bluuebunny/crossref_metadata_2025 huggingface dataset:
Cascade Catalysis Systems That Use a 3-Terminal Tandem Architecture
Authors: Salazar Matthew , Greenaway Ann L , Warren Emily L. , Houle Frances
Published: August 2024

The 3 terminal tandem (3TT) photovoltaic architecturea is ideal for driving cascade catalysis systems for conversion of CO2 into more complex products because it provides the flexibility to hold 2 different catalytic regions at different potentials, optimized to drive sequential reaction steps. In this work, we explore how this architecture can be adapted to heterogeneous CO2 reduction using Ag and Cu catalyst regions coupled by diffusion within the boundary layer adjacent to the electrodes using stochastic kinetics simulations. The goal is to evaluate the geometric and voltage requirements of the two parts of cascade, and identify useful layouts. The calculations take into account the full chemistry of the interfacial reactions as well as that of the electrolyte, providing insights to how the two catalytic regions interact. We anticipate that the resulting model will provide a platform for generalizing cascades to other catalyst systems involving operation at 2 different voltages. a Warren et al, ACS Energy Lett 5 (2020) 1233.
Drivers of Membrane Fouling in the Non-Aqueous Vanadium Acetylacetonate Redox Flow Battery
Authors: Rungta Rohit , Monroe Charles W.
Published: August 2024

Due to their unique advantages in terms of long cycle life and modular design, redox flow batteries (RFBs) are being developed to load-level and peak shave energy from intermittent sources such as wind and sunlight. RFBs have yet to meet the stringent cost requirements needed to achieve broad market penetration, however. The second largest cost associated with state-of-the art RFBs after the electrolyte itself is the ion-exchange membrane, which accounts for 30% of the total cell cost [1]. Porous separators provide a pathway to substantially decrease the cost of RFBs, but long-term performance has been difficult to assess due to the coupling of electrolyte degradation, self-discharge, and membrane fouling. This study applies an adaptive observer model to estimate crossover from the open-circuit voltage relaxation of RFB cells, providing detailed information that can be used to decouple membrane fouling from electrolyte degradation by side reactions.

For this study the nonaqueous V(acac)3 (vanadium acetylacetonate) electrolyte chemistry [2] is used. Because the RFB cell reaction is based on an electrochemical disproportionation of the neutral V(acac)3 complex, crossover of the active species in this system only results in reversible self-discharge.

A novel set of 'canary cell' experiments unequivocally point to membrane fouling as the predominant factor that drives permanent cell degradation. An adaptive observer [3] is used to monitor the crossover rate, which is a proxy for membrane porosity, during self-discharge experiments where the cell is fully charged and the voltage is monitored during an open-circuit relaxation. Figure 1 shows that the porous Daramic separator starts off with ideal Fickian behavior because crossover is a linear function of the state of charge. Over time, however, the cell deviates, with active-species crossover becoming non-Fickian as the membrane fouls. The mass transfer coefficient (determined by the slope of the curve) decreases with exposure to current. It is hypothesized that pore clogging is responsible for this decreasing mass transfer coefficient, and in turn the diminution of cell performance. Deconvoluting membrane and electrolyte processes is a crucial step to determine the stability and long-term viability of RFB electrolyte systems.

References

[1] J. Noack, L. Wietschel, N. Roznyatovskaya, K. Pinkwart, and J. Tübke, "Techno-Economic Modeling and Analysis of Redox Flow Battery Systems", Energies, 9 (8), Aug. 2016.

[2] Q. Liu, A. E. S. Sleightholme, A. A. Shinkle, Y. Li, and L. T. Thompson, "Non-aqueous vanadium acetylacetonate electrolyte for redox flow batteries", Electrochem. Commun., 11 (12), Dec. 2009.

[3] P. Ascencio, K. Smith, C. W. Monroe, and D. Howey, "Adaptive Observer for Charge-State and Crossover Estimation in Disproportionation Redox Flow Batteries undergoing Self-Discharge", American Control Conference (ACC), Jul. 2019.

Figure 1
(Invited) Recent Progress in Organic-Based Aqueous Flow Batteries
Authors: Aziz Michael J.
Published: August 2024

We have developed high performance flow batteries based on the aqueous redox behavior of small organic and metalorganic monomers composed of earth-abundant elements. These redox active materials can be inexpensive and exhibit rapid redox kinetics and high solubilities, potentially enabling rapid scaling of flow batteries at reduced cost. Adequate molecular lifetime has been one of the most challenging requirements to satisfy. We have shown that the amount of lost capacity is determined by the molecular calendar life, which can depend on state of charge, but is independent of the number of charge-discharge cycles imposed. I will discuss recent progress in molecule development and in measuring extremely small capacity fade rates and will discuss how an understanding of molecular decomposition mechanisms has permitted us to design molecules with decadal projected lifetimes and even to reverse capacity fade by recomposing decomposed molecules within the functioning battery electrolyte.
Importance of Controlling Cycling Conditions to Improve the Lifetime of Anthraquinone-Based Negolytes with a Potentially Low Cost of Manufacture
Authors: Vallem Veenasri , Hamedi Amir Sina , Beh Eugene S. , Bahari Meisam
Published: August 2024

Organic redox flow batteries (RFB) in general and anthraquinones in specific have shown a great promise for developing cost-effective alternatives to vanadium RFBs. Two main hurdles, however, have been the fast fade rate and a high estimated cost of manufacture (COM) that have slowed down the scale up of organic RFBs. In this study, 1,8-dihydroxy-2,7-dicarboxymethyl-9,10-anthraquinone (1,8-DCDHAQ), 1,5-dihydroxy-2,6-dicarboxymethyl-9,10-anthraquinone (1,5-DCDHAQ) and 1,3,5,7-tetrahydroxyanthraquinone (THAQ) have been explored. These negolytes are expected to have a reasonably low COM due to their simple synthesis route. Additionally, these electroactive species have a low fade rate. Nevertheless, the fade rates are not adequately low for scaleup and commercialization purposes. Therefore, the effect of various factors including the electrolyte flow rate, cutoff voltages, SOC limits, and OH- concentration on the cycling performance have been explored in order to further reduce the fade rate.

