bluuebunny/crossref_metadata_2025 huggingface dataset:
Challenges in Practical Button Cell Testing for Hydrogen Production from High Temperature Electrolysis of Water
Authors: Priest Cameron , Gomez Joshua , Kane Nicholas , Hartvigsen Jeremy , Wang Lucun , Ding Dong , Casteel Micah , Stewart Frederick , Wu Gang
Published: August 2024

High temperature electrolysis of water using solid oxide electrochemical cells (SOEC) is a promising technology for hydrogen production with high energy efficiency and may promote decarbonization when coupled with renewable energy sources and excess heat from nuclear reactors. Over the past several decades there have been extensive scientific and engineering studies on cell materials and degradation behaviors that have greatly improved current density, decreased total resistance, and lowered degradation rates. Although the technology is now at a near-commercial level, maintaining consistency in cell testing and minimizing variance in practical testing environments is an often overlooked but crucial topic. To promote high quality data collection, testing procedures and balance of plant component details are extremely important to consider. This work discusses some key factors affecting the reproducibility of practical SOEC testing on the button cell level, namely current collection layers, cell sealing procedures, the reliability of steam and hydrogen delivery systems, cell testing fixture design, and reduction procedures. To provide a baseline and a level of standardization for the SOEC community, this work also discloses details of the standard operating procedure and techniques adopted for o-SOEC testing at Idaho National Laboratory (INL).
Design and Performance Evaluation of a Specialized Bubbler System for Accurate and Repeatable Solid Oxide Electrolysis Cell (SOEC) Testing
Authors: Gomez Joshua , Kane Nicholas , Hartvigsen Jeremy , Priest Cameron , Wang Lucun , Ding Dong , Casteel Micah , Wu Gang
Published: August 2024

Accurate assessment of Solid Oxide Electrolysis Cell (SOEC) performance demands standardized testing conditions, particularly in stable steam delivery. Fluctuations in steam concentration and flow rate can significantly impact measured open-circuit voltage (OCV) and polarization behavior. Although direct steam injection is straightforward, it is often hindered by instability resulting from intermittent liquid water flux, pressure fluctuations, and fractional distillation effects. Bubbler humidification systems have the potential to offer consistent steam, but tailored designs for SOEC testing are currently absent.

This study introduces a specialized bubbler system designed to deliver stable steam to SOEC test stands accommodating both oxygen-conducting (O-SOEC) and proton-conducting (H-SOEC) cells. The bubbler components include a refill water reservoir, a level control module, heating elements, pressure relief valves, check valves, tubing, and fittings integrated with the test stand. The system humidifies the sweep gas, transporting steam to the cell test fixture situated within a high-temperature furnace.

The design process involved meticulous considerations of materials compatibility, hydrogen safety, and overtemperature protection. All wetted components employ stainless steel, glass, or PTFE materials in their construction construction. Redundant thermocouples ensure safe process temperatures with automated overtemperature shut off. The refill reservoir and bubbler headspace operate near ambient pressure, facilitated by an exhaust line vent sized for minimal backpressure.

In various executed O-SOEC tests, the bubbler maintained OCV stability within ±5 mV over several hundred hours for each cell operating at 750°C, eliminating spikes caused by steam fluctuations observed with direct injection methods. This facilitates precise electrochemical analysis and determination of area-specific resistance losses. Polarization curves align with expected behavior based on the Nernst equation. The system has demonstrated safe and stable functionality for over thousands of hours across various operating conditions.

The bubbler design presents researchers with notable advantages over existing steam supply options for SOEC test stands, addressing performance, safety, and flexibility concerns. Online instrumentation enables closed-loop control of steam conditions, enhancing stability. Standardization of test equipment is crucial for quality results, and this work contributes progress toward reproducible protocols in the international SOEC community. The modular bubbler approach, integrated with safety features, also signifies safer methodology choices for lab-scale experimental research.
Accelerating the Development of Oxygen Electrodes for Solid Oxide Cells Using Two-Stage Machine Learning
Authors: Hu Xueyu , Zhou Yucun , Luo Zheyu , Liu Meilin
Published: August 2024

