bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Demystifying the Electrode/Electrolyte Interface in Carbon-Based Electrochemical Capacitors with Specs Technique and Electrochemical Dilatometry
Authors: Fic Krzysztof , Galek Przemyslaw , Menzel Jakub , Bujewska Paulina , Donne Scott W
Published: December 2020

It is often said that the highly developed surface area of electrode materials ensures high capacitance, power and energy in electrochemical capacitors. However, the real ‘efficiency’ of the surface exploited in charge storage remains unknown. Recently, it turned out that the Step Potential Electrochemical Spectroscopy (SPECS) technique can be a useful tool for determining it.

The SPECS technique allows for the comprehensive analysis of the total current output and evaluation of the capacitive, redox and other components. Together with the physicochemical data from nitrogen and CO2 adsorption techniques, we aim at the determination of the real electrode/electrolyte interface surface.

Based on the knowledge gained to date, we assume that the efficiency of the interface ‘exploitation’ depends on many factors: pore size distribution, wettability of the electrode material by electrolyte, as well as the size of the ions. Thus, inappropriate selection of one of these parameters can aggravate the device performance, even if the excellent carbon material is applied as electrode component.

The paper will provide the results from SPECS correlated with the physicochemical properties of carbon materials. It appears that the electrochemically accessible surface does not exceed 30% of the values estimated by N2 or CO2adsorption. The results will be supported by the recent findings from electrochemical dilatometry experiments.
(Invited) Internal Gas Pressure Measurement of Packaged Electric Double Layer Capacitors
Authors: Miller John R. , Butler Sue M.
Published: December 2020

One mode of electric double layer capacitor failure is package rupture, which usually leads to rapid deterioration of its electrical performance. This typically is caused by gas generated within a sealed capacitor with a subsequent pressure rise that eventually leads to the package bursting. The rate of gas generation, which ultimately can determine capacitor life, depends on materials purity, capacitor operating voltage, and the capacitor operating temperature. We measured the internal gas pressure and rate of gas pressure rise in spiral-wound, packaged electric double layer capacitors using an indirect and a direct approach. The indirect approach relied on physically measuring capacitor package deformation that had been caused by the internal gas pressure. This was then quantified by comparing the value with deformation caused by a known applied gas pressure. The direct approach relied on the use of an attached and calibrated solid-state pressure transducer. Internal gas pressure measurements using both approaches were made on 100-F-size electric double layer capacitors held at several temperatures with different applied voltages. Experimental details are reported with internal pressure measurements shown for 2000 hours of capacitor aging at 65 oC.

Figure 1
Carbon Supported PtRu-Ni Ternary Nanoparticles with a PtRu Rich Shell Using a Polydopamine Protective Coating As CO Tolerant Electrocatalyst
Authors: Lee Hojin , Kim Hansung
Published: December 2020

Carbon supported PtRu-Ni/C catalysts with a Ni-rich core structure are prepared through high temperature treatment of as-prepared polyol PtRu/C catalysts. It is well acknowledged that in conventional PtRu alloys, Ru prevents the adsorption of carbon monoxide on Pt surface via bifunctional mechanism. Also, the ligand effect is known to alter the electron structure of Pt for increased CO tolerance. In this work, the optimal Ni amount is determined for enhanced high resistance to carbon monoxide poisoning. The diffusion of Ni into the core of the catalysts is conducted by controlling the temperature during heat treatment. The as-prepared polyol PtRu/C catalysts have carbonized polydopamine layer on the surface, which prevents particle segregation during high temperature heat treatment. The carbon layer also partakes the role of transferring Ni particles into the core of the catalyst. When compared to using without protective coating method to directly fabricate PtRu-Ni/C catalysts, this method is far more superior. In general, Ni species on the surface is easily to be dissolved in acidic medium in PEMFC. But, PtRu-Ni/C with protective coating, in which Ni species is located inside the bulk of nanoparticles, would prevent it from dissolution in acidic medium while keeping the interaction between Ni and surface Pt.

In this study, Energy-dispersive X-ray spectroscopic line scan profile confirm that the PtRu-Ni/C catalyst has a Ni-rich core and PtRu-rich shell structure. From polymer electrolyte membrane fuel cell tests using CO containing H2 gas, the core-shell structured PtRu-Ni/C alloy formed by protective coating method is demonstrated to have higher tolerance to CO poisoning than PtRu/C catalysts synthesized by polyol method.
Synthesis and Electrocatalytic Activity of Pt-Ni Nanowire
Authors: Iguchi Yoshimi , Li Tianchi , Kato Masaru , Yagi Ichizo
Published: December 2020

Polymer electrolyte fuel cells (PEFCs) are known as sustainable devices and can produce the electricity with no emission of CO2 gas. The oxygen reduction reaction (ORR) occurs at the cathodes in PEFCs and platinum nanoparticles (NPs) are generally used as an ORR catalyst. Pt on the surface of the catalysts can be oxidatively dissolved under catalytic conditions and then their ORR activity decreases.[1, 2] Because alloying and nanostructuring are known to improve the tolerance of the catalyst to the oxidative dissolution[3], we have studied Pt-Ni nanowires (NWs) as an ORR catalyst.[4] NWs can be expected to show stronger interactions between the Pt surfaces and carbon supports than NPs.[5, 6] However, there is a lack of detailed researches on the durability of NWs.