Our experimental analysis suggests that: (1) the electrolyte flow rate and the extent of mixing in the electrolyte reservoir may lead to inaccurate capacity utilizations and fade rates, (2) increasing the OH- concentration significantly lowers the fade rate and the effect continues even at concentrations higher than 1.0 M, (3) choosing an unnecessarily low discharge cutoff voltage has a detrimental effect on the fade rate of anthraquinones, (4) SOC limit is a very important tool that significantly lowers the fade rate. Through controlling these cycling conditions, the lifetime can be improved by at least a factor of 10. Under properly chosen conditions, the fade rate of 1,5-DCDHAQ and THAQ remains < 0.001%/day (< 0.4%/year). To further verify the effect of the operating conditions, cyclic voltammetry and HPLC techniques were used to identify and/or characterize the side products in the electrolyte. COM of 1,5-DCDHAQ and THAQ at scale are estimated to be 27.99 and 47.44 $/kAh (or 24.13 and 37.95 $/kWh), respectively. 1,8-DCDHAQ and 1,5-DCDHAQ are expected to have a similar COM.

Due to the expected low COM for the abovementioned anthraquinones and their very low fade rate under optimum cycling conditions explored in this study, these molecules now present a distinctive prospect for developing and commercializing an affordable and long lifetime organic RFB chemistry.
Cu/F Dual-Doping on the Ni–Mn Based Layered Oxide As Cathode Material for Sodium-Ion Batteries
Authors: Chen Hsiang Jung , Chen Han-Yi
Published: August 2024

As demands for energy storage are ever-increasing, sodium ion batteries (SIB) have been widely conducted for superior electrochemical performance and reduction in cost compared to lithium ion batteries (LIBs), one of the most commonly used energy storage devices nowadays. Among all the parts in batteries, cathode materials play a crucial role with regard to performance. Here, layered transition metal oxides (LTMOs) (NaxTMO2, TM = Cu, Mn, Fe, Ti, Co, Cr, Ni, etc.) have kept catching researchers’ eyes due to their mature developments in commercial LIBs over decades.

P2-type Ni/Mn-based LTMOs (such as Na0.67Ni0.33Mn0.67O2, NNMO) exhibit high theoretical specific capacity (~173 mAh g−
1) with environmentally friendly and cheap elements. However, they show limited stability upon charging over 4.2 V, directly restricting their energy density and lowering operating voltage. Besides, disadvantages such as poor rate performance and air/moisture sensitivity are remaining improvements for commercialization. Hence, our study mainly focuses on improvements for shortages of NNMO by applying a facile cation-and-anion co-doping strategy. Via transition metal Cu ion doping, the cycling stability of NNMO can be improved without sacrificing too much capacity, and the air stability can also be improved. In addition, F doping to replace oxygen can further enhance the structural stability and increase the rate performance by modifying interlayer spacing of the layered structure. A facile sol-gel method with heat treatment is used to synthesize cation-and-anion co-doped NNMO. The material characterization shows successful synthesis after cation and anion doping. In addition, the long cycle test shows that capacity retention increases from ~50% to ~90% over 100 cycles after Cu doping. The specific discharge capacity also increases from ~110 mAh/g to ~130 mAh/g at 0.1C with a slight increase in cycle retention from ~75% to ~77% after F doping. Also, the capacity at 20C could be maintained at ~50 mAh/g, around 45% of the initial capacity at 0.1C. The detailed charge storage mechanism will be studied by applying operando X-ray absorption spectroscopy and ex-situ X-ray photoelectron spectroscopy. As for the moisture sensitivity part, the XRD spectra indicate that no noticeable structural changes or impurity formation occurred after air exposure for one month, showing good air stability. Furthermore, operando XRD is conducted to confirm structural reversibility during charging and discharging.

In summary, by applying a simple Cu/F co-doping strategy, Na0.67Ni0.13Cu0.20Mn0.67O2-xFx exhibits sufficient cycle stability for over 100 cycles as well as excellent rate capability even at a high current density of 20C, which proves itself a promising candidate as high-performance cathode material in SIBs. In addition, the cheap and environmentally friendly elemental usage (Ni, Mn and Cu) and air-stability enhancement also increase possibility of this material for large-scale energy storage application in industry.
High Electrocatalytic Activities of the Electrochemically Exfoliated Graphene Deposited Carbon Paper Electrodes for Vanadium Redox Flow Batteries
Authors: Jae Ho Jo , Paick Jihun , Lee Doohwan
Published: August 2024

