. The proposed approach is based on the utilization of magnetron sputtering. The novelty of our patented approach is in simultaneous plasma etching of the PEM and deposition of CeOx thin film onto its surface. The CeOx layer serves as a masking element - the loss of material is hindered at the places with its sufficient coverage; in contrast, unprotected places are being continually etched out. This result in formation of a fiber-like structure with cross-sectional dimensions much smaller than their height. The modified surface of the PEM itself is therefore sufficiently large to carry the subsequently deposited thin-film catalyst completely on its own. Our study comprises characterization of the modified PEM morphology, electrochemical active surface area determination via rotating disk electrode and in-cell PEM-WE performance testing, including electrochemical impedance spectroscopy.

Figure 1
Transient Oxygen Reduction Reaction Kinetics in PEM Fuel Cell
Authors: Yarlagadda Venkata , Gu Wenbin , Arisetty Srikanth , Lenert Andrej , Kongkanand Anusorn
Published: May 2020

Oxides on the surface of an electrocatalyst inhibit oxygen reduction reaction (ORR) activity at high potentials. Although this process has been described for Pt/Vulcan electrocatalysts by an ORR kinetic model1, there is an opportunity to improve the existing model to accurately predict performance loss under non-standard temperature, relative humidity and transient operating conditions. Also, the established kinetic model does not accurately predict the performance for Pt-alloy electrocatalysts.

Here, we conducted time-resolved measurements of ORR kinetics for both Pt and Pt-alloy electrocatalysts under various temperature and relative humidity conditions in a PEM fuel cell. The oxide coverage was measured in a H2-N2 environment using cyclic voltammetry. ORR polarization measurements were conducted in H2-O2 environment. The experimental data was used to develop a kinetic model that depends on the oxide coverage, which showed improved prediction capability based on dynamic polarization measurements of Pt and Pt-alloy catalysts.

This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.

Reference

1. P. Subramanian, T. A. Greszler, J. Zhang, W. Gu, and R. Makharia, Journal of The Electrochemical Society, 159 (5), B531-B540 (2012)
Plasma Treatment As an Effective Way of Modifying Carbon-Based Electrocatalysts for an Enhanced Oxygen Reduction Reaction
Authors: Schechter Alex , Mohan Roopathy , Modak Arindam
Published: May 2020

Oxygen reduction reaction (ORR) is pivotal in renewable energy technologies such as in fuel cells and metal-air batteries. Precious metal-free electrochemical ORR is a critical component in designing cost-effective electrochemical energy conversion devices. In this report we demonstrate an efficient surface modification of carbon nanotubes (CNT) through one-step oxygen plasma irradiation that induces doping and charge redistribution around the doped heteroatom oxygen that promotes ORR activity. The defect sites generated owing to oxygen dopant in CNTs were confirmed by Raman spectra, X-ray photoelectron spectroscopy (XPS) surface composition and CHNO elemental analysis. The O-doped CNTs were thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) measurements. Our research shows that plasma-treated single-walled carbon nanotubes (SWCNT) are more effective ORR catalyst compared to multi-walled carbon nanotubes (MWCNT) due to the inherent structure of SWCNT that can access more defects and surface functional groups than MWCNT.

In the following study, plasma modification approach was implemented in the synthesis of a highly active robust Metal-Nitrogen-Carbon (M-N-C) catalysts through NH3-plasma pretreatment on high surface area black pearl carbon. Pre-treated FeNC/NH3-C contains Fe3C and Fe-Nx as catalytically active sites. XPS confirms the presence of a high surface concentration of pyrrolic to pyridinic nitrogen and ferrous sites on FeNC/NH3-C that promotes low oxygen reduction overpotential (0.80 V vs RHE in 0.5 M H2SO4 and 0.96 V vs RHE in 0.1 M KOH). Hence plasma activates the surface and incorporates nitrogen which forms stable Fe-N coordination for accelerating oxygen reduction. Importantly, FeNC/NH3-C shows lower peroxide yield at 0.6V/RHE (<20% in 0.5 M H2SO4 and <2 % in 0.1 M KOH) that can reduce the detrimental effect of H2O2 on the catalysts support and exhibits high stability, seen from thousands of potential cycling stability tests of FeNC/NH3-C in acid solutions. Thereby this plasma-based new synthetic approach can promote more active and stable non-precious metal catalysts.
Application of Au Nanoparticles Supported Nitrogen-Doped Carbon for Direct Ethanol Fuel Cells
Authors: Tamašauskaitė-Tamašiūnaitė Loreta , Upskuvienė Daina , Balčiūnaitė Aldona , Šimkūnaitė Dijana , Vaičiūnienė Jūratė , Niaura Gediminas , Kruusenberg Ivar , Kaare Kätlin , Volperts Aleksandrs , Dobele Galina , Zurins Aivars , Norkus Eugenijus
Published: May 2020