In this research, we synthesized Pt-Ni NWs, conducted an accelerating durability test (ADT) for the ORR activity and investigated the effect of the ADT on the electronic states of NWs by ex situ X-ray photoelectron spectroscopy (XPS) and in situ Pt L3-edge X-ray absorption spectroscopy (XAS). We also characterized NWs by scanning transmission microscopy (STEM), inductively coupled plasma mass spectrometry (ICP-MS) and powder X-ray diffraction (pXRD). Cyclic and linear sweep voltammograms of NWs showed that the mass activity of the NWs was higher than that of NPs. Interestingly, the mass activity of the NWs increases after the ADT whereas the activity of typical NPs decreases.[7] XPS peaks of the NW catalyst in the Pt 4f region were shifted to the higher binding energy after the ADT, compared to those before the ADT. This result suggests that the d-band center of the surface Pt of the NWs were downshifted after the ADT.[8]
In situ Pt L3-edge XAS revealed that the potential dependence of the intensity of the NW catalyst in the white line region after the ADT is smaller than that of before the ADT. This result suggests that the formation of Pt oxide was suppressed after the ADT,[1] leading to the improvement of the mass activity.

References

[1] K. Nagasawa, et al., J. Am. Chem. Soc., 137, 12856 (2015).

[2] H. Nejc, et al., Acc. Chem. Res., 49, 2015 (2016).

[3] L. Robner et al., ACS Catal.,
9, 2018 (2019).

[4] L. Xhikun, et al., RSC Adv., 10, 6287 (2020).

[5] I. Stephens, et
al., Science, 354, 1378 (2016).

[6] M. Li, et al., Science, 354, 1414 (2016).

[7] G. Mingxing, et al., ACS Catal., 9, 4488 (2019).

[8] M. Wakisaka, et al., J. Phys. Chem. B, 110, 23489 (2006).

Acknowledgements

This work was supported by NEDO.
Manufacturing Process of Electrode Films
Authors: Banas Charles Joseph , Aponte Bryan , Pasaogullari Ugur
Published: December 2020

Rotating disk electrode experiments form a key experimental characterization technique for measuring electrocatalyst performance and durability. Numerous studies have been performed to gauge catalyst performance and suitability for polymer electrolyte fuel cells. However, those studies can show for a wide range of performance measurements for the same catalyst.1

Standard rotating disk electrode testing protocols have been documented, and used repeatedly in available literature.1 Little research has been devoted to the catalyst film preparation however. Catalyst films are formed from the drying of a catalyst solution consisting of a catalyst-water-ethanol-Nafion solution on a glassy carbon working electrode surface.

Experiments within our group show large variation in catalyst performance characterization for catalyst films dried under ambient conditions, which result from inconsistent and non-uniform catalyst distribution on the electrode surface. To promote consistent film production, a controlled environmental chamber was constructed. The objective of this chamber was to establish conditions for equalizing water and alcohol evaporation in the catalyst solution by controlling relative humidity. Catalyst film quality was shown to improve when using the chamber, improving film catalyst distribution uniformity, along with electrochemical catalyst performance. This paper will detail the construction and the environmental control chamber, and the effect of environmental conditions on the catalyst film quality and electrochemical measurements.

Reference

1. S. Kocha et al., “Best Practices and Testing Protocols for Benchmarking ORR Activities of Fuel Cell Electrocatalysts Using Rotating Disk Electrode,” Electrocatalysis, vol. 8, no. 4, pp. 366–374, Jul. 2017, doi: 10.1007/s12678-017-0378-6.

Figure 1
Effect of Polymer Wrapping of Carbon Black for Pt Utilization of Polymer Electrolyte Membrane Fuel Cells
Authors: Jayawickrama Samindi Madhubha , Fujigaya Tsuyohiko
Published: December 2020

To reduce the usage of platinum (Pt) in polymer electrolyte membrane fuel cell (PEMFC) electrocatalyst, it is crucial to increase Pt utilization efficiency. In this study, an effect of polybenzimidazole (PBI) wrapping on carbon blacks (CBs) for the improvement of Pt utilization efficiency in PEMFC is investigated using CBs having high surface area (HSA) and low surface area (LSA) as well as structure-efficiency relationship is explored. Comparison study of single-cell measurements using PBI-coated and non-coated HSA and LSA electrocatalysts reveals that HSA CB is more effective to improve Pt utilization efficiency and about 33% improvement of the power density is achieved, while LSA CB marks 10% improvement under 80 °C at 100% relative humidity. The mechanism behind the greater improvement especially for HSA CB is mainly because of micropore capping by PBI wrapping, which increases the electrochemical active surface area as well as the proton conductivity and O2 diffusion. On the other hand, even though the degree of improvement is lower for LSA CB, the increase of Pt utilization efficiency is realized mainly due to the loading of uniformly dispersed smaller Pt.
The Morphological Transitions of Ni/C Catalyst for Hydrazine Oxidation
Authors: Park Jihyeon , Lee Jaeyoung
Published: December 2020