The cost-effective and process-efficient preparation of highly electrocatalytic carbon electrodes on a large scale is crucial for enhancing the competitiveness of vanadium redox flow batteries (VRFBs). In this work, electrochemically exfoliated graphene oxides (Exf-GOs) are prepared form graphite foil at large scale with a multi-electrodes equipped continuous Exf-GOs production system. The Exf-GOs are deposited on the activated carbon paper (A-CP) substrate by a direct infiltration-deposition approach. Collective electro-kinetics analysis applying cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed that the resulting Exf-GO/A-CP electrodes exhibit two orders magnitude greater intrinsic electrocatalytic activities than the A-CP electrode for the VO2+/VO2
+ redox reactions. A trade-off between the Exf-GO deposition amount and the open pore volume through the Exf-GO/A-CP electrodes was found that have critical impacts on the overall electro-kinetic performance of the electrodes. Compared to the A-CP electrode, the Exf-GO/A-CP electrode provided the VRFB with more than two-fold enhancements in the energy storage capacity and at least 10 – 15 % higher voltage and energy efficiencies. The results collectively demonstrate the high effectiveness of the Exf-GO/A-CP electrodes for VRFBs that can be prepared cost and process efficient approach at large scales.
Modeling of Lithium-Flow Batteries with Aqueous Electrolyte
Authors: Law Destiny , Andrei Petru , Liu Shengyi , Goss Roger
Published: August 2024

Flow batteries with aqueous electrolyte at the cathode are safe, low-cost and ecofriendly energy storage systems. When the aqueous cathode is coupled with a Li-metal anode with organic electrolyte, these batteries have extremely high energy densities (over 4,000 Wh/Kg), which makes them attractive not only for grid applications (where flow batteries are often used) but also in maritime applications such long endurance surface vessel systems and wave gliders [1-4]. In this presentation, we derive the mathematical model for lithium-flow batteries and use this model to predict the performance of the batteries under different discharge conditions, cathode microstructures, water flow velocities, etc. The results are then compared to experimental data already available in the literature. The mathematical model is based on coupling the flow equations (Navier-Stokes) with electrochemical equations for reaction rates and using average microscopic models for the cathode. For instance, Fig. 1 shows the voltage of a flow battery as a function of time for different water velocities in a flow battery simulated by solving the above model. For low water velocities, the water is not able to provide enough oxygen in the cathode and the voltage of the battery collapses after a few seconds. However, as long as the water velocity is above approx. 1.2 cm/s, the battery will have enough oxygen to operate continuously; in this case, the higher the flow of the water, the higher the voltage of the battery in the stationary state will be because of lower overpotential losses. In these simulations, the anode contained Li-metal. The cathode had a length of 1 cm (measured in the direction of water flow) and a thickness of 100 μm. The cell was discharged at a small rate of 0.01 mA/cm2. The incoming water had an oxygen concentration of 5 mg/l (which is equal to the oxygen concentration in seawater) and was pumped through the cathode at different velocities. A detailed derivation of the mathematical model and more simulation results and predictions will be presented at the meeting.

References:

[1] R. E. Davis and J. T. Sherman, “Evaluating a Lithium-Seawater Battery on Gliders,” J. Atmospheric Ocean. Technol., vol. 34, no. 5, pp. 1175–1182, May 2017, doi: 10.1175/JTECH-D-16-0151.1.

[2] X. J. Chen, A. Shellikeri, Q. Wu, J. P. Zheng, M. Hendrickson, and E. J. Plichta, “A High-Rate Rechargeable Li-Air Flow Battery,” J. Electrochem. Soc., vol. 160, no. 10, pp. A1619–A1623, Jan. 2013, doi: 10.1149/2.012310jes.

[3] J. P. Zheng, P. Andrei, M. Hendrickson, and E. J. Plichta, “The Theoretical Energy Densities of Dual-Electrolytes Rechargeable Li-Air and Li-Air Flow Batteries,” J. Electrochem. Soc., vol. 158, no. 1, pp. A43–A46, 2011, doi: 10.1149/1.3515330.

[4] B. Horstmann, T. Danner, and W. G. Bessler, “Precipitation in Aqueous Lithium–Oxygen Batteries: a Model-Based Analysis,” Energy Environ. Sci., vol. 6, no. 4, pp. 1299–1314, 2013, doi: 10.1039/C3EE24299D.

Figure 1
Advancing Low-Cost Iron Redox Flow Batteries for Grid Storage
Authors: Jayathilake Buddhinie Srimali , Ivanovskaya Anna N. , Overland Alexandra E. L. , Chandrasekaran Swetha , Clemens Auston L.
Published: August 2024

Iron-based redox flow batteries are promising and low-cost energy storage technologies for grid level showing the potential to meet DOE’s cost targets LCOS, $0.05/kWh due to its natural abundancy and eco friendliness. Iron deposition process has a parasitic hydrogen evaluation reaction (HER) controlling the storage capacity and efficiency. HER reaction imbalances the electrolyte composition and causes durability issues. Our present study shows how the performance of the iron flow battery can be increased by introducing advanced 3D electrodes and engineered electrolytes.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Funding was provided by Lawrence Livermore National Laboratory Directed Research and Development (LDRD) Grant 22-DR-014. IM release number: LLNL-ABS-858432
Development of Next Generation Membranes for PEM Water Electrolysis in AGC
Authors: Hayabe Shintaro , Salem William , Sawada Toshiaki
Published: August 2024

AGC’s FORBLUETM product family has over 70 years of experience in ion-exchange membranes (IEMs). S-SERIES, a FORBLUETM member, is a per-fluorinated sulfonic acid polymer (PFSA) membrane utilized in various electrochemical devices and industrial electrolysis. AGC’s IEM technology had a lot of experience in the chlor-alkali application and was further developed for the PEM water electrolysis industry.

