bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective Non-Precious Metal Oxide Supported Carbon as a High Performance Bifunctional Electrocatalyst for All Vanadium Redox Flow Batteries
Authors: Bayeh Anteneh Wodaje , Kabtamu Daniel Manaye , Wang Chen-Hao
Published: August 2024

As one of the most promising electrochemical energy storage systems, vanadium redox flow batteries (VRFBs) have received increasing attention owing to their attractive features for large-scale storage applications. However, their high production cost and relatively low energy efficiency still limit their feasibility. One of the critical components of VRFBs that can significantly influence the effectiveness and final cost is the electrode. Therefore, the development of an ideal electrocatalyst with low cost, large active surface area, good chemical stability, and excellent electrochemical activity toward the VO2+/VO2
+ and V2+/V3+ redox reactions is essential for the design of VRFBs. Hence, we prepared a stable, high catalytic activity and uniformly distributed non-precious metal oxide nanoparticles on the surface graphene sheets via two step routes, hydrothermal followed by annealing at optimum temperature for VRFB applications. Among the samples, the prepared electrocatalyst shows the best electrochemical activity with lowest peak potential separation and highest peak current density toward VO2
+/VO2+ and V2+/V3+ redox reactions. This observation is due to the synergistic effects related to the presence of excess oxygen vacancies on the metal oxide, the high content of oxygen functional groups, and the high electrical conductivity of the graphene sheets. Hence, the prepared electrocatalyst grown on the surface of graphite felt (GF) support demonstrates the optimal electrochemical activity with the energy and voltage efficiencies of 76.8% and 80.9%, respectively, which are much greater than those of the 59.8% and 63.2% attained from pristine GF at 100 mA cm–2. Moreover, the electrode presented good stability and durability in acidic electrolyte during long-term operations for 100 cycles at a higher current density of 100 mA cm–2.
Titanium-Cerium Redox Flow Batteries for Grid-Scale Electrical Energy Storage
Authors: Xie Jing , Sankarasubramanian Shrihari , Ramani Vijay K
Published: August 2024

The development of redox flow batteries (RFBs) has gained increased attention due to the need of mitigating emission pollution from fossil fuels by developing renewable energy storage system. Among all the different types of RFBs, all vanadium one (VRFBs) are the most prevalent type because crossover contamination is avoided by using only one metal element. However, VRFBs still suffer from limitations such as low output voltage, low efficiency, and high material cost. Titanium (Ti) and cerium (Ce), on the contrary, are available in abundance and have lower cost. Moreover, the standard potential of Ti-Ce combination is much higher than that of VRFBs (1.61 vs. 1.23 V). Herein, we have studied and compared the performance of Ti-Ce RFBs with sulfuric acid (SA) and methanesulfonic acid (MSA) serving as the supporting electrolyte. We applied an asymmetric electrode configuration, i.e., carbon felt for Ti side and carbon paper for Ce side, to further promote the batteries performance. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to analyze the mass transport and reaction kinetics of the Ti-Ce system. Electrochemical impedance spectroscopy (EIS) was used to analyze the contribution of different types of polarization. Ti-Ce RFBs demonstrated an energy efficiency around 80 % at 100 mA/cm2, and excellent capacity retention.
(Invited) Development of Mildly Acidic Aqueous Zinc Batteries: Anode, Cathode, and Electrolyte
Authors: Li Xiaolin , Fayette Matthew , Lim Wonkwang , Han Hyungkyu , Grady Zane , Reed David M
Published: August 2024

Aqueous zinc batteries use earth abundant materials and has stable supply chains, making them one of the promising battery technologies for grid-scale energy storage applications. However, the limited cycle life because of the dendrite formation of zinc anodes, poor reversibility of cathodes, and consumption of electrolyte has greatly hampered its practical application. Recently, extensive research effort has been made on the development of rechargeable alkaline batteries and mildly acidic zinc ion batteries. Novel structured zinc anodes, intercalation cathode materials and new electrolytes have been developed to improve the performance. Here, we would like to present our effort towards aqueous zinc batteries under practical conditions. Zinc alloy anodes, organic cathode materials, and the use of new binders and electrolyte additives will be discussed.
Solar Flow Battery for Grid Innovation: Exploring Novel Cell Designs and Osmotically Balanced Neutral pH Electrolytes
Authors: Kim Jungmyung , Bae Dowon
Published: August 2024

The demand for clean and efficient energy with low carbon emissions has been increased continuously. In 2022, 29.9% of global electricity production came from renewable energy sources, and the UK contributed a relatively high percentage of 41.5%. However, it appears to lag behind the Nordic countries, showing an impressive 81.2% of its electricity from renewable sources. The primary hurdle to expanding the share of renewable energy is intermittency. There is a crucial need for research and development in energy storage systems to enhance this aspect. Among various renewable energy storage technologies, redox flow battery (RFB) has recently come into the spotlight because of its scalability, long-term storage capability, and fast kinetics. However, the highly concentrated acidic condition and high voltage of the conventional RFB electrolytes make applying this technology for the integration of Photovoltaic cells difficult. Here, we report a, efficient solar-rechargeable redox flow battery (SRFB) with significantly enhanced safety and stability. Particularly, we introduce a competitive osmotically-balanced neutral pH aqueous Iodine/Bromine electrolyte combination, which has not been used for solar-to-electricity storage technologies. The present work holds great potential for safe and reliable charging/discharging operations to existing photovoltaic-assisted battery technologies. These results promote the utilization of existing solar cell facilities and are a cornerstone for the development of SFBs for practical and efficient energy storage devices.
Sodium-Metal Battery Based on Reversible Oxide Chemistry at the Cathode
Authors: Azaribeni Adel , mosen Harzandi Ahmad , Asadi Mohammad
Published: August 2024