In this study, the synthesis of gold nanoparticles (AuNPs) supported nitrogen-doped activated carbon (N-doped C) nanocomposites and their application for the electro-oxidation of ethanol in an alkaline medium is presented. The AuNPs have been deposited on the N-doped C material using chemical reduction with glucose and ascorbic acid as reducing agents and microwave-assisted synthesis. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, X-ray diffraction (XRD) and inductively coupled plasma optical emission spectroscopy (ICP-OES) were used for the characterization of morphology, structure and composition of the resulting nanocomposites, whereas, the electrocatalytic activity of the ones for the electro-oxidation of ethanol in an alkaline medium has been investigated using cyclic voltammetry and chrono-techniques.

It has been determined that the AuNPs/N-doped C nanocomposites have a higher electrocatalytic activity for the electro-oxidation of ethanol than the pure Au or N-doped carbon alone, indicating the synergistic effect of AuNPs and N-doped carbon material. The obtained N-doped carbon supported AuNPs catalyst seems to be an efficient anode material for direct ethanol fuel cells (DEFCs).
Irreversible Structural Dynamics in Bimetallic Pt-Ni Alloy Catalyst Under Alternating Redox Environments
Authors: Khalakhan Ivan , Vega Lorena , Viñes Francesc , Vorokhta Mykhailo , Skála Tomáš , Yakovlev Yurii , Neyman Konstantin , Matolínová Iva
Published: May 2020

The better understanding on the structural dynamics of a bimetallic catalyst during its interaction with reactive environments is a prerequisite for the development of an efficient catalyst for proton exchange membrane fuel cells (PEMFCs). The main focus should be given to the outermost layers of catalytically active material which are directly involved in catalysis.

Herein, we applied the synchrotron radiation photoelectron spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS) techniques to investigate surface chemistry aspects in a PtNi alloy catalyst under alternating oxidation (O2) and reduction (H2) atmospheres at different temperatures that simulate its behavior as a cathode catalyst in PEMFCs. The experimental results are substantiated by theoretical calculations on model PtNi nanoalloys.

We showed that PtNi alloy does not maintain its chemical integrity and undergoes surface reconstruction during the switching between oxidizing and reducing conditions in terms of relative surface nickel enrichment. Along with compositional changes catalyst coarsening was observed by atomic force microscopy (AFM).

The revealed behavior of the PtNi alloy provides valuable fundamental insights that help to gain advanced understanding of PtNi alloy catalytic activity in real conditions.

Figure 1
Interface Engineering: On the Impact of Micro-Porous Layers on Polymer Electrolyte Water Electrolysis Performance
Authors: Schuler Tobias , Schmidt Thomas J. , Büchi Felix N.
Published: May 2020

In polymer electrolyte water electrolysis (PEWE), operational cost represents the main cost fraction. Losses induced by kinetic, ohmic as well as mass transport overpotentials limit cell efficiency and in turn lead to lower volumetric power density and higher energy consumption.

The interplay of porous transport layer bulk/surface properties1,2, providing thermal and electrical conductivity as well as fluid management between bipolar plates and catalyst layer, and cell efficiency is a disputed question in literature. Governing design parameters for porous transport layers, as well as fundamental limiting process haven’t been addressed so far. This study aims to close the gap between fundamentals and highly efficient PTL microstructure design. A novel class of hierarchically structured porous transport layers is fabricated based on sintering of economically viable Ti powder, see Figure 1..

A series of four different PTL materials including three different MPL types was analysed. Structural properties, characterized by laboratory and synchrotron based X-ray tomographic microscopy (XTM) were correlated to in-depth electrochemical analysis. Performance of the novel PTLs was probed by comparison to state-of-the-art PTL materials and stack technology. The superior surface properties of the microporous-layer enabled the use of ultra-thin membranes with Ti PTLs for the first time. To elucidate the MPL effect and reveal the mechanism of partial catalyst utilization3,4, the catalyst layer conductivity was studied as function of hydration state and ionomer content.

Reference

1 S. A. Grigoriev, P. Millet, S. A. Volobuev and V. N. Fateev, International Journal of Hydrogen Energy, 2009, 34, 4968-4973.

2 T. Schuler, R. De Bruycker, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2019, 166, F270-F281.

3 Z. Kang, J. Mo, G. Yang, S. Retterer, D. Cullen, T. Toops, J. Green Jr, M. Mench and F.-Y. Zhang, Energy and environmental science, 2017, 10, 166-175.

4 T. Schuler, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2019, 166, F555-F565.

Figure 1. XTM rendering of hierarchically structured porous transport layer.

Figure 1