Reversible Solid Oxide Cells (RSOCs) stand out as highly efficient and cost-effective devices for energy storage and conversion. However, the pursuit of high-performance and durable RSOCs is impeded by the lack of efficient and stable oxygen electrodes. The conventional trial-and-error approach used for the development of oxygen electrodes is resources and time-consuming. In this presentation, we introduce a novel "two-stage machine learning" approach designed to expedite the discovery of optimal oxygen electrodes for efficient oxygen reduction/evolution reaction (ORR/OER) in SOCs. In the initial stage, we employed a high-throughput calculation approach to generate four ORR/OER related descriptors (energy above the convex hull, p-band center, d-band center, and vacancy formation energy) for a set of 4455 perovskite oxide candidates. Subsequently, we successfully predicted these descriptors using machine learning techniques based on the fundamental physico-chemical features of the candidates. Moving to the second stage, we measured the polarization resistances - directly related to ORR/OER activity - of 142 oxygen electrodes and employed them as prediction targets. Through our machine learning method, we accurately predicted experimental results based on the fundamental physico-chemical features of the candidate materials. Notably, among the 4455 candidates studied, a specific oxygen electrode material is predicted to exhibit both high activity and stability. When applied to an RSOC based on a proton-conducting electrolyte operated at 600 °C, a high peak power density of >1.5 W cm−2 is demonstrated in the fuel cell mode, and a high current density of >2.5 A cm−2 is achieved at a cell voltage of 1.3 V in the water electrolysis mode while maintaining stable operation for 500 hours.
Modeling Water Transport in Polymer Electrolyte Membrane Electrolyzers Using a One-Dimensional Transport Model
Authors: Motupally Shikhar , Mishra Lubhani , Thiagarajan Raghav Sai , Subramanian Venkat R.
Published: August 2024

In this work, we present a water transport model to quantify the movement of water across Nafion® membranes in a proton exchange membrane electrolyzer as a function of varying operating conditions and membrane parameters. This physics-based model is based on the three main water transport mechanisms: diffusion, electro-osmotic drag, and pressure-driven flow. Three sets of equations are obtained to model the movement of water on the cathode side – I. Material balances for hydrogen and water in the flow channel (z-direction), II. Water movement across the membrane in the x-direction, and III. Expressions for variable membrane properties to serve as model inputs. The condensation of water at the cathode is also modeled to understand the respective transport contributions from the vapor and liquid phases. The coupled equation sets are solved numerically with appropriate boundary conditions. An analytical solution is also obtained for the governing differential equation for the mole fraction of water in the vapor phase. This study is perhaps the first effort for a detailed physics-based transport model to predict the water transport in the electrolyzer in one dimension using the actual measured values for the physical parameters of the system. The model results are compared with the experimental data available for water transport, and a good agreement is observed over the wide range of current, temperature and pressure differentials. Further, with the help of this simple transport model, the numerical analysis is performed to delineate the effect of electrolyzer operating conditions on the net water transport across the membrane, water condensation at the cathode, individual contribution of the transport fluxes, and electrolyzer design. Finally, the model is exercised to simulate the dependence of water transport as a function of membrane thickness. This confirms the validity of the current approach of using thin reinforced membranes by electrolyzer fabricators.

Figure 1
Facile in-Situ Straining Platform for Transmission Electron Microscopy with Quantification of Strains
Authors: Wood Nathan , Sari Bengisu , Dhall Rohan , Dandu Medha , Hochhalter Jacob , Doeff Marca M. , Warren Roseanne
Published: August 2024

This work aims to design and model an experimental platform to perform in-situ straining experiments in a transmission electron microscope (TEM), enabling structural characterization of materials under tensile strain. The ability to visualize changes in the crystal structure of materials under strain can provide important insights into failure modes and improve understanding of process-structure-property relationships. Existing methods of in-situ straining typical involve complex sample preparation and are not well-suited to the study of thin films or sensitive battery materials. In this work, thin films of materials are deposited on a conventional TEM grid adhered to a copper template. The template is mounted in a Gatan 654 single tilt straining holder and strained within the TEM. Electron diffraction patterns are taken from the specimens, and strain can be calculated based on shifts in the Bragg reflections.