Sodium-metal batteries are considered as a promising energy storage alternative for currently available lithium-based batteries owing to their high gravimetric energy density and more specifically the natural abundance and the low price of Na metal that can lead to an inexpensive and low weight battery technology.

In this study, we employ a Na-metal cell design that works based on reversible phase/composition change of sodium oxides (superoxide and peroxide) using a highly active cathode catalyst and an ether-based ionic-liquid electrolyte. The process involves in-situ production of sodium oxides in the controlled oxygen environment at the cathode. Subsequently, the cathode composed of sodium oxide compositions is assembled into a Na-metal architecture to do performance study and analysis. Our results indicated that the designed Na-metal battery demonstrates stable performance over 50 cycles with an overpotential of less than 100 mV and a coulombic efficiency exceeding 99%. Various electrochemical and physicochemical characterization techniques, including Raman spectroscopy, X-Ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Transmission Electron Microscopy (TEM), were employed to gain insight into cell chemistry and mixed ion-electron conduction mechanism. The findings underscore the significance of well-designed cell components in Na-O2 battery technologies, positioning them as a promising avenue in energy conversion and storage systems.
Operando X-Ray Fluorescence Analysis of Dynamic Cerium Radical Quencher Motion Perpendicular to MEA
Authors: Orikasa Yuki , Takezawa Aika , Morita Kaoruko , Zhong Chengchao , Tsuji Yoichiro , Asaoka Takahiko , Ohki Maria , Sekizawa Oki , Nitta Kiyofumi
Published: August 2024

Polymer electrolyte fuel cells (PEFCs) are required to have a durability of over 50,000 hours. One of the degradation factors is chemical degradation of perfluorosulfonic acid (PFSA) electrolyte membrane. The reaction of hydrogen peroxide with iron impurities produces hydroxyl radicals that break the chemical bonds in the PFSA membrane. Cerium ions are added to electrolyte membranes to absorb these radicals and act as a radical quencher, contributing to improved membrane durability.1 However, cerium ions have been shown to move in both the planar and through-plane directions under fuel cell operating conditions.2,3 The spatial scale of migration in the membrane planar direction is large, and therefore the time scale is also large, where analysis of end-of-life samples has been reported. On the other hand, the observation of the movement in the membrane direction is not easy because the thickness of the electrolyte membrane is 10 micrometers, and it is estimated to be significantly different between the post-disassembly condition and the operating condition. Therefore, it is necessary to establish operando measurement technique for cerium ion concentration with high spatial and temporal resolution in the direction perpendicular to the membrane. We developed an operando X-ray fluorescence spectroscopy technique using a combination of high-energy X-rays and a focused microbeam, and analyzed the behavior of cerium concentration change under current-applied conditions.4 The distribution behavior of cerium ions in the membrane is significantly different depending on the current and humidity. In a high-humidity environment, the ions move in the membrane in the vertical direction in about 1 second. Therefore, in this study, we developed a method to continuously measure the cerium ion concentration in the membrane on a sub-second scale and were able to estimate the effective cerium diffusion coefficient. It was also found that cerium ions migrate to the cathode layer under current-applied conditions. This behavior is accelerated in low humidity environments. This is because the diffusion coefficient of cerium ions is smaller at lower humidity and the back-diffusion flux is smaller.

This work is based on results obtained from the project commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

[1] E. Endoh, ECS Trans., 16, 1229–1240 (2008).

[2] Y. Lai, K. M. Rahmoeller, J. H. Hurst, R. S. Kukreja, M. Atwan, A. J. Maslyn,C. S. Gittleman, J. Electrochem. Soc., 165, F3217-F3229(2018).

[3] S.M. Stewart, D. Spernjak, R. Borup, A. Datye, F. Garzon, ECS Electrochem. Lett., 3, F19-F22 (2014).

[4] Y. Orikasa, A. Takezawa, K. Amemiya, Y. Tsuji, T. Asaoka, M. Ohki, O. Sekizawa, K. Nitta, ECS Trans.,
109 109 (2022).
Achieving High Performance with High Oxygen Permeability Ionomer (HOPI) in Heavy Duty Fuel Cell MEAs
Authors: Macauley Natalia , Strasser Derek James , Coletti Kathryn , Ding Shuo , Tong Emily , Zhang Bingzhang , Liang Jiashun , Wu Gang
Published: August 2024

Heavy-duty PEM fuel cells are expected to last 25,000-30,000 hours in the field. Therefore, materials, components, and interfaces used in these systems must be highly resistant to severe mechanical and chemical stress. Novel, highly active stable Pt and ordered PtCo intermetallic nanoparticles with well-controlled particle size and composition have been synthesized on a highly efficient PGM-free single metal active site rich carbon, to maximize their synergistic effects for enhanced performance and durability. Integrating these catalysts integrated with high O2 permeability ionomer (HOPI) in membrane electrode assemblies (MEAs) improved their fuel cell performance and durability, allowing the MEAs to achieve >1.2 A/cm2 at 0.7 V after 150k square wave accelerated stress test (AST) cycles, with a performance loss < 40 mV after 150K AST cycles.