Hydrazine fuel cell is one of the promising liquid fuel cells because of high theoretical voltage, high energy density, and no green gas emission. However, hydrazine can be decomposed chemically or electrochemically as a function of the type of catalyst used. Platinum, despite a noble metal, is an ambiguous catalyst due to faradaic reaction catalyst of hydrazine as well non-faradaic reaction. Therefore, in the aspect of the fuel efficiency, platinum is not suitable for hydrazine catalyst. Nickel, which is the same family with platinum, is non-noble metal and has quite good performance for hydrazine oxidation due to its similar structure to platinum. In these aspects, hydrazine fuel cell is further important, not requiring the expensive noble metal. Here, we synthesized Ni nanoparticles via polyol method changing the type of Ni precursor, since chemical, physical, and electro-chemical properties of a metal nanoparticle depend on its morphology and size. When using nickel nitrate, Ni nanoparticle size is smallest with shapeless morphology, whereas using nickel chloride, size is somewhat big but particles are well-spreaded on carbon support. Then, in order to confirm hydrazine electro-oxidation performance, catalyst ink was loaded on the rotating disk electrode (RDE), and cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were carried out.
Influence of Quaternary Ammonium Cation Chemistry on Interfacial Morphology of Anion-Conducting Block Copolymers at a Silver Interface
Authors: Buggy Nora Catherine , Du Yifeng , Kuo Mei-Chen , Coughlin E. Bryan , Herring Andrew M.
Published: December 2020

The heterogeneous microstructure of the electrode in polymer electrolyte-based electrochemical devices features a complex mixture of interacting species, including ionomer, catalyst particles, and typically a conductive carbon support. The triple-phase boundary which forms between these three components significantly impacts the transport of water, ions, and reactant and product species to and from reaction sites. Hence, overall performance of the electrochemical device is significantly impacted by the structures that form in the electrode, which are driven by interactions between the ionomer and catalyst components. It is known that interactions at the ionomer-catalyst interface can facilitate restructuring of the ionomer morphology, ultimately affecting transport networks. Therefore, a more fundamental understanding of ionomer-catalyst interactions can aid in the development of ionomer chemistries that result in desirable interfacial morphologies and electrode structures.

Since alkaline systems can leverage the ORR capabilities of non-noble metal catalysts beyond Pt, this work focuses on interactions with silver, which has been shown to have ORR activity akin to Pt catalysts. Our previous work has shown that the quaternary ammonium cations trimethylammonium (TMA) and methylpiperidinium (MPRD) both interact with silver and can affect bulk properties of the ionomer, including crystallinity and water uptake. To continue this study, a set of tunable block copolymers, post-functionalized with either TMA or MPRD, are used to investigate how cation chemistry influences the resulting interfacial morphology of the ionomer. Model interfaces between ionomer thin films and silver surfaces are fabricated and studied using a combination of environmental GISAXS and AFM to assess morphological characteristics such as domain size and orientation under relevant electrochemical device conditions. These efforts will lead to a better understanding of the ionomer-catalyst interface and will provide key insight toward rationally designing block copolymers for the alkaline electrochemical devices.
Influence of Cyano Substituents on the Electron Density and Catalytic Activity Towards the Oxygen Reduction Reaction for Iron Phthalocyanine
Authors: Tasca Federico , Govan Joseph , Abarca Gabriel , Orellana Walter , Zagal Jose H
Published: December 2020

Iron(II) 2,3,9,10,16,17,23,24-octa(cyano)phthalocyanine (OCNFePc), was tested as a catalyst for the oxygen reduction reaction (ORR) adsorbed on carbon nanotubes. The composite was analyzed spectroscopically and electrochemically characterized at pH 13 and pH 1. The composite showed close to 4 electron processes at pH 13. Computational analysis indicates that the O2 molecule binds end-on to the metal center and that the dioxygen molecule is dissociated on both the Fe metal center and the corral ring. An Analysis of the molecular electrostatic potential confirms the behavior of cyano residues as electron-withdrawing moieties in OCNFePc. As a result of its catalytic behavior and theoretical analysis of its O2 binding energy, OCNFePc was placed in a high position on a volcano correlation of similar phthalocyanine composites.
Single Site Substitution in 2D Molybdenum Carbide: Applications in Electrocatalysis
Authors: Kuznetsov Denis A. , Chen Zixuan , Kumar Priyank V. , Abdala Paula M. , Fedorov Alexey , Müller Christoph R.
Published: December 2020

Two-dimensional carbides and nitrides (MXenes) represent an excellent platform for the fundamental catalysis studies due to their well-defined and tunable structure and theoretically predicted high activity in numerous catalytic reactions.1 However, the scope of metals capable of forming thermodynamically stable MXenes is limited mostly to early transition metals, making the investigation of properties inherent to mid or late transition metal carbides/nitrides challenging. Here, we present the synthesis and structural characterization of the Mo2CTx
:M phases (M = Co, Fe; Tx
= O, OH, F surface terminations), where M substituents occupy molybdenum positions in the Mo2CTx
lattice, providing isolated Co/Fe sites. Our experimental and DFT studies demonstrate that metal M substitution renders Mo2CTx
:M carbides active catalysts for the hydrogen evolution reaction. Overall, our work expands the compositional space of the MXene family by introducing materials with isolated metal sites incorporated into the matrix of Mo2CTx
. The results discussed here highlight the general applicability of the developed synthetic approach and illustrate that tailoring the properties of MXenes for a specific application can be achieved via targeted substitution of the host metal.