AGC R&D has developed S-SERIES membranes with a smaller thickness, improved reinforcement, and high ion exchange capacity (IEC) that enhanced not only an electrochemical performance but also dimensional stability.

A membrane electrode assembly (MEA) was fabricated using a developed membrane with high IEC polymer (IEC 1.25 meq/g). As a result, IV characterization of a single cell with 25 cm2 electrode area at 80°C showed a significant voltage reduction compared to a commercial membrane in the PEM water electrolysis market. In addition, H2 crossover during the electrolysis was evaluated in a single cell with a 25 cm2 electrode area at 80°C and ambient pressure, and the H2 concentration in O2 at the anode side was compared at a current density of 1.0 A/cm2. The developed membrane showed 0.3 vol% H2 crossover, whereas the commercial membrane showed 0.5 vol%.

Furthermore, next-generation membranes with gas recombination catalysts (GRC) and radical scavengers leading to lower gas crossover and higher chemical stability are under development. Recently, high-pressure electrolyzers have been getting more attention and the increase of H2 crossover is a concern against the lower explosive limit (LEL) for hydrogen in oxygen. In general, PFSA membranes are considered to have high chemical durability, however, F ion release is observed, that indicate that this PFSA polymer is attacked by OH radicals generated in the PEM water electrolysis system. AGC has been investigating the application of GRC and radical scavengers to the newly developed membranes. It was evaluated in a single cell with 25 cm2 electrode area at 80°C and 2.0 A/cm2. As a result, the H2 crossover and F ions release rate (FRR) were reduced compared to the membrane without both additives. The data will be presented on these improved performances.
(Invited) Breaking the Activity-Durability Tradeoff of Fe-N-C Fuel Cell Catalysts Via Controlling Thermal Activation Atmosphere
Authors: Zeng Yachao , Zachman Michael J. , Cullen David A. , Myers Deborah J. , Wu Gang
Published: August 2024

Fe-N-C catalysts, the most promising platinum group metal (PGM)-free oxygen-reduction catalysts, often simultaneously contain pyrrolic N- (S1) and pyridinic N (S2) -coordinated FeN4 sites. These two types of active sites show significantly different intrinsic activity and stability. S1 sites are more active but less stable compared to S2 sites. Designing a Fe-N-C catalyst, which exclusively contains active S1 sites with enhanced intrinsic stability, is highly desirable to break the activity-stability trade-off. Herein, we report a Fe-N-C model catalyst that solely comprises S1 sites prepared by adding H2 in the pyrolysis atmosphere (i.e., 10% H2/Ar). A membrane electrode assembly (MEA) with the Fe-N-C cathode demonstrated compelling activity and generated a current density of 50.8 mA cm−2 at 0.9 ViR-free (H2-O2) and 211 mA cm−2 at 0.8 V (H2-air), which have significantly exceeded the U.S. DOE 2025 targets. The highly active Fe-N-C catalyst also demonstrated improved stability during life tests and accelerated stability tests (ASTs). The knowledge obtained from experimental and theoretical results elucidates that the FeN4 site formation process can be controlled by thermal activation atmospheres, which is essential to breaking activity-stability trade-off and design viable Fe-N-C catalysts with adequate activity and stability for proton exchange membrane fuel cells.
A Paper-Based Microfluidic Methanol Fuel Cell Catalyzed By Ni-Co@LTA Electrocatalyst for Micro-Nano Power Systems
Authors: Baruah Sarmistha , Kumar Akshai , Peela Nageswara Rao
Published: August 2024

Sustainable energy generation has recently gained popularity due to the rising energy demand and environmental concerns caused by conventional non-renewable energy sources. In the context of portable electronics, and microsystems all would require fully integrated, dependable power generation. In this regard, paper-based microfluidic fuel cells (PMFC), have drawn significant attention. By utilizing the inherent properties of paper substrate and microfluidic reactant streams, this fuel cell device takes away the requirement of any membranes or external pumps that are necessary for conventional FCs. In co-laminar flow, where PMFCs work, a unique diffusive mixing area serves as a pseudo-membrane by preventing the convective mixing of two reactants. The reactants flow by capillary action with the aid of an absorbent pad. While the ions transport across the channel through the mixing zone. This not only makes the pumping of fluids into paper-based systems simpler, but also provides numerous other benefits such as cost-effectiveness, simplicity in manufacturing, ease of disposal, and portability over traditional FCs. In this work, we synthesized a Ni-Co catalyst encapsulated within zeolite 4A (also known as LTA) via a hydrothermal synthesis route. The resulting catalyst exhibited better catalytic activity of 12.1 mA cm-2 at 1.12 V vs Ag/AgCl and retained remarkable stability (~77%) even after 1000 cycles CV test in 0.1 M KOH + 1 M methanol. By utilizing this catalyst as anode and Pt/AC (5 wt%) as cathode, we demonstrate a Y-shaped membraneless PMFC using Whatman filter paper grade 41 as paper substrate. It has been shown that the device can deliver power densities in the range of 2 - 10 mW cm-2 (Fuel: methanol, Oxidant: KMnO4), and can retain power output for at least 30 min. Additionally, the power of the cell can easily be raised by connecting two or more cells in series, making these PMFCs suitable for micro/nano power generation systems.