In a PEM fuel cell, the catalyst ink formulation and mixing processes control catalyst layer coating quality, electrode morphology, and the resulting fuel cell performance and durability. Catalyst ink properties are a result of complex solvent-catalyst-ionomer interactions that depend on the mixing method employed. Here, we compare the performance and durability of electrodes made from ball milled inks for Mayer rod coating before and after the catalyst scale up. Ink rheology and catalyst particle size are used to correlate ink properties to electrode morphology and structure and ensure consistency from batch to batch, and from small lab scale to subsequent scale-up. We evaluate and discuss the challenges that arise when coating the more viscous inks on decals, where the HOPI creates many bubbles in the ink. We also present the challenges of hot-pressing inks that contain HOPI, and how employing a Nafion overspray made with different solvents (isopropanol vs. ethanol) can improve hot-pressing. We investigate the how ionomer to carbon ratio affects hot pressing with HOPI and crack formation in the electrode via scanning electron microscopy (SEM).

This work provides a comprehensive understanding of interactions between Pt, PtCo, carbon, ionomer, membrane, and GDLs and their impact on electrode structure, fuel cell performance and durability, as well as considerations for scale up to a R2R fabrication process. The attained information will be used to improve fuel cell electrode design, fabrication and scale-up.

Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-FOA-0002360 (Phase I) and DE-SC0021671 (Phase II).

Figure 1
Manganese Oxide Gas Diffusion Electrode Conditioning and Electrochemical Doping for Reversible Oxygen Reduction/Evolution Reactions
Authors: Pei Yu , Wu Wen Yu , Wilkinson David P. , Gyenge Elod L.
Published: August 2024

Developing durable and active bifunctional gas diffusion electrodes for reversible oxygen reduction/evolution (ORR/OER) reaction catalysis is crucial yet challenging in the development of numerous electrochemical energy conversion systems, including regenerative fuel cells and rechargeable metal-air batteries. This research is focused on developing manganese oxide-based gas diffusion electrodes for reversible oxygen electrodes.

Core-porous shell Mn/Mn3O4 (abbreviated as MnOx) nanoparticles (QSI) demonstrated increased ORR/OER activities compared to γ-MnO2 (EMD) and b-MnO2.[1] The unique behaviour of core-shell MnOx is attributed to the charge transfer between the low-valent Mn core and the high-valent Mn3O4 shell, thereby regenerating Mn(III) active sites through comproportionation.[1]

The stability of transition-metal-based reversible oxygen electrodes remains a challenge. As shown in Figure 1, the deterioration of Mn/Mn3O4 during ORR and OER cycling can be attributed to three aspects: Mn active sites oxidation (Figure 1a), less active MnOx phase formation (Figure 1b), and material loss (carbon corrosion and dissolved MnO4
- formation) (Figure 1c).[2] As a result, the QSI MnOx electrode transformed from pristine to inactive status within 15 galvanostatic ORR/OER cycles. To improve the stability of the electrode, a set of in-situ electrochemical conditioning and electric field-driven metallic cation incorporation into MnOx GDE was investigated. Among the explored metal cations, the Ni2+ incorporation showed the most significant improvement in terms of activity and cyclic stability. The Ni-MnOx GDE demonstrated excellent stability for over 120 galvanostatic cycles at ±10 mA cm-2 in O2-saturated KOH without losing OER activity, surpassing the Pt/C-IrO2 benchmark.[3]

These findings position the MnOx electrodes as promising and sustainable alternatives to precious metal-based electrodes for ORR/OER catalysis and provide valuable insights into designing reversible oxygen electrodes for energy conversion and storage in alkaline systems, contributing to a green future.

[1] Pei, Y., Wilkinson, D. P., & Gyenge, E. L. Insights into the electrochemical behavior of manganese oxides as catalysts for the oxygen reduction and evolution reactions: monometallic core‐shell Mn/Mn3O4. Small, 2023, 19, 2204585.

[2] Pei, Y., Wilkinson, D. P., & Gyenge, E. L. Gas Diffusion Electrode Design and Conditioning with Manganese (III/IV) Oxide Catalyst for Reversible Oxygen Reduction/Evolution Reactions. ACS Energy & Fuels (2023), 37, 23, 19278–19291.

[3] Pei, Y., Wu, W. Y., Wilkinson, D. P., & Gyenge, E. L. High-Performance Reversible Oxygen Reduction/Evolution Gas Diffusion Electrodes with Multivalent Cation Doped Core-Shell Mn/Mn3O4 Catalysts. ChemElectroChem, in press.