(1) Anasori, B.; Lukatskaya, M. R.; Gogotsi, Y., Nat. Rev. Mater.
2017,
2, 16098.
Cobalt/Dihydroxybenzimidazole-Derived Amorphous MOF TAL-2 As a Single Precursor for Trifunctional ORR/Oer/HER Electrocatalyst Material
Authors: Kongi Nadezda , Alam Mahboob , Ping Kefeng , Bhadoria Rohit , Kazimova Nargiz , Starkov Pavel
Published: December 2020

Preparation of cost-efficient noble metal-free multifunctional electrocatalyst materials with high performance and stability for oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) – referred to as trifunctional catalysts – remains an outstanding challenge. The catalyst material was prepared from amorphous metal–organic framework TAL-2, which was obtained from cobalt salt and dihydroxybenzimidazole and outperformed the benchmark catalysts in ORR and OER reactions (0.1 M KOH: ∆E = 0.73 V, AMFCs: j = 1100 mA cm–2, P = 400 mW cm–2). Use of dopants or modifying conditions was unnecessary for this material to be used as a trifunctional electrocatalyst.
Performance Degradation in Alkaline-Membrane Electrolyzers
Authors: Krivina Raina A , Capuano Christopher , Ayers Katherine E. , Boettcher Shannon W.
Published: December 2020

Anion exchange membrane (AEM) electrolysis uses a hydroxide-conducting polymer membrane providing a basic environment for the anodic oxygen evolution reaction (OER) and thus an environment that is suitable for earth-abundant catalyst materials. Currently, concentrated KOH is often added to the system to reduce interface resistive losses, with the unintended consequence of increased corrosion and complicating system design. In contrast, K2CO3 provides high conductivity and is nominally non-corrosive. Surprisingly, a rapid AEM stack failure has also been observed for several catalysts during testing in 1 wt. % K2CO3. This failure mechanism remains unclear. Here, I will present the results of a carbonate-induced degradation study performed in collaboration with Proton OnSite (Nel Hydrogen) using analytical and surface characterization techniques. Our results obtained via XPS and three-electrode measurements taken together show that the ionomer degrades during electrolysis into oxidized fragments and that the rate of degradation appears to be catalyst-dependent: some catalyst show a lower rate of ionomer oxidation than others. We hypothesize this difference is related to the ability to form a non-conductive shell during OER. The shell may prevent direct electrical contact of the ionomer with the highly oxidizing catalyst surface during OER. Our findings not only elucidate degradation mechanisms, but also point towards degradation mitigation strategies, such as the informed sculpting of the binder/catalyst interface specifically targeting the conductivity of the catalyst shell. In the remainder of the presentation, I will discuss analogous degradation studies with a pure water feed, and present a preliminary model of degradation phenomena in alkaline membrane electrolyzers.

Figure 1
Catalyst Assessments and Device Incorporation in Low Temperature Electrolysis
Authors: Alia Shaun M , Reeves Kimberly Shawn , Ha Mai-Anh , Larsen Ross E , Cullen David A.
Published: December 2020

Although hydrogen has a significant role in transportation and agriculture, its use in energy consumption overall has been limited, particularly when produced through electrochemical water splitting. With decreasing electricity prices, electrolysis cost reductions can be achieved and allow for an opportunity for greater use.(1) While load following renewable power sources can reduce feedstock cost, further cost reductions rely on minimizing the capital cost by reducing the platinum group metal (PGM) content.(2) Efforts are needed to understand and mitigate electrolyzer degradation, particularly when accounting for lower PGM loadings and intermittent operation.

Previous efforts have developed accelerated stress tests focused on catalyst layer and interfacial loss with standard material sets. (3) Expanded studies have incorporated advanced materials, including higher surface areas, different oxide compositions, supports, and multicomponents. Kinetic improvements were found to lessen load requirements and can mitigate catalyst loss. Cell performance loss during extended operation, however, tended to qualitatively correspond to ex-situ dissolution rates of less stable materials leading to accelerated catalyst layer thinning, migration into the membrane, and interfacial tearing, as determined in post-mortem electron microscopy analysis.

While individual components dictate cell-level performance and durability, how components are integrated into membrane electrode assemblies was found to have an impact on catalyst layer properties and electrolyzer performance/durability. Catalyst layers were modified using an ultrasonic spray approach due to the number of variables that could be tuned. While changes to these variables affect several properties and loss mechanisms, trends were found with regards to how catalyst-ionomer integration and catalyst layer uniformity affected performance nonidealities and how losses grew during extended operation. These approaches are useful in diagnostics, to identify and mitigate lower performance and durability. Understanding catalyst layer formation and the relationship between catalyst layer properties and electrolyzer performance/durability is critical to establishing baselines and better informing catalyst development and fabrication efforts.