Keywords: Fuel cell, Microfluidic, Paper substrate, Co-laminar flow, Zeolite 4A.
Multi-Substituted Phosphonated and Sulfonated Polymer Materials: Characterization and Blends with Basic Polymers
Authors: Stigler Theresa , Byun Jiwon , Thiele Simon , Kerres Jochen Alfred
Published: August 2024

The growing demand for energy, limited resources, and climate warming call for alternative sustainable energy production. A promising candidate is the proton-exchange membrane fuel cell (PEMFC) using a proton conducting polymer as an electrolyte membrane. The most common proton-exchange membranes are based on sulfonated polymers, such as Nafion®. Since their proton conduction is driven by hydronium ions (H3O+) and hence require water, the operating temperature is limited to 100°C. Unlike in sulfonated polymer materials, the proton conduction in materials with phosphonic acid groups occurs via a hopping process and does not require water.1 This study introduces a highly substituted phosphonated and sulfonated polymer based on poly(pentafluorostyrene), which makes the material adaptable in anhydrous and hydrous operating conditions since the phosphonic acid and sulfonic acid units can conduct cooperatively. The phosphonic acid group is introduced via the nucleophilic aromatic substitution Michaelis-Arbuzov reaction. The Para-Fluoro-Thiol reaction was used to introduce sulfonic acid groups into the polymer backbone. In the past, both reaction steps were well investigated.2,3 The highly substituted polymer material was blended with a basic polymer to circumvent water solubility and investigated according to its proton conductivity, thermal stability, and mechanical properties.

(1) Kumar, A. J. Mater. Chem.
A
2020, 8 (43), 22632–22636. DOI: 10.1039/d0ta07732a.

(2) Atanasov, V.; Oleynikov, A.; Xia, J.; Lyonnard, S.; Kerres, J. Journal of Power Sources
2017, 343, 364–372. DOI: 10.1016/j.jpowsour.2017.01.085.

(3) Delaittre, G.; Barner, L. Polym. Chem.
2018, 9 (20), 2679–2684. DOI: 10.1039/c8py00287h.
Colloidal Nafion in Liquid Media: Insight from SANS Analysis and Molecular Dynamics Simulations
Authors: Klein Jeffrey Michael , Welch Cinthia , Ponnurangam Sathish , Tarokh Atefeh , Karan Kunal , Hawley Marilyn , Sokolova Anna , Yim Sung-Dae , Hjelm Rex , Kim Yu Seung
Published: August 2024

Colloidal Nafion™ morphology in liquid media plays a critical role in determining the electrode performance of fuel cells and electrolyzers. In this presentation, we demonstrate that commonly reported, cylindrical morphologies of Nafion in liquid media are not ubiquitous among Nafion dispersions and assuming such may provide inaccurate information.1 Here we compare colloidal Nafion™ morphology in N-methyl-pyrrolidone (NMP) and water using small angle neutron scattering (SANS) and all atomistic molecular dynamics simulations (MD).2 Our SANS analyses using model-dependent and model-independent techniques combined with MD simulations demonstrated highly gel-like particles best describe Nafion particles in NMP, which is in stark contrast to the commonly assumed cylindrical morphology. In high dielectric constant dispersants such as water, the cylindrical morphology is a feasible choice to describe the scattering data, however, the particle radius is much lower than previous report (R = 10 Å). MD simulations support the SANS analysis and show that the sulfonic acid groups are fully dissociated and strongly solvated on the outer wall of the particle suggesting that the structure is driven by hydrophobic interactions.

References

Aldebert, B. Dreyfus, G. Gebel, N. Nakamura, M. Pineri, F. Volino, Macromolecules, 19, 2651-2653 (1986).

Jeffrey M. Klein, Cynthia Welch, Sathish Ponnurangam, Atefeh Tarokh, Kunal Karan, Marilyn E. Hawley, Anna Sokolova, Sung-Dae Yim, Rex P. Hjelm, Yu Seung Kim,
ACS Macro Letters, 12, 1648-1653 (2023).
Raman Microscopic Investigation of Organic Solvent Concentration Profiles in Proton Exchange Membranes and Their Permeability
Authors: Götz Carina , Komma Miriam , Dworschak Dominik , Thiele Simon , Boehm Thomas
Published: August 2024

Direct alcohol fuel cells (DAFCs) suffer from severe problems related to the employed polymer electrolyte membranes, such as fuel crossover, resulting in low faradaic efficiency and performance of the fuel cell.1,2,3 We introduce a 3D-printed diffusion cell setup, which is capable of determining the interaction of membranes and organic solvents via confocal Raman microscopy.4 Thus, the suitability of proton exchange membranes (PEMs) for usage in DAFCs can be evaluated. In this setup, the membrane is clamped between two flow channels, similar to the flow field plates of a fuel cell. The donor channel is filled with an organic solvent-water mixture, and the receptor channel is filled with water. Depth scans through the membrane and the two flow channels provide concentration profiles of the organic solvent within the membrane, which are used to calculate membrane properties such as permeability and sorption coefficient (see Fig. 1).

In this study, the membrane-solvent interactions between standard unreinforced and composite PEMs and various organic solvent solutions, such as 2-propanol, acetone, and ethanol, are investigated. All membranes analyzed show a preference for organic solvent absorption from 1 M solutions, with sorption coefficients ranging from 2.5 to 3.0. In addition to the absorption, the organic solvents permeate through the membrane. The corresponding permeabilities range from 10-5 to 10-4 cm² s-1. However, the permeabilities of the membranes for different solvents do not scale with their sorption coefficients, in contrast to the membrane swelling.