Figure 1
(Invited) Chemical Kinetic Method for Active-Site Quantification in Fe-N-C Catalysts and Correlation with Molecular Probe and Spectroscopic Site-Counting Methods
Authors: Bates Jason S. , Martinez Jesse J. , Hall Melissa N. , Al-Omari Abdulhadi A. , Murphy Eamonn , Zeng Yachao , Luo Fang , Primbs Mathias , Menga Davide , Bibent Nicolas , Sougrati Moulay Tahar , Wagner Friedrich E. , Atanassov Plamen , Wu Gang , Strasser Peter , Fellinger Tim-Patrick , Jaouen Frederic , Root Thatcher W. , Stahl Shannon S.
Published: August 2024

Heterogeneous catalysts consisting of iron cations incorporated into nitrogen-doped carbon (“Fe-N-C”) have received extensive attention as leading alternatives to Pt for the electrochemical oxygen reduction reaction (ORR). Fe-N-C catalysts host mononuclear nitrogen-ligated active centers, FeNx, that frequently coexist with agglomerated Fe species. Although FeNx are the dominant active centers for ORR and other electrocatalytic reactions, the relative accuracies of methods to quantify them are still debated. Here, we develop a kinetic probe-reaction approach to quantify FeNx centers and compare it with spectroscopic and molecular probe methods.

Model Fe-N-C catalysts were synthesized to contain mononuclear FeNx species at low loadings (0.1–0.4 wt% bulk Fe) on solvent-accessible surfaces using a postsynthetic metalation approach and their Fe speciation was confirmed by low-temperature 57Fe Mössbauer spectroscopy. The initial rate of oxidation of a water-soluble hydroquinone molecule (per gcatalyst) catalyzed by these model materials correlates linearly with their density of FeNx centers, reflecting their intrinsic turnover frequency (TOF) for this reaction. This TOF, in turn, enables the estimation of the active-site density on any other Fe-N-C catalyst through a simple rate measurement. Kinetically determined FeNx site densities are measured on a suite of fourteen Fe-N-C catalysts with diverse synthetic origins and Fe speciation (0.3–8.4 wt% bulk Fe) and are compared with those estimated by low-temperature 57Fe Mössbauer spectroscopy, CO pulse chemisorption, and electrochemical stripping of NO derived from NO2
−. Kinetic quantifications of FeNx centers correlate well with those obtained from the CO pulse chemisorption method and Mössbauer spectroscopy. The broad survey of Fe-N-C materials also reveals the presence of outliers and challenges associated with each site quantification method. The kinetic method developed here does not require pretreatments that may alter active-site distributions nor specialized equipment beyond reaction vessels and standard analytical instrumentation, offering an attractive complementary approach.

Figure 1
Investigation and Characterization of Interfacial Transport Phenomena in the Catalyst Layer Using Rheo-Impedance Measurement
Authors: Mora Joy Marie , Chuang Po-Ya Abel
Published: August 2024

Electrodes or catalyst layers (CLs) are the heart of fuel cell and electrolyzer cell devices. They are mainly heterogeneous porous electrodes composed of catalyst particles, ion-conducting polymer material, and void spaces that make up the triple-phase boundary (TPB). It is important to tailor the CL’s microstructure such that there are abundant TPBs where reactions take place to maximize catalyst utilization and improve cell performance. However, this is a critical challenge due to lack of fundamental understanding of the interfacial transport within the CL. Understanding how catalyst ink parameters affect ink properties and how ink components interact, and ultimately, their relationship with CL microstructure formation and cell performance, are essential to designing electrodes. Electrode morphology is important and is controlled by the ionomer/catalyst interactions formed in precursor inks that evolve during mixing and electrode fabrication.

In this study, we probe interactions in catalyst inks with different formulations (ionomer-to-carbon ratio and IPA/water) using a new experimental method to unravel the complexities of ionomer/catalyst particle interactions. The new experimental method is a combination of rheological and electrical impedance spectroscopy measurements (rheo-EIS) that takes advantage of the dynamic nature of catalyst ink and the fact that the rheological and electrical behaviors of the ink are coupled to the microstructure of the material. Using rheo-EIS tool, in combination with zeta (ζ) potential and dynamic light scattering (DLS) measurements, we were able to systematically study how the level of agglomeration of the inks and microstructures evolve with respect to different I/C ratios, solvent formulation, and external shear forces. Results from the three-phase rebuilt test designed to simulate the ink coating condition with single-frequency EIS measurement give information on how the ionomer/catalyst particle interactions form and recover during the coating process. In addition, the full frequency range EIS measurements provide complementary data of the ionic and electrical resistance of the ink before and after high shear applications. Furthermore, the observations of the effect of I/C and IPA/water ratios from this study provide insights on how to better engineer suitable catalyst inks and how to control specific CL microstructure without the need for time-consuming optimization and empirical studies.
Concentrated Chloride Electrolyte Enabling SEI for Fe Metal Anode
Authors: Jung Min Soo , Yang Sungjin , Ji Xiulei (David)
Published: August 2024