An essential component of in-situ straining experiments is the quantification of applied strains. For our facile straining platform, we calculate the expected values of strain on our specimen using a finite element model. The finite element strain simulation data was compared with experimental data collected during in-situ straining experiments. Experimental results on a variety of material systems, including those applicable to lithium-ion batteries, are within the bounds of our model. Overall, the ability to accurately simulate in-situ strains using the finite element model enables researchers to better explain observation in the TEM, improve the reproducibility of the experiments, and optimize straining geometries to be tested.

Figure 1
(Invited) Lithium Plating on Brittle Solid Electrolytes: Mechanics, Heterogeneities and Coatings
Authors: Chueh William C.
Published: August 2024

Solid-state batteries employing lithium metal as a negative electrode promise high energy and safety. Plating at the lithium metal/solid electrolyte interface is fundamentally complex compared to plating in a liquid electrolyte due to mechanical considerations as well as heterogeneities. Ideally, lithium metal should plate densely in a planner fashion, growing away from the solid electrolyte. In reality, however, lithium plating is heterogeneous and can be directed towards the solid electrolyte, ultimately leading to short-circuit and penetration through the solid electrolyte. In this talk, I will overview our recent efforts to understand and control chemo-mechanics in garnet solid electrolytes. Specifically, we employ local electrochemical probes to correlate current-voltage behavior to defect and mechanical forces, both locally and macroscopically. Building on these fundamental understanding, I will show how interfacial engineering through coatings enable more uniform lithium plating.
Unveiling the Mechanical and Electrochemical Evolution of Nanosilicon Composite Anodes in Sulfide-Based All-Solid-State Batteries
Authors: Zhu Hongli , Cao Daxian
Published: August 2024

The utilization of silicon (Si) anodes in all-solid-state lithium batteries (ASLBs) provides the potential for high energy density. However, the compatibility of sulfide solid-state electrolytes (SEs) with Si and carbon is often questioned due to potential decomposition. To investigate this, operando X-ray absorption near-edge structure (XANES) spectroscopy, ex-situ scanning electron microscopy (SEM) and ex-situ X-ray nano-tomography (XnT) were utilized to study the chemistry and structure evolution of nano Si composite anodes. Results from XANES demonstrated a partial decomposition of SEs during the first lithiation stage, which was further accelerated by the presence of carbon. But the performance of first three cycles in Si-SE-C was stable, which proved the generated media is ionically conductive. XnT and SEM results showed that the addition of SEs and carbon improved the structural stability of the anode with fewer pores and voids. A chemo-elasto-plastic model revealed that SEs and carbon buffered the volume expansion of Si, thus enhancing mechanical stability. The balance between the pros and cons of SEs and carbon in enhancing reaction kinetics and structural stability enabled the Si composite anode to demonstrate the highest Si utilization with higher specific capacities and better rate than pure Si and Si composite anodes with only SEs.
(Invited) Probing the Reaction Microenvironment during Electrochemical Nitrate Reduction to Ammonia
Authors: Corson Elizabeth R. , Guo Jinyu , Brimley Paige N , Liu Matthew Junjie , Munoz Carolina , Smith Wilson A , Tarpeh William Abraham
Published: August 2024

Nitrate pollution of wastewater from agricultural runoff and industrial waste streams is common around the globe. Nitrate negatively impacts the environment through harmful algal blooms and can be dangerous for human consumption. Strict limits have been set on nitrate discharge and the concentration in drinking water (< 50 ppm). Nitrate is currently removed from water by conversion to nitrogen through a biological process that requires chemical inputs (e.g., methanol) and post-treatment to remove biomass and organics.

Electrochemical reduction of nitrate (NO3RR) to ammonia can remove nitrate from water and is an alternative to Haber-Bosch (HB) ammonia production, a significant source of global CO2 emissions. Ammonia is an important chemical precursor with potential applications in sustainable energy as a fuel or H2 carrier, or can be used as a fertilizer in the form of ammonium sulfate. This research addresses the water–energy nexus by converting nitrate to a valuable product, off-setting the cost of water treatment, and reducing demand for HB.