This diffusion cell setup is an accessible and fast pre-screening method, which can enhance the development and evaluation of new ion exchange membranes for use in DAFCs and related applications.

References:

H. R. Corti, E. R. Gonzalez, Direct Alcohol Fuel Cells, Springer Netherlands, Dordrecht 2014.

S. Deabate, R. Fatnassi, P. Sistat, P. Huguet, J. Power Sources
2008, 176, 39.

P. Scharfer, Zum Stofftransport in Brennstoffzellenmembranen, Karlsruhe 2009.

C. Götz, M. Komma, D. Dworschak, S. Thiele, T. Böhm, Adv. Mater. Interfaces
2023.

Figure 1
(Invited) Engineering Nanocomposite Substrates for Metal Deposition
Authors: Liu Ping
Published: August 2024

Reversible metal plating is at the heart of aqueous based energy storage. Since virtually all metal anodes, e.g., Fe, and Zn, operate outside the stability window of water, it is thus essential to minimize their surface area by controlling the nucleation and growth during deposition and the pit formation during stripping.

While epitaxial growth has shown promise as exemplified by the horizontal zinc deposition on graphene, an approximate heteroepitaxy, we will focus our effort in developing a nanocomposite substrate that promotes uniform nucleation sites and fast surface transport. The strategy is potentially highly scalable to address the need for large scale storage. Recently, we have shown that a nanocomposite substrate can induce single crystalline Li growth. By reacting FeF3 with Li, a nanocomposite of Fe and LiF is formed which features Fe nanoparticles of < 2 nm in size uniformly distributed in a matrix of LiF. Despite the global lithiophobility of the substrate, nano Fe domains provide energetically uniform nucleation sites for Li deposition while LiF enables rapid surface transport. Corporative merging of neighboring seeds lead to the formation of single crystalline Li. Unlike single crystal substrates, the nanocomposite features uniformly distributed, energetically equivalent sites for nucleation.

We have adopted a similar strategy for Fe and Zn deposition. Preliminary results show that significantly improved macroscopic uniformity is achieved with the nanocomposite substrate. We will discuss materials requirements for operation in an aqueous environment and the general applicability of the approach for other materials.
HE3DA Thick Tablet Electrode Architecture - Large Lithium Cells for Energy Storage
Authors: Prochazka Jan
Published: August 2024

Large energy storage applications require ultimate safety, economical manufacturing and full recyclability of the batteries. HE3DA lithium battery technology platform with 3-D electrode architecture meets all these demands. The 3D cell construction, together with ceramic composite separator increases battery safety by orders of magnitude. Easy disassembling and separating of the materials after the life end of the battery makes recycling a profitable secondary source of battery materials. Recycling of this type of battery already meets parametres set for 2050.

Main features of this technology and 3D cell parameters produced in the commercial production will be discussed. Advantages of these cells in large energy storage units will be demonstrated.

Figure 1
Diketopyrrolopyrroles As Performance Enhancing Additives for Lithium-Sulfur Batteries
Authors: Searle Joanne , Denison Benjamin , Malagreca Ferdinando , Kibler Alexander , Saywell Alexander , Walsh Darren Anthony , Johnson Lee R , Newton Graham
Published: August 2024

Although the lithium-ion battery (LIB) has been instrumental in global electrification, more premium applications (such as electrification of aircraft) require capacities and performance beyond the capabilities of traditional LIB chemistries[1]. Lithium-sulfur (Li-S) batteries are a front runner among next generation battery technologies thanks to their very high theoretical capacities (1675 mAh g-1) and impressive gravimetric energy densities (2,700 Wh kg-1) [2,3]. Despite their potential, there are numerous chemical challenges (polysulfide shuttle, dendrite formation etc.) that must be overcome before widespread adoption of the technology [4]. Electrolyte additives have been explored as a means to facilitate the electron transfer reactions that occur within the cell and improve cell capacity and cyclability [5].

Diketopyrrolopyrroles (DPPs) are a class of organic π-conjugated compounds that have garnered significant interest in a variety of electrical applications, including solar cells and sensors [6]. The high electrochemical tunability, made possible through the editable organic structure, makes them suitable candidates for redox active electrolyte additives. Here, we explore DPP derivatives as a novel class of electrolyte additive for improving the cell cycling performance of Li-S batteries. A variety of electrochemical and analytical techniques have been utilised to assess the suitability of DPPs as redox active additives, building an understanding of their interactions with active materials in a Li-S cell. Galvanostatic cycling allows us to connect these electrochemical findings to cell cycling performance, where we observe a large enhancement in capacity. We also present an alternative statistical approach to cell data analysis, providing a more concrete method to assessing cycling enhancement than that shown throughout literature.

Figure 1. A box plot displaying the discharge capacities at specific cycle numbers for standard (light grey) and DPP (dark grey) cells to provide a statistical comparison.

References:

[1] T. Kim, W. Song, D.-Y. Son, L. K. Ono and Y. Qi, J. Mater. Chem. A, 2019, 7, 2942–2964.

[2] A. Fotouhi, D. J. Auger, L. O’Neill, T. Cleaver and S. Walus, Energies , 2017, 10.

[3] S. Gifford and J. Robinson, Faraday Insights, 2020, 1-5.

[4] A. Manthiram, Y. Fu, S.-H. Chung, C. Zu and Y.-S. Su, Chem. Rev., 2014, 114, 11751–11787.