Iron is one of the most abundant metal elements in the Earth’s crust and has been widely used worldwide since ancient times. Due to this natural abundance and well-established mass production methods, iron is a promising candidate as a battery electrode for cost-effective large-scale energy storage systems. Edison’s Ni-Fe battery, invented in 1900, used an alkaline electrolyte without ferrous or ferric ions that eventually limited its anode design using iron oxide. More recent Fe redox flow batteries and the newly suggested Fe-ion batteries that use an acidic electrolyte containing ferrous ions (Fe2+) can utilize iron foil as an anode. Combining iron foil with Fe2+ electrolyte enables a simple design and faster kinetics on the anode side. However, introducing acidic electrolytes accelerates hydrogen evolution reaction (HER) on the iron surface. Severe HER affects cell performance in various ways, including lower Coulombic efficiency (CE), drying out of the electrolyte by water consumption, and precipitation of Fe2+ ions due to increased pH of the electrolyte. In this work, a concentrated chloride-based electrolyte was introduced to Fe-ion batteries to suppress HER and achieve a high-CE Fe2+/Fe electrode. With the help of nonpolar [ZnCl4]2- which enables low-polarity organic additives to be soluble in the aqueous solution, an organic solid electrolyte interface (SEI) can be formed on top of the electrode while plating iron. Fe anode protected by the SEI shows a noticeable decrease in HER during cycling, which leads to higher CE of more than 98% and twice longer cycle life.
Passivation of Lead-Acid Batteries Lead Negative Electrodes by PbSO4 Crystals: Analysis from Modeling Cyclic Voltammetry Responses
Authors: Effat Mohammed , Knehr Kevin , Ferels Crystal , Chaudhari Nikhil , Papa Lopes Pietro Papa , Fister Tim
Published: August 2024

Lead-acid batteries (LABs) play a pivotal role in the energy storage sector with applications spanning from starting-ignition-lightning batteries to grid energy storage. Passivation of lead negative electrodes by PbSO4 crystals is a one fundamental mechanism limiting the performance of LAB. In this regard, we developed an electrochemical mathematical model that simulates the nucleation and growth dynamics of PbSO4 crystals on a flat lead electrode, responsible for its passivation. The model considers the electrochemical dissolution of Pb2+ from lead electrode and the ternary transport of lead, bisulfate, and hydrogen ions in H2SO4 electrolyte. We have validated the model with a rich dataset of cyclic voltammetry (CV) responses collected at several scan rates and several concentrations of H2SO4. The model shows remarkable qualitative and quantitative agreement with the experimental data including the onset potential, center, height, and width of the CV peaks, discharge capacity, and particle size. The model is used to give insights on how different physical and operational parameters can influence the electrochemical response of lead negative electrodes.

Keywords: lead-acid battery, nucleation and growth, passivation, cyclic voltammetry
Hydrogen Fuel Cells Vs Lithium-Ion Batteries in Electric Vehicles
Authors: Abghoui Younes
Published: August 2024

I will compare two prominent energy storage technologies—Hydrogen Fuel Cells (HFCs) and Lithium-Ion Batteries (LIBs)—with a focus on their application in electric vehicles (EVs). As the demand for sustainable transportation solutions intensifies, we look into the technological advancements, challenges, and sustainability perspectives associated with these two key players in the electrification of the automotive industry. I will showcase the performance metrics of HFCs and LIBs, including energy density, efficiency, rechargeability, and environmental impact. By considering the latest developments in both technologies, this offers insights into their respective strengths and limitations, shedding light on their suitability for different use cases within the EV ecosystem.Furthermore, I will discuss the infrastructural requirements and economic implications associated with the adoption of HFCs and LIBs in electric vehicles. It critically evaluates the current state of both technologies and anticipates future trends that may shape their role in sustainable transportation. This submission aims to contribute to the ongoing discourse surrounding alternative energy storage solutions for EVs, providing a balanced analysis that can inform policymakers, researchers, and industry professionals engaged in the pursuit of environmentally friendly and efficient mobility solutions.

I also will show some results on cathode exploration for the hydrogen evolution reaction on some novel materials towards the end which would be interesting for further investigation towards commercialisation.
2D Porous Frameworks for Sustainable Energy Storage Applications
Authors: Yu Minghao
Published: August 2024

Two-dimensional (2D) porous frameworks have garnered significant research interest as a new generation of multifunctional materials. Examples of such frameworks include 2D covalent organic frameworks and 2D conjugated metal-organic frameworks. These structures are characterized by their regular porosities, large specific surface areas, and exceptional chemical stability. Moreover, 2D porous frameworks exhibit distinct properties, such as designable topologies and well-defined redox-active sites, which have sparked increased exploration of these materials for electrochemical energy storage applications.[1] In this presentation, I will illustrate how 2D porous frameworks offer promising electrode alternatives for the next generation of energy storage devices. This will be demonstrated through examples including 2D polyarylimide covalent organic frameworks for multivalent metal batteries[2-3] and 2D conjugated metal-organic frameworks, which serve as appealing pseudocapacitive electrodes[4-5]. Besides, I will present our recent endeavors in exploring 2D crystalline polymers as effective interfacial coatings for batteries.[6-7] These coatings facilitate efficient interfacial ion transport and charge transfer, thus effectively enhancing the overall electrochemical reaction kinetics, reversibility, and durability.