[1] B. Pivovar, N. Rustagi and S. Satyapal, The Electrochemical Society Interface, 27, 47 (2018).

[2] K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar and M. Bornstein, Annual Review of Chemical and Biomolecular Engineering, 10, 219 (2019).

[3] S. M. Alia, S. Stariha and R. L. Borup, J. Electrochem. Soc., 166, F1164 (2019).
Interface Engineering: On the Impact of Micro-Porous Layers on Polymer Electrolyte Water Electrolysis Performance
Authors: Schuler Tobias , Schmidt Thomas J. , Buechi Felix N.
Published: December 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 series of four different PTL materials with different MPL types was analysed3. Structural properties, characterized by 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 enables the use of thin membranes with Ti PTLs for the first time.

References

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

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

T. Schuler, J.M. Ciccone, B. Krentscher, F. Marone, C. Peter, T.J. Schmidt, and F.N. Büchi, Hierarchically Structured Porous Transport Layers for Polymer Electrolyte Water Electrolysis, Advanced Energy Materials, 2020, 10, 1903216.

Figure 1
Iron Contamination and Local Distribution within a 50 Cm Single-Channel Proton Exchange Membrane Water Electrolysis Cell
Authors: Immerz Christoph , Singer Matthias , Hasché Frédéric , Bensmann Boris , Suermann Michel , Hanke-Rauschenbach Richard , Oezaslan Mehtap
Published: December 2020

Proton exchange membrane water electrolysis (PEMWE) will play a major role in the clean and versatile energy conversion in the near future.[1] Offering scalable solutions of PEMWE are of high industrial interest and have to provide a sufficient durability and reliability.[2] To achieve this, a better understanding of the impact of contamination on the PEMWE performance is very crucial. In this context, the membrane electrode assembly (MEA) is susceptible to several degradation processes like metallic cations (Fe3+/2+ stemmed from tubing). In particular, soluble and reduced iron species forming by Fenton reaction might attack via radicals the MEA.[3,4] Hence, analyzing impurities and their resulting impacts on e.g. the proton transport resistance and degradation mechanisms at different length scales and local distributions are of large interest.

In this work, the influence of spatially resolved iron contamination in MEAs on the cell performance has been investigated using a 50 cm single-channel PEMWE cell equipped with local current density measurement setup.[5] Adding defined amounts of FeSO4 via the anode inlet feed, the changes on the three main regimes of overpotentials, i.e. kinetic, ohmic and mass transport, is correlated with the current density mapping as well as local and global electrochemical impedance spectroscopy (EIS) measurements. Ex-situ scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are used to detect the distribution and agglomeration of iron species within the MEA.

With this combined approach of electrochemical and ex-situ physical methods, the contamination pathways and their effects of (spatially resolved) iron contamination on the overall performance of MEA are investigated as a function of degree of contamination and operating conditions. Especially, the (spatially resolved) overpotential-specific degradation processes along the 0.5 m channel, which mimic a technically relevant stack size, allow us to conclude on the optimum design of MEA, targeting use of mitigation strategies and development of accelerated stress test protocols.

[1] M.A. Pellow, C.J.M. Emmott, C.J. Barnhart, S.M. Benson, Energy Environ. Sci. 8 (2015) 1938-1952.

[2] P.K. Shen, C.-Y. Wang, S.P. Jiang, X. Sun, J. Zhang, Electrochemical Energy: Advanced Materials and Technologies, CRC Press, 2015.

[3] X. Wang, L. Zhang, G. Li, G. Zhang, Z.-G. Shao, B. Yi, Electrochim. Acta 158

(2015) 253-257.

[4] C. Rozain, P. Millet, Electrochim. Acta 131 (2014) 160e167.

[5] C. Immerz, B. Bensmann, P. Trinke, M. Suermann, R. Hanke-Rauschenbach, JECS 165 (16) (2018)
Manufacturing Challenges and Opportunities for PEM Electrolysis
Authors: Capuano Christopher , Ayers Kathy , Manco Judith , Wiles Luke , Keane Alex , Dalton Luke
Published: December 2020

Hydrogen generation via electrolysis has gained much attention internationally as not only a sustainable source of fuel for the transportation, but as a carrier of energy to capture stranded renewable due to the carbon-free chemical cycle and response characteristics of the technology. The barrier to entry preventing this technology from being widely adopted is the overall cost associated with both the upfront capital expense as well as the operating cost incurred over the product life. The majority of this cost is driven by 1) low electrical efficiencies due to the high ohmic resistance of thicker membranes required by electrolysis systems to electrochemically compress generated hydrogen for storage and the overpotential associated with the water splitting oxygen evolution reaction (OER) catalysts typically used, 2) high cost of system and cell stack materials, which need to be durable for up to 100,000hrs at a potential of 2V in both reducing and oxidizing environments, and 3) the lack of a robust supply chain for high volume manufacturing to further drive down cost through economies of scale.