NO3RR can be done from small to large scales, use renewable electricity, and eliminate the need for expensive and hazardous chemicals. However, NO3RR processes must exhibit selectivity toward ammonia to avoid the formation of other undesired products and occur at a low overpotential to minimize operating costs from electricity. To address these challenges, we must understand the reaction environment at the electrode–electrolyte interface, where heterogeneous electrochemical reactions occur. We use in situ attenuated total reflectance–surface-enhanced infrared adsorption spectroscopy (ATR–SEIRAS) to investigate the adsorbed reactants, intermediates, and interfacial pH. We studied the repeatability of the technique for in situ interfacial pH measurement and recommend controls to the community when using this method. The ATR–SEIRAS results are correlated with electrochemical experiments measuring NO3RR selectivity, activity, and efficiency. NO3RR products are measured by ion chromatography and gas chromatography. Our results relate bulk electrolyte properties with interfacial properties, and interfacial properties with reaction activity and selectivity. This understanding could lead to the development of electrolyte engineering strategies to optimize ammonia production in electrochemical NO3RR.
(Invited) Curvature-Enhanced Hydrophobicity: A Counter-Intuitive Strategy for Efficient Electroreduction of Nitrate into Ammonia
Authors: Zhang Wen , Gao Jianan
Published: August 2024

The electrochemical upcycling of nitrate (NO3
−) to ammonia (NH3) holds promise for synergizing both wastewater treatment and NH3 synthesis. Efficient stripping of gaseous byproducts (NH3, H2, and N2) from electrocatalysts is crucial for continuous and stable electrochemical reactions. This study evaluated a layered electrocatalyst structure using copper (Cu) dendrite to enable a high curvature and hydrophobicity and achieve a stratified liquid contact at the gas-liquid interface of the electrocatalyst layer. As such, gaseous product desorption or displacement from electrocatalysts was enhanced due to the separation of a wetted reaction zone and a non-wetted zone for gas-transfer. Consequently, this electrocatalyst structure yielded a 1.9-fold boost in per active site activity compared to that with a low curvature and high hydrophilic counterpart. Moreover, a high NH3 Faradaic efficiency of 90.9 ± 2.3% was achieved with nearly 100% NO3
− conversion. This high-curvature hydrophobic Cu dendrite was further integrated with a gas-extraction membrane, which demonstrated outstanding NH3 yield from the real reverse osmosis retentate brine.

Figure 1
Electrocatalytic Synthesis of Urea
Authors: Costa Figueiredo Marta
Published: August 2024

Many industrial chemical processes involve a high-energy demand (often still derived from fossil fuels). Urea is an important chemical for the agricultural industry, which accounts for 70% of the global nitrogen-containing fertilizer usage. Currently, urea is produced by the reaction of liquid NH3 and CO2
[1] in a process known as the Haber-Meiser process. Despite its importance, this process suffers from high energy demand and CO2 emissions, mainly due to the NH3 synthesis step (Haber- Bosch process), which relies on fossil fuel resources. Making urea with electrochemical methods has recently gained interest from the scientific community as this approach provides a way to reduce the high CO2 emissions currently associated with urea production. Among the various nitrogen sources explored for urea electrosynthesis, nitrate (NO3-) is attractive because of its high solubility in water, low dissociation energy and potential to mitigate NO3
− contaminations in water. Even though the mechanism of urea synthesis via CO2 and NO3
- coupling is still controversial and not broadly studied, most reports implicate CO* and NH2* surface intermediates in urea synthesis.[2] Cu is an attractive electrocatalyst as it can reduce CO2 to CO and further products and it is also an active catalyst for the reduction of nitrate to ammonia Previous reports on Cu and Cu-based materials showed that urea can be obtained from NO2
-.[3,4] Early research by Shibata et al. with various catalysts demonstrated that the highest faradaic efficiency towards urea from NO3
- was achieved with a Zn catalyst.[5] In this presentation, I will show our latest results on the development of Cu bimetallic catalysts ( CuRh) for urea electrosysnthesis from CO2 and NO3
-[6,7].

References:

[1] P. N. Cheremisinoff, Waste Minimization Cost Reduct. Process Ind.
1995, 222–284.

[2] X. Liu, Y. Jiao, Y. Zheng, M. Jaroniec, S. Z. Qiao, Nat. Commun.
2022, 13, 1–9.