References:

[1] M. Yu et al., J. Am. Chem. Soc. 2020, 142, 12903-12915.

[2] M. Yu et al., J. Am. Chem. Soc. 2020, 142, 19570-19578.

[3] M. Yu et al., J. Am. Chem. Soc. 2023, 145, 6247-6256.

[4] M. Yu et al., J. Am. Chem. Soc. 2021, 143, 10168-10176.

[5] M. Yu et al., Angew. Chem. Int. Ed. 2023, e202306091.

[6] M. Yu et al., Small 2022, 18, 2107971.

[7] M. Yu et al., Nat. Commun. 2023, 14, 760.
Coupling Microkinetics with Continuum Transport Models to Understand CO2R on Planar and Optimized Patterned Electrodes
Authors: Lin Tiras Y , Roy Thomas , Govindarajan Nitish , Guo Jack , Hahn Christopher , Varley Joel
Published: August 2024

Electrochemical CO2 reduction has emerged as an attractive technique to sustainably produce valuable fuels and chemicals, while reducing CO2 emissions. In addition to the specific electrode material, the microenvironment local to the electrode interface – e.g., the electrolyte pH, CO2 concentration, buffer concentration – plays a significant role in determining the selectivity and activity of the electrolyzer. In this work, we demonstrate a multi-scale approach, where microkinetic simulations of Au are coupled to a two-dimensional continuum transport model in a flow reactor configuration. Specifically, concentrations and potentials solved for in the continuum model are fed into microkinetic models along the planar electrode surface, which return concentration fluxes that are used to update the continuum model. We find that local quantities at the electrode interface, such as the CO2 concentration and pH, vary not only with the applied potential and flow rate, but also with position on the electrode. We investigate two ways to increase CO2 availability at the interface: (1) increasing the applied flow rate, thus reducing the boundary layer thickness, and (2) introducing an inert defect in the middle of the electrode, allowing CO2 to partially replenish within the depletion boundary layer. Inspired by the effect of a single inert defect, we explore electrodes patterned with inert defects and multiple catalyst materials, i.e. a generalized tandem system. We show how the specific pattern of the electrode can be optimized in order to target a specific desired product. The different parts of the electrode have different goals that work together: converting CO2 to CO, converting CO to C2+ products, and allowing concentrations to replenish through the boundary layer. Overall, our aim is to demonstrate the need for multi-dimensional, multi-scale approaches to simulating CO2 reduction to elucidate the reaction environment near the electrode.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number: LLNL-ABS-857537.
(Invited) Challenges and Opportunities in the Integration of CO2 Capture and Conversion
Authors: Kenis Paul J.A
Published: August 2024

Over the past 15 years or so, the electroreduction of CO2 for the synthesis of intermediates for the chemical industry as well as for the synthesis of small molecule fuels has become a very active area of research. Activities span the whole value chain from electro-catalyst synthesis and characterization, to electrode and cell design and optimization, as well as studies on techno-economic feasibility and life cycle assessment of envisioned overall processes. In the vast majority of these studies, >98% pure CO2 is being used as the feed. In reality, CO2 feeds captured from industrial flue gasses or even those captured from air may not be close to 100% in CO2.

This presentation will explore the integration of a nanomembrane-based CO2 capture method with different CO2 electrolysis approaches. The nano-membrane-based CO2 capture is based on work by Fujikawa and Selyanchyn (Polymer J.
2021, 53, 111), using polydimethylsiloxane-derived membranes that are preferentially permeable to CO2 over nitrogen. Multistage arrangement of modules comprised of arrays of membranes allows for efficient concentration of CO2 from air, from 420 ppm to tens of percent, using just vacuum pumps to drive the process. We explore the use of these concentrated CO2 streams that still contain nitrogen and some oxygen as the feed in subsequent CO2 electrolysis conversions to CO, to methane, or to other products, depending on catalyst choice. We study the effects of feed composition, catalyst chosen, and cell configuration on product speciation, conversion efficiency, etc.
(Invited) Atomically Dispersed Metal Electrocatalysts for CO2 to CO Conversion: From Single to Dual Metal Sites
Authors: Wu Gang
Published: August 2024

Carbon-supported nitrogen-coordinated single-metal site catalysts (i.e., M−N−C, M: Fe, Co, or Ni) are active for the electrochemical CO2 reduction reaction (CO2RR) to CO.(1) We comprehensively engineered FeN4 and NiNx sites for electrochemical CO2 reduction to CO considering the particle sizes of the catalysts, metal content, and the M−N (M: Fe or Ni) bond structures.(2, 3)The unique M-N-C model allows us to elucidate each factor′s role exclusively regarding the promotion of CO2 reduction.(4)Optimal particle sizes and Fe content provide favorable external factors to improve mass activity. Structural changes of M−N bonds controlled by thermal activation temperatures can intrinsically enhance CO selectivity and kinetic activity. Notably, the NiN3 active sites with optimal local structures formed at higher temperatures (e.g., 1200 °C) are intrinsically more active and CO-selective than NiN4, providing a new opportunity to design a highly active catalyst via populating NiN3 sites with increased density. Further improving their intrinsic activity and selectivity by tuning their N−M bond structures and coordination is limited. We further expand the coordination environments of M−N−C catalysts by designing dual-metal active sites.(5)The Ni-Fe catalyst exhibited the most efficient CO2RR activity and promising stability compared to other combinations. Advanced structural characterization and theoretical prediction suggest that the most active N-coordinated dual-metal site configurations are 2N-bridged (Fe-Ni)N6, in which FeN4 and NiN4 moieties are shared with two N atoms. Two metals (i.e., Fe and Ni) in the dual-metal site likely generate a synergy to enable more optimal *COOH adsorption and *CO desorption than single-metal sites (FeN4 or NiN4) with improved intrinsic catalytic activity and selectivity.