With 95% of hydrogen currently being produced through the reformation of cheap natural gas, significant cost reductions are necessary for electrolysis to become a viable alternative to the incumbent. Commercial proton exchange membrane (PEM)-based electrolysis has reached scales of several hundred kg/day, providing a relevant pathway for industrial scale hydrogen generation with tremendous opportunity for continuing cost reduction by leveraging system and manufacturing scaling laws by leveraging advancements in PEM fuel cell materials, manufacturing, and analysis tools. Order of magnitude improvements in some of the highest cost elements are easily achievable and with more research funding being directed towards hydrogen production, the realization of these reductions are occurring at a faster rate. While many improvements in stack design and materials of construction have been identified and implemented, there are still numerous opportunities to explore that would move electrolysis towards a viable, cost-effective alternative to natural gas reformation. This talk will describe some of the areas of success, where research is still needed, and ultimately how each of these improvements translate into cost and the path to reformation parity.
The Relationship between Activity and Durability of Surface Area and Catalyst Loading of IrOx Anode Catalyst in Proton Exchange Membrane Water Electrolysis (PEMWE)
Authors: Fujita Mitsuharu , Arima Ikkei , Goto Hiroki , Konaka Saki , Tada Tomoyuki
Published: December 2020

The R&D of highly active and durable anode catalysts for the oxygen evolution reaction (OER) is very important for high efficiency Proton Exchange Membrane Water Electrolysis (PEMWE). The reason is that the high overpotential of OER reaction is the main factor of the energy loss. At present, the use of highly active and durable iridium catalyst is one of the resolutions for reducing overpotential. From the perspective of iridium production, not only is limited the producing area, but production amount is limited because iridium is by-product of PGM mine in South Africa. Therefore, in order to popularize hydrogen production by large-scale PEMWE, it is necessary to to achieve the high performance with the minimum amount of iridium material. In this study, we report the activity and durability of catalysts coated membranes (CCMs) based on the IrOx catalyst surface area and loadings.

High surface area IrOx catalyst (SA100) and a low surface area IrOx catalyst (SA5) from Tanaka Kikinzoku Kogyo K.K. were used for OER catalysts in this study. These catalysts were characterized by ICP-AES analysis, powder XRD, N2-BET, and SEM images. CCMs were prepared by spray-coating and hot-press with IrOx catalysts at the anode and carbon supported platinum at the cathode (TEC10E50E, Tanaka Kikinzoku Kogyo K.K.). Single cell electrochemical analysis including initial polarization curves, cyclic voltammetry, and durability tests (at 50℃, 2A/cm2) and SEM cross section images was studied for all CCMs.

The SEM images of the CCMs microstructure near the catalyst layer were shown in Figure 1-A and 1-B. The particle size of IrOx (SA100) was found to be ca.5nm. For IrOx (SA5), the particle size was less than 2nm. The cell voltages focused on the iridium loadings were confirmed in Figure 2-A and 2-B. Although there was significant difference in SEM cross section images of catalyst layers, the trend obtained for the SA100 was consistent with the trend in the SA5. The IrOx loaded from 0.1 to 0.3 mg/cm2 range exhibited a gradual increase in cell potential. Furthermore, the catalytic durability and CV studies using single cells at 2A/cm2, 50℃ will be discussed. This report will be one of the valuable source of information for CCM design for general PEMWE.

Figure 1
Applying the Lattice Boltzmann Method to Simulate Bubble Growth in Porous Media for PEM Water Electrolysis
Authors: Satjaritanun Pongsarun , Lopata Joseph Steven , Cho Hyun-Seok , Kim Min-Joong , Zenyuk Iryna V. , Shimpalee Sirivatch
Published: December 2020

Polymer electrolyte membrane water electrolysis (PEMWE) is one of the most appealing options to produce hydrogen and oxygen from water. Understanding bubble growth and flow transport behavior is essential to improve the cell performance and reduce the cost of PEMWE devices, especially at high current densities. This work presents and discusses the modeling results obtained for PEMWE under different operating conditions. In this work, the Lattice Boltzmann Method (LBM) [1-3] of computational fluid dynamics (CFD) is used to investigate the characteristics of bubble growth and transport through the porous transport layer (PTL) used in PEMWE. Studies of the evolution, growth profile, size distribution, and velocity distribution of propagating bubbles are explored. The model geometries of PTLs used in this study were obtained via X-ray computed tomography (CT). Figure 1 shows the bubbles in the PTL after they have detached from the electrode surface. This approach is able to examine the bubble characteristic regarding cell operating condition changes within different PTL samples. These findings should be useful for improving the modeling of bubble transport and enhancing our understanding of processes in PEM water electrolysis.

References:

P. Satjaritanun, J. W. Weidner, S. Hirano, Z. Lu, Y. Khunatorn, S. Ogawa, S. E. Litster, A. D. Shum, I. V. Zenyuk, S. Shimpalee, Journal of The Electrochemical Society, 164, (2017) E3359-E3371.

P. Satjaritanun, S. Hirano, A. D. Shum, I. V. Zenyuk, A. Z. Weber, J. W. Weidner, S. Shimpalee, Journal of The Electrochemical Society, 165, (2018) F1115-F1126.