[3] S. Liu, S. Yin, Z. Wang, Y. Xu, X. Li, L. Wang, H. Wang, Cell Reports Phys. Sci.
2022, 3, 100869.

[4] N. Cao, Y. Quan, A. Guan, C. Yang, Y. Ji, L. Zhang, G. Zheng, J. Colloid Interface Sci.
2020, 577, 109–114.

[5] M. Shibata, K. Yoshida, N. Furuya, J. Electrochem. Soc.
1998, 145, 595–600.

[6] D. Anastasiadou, B. Ligt, Y. He, R van de Poll, J. Simons, M C Figueiredo. . Communications in Chemistry, 6, 199, 2023

[7] D. Anastasiadou, B. Ligt, , M C Figueiredo, in preparation.
Electrical TP-Resistance Measurement at Gas Diffusion Layers (GDL) for Pemfcs – Separation of Bulk and Contact Resistances
Authors: Koenig Lukas , Messerschmidt Matthias
Published: August 2024

At electrical TP-resistance measurements of PEMFC GDLs often the separation of bulk and contact resistance is of interest. There are two possibilities for this task: 2-pole measurement with stacking of GDLs and 4-pole measurement with two non current conductive poles for pure voltage measurement. Both methods are discussed and evaluated within this poster.

The results presented are acquired within the project QM-GDL (GDL quality assurance for the market run-up), which is funded by the German Federal Ministry for Digital and Transport under grant agreement number 03B11016C.
Understanding Phosphoric Acid Dynamics in High-Temperature Pemfcs: Mechanisms and Durability of PA-PBI and Ion-Pair-Based Systems.
Authors: Lim Katie Heeyum , Lee So Young
Published: August 2024

High-Temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) can operate at > 100 oC under anhydrous conditions, providing benefits such as system simplification and superior contaminant tolerance. Most researches on HT-PEMFC have focused on PA-PBI-based system since 1995, however the durability of this system is still on controversial. Some insisted the stable operation of PA-PBI HT-PEMFC, which showed the stability under mild conditions such as low current density about 0.2 A cm-2, while others pointed out the instability specifically under accelerated stress conditions with higher current densities above 0.6 A cm-2, lower ( < 140 oC) or higher ( > 180 oC) operating temperatures, or dynamic protocols like start-up/shut-down cycles, etc.

This limited durability of PA-PBI HT-PEMFC is known to be related to acid loss from the membrane-electrode-assemblies (MEAs). Several mechanisms were proposed to explain the linear and nonlinear acid loss behaviors. PA evaporation and steam-distillation are known to explain the constant PA loss. Despite the extensive efforts on mechanisms and acid loss mitigation strategies, current PA-PBI systems still struggle against the limited durability due to PA loss. To improve the durability of HT-PEMFC, a novel system was introduced based on the quaternary ammonium-biphosphate ion-pair coordinated PEM [1]. Due to a stronger interaction in the ion-pair PEMs, the durability was also improved by alleviating the PA loss during PEMFC operation. Nonetheless, the acid retention mechanism of this novel system is not explored yet.

Here, we investigate the mechanisms of PA loss and PA retention within electrodes of both PA-PBI-based and ion-pair-based HT-PEMFC systems. Through PA energetics studies and experimental investigations under controlled stress conditions, we elucidate distinct PA loss/retention mechanisms in these systems, leading to different durability behaviors. Our findings offer insights for enhancing the durability of both HT-PEMFC systems [2].

[1] Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S. Protonated phosphonic acid electrodes for high power heavy-duty vehicle fuel cells, Nature Energy, 7, 248 (2022).

[2] Lim, K. H.; Matanovic, I.; Maurya, S.; Kim, Y.; Castro, E. S.; Jang, J-H.; Park, H.; Kim, Y. S. High temperature polymer electrolyte membrane fuel cells with high phosphoric acid retention, ACS Energy Letters, 8, 529 (2023).
Enhancing PA-PBI Composite Membrane with Metal Oxides Incorporation for HT-PEMFC Operating Above 200 oc
Authors: Lee So Young , Kim Seongwoo , Kim Joonbyum , Gwak Gyeongseok , Nam Suk-Woo
Published: August 2024

High-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are renowned for their excellent CO tolerance and rapid reaction kinetics [1]. Among the various membrane types, phosphoric acid doped polybenzimidazole (PA-PBI) membranes, phosphoric acd (PA) acts as a proton conductor, facilitating proton transfer through hydrogen bond rearrangement between PA molecules and the PBI backbone [2]. However, the operating temperature of PA-PBI membrane-based HT-PEMFC is constrained by the condensation of PA, limiting their use to below 180 oC and posing a significant challenge for achieving efficient operation above 200 oC.