References

Pan F, Zhang H, Liu K, Cullen D, More K, Wang M, et al. Unveiling Active Sites of CO2 Reduction on Nitrogen-Coordinated and Atomically Dispersed Iron and Cobalt Catalysts. ACS Catalysis. 2018;8(4):3116-22.

Li Y, Adli NM, Shan W, Wang M, Zachman MJ, Hwang S, et al. Atomically dispersed single Ni site catalysts for high-efficiency CO2 electroreduction at industrial-level current densities. Energy & Environmental Science. 2022;15(5):2108-19.

Mohd Adli N, Shan W, Hwang S, Samarakoon W, Karakalos S, Li Y, et al. Engineering Atomically Dispersed FeN4 Active Sites for CO2 Electroreduction. Angewandte Chemie International Edition. 2021;60(2):1022-32.

Li J, Zhang H, Samarakoon W, Shan W, Cullen DA, Karakalos S, et al. Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction. Angewandte Chemie International Edition. 2019;58(52):18971-80.

Li Y, Shan W, Zachman MJ, Wang M, Hwang S, Tabassum H, et al. Atomically Dispersed Dual-Metal Site Catalysts for Enhanced CO2 Reduction: Mechanistic Insight into Active Site Structures. Angewandte Chemie International Edition. 2022;61(28):e202205632.
Modeling Bicarbonate Kinetics on Silver Catalysts for CO2 Electrolysis
Authors: Ehlinger Victoria Marie , Lee Dong Un (Daniel) , Lin Tiras Y , Govindarajan Nitish , Varley Joel , Duoss Eric B , Baker Sarah , Jaramillo Thomas F. , Hahn Christopher
Published: August 2024

Low-temperature CO2 electrolyzers transform captured CO2 into more useful chemicals, such as syngas (CO and H2) for systems with silver or gold catalysts and ethylene and other C2+ products for systems with copper catalysts. At low overpotentials, bicarbonate ions act as proton donors and have been shown to have enhanced activity1, leading to nonlinear Tafel slopes for the hydrogen evolution reaction (HER). We have developed a 1D planar electrode model for CO2 electrolysis, similar to the model developed by Gupta et al.,2 including a thin ionomer layer on top of a silver catalyst layer surface. The model includes buffer chemistry and ion transport in the boundary layer as well as the ionomer thin-film layer. Tafel parameters are fit for both bicarbonate and water as proton donors for HER using the model results to account for mass transport in the boundary layer. A comparison against a bare silver electrode shows that the Donnan potential across the ionomer/electrolyte interface has a significant effect on the ion concentrations at the catalyst layer surface, leading to enhanced HER from bicarbonate at low overpotentials. These results are then compared against Butler-Volmer parameters that are derived from a full microkinetic model. The Tafel kinetic parameters were then used in a 1D full-cell membrane electrode assembly (MEA) model, and we found good agreement with experimental data, illustrating that the ionomer in contact with the catalyst layer surface impacts the underlying kinetics both in planar electrodes and industrially-relevant MEA systems.

References

D. M. Koshy et al., J. Am. Chem. Soc., 143, 14712–14725 (2021) https://doi.org/10.1021/jacs.1c06212.

N. Gupta, M. Gattrell, and B. MacDougall, J. Appl. Electrochem., 36, 161–172 (2006).

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was partially supported by a Cooperative Research and Development Agreement (CRADA) between Lawrence Livermore National Laboratory, Stanford University, and TotalEnergies American Services, Inc. (affiliate of TotalEnergies SE) under Agreement No. TC02307 and Laboratory Directed Research and Development (LDRD) funding under project 22-SI-006.

LLNL-ABS-857478

Figure 1
Assessing the Activity and Stability of Cu-Based Gas Diffusion Electrodes for the CO2 Conversion in Different Electrolytes: Bicarbonate Vs. Ionic Liquid/Acetonitrile
Authors: Zammillo Federica , Guzman Hilmar , Polino Daniela , Miro Serra Roger , Lopera Alberto , Parisi Emmanuele , Simone Elena , Lopez Tendero Maria J. , Diaz de los Bernardos Miriam , Pavan Giovanni Maria , Hernandez Simelys
Published: August 2024