[5] J. M. Cameron, C. Holc, A. J. Kibler, C. L. Peake, D. A. Walsh, G. N. Newton and L. R. Johnson, Chem. Soc. Rev., 2021, 50, 5863–5883.

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Figure 1
Electrochemical CO2 Reduction on Silver – a Perspective through Electrochemical Impedance Spectroscopy
Authors: Sivasankaran Monisha , Sorrentino Antonio , Vidakovic-Koch Tanja
Published: August 2024

Anthropogenic carbon rise in the earth's atmosphere is the leading cause towards global warming. Electrochemical CO2 reduction (eCO2RR) is one of the most promising sustainable pathways for the utilization and recycling of anthropogenic carbon. The current challenge in eCO2RR is to make the process more energy efficient and to drive the selectivity toward the desired products. eCO2RR normally takes place in parallel with hydrogen evolution reaction (HER). Additionally, dependent on catalyst material and potential different C-products can be obtained. The mechanistic understanding of the interplay between different reactions is still limited, since the involved reactions are characterized by faster kinetics and/or different adsorbed species as well as mass transfer dependences than the other ones. Moreover, we have recently shown that under dynamic conditions eCO2RR product selectivity towards CO can be tuned1. In that study, we developed a simple model and identified key kinetic parameters which govern product selectivity under dynamic conditions. The model included only the electrochemical kinetics of two parallel reactions without consideration of adsorbed species or mass transport limitations. Therefore, some of the experimental observations could not be completely explained. In such complicated cases involving different physicochemical phenomena acting in parallel at different time scales, the use of electrochemical impedance spectroscopy (EIS) to analyse the system could shed light on the understanding of the process.

In this contribution, we have developed a mathematical model which couples micro-kinetics with continuum transport. At first, the model was validated under steady-state conditions. The experiments have been performed under different conditions (mass transport and buffer concentrations) on silver rotating disk electrodes and the product distribution (H2 and CO) has been determined with the help of online gas chromatography. This model was then used to calculate EIS. Based on this approach, we present here a detailed interpretation of the EIS spectrum during eCO2RR and the features obtained at different applied electric potentials. Key insights are drawn about the role of charge and mass transport as well as adsorbed intermediates on the observed features.

References

1.Miličić, T.; Sivasankaran, M.; Blumner, C.; Sorrentino, A.; Vidakovic-Koch, T., Pulsed electrolysis: explained. Faraday Discussions 2023.
CO2 Capture By Hybrid Electrolyte Membrane Electrode Assembly
Authors: Bian Wenjuan , Zhao Zeyu , Wu Wei , Ding Dong
Published: August 2024

In the pursuit of decarbonizing transportation sectors, there has been considerable enthusiasm from both industries and academia regarding the utilization of atmospheric CO2 as a chemical feedstock. To mitigate the energy requirements associated with carbon capture, utilization, and sequestration, research efforts are focused on developing and exploring electrochemical cell technologies. Here, we present an innovative solid oxide electrochemical cell configuration featuring a hybrid electrolyte membrane electrode assembly (HE-MEA) designed for efficient CO2 capture and separation. Our approach involves optimizing the process through the tuning of electrolyte and electrode compositions and operation conditions, aiming to capture CO2 effectively under various conditions. The investigation of the cathode's working mechanism, employing advanced characterization techniques, will be presented. This study marks a significant step forward in CO2 capture, particularly at elevated temperatures, and contributes to the broader effort of advancing sustainable practices in transportation and combating climate change.
Ru Decoration By PEALD for Bifunctional Oxygen Electrocatalysis in Solid Oxide Cells
Authors: Li Haoyu , Kim Hyong June , Garcia ThomasJae , Park Geonwoo , An Jihwan , Lee Min Hwan
Published: August 2024

Solid oxide cells (SOCs) are electrochemical devices that have garnered significant attention due to their high efficiency, fuel flexibility, and reversibility for operation in both fuel cell and the electrolysis modes. However, the relatively high operating temperature (typically > 800 °C) required presents various challenges such as fast degradation, high operating costs, and slow start-up. To overcome these issues, significant efforts have been made to decrease the operating temperature, but this causes a dramatic decrease in performance due to the low catalytic activity of typical electrode materials. One strategy to increase the catalytic activity is to introduce highly active nanoparticles onto a conventional electrode backbone, but while noble metals such as Ru and Ir have been utilized as oxygen evolution reaction (OER) catalysts, their widespread application in SOECs is hindered by their high cost and limited availability.

In this presentation, we demonstrate a highly effective approach to enhance air electrode performance through the deposition of an ultrathin layer of metallic Ru, as thin as ∼7.5 Å, onto (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) using plasma-enhanced atomic layer deposition (PEALD). The Ru-decorated cell exhibited a current density of 656 mA cm–2 at 1.3 V, significantly outperforming a bare cell (440 mA cm–2 at 1.3 V). The decorated cell also showed a largely enhanced cell durability, which is ascribed to the beneficial role of SrRuO3 that emerges from the reaction between PEALD-based Ru and surface-segregated Sr species, in suppressing Sr segregation and maintaining favorable oxygen desorption kinetics. Further, the PEALD Ru coating on LSCF also reduces the resistance to the oxygen reduction reaction (ORR), highlighting the bifunctional electrocatalytic activities for reversible fuel cells. When the LSCF electrode of a test cell is decorated with ∼7.5 Å of the Ru overcoat and tested in fuel cell mode at 700 °C, this results in a current density of 656 mA cm-2 at 1.3 V in electrolysis mode and a peak power density of 803 mW cm-2, corresponding to an enhancement of 49.1% and 31.9%, respectively, compared to the pristine cell.
Microtubular Electrodes for Efficient Electrochemical CO2/CO Reduction to Value-Added Products
Authors: Rabiee Hesamoddin , Ge Lei , Zhu John
Published: August 2024