Recent research endeavors have focused on enhancing PA-PBI membranes by incorporating metal oxides to extend their operational temperature range beyond 180 oC. The addition of metal oxides into PA solution leads to the formation of metal hydrogen phosphate, effectively preventing PA evaporation at elevated temperatures ( > 180 oC) and maintaining membrane performance without degradation. Furthermore, the presence of metal oxides facilitates proton transfer to the metal hydrogen phosphate surface, thereby improving ionic conductivity even at temperatures exceeding 200 oC.

In this study, we present the synthesis of poly(2,2’-(1,4-phenylene)-5,5’ bibenzimidaozle) (pPBI) composite membranes through an in-situ method, where various metal oxides (SnO2, TiO2, ZrO2) are introduced into the synthesis solution. Through systematic investigation, we evaluate the impact of these metal compounds on fuel cell performance and durability at high temperatures exceeding 200 oC. Our findings shed light on the potential of metal oxide-modified PA-PBI composite membranes for advancing the performance and reliability of HT-PEMFCs in demanding operating conditions.

References

[1] J. M. L. e Canut, R. M. Abouatallah, D. A. Harrington, J. Electrochem. Soc, Sci, 153 (2006) A857.

[2] Z. Wang, J. Zhang, S. Lu, Y. Xiang, Z. Shao, S. P. Jiang, Adv. Sustainable Syst, 7, (2023) 2200432.
(Invited) Mechanistic Insights Gained through Ten Years of Collaboration with Diane Smith
Authors: Gustafson Jeffrey
Published: August 2024

In this talk I will discuss projects my lab carried out in collaboration with Diane Smith and some key mechanistic insights that were provided by the collaboration. Particular focus will be placed on a light mediated perfluoroalkylation of heterocyclic and a photocatalytic oxidative C-H thiolation.
Electropolymerization of Pyrrole Using a Single-Electrode Electrochemical System
Authors: Inagi Shinsuke , Shi Yulin , Villani Elena , Xu Guobao
Published: August 2024

Bipolar electrochemistry emerges as an appealing technique for gradient surface fabrication thanks to the controllable potential distribution on bipolar electrodes (BPEs) in a wireless manner [1]. Here we report a BPE array named the single-electrode electrochemical system (SEES) [2] for the high-throughput electrosynthesis of gradient polypyrrole (PPy) films via electropolymerization. The SEES consists of a plastic board with holes attached to an indium-tin oxide (ITO) electrode to create multiple microelectrochemical cell arrays. Benefiting from this technique, the effects of various electrolysis conditions on film growth, such as applied voltage, electrodeposition time and electrolyte, etc., were systematically investigated. The length, thickness, surface morphology, and wettability, of the obtained PPy films were investigated [3]. The SEES provides a straightforward comparison of experimental results and hence facilitates the condition screening process.

References:

N. Shida, Y. Zhou, S. Inagi, Acc. Chem. Res., 2019, 52, 2598.

W. Gao, K. Muzyka, X. Ma, B. Lou, G. Xu, Chem. Sci., 2018, 9, 3911.

Y. Shi, E. Villani, Y. Chen, Y. Zhou, Z. Chen, A. Hussain, G. Xu, S. Inagi, Anal. Chem., 2023, 95, 1532.
(Invited) Electroanalytical Meat Science
Authors: Krishnan Sadagopan , Bhandari Silan , Ayabadda Devage Sachinthani , Avery Athena , Kasthuri Dias Sandun Bogahawaththa , Kumar Rishav , Ramanathan Ranjith
Published: August 2024