In the context of sustainable strategies proposed to convert CO2 to valuable products, the electrochemical reduction of CO2 (ECR-CO2) represents one of the most promising alternatives1. Herein, the ECR-CO2 has been carried out employing for the first-time synthesised core-shell Cu2O/SnO2-based nanoparticles within a continuous flow cell both in aqueous solution and in the presence of ionic liquids (ILs), which have been known to boost CO2-derived products2. Interestingly, in aqueous potassium bicarbonate-based electrolyte, the synthesised material demonstrated a stable syngas production at -20 mA cm-2, with a CO/H2 ratio of about 10. The electrode stability and selectivity in aqueous environment has been further demonstrated for 24 hours of continuous operations at 10 cm2 scale. However, a CO/H2 ratio of about 3 was reached with 1-Butyl-3-methylimidazolium triflate ([BMIM][TfO]) in acetonitrile (ACN)3. In the aprotic media, stability issues have been faced during operations, visualized in the darkening of the gas diffusion electrodes and in colour changes of the electrolyte. Raman spectroscopy, Field Emission Scanning Electron Microscopy and Electrochemical Impedance Spectroscopy techniques have been employed for the physicochemical characterization of the electrodes and to assess the evolution of the electrochemical interfaces within the system over time. Molecular dynamics simulations have shown that the instability of the GDE could start with the displacement of Cu surface atoms from their equilibrium position by ACN molecules. Furthermore, we observed that the immobilization of ruthenium and rhenium complexes on the catalyst can be crucial to determine its suitability for either the hydroformylation or the carbonylation reaction, making this technology a promising solution for the green transition of the chemical industry.

Acknowledgments

The financial support of the SUNCOCHEM project (Grant Agreement No 862192) of the European Union’s Horizon 2020 Research and Innovation Action programme and of Fondazione CRT are acknowledged.

References

IEA. Global Energy Review: CO2 Emissions in 2021. (2021).

Kunene, T., Atifi, A. & Rosenthal, J. Selective CO2 Reduction over Rose’s Metal in the Presence of an Imidazolium Ionic Liquid Electrolyte. ACS Appl. Energy Mater.
3, 4193–4200 (2020).

Fortunati, A., Hernández, S., et al. Understanding the role of imidazolium-based ionic liquids in the electrochemical CO2 reduction reaction. Communications Chemistry, 6(1), 1–13 (2023).
Quantifying Individual Electrode Polarization and Unraveling Theinteractive Phenomenon in Solid Oxide Fuel Cells
Authors: Wang Yudong , Xu Nengneng , Zhou Xiao-Dong
Published: August 2024

In electrochemically active systems, such as fuel cells, electrolyzers, and batteries, researchers often modify the material chemistry or operating variables at one of the electrodes (e.g., the cathode) to investigate its properties. This approach assumes that changes in measured polarization and cell performance result solely from the modifications made to the selected electrode, while the conditions at the other electrode (e.g., the anode) remain constant. However, the potential interactions between the polarizations of these two electrodes have remained unclear. In our study, we utilize a voltage probe capable of precisely determining electrode polarization. Our findings reveal three key insights:1. The quantification of electrode polarization becomes feasible through the implementation of a voltage probe. 2. The fuel electrode plays a pivotal role in the performance of state-of-the-art solid oxide cells, with its influence being comparable to that of the oxygen electrode. 3. A reciprocal interaction exists between the two electrodes within a solid oxide cell. Consequently, when there are changes in the chemistry or operational conditions at one electrode, the polarization of the other electrode changes simultaneously
(Invited) Tuning Selective CO2 Electrohydrogenation Under Mid Temperature and Pressure
Authors: Li Meng , Ding Dong
Published: August 2024

To address rising environmental concerns and energy challenges, it is highly desirable to develop green technologies for a sustainable future. Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds. Electrochemical CO2 hydrogenation using renewable electricity is considered one of the most promising pathways to reach the environmental economics. Among various electrochemical devices, a solid state electrolyzer working at intermediate temperatures has the advantages of high reaction rates and low overpotentials. As CO2 molecules is quite stable, it is critical to develop electrocatalysts with high activity to reduce electricity engagement. Also, CO2 hydrogenation has multiple pathways which normally results in low selectivity for a target product. A tunable electrocatalyst with high selectivity to different products is desirable for CO2 conversion reactions. Heterostructured nanomaterials attracts great attentions in electrochemical systems. With careful design, they can show very high activity and selectivity towards an electrochemical reaction pathway. In this work, we combine theoretical simulations, including density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations, with experimental methods (characterizations and electrochemical measurements) for rational design of highly efficient heterostructured nanomaterials for CO2 hydrogenations. We studied the strong metal-support interaction (SMSI) in a doped CeO2 supported noble metal nanoparticles (NPs) system using theoretical calculations. The results indicate that SMSI largely depends on chemical conditions of the support and particle size of dispersed metal NPs. By tuning the SMSI, we can successfully change the catalytic activity and selectivity towards CO2 hydrogenation reactions. Based on these findings, we designed tunable heterostructured nanomaterials for efficient hydrogenation reactions at intermediate temperatures. These predictions were further confirmed by experimental method. By using a combination of high-throughput theoretical calculations and electrochemical measurements, we successfully developed highly active catalysts for electrochemical CO2 hydrogenation reactions. This framework is also applicable to other electrochemical systems using heterostructured materials.