The conversion of carbon dioxide (CO2) or carbon monoxide (CO) to commodity fuels and chemicals, empowered by low-carbon electricity, has attracted much attention as an alternative to conventional routes of chemical production [1]. Numerous studies have focused on CO2 reduction to CO or formic acid and active/efficient electrocatalysts with high Faradaic efficiencies (FEs) have been developed [2]. However, CO2 reduction to higher value C2+ products needs the critical C-C coupling step, and to date, Cu has been the main electrocatalyst for this conversion [3]. Electrochemical carbon monoxide reduction (CORR) to C2+ products has advantages over electrochemical CO2 conversion (CO2RR) as issues such as carbonation, and CO2 loss during CO2RR are omitted in CORR due to the stability of CO in alkaline solutions. Facing common challenges as CO2RR, CORR suffers more from mass transport resistance and intrinsically lower aqueous CO solubility. Therefore gas-diffusion electrodes (GDEs) are desired to boost the formation of triple phases and active sites to obtain higher reaction rates.

Herein for the first time we design Cu-based HFGDEs for efficient CORR to C2+ products with ethylene as the main product. The pristine Cu HFGDEs showed low selectivity towards C2+ products. Therefore, we tuned the Cu catalyst shape morphology and orientated growth of nanocubes on the outer surface of HFGDEs by electrodeposition. Due to the efficient C-C coupling and high C2+
_selectivity of copper nanocubes with dominant Cu(100), the HFGDEs showed exceptionally high current densities in the 1.0 M KOH electrolyte, outperforming conventional GDEs tested for CORR under similar conditions. Compared with CO2RR in a bicarbonate medium, significantly higher current densities and FEs of C2+ products (>90%) and ethylene (>65%) were achieved when the HFGDE were used for CORR. Moreover, lower partial current densities of C2+ were obtained when using the hollow fibers in the non-GDE mode, confirming the significant performance of HFGDEs for achieving high-rate and selective CO reduction through maximizing triple-phase interfaces and local CO concentration. By increasing the concentration of KOH, an ethylene partial current density of 472 mA cm2- was obtained using the flow-cell reactor, indicating the promises of HFGDEs as an emerging electrode configuration for efficient CORR to C2+ products.

Figure 1
Electrochemical CO2 Reduction in the Presence of Flue Gas Impurities: Effect of NOx, SOx and O2
Authors: Van Daele Sam , Hintjes Lieven , Bohlen Barbara , Daems Nick , Breugelmans Tom
Published: August 2024

Electrochemically converting CO2 to valuable chemical products using renewable energy sources may present solutions to alter current increasing CO2 emission trends. Currently, electrolyzer research is almost exclusively done with pure CO2 streams that - in practice - would originate from carbon capture units that prevent CO2 release to the atmosphere [1]. The capture and purification steps are cost intensive processes which is why direct usage of flue gases that contain impurities is a highly interesting approach. For this reason, the performance of CO2 electrolyzers equipped with state-of-the-art Bi2O3 or Ag catalysts is investigated in this work with an impure CO2 feed stream containing SO2, NO or O2. The short-term effect of highly concentrated SO2 (10 000 ppm) and NO (8 300 ppm) impurities during CO2 electrolysis was previously described [2,3]. Our work [4] elaborates further on this matter through 20 h experiments with flue gas-like concentrations of 200 ppm SO2 or NO. The results show a stable operation without severe FE losses (remains >90%) and structural adaptations to neither Ag nor Bi2O3 by these impurities. The presence of oxygen in flue gas streams at concentrations of several percent is common and causes a major decrease in FE to the target products (CO or HCOO-) during electrolysis. This is a result of the competition between the ORR and CO2RR with the former occurring more preferentially. To overcome this, we have discovered two possible strategies, which allow high FE’s to CO2RR products even in the presence of oxygen. (1) By operating the electrolyzer at a sufficiently high overall current density, all of the O2 entering and reaching the electrode surface gets reduced, allowing the CO2RR to become the dominant reaction. Although this approach has a higher electricity penalty, the extra cost is negligible compared to the cost otherwise associated with the CO2 purification for CO2 streams with an O2 content below 3%. (2) Given that the ORR is mostly occurring at the carbon-based gas diffusion layers another approach to improve CO2RR efficiency in the presence of oxygen is to replace this conventional support with ultra hydrophobic PTFE membrane filters. Since they are inefficient oxygen reduction catalysts, CO2RR again takes up the major fraction of the applied current density. A downside of using PTFE is that an additional conductive layer is required in case the catalyst itself (e.g. for bismuth oxide) is not conductive enough. These results thus not only offer new insights into the impact of gaseous impurities during CO2 electrolysis, but also suggest a strategy to improve electrolyzer performance with O2-containing feed streams.

Bibliography

[1] Lee M.Y., Environ. Sci. and Technol.; DOI: 10.1080/10643389.2019.1631991

[2] Luc W.; JACS, DOI: 10.1021/jacs.9b03215

[3] Ko B., Nature Comm. DOI : 10.1038/s41467-020-19731-8

[4] Van Daele S ., J. Appl. Catal. B, Environ.; DOI: 10.1016/J.APCATB.2023.123345

Figure 1