P. Satjaritanun, S. Hirano, I. V. Zenyuk, J. W. Weidner, N. Tippayawong, S. Shimpalee, Journal of The Electrochemical Society, 167, (2020) 013516.

Figure 1
(Invited) Details Matter: Applying Computed Tomography and X-Ray Imaging to Advancing PEFCs
Authors: Litster Shawn
Published: December 2020

Polymer electrolyte fuel cells (PEFCs) continue to reach new levels of performance and are increasingly being used in passenger vehicles, heavy-duty vehicles, and stationary power supplies. In concert with these advancements, the tools used to identify new opportunities to further advance power density and durability as well as reduce costs must increasingly scrutinize finer details. Such details include the role of heterogeneities in bulk layers, unintentional or intentional gradients in material properties stemming from the manufacturing and film casting processes, the impact of interfacial zones, spatial distributions of the current generation and material degradation, as well as the impact of the three-dimensional (3D) micro/nanostructure. This talk will share recent advances in the application of micro-scale and nano-scale computed tomography (CT), including X-ray and electron CT, and will outline the state-of-art capabilities. Advanced methodologies that will be introduced include <50 nm resolution X-ray nano-CT and plasma focused ion beam-scanning electron microscopy (pFIB-SEM) for high-throughput, large field of view 3D imaging at <5 nm resolution. The talk will highlight recent advances in multi-modal/multi-scale imaging, CT-informed and image-based modeling, and operando X-ray imaging. Some examples include multi-modal X-ray CT imaging of catalyst layers to understand how ink properties and casting affects the structure, including the reorganization of ionomer during casting and drying. Regarding degradation analysis, the use of nano-CT for imaging the 3D redistribution of Pt in MEAs and pore structure evolution with accelerated stress tests will be highlighted. The talk will emphasize the various levels of using CT data to inform simulations, including recent applications of high-performance computing and open-source software to model coupled transport-reaction in large image domains resolving both the true pore and ionomer 3D distributions as well as the use of electron tomography images to simulate nm-scale gas and ion transport in single Pt/C aggregates. Finally, there will be a discussion of emerging operando X-ray imaging methods at sub-micrometer resolution for understanding the temporal evolution of materials, including catalyst layers and membranes.
Detecting Solid Oxide Fuel Cell Stack Failure from Impedance Spectroscopy Using Machine Learning
Authors: Le Giang Tra , Adler Stuart B.
Published: December 2020

Solid oxide fuel cells (SOFC) offer great potential for efficient use of renewably-generated storage fuels. However, commercialization of SOFCs is currently limited by a lack of long-term durability. This work explores the potential of using electrochemical impedance spectroscopy (EIS) as in-situ diagnostic of SOFC stack and system health based on machine learning. A multi-physics 2D/3D-model of SOFC, operating with humidified hydrogen or natural gas fuel, is used to simulate impedance data at various nominal operating conditions. The model is also used to simulate impedance responses under different critical failure modes, such as uneven fuel distribution that leads to high local fuel utilization, electrode delamination or deactivation. Based on impedance simulations, classification models are synthesized to recognize patterns and distinguish different degradation mechanisms. Based on these models, we believe that impedance measurements can provide better indications of SOFCs system health compared to polarization curves.
Surface and Grain Boundary Effect in the Local Ionic Transport of (La,Sr)(Co,Fe)O3 Observed By in Situ Scanning Probe Microscopy
Authors: Kang Hung-Sen , Barkhordarian Orbel , Lee Min Hwan
Published: December 2020

Ionic transport in solid oxides lays the fundamentals of solid-state electrochemical energy and sensor devices. The transport is understood as a thermally activated hopping of point defects (i.e. oxygen vacancies), and its kinetics is highly dependent upon the bonding state of the ionic species with their surrounding lattice environment. While the heterogeneous ionic transport in polycrystalline oxides has been studied for decades, the exact role of interfaces and surfaces in the transport is still an open question.

In this presentation, we report our recent effort to directly observe the ionic transport in (La,Sr)(Co,Fe)O3 (LSCF), the most widely used cathode material for intermediate temperature solid oxide fuel cells, by the use of Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (CAFM). By providing a positive bias to the tip-LSCF contact in a CAFM mode, oxygen vacancies are generated via oxygen evolution reaction and the amount of newly formed oxygen vacancies are quantified by measuring the total charge transferred during the bias application. Subsequently, the evolution of charge distribution (and thus the distribution of oxygen vacancies) are observed by KPFM at various temperatures. The resulting KPFM maps were analyzed to gauge the heterogeneous ionic transport, in particular, around the grain boundary (GB) areas, and the effective ionic diffusivity within each grain and across GBs were to quantified. From this practice, a direct observation of charge transport was made to confirm the ionic diffusion across GBs is indeed much slower than those within each GB, and the effective resistance in ionic transport through GB was quantified.

In addition, 3D KPFM maps were also acquired by an in situ etching with a diamond-coated tip, providing the charge distribution map with depth. From this, it was directly observed that the ionic transport along the surface (~5 nm) is significantly higher than the transport through the interior of a grain. In combination with a simplified Monte Carlo simulation, the ionic diffusivity and its activation energy were quantified for both surface and bulk diffusion, respectively.

The authors acknowledge the support by U.S. National Science Foundation CAREER Award (DMR 1753383).
Low-Temperature Operation of CeO2-ZrO2-Based Oxygen Storage Materials
Authors: Sugawara Yoko , Oikawa Itaru , Takamura Hitoshi
Published: December 2020

CeO2-ZrO2-based oxides are widely used in automobiles to remove harmful components in exhaust gas. Ce0.5Zr0.5O2 (CZ55) shows an excellent oxygen storage capacity (OSC); however, it is difficult to keep its OSC at low temperatures such as 400 °C. This is because of limited oxygen transport in this temperature range. Our previous research revealed that the addition of CoFe2O4 (CFO) was effective to improve its OSC at low temperature. The purpose of this study is to clarify the role of CFO on the phases present and OSC properties including surface kinetics of CZ55. CFO-added CZ55 was prepared by Pechini and solid-state reaction techniques. OSC was evaluated by thermogravimetric analysis (TGA) at 400°C in 5%H2-Ar and synthetic air. Surface exchange reaction rates were analyzed by a pulse isotope exchange (PIE) technique. CFO was found to be soluble in CZ55 up to 5 vol%. The 5 vol%CFO-added CZ55 showed an excellent OSC at 400 °C. The activation energy of surface exchange kinetics was also affected by CFO addition.
(Invited) Switching on Electrocatalytic Activity for Synthetic Fuel Production
Authors: Irvine John T.S.
Published: December 2020

The greatest challenge facing Solid oxide cells (SOC), in both fuel and electrolysis cell modes (i.e SOFCs and SOECs) is to deliver high, long-lasting electrocatalytic activity while ensuring cost and time-efficient electrode manufacture. Ultimately, this can best be achieved by growing appropriate nanoarchitectures under operationally relevant conditions, rather than through intricate ex situ procedures.

In our approach, metal particles are grown directly from the oxide support though in situ redox exsolution. We demonstrated that by understanding and manipulating the surface chemistry of an oxide support with adequately designed bulk (non)stoichiometry, one can control the size, distribution and surface coverage of produced particles. We also revealed that the emergent particles are generally epitaxially socketed in the parent perovskite which appears to be the underlying origin of their remarkable stability, including unique resistance of metal particles to agglomeration and to hydrocarbon coking, whilst retaining catalytic activit.

Operando redox treatments yield emergent nanomaterials at potentials in excess of 2V. Here we apply this technique to drive steam, CO2 and coelectrolysis processes at emergent metals and alloy particles.
(Invited) Epitaxial Thin Films of Solid-State Battery Material
Authors: Takada Kazunori , Ohnishi Tsuyoshi
Published: December 2020

Solid-state batteries are regarded as next-generation batteries, which will play important roles in the coming low-carbon society; however, they have been suffering from their low power densities. Although low ionic conductivities of solid electrolytes had been the reason for the low power densities, intense studies have given solid electrolytes with high ionic conductivities: The highest conductivity exceeded 10−3 S cm−1 in 1990s and has reached 10−2 S cm−1 recently among sulfides. These conductivities are comparable to, or higher than, those of organic-solvent liquid electrolytes; however, even such high conductivities do not lead to high power densities without fast ionic conduction at the interfaces between the battery materials. In spite of the importance, studies on interfacial transport phenomena are still pioneering stage. For example, although high interfacial resistances between high-voltage cathodes and sulfide solid electrolytes have successfully reduced [1], mechanism of the high interfacial resistance is still in an argument; and although oxide systems have been suffering from high grain boundary resistance [2], origin of the grain boundary resistance is still unclear.

Thin-film systems are ideal for such fundamental studies on the interfaces owing to their simple geometry, in which the interface can be a plane, and the ionic conduction can be regarded as one-dimensional. The thin films should be single crystal with controlled crystal orientation in order to construct interfaces formed between defined crystal planes and free from any defects including grain and domain boundaries.

We have been focusing our attention on making such thin films by epitaxial growth. We have successfully formed some battery materials into single-crystal-like thin films with controlled crystal orientation [3–5]. An epitaxial film of perovskite-type solid electrolyte shows the influence of domain boundaries on ionic conduction, while anisotropic ionic conduction expected in LiCoO2 is clearly observed in a high-quality epitaxial film for the first time.

References

[1] N. Ohta, K. Takada, L.Q. Zhang, R.Z. Ma, M. Osada, and T. Sasaki, Adv. Mater., 18, 2226 (2006).

[2] Y. Inaguma and M. Nakashima, J. Power Sources, 228, 250 (2013).

[3] K. Nishio, T. Ohnishi, K. Akatsuka, K. Takada, J. Power Sources, 247, 687 (2014).

[4] T. Ohnishi, K. Mitsuishi, K. Nishio, and K. Takada, Chem. Mater., 27, 1233 (2015).

[5] K. Okada, T. Ohnishi, K. Mitsuishi, and K. Takada, AIP Advances, 7, 115011 (2017).