Meat color is a crucial factor that drives consumers’ purchase decisions at the point of sale. Consumers prefer the bright-cherry red color of beef. A recent study from our research team reported that the US beef industry loses $3.7 billion annually, and 400 million pounds of beef/animal protein is discarded due to meat discoloration (brown color), raising concerns over food security, the economy, and the environment. The red color of meat is strongly associated with the ratio of oxymyoglobin to metmyoglobin. This presentation will discuss our innovative use of electrochemistry to understand the redox signals of meat discoloration covering purified myoglobin protein, various species types, and sarcoplasmic extract studies. The knowledge gained from our research is expected to allow the implementation of new electroanalytical tools useful for meat and food science fields.
Radical Cation Alkene Functionalization Using Anodic Oxidation
Authors: Adachi Sota , Okada Yohei
Published: August 2024

Oxidative functionalization of alkenes is a promising molecular transformation technique, where intramolecular reactions enable the synthesis of saturated heterocycles1), which are often found in natural products and pharmaceuticals. In addition to the widely studied palladium-catalyzed oxidative functionalization of alkenes2), electrochemical3), 4) and photocatalytic5) methods have recently been developed. These one-electron oxidation-based methods have been applied to trisubstituted and tetrasubstituted alkenes with large steric hindrance, which is difficult to achieve with conventional palladium-catalyzed reactions. In many cases, these methods reported previously form rings as neutral radicals under basic conditions. On the other hand, radical cationic cyclization is relatively rare and have not yet been fully discussed. In this study, we developed an alkene oxidative functionalization using electrolysis for radical cationic cyclization.

After optimizing the reaction conditions using trisubstituted alkene (1a) as a model substrate, we succeeded in obtaining the target compound (2a) in 90% yield (Scheme 1). In this reaction, a six-membered ring is formed as a byproduct, but the anion species of the supporting salt affects the reaction selectivity, and it was found that a five-membered ring was formed with high selectivity when ClO4- or TfO- were used. Furthermore, using a 1:9 mixture of highly polar CH3CN and low-polar 1,2-DCE as the reaction solvent improved the solubility and conductivity of the supporting salt, resulting in a significant increase in yield. The use of carbon felt, which has a large surface area, as the working electrode also contributed to the yield improvement by suppressing the voltage increase.

For sulfonamides (1b-d) with various substituents on the aromatic ring, we were able to obtain five-membered ring compounds (2b-d) in good yields in all cases. In addition to these results, the details of the condition studies and other substrates will be discussed.

1) Nakamura, I.; Yamamoto, Y. Chem. Rev.
2004, 104, 2127-2198.

2) McDonald, R. I.; Liu, G.; Stahl, S, S. Chem. Rev. 2011, 111, 2981-3019.

3) Xu, H.-C.; Moeller, K. D. J. Am. Chem. Soc. 2010, 132, 2839–2844.

4) Huang, C.; Li, Z.-Y.; Song, J.; Xu, H.-C. Angew. Chem. Int. Ed.
2021, 60, 11237–11241.

5) Reed, N. L.; Lutovsky, G. A.; Yoon, T. P. J. Am. Chem. Soc.
2021, 143, 6065-6070.

Figure 1
Anodic Cyclization Reactions and an Approach to the Chrysosporazine Family of Natural Products
Authors: Moeller Kevin D , Medcalf Zachary , Wu Tiandi
Published: August 2024

Electrochemistry has long offered new opportunities for the construction of biologically relevant molecules. Many of these opportunities are based on the ability that electrochemistry provides for reversing the polarity of known functional groups. For example, consider the brief retrosynthetic analysis shown in the Scheme below. The analysis proposes a route to the Chrysosporazine family of natural products (specifically Chrysosporazine D in this case) from readily available amino acid and lignin derived starting materials. The Chrysosporazines are efflux inhibitors that improve the effectiveness of chemotherapy agents.1 The plan calls for a coupling of the two starting materials to afford a cyclization substrate. However, the proposed cyclization reaction would combine a nucleophilic amide nitrogen with a nucleophile electron rich styrene derivative. In principle, an anodic oxidation reaction can solve this issue by either converting the amide nitrogen into a radical or oxidizing the styrene derivative to form a radical cation. Either mode would effectively reverse the polarity of one of the nucleophilic groups and allow for the cyclization.

Previous efforts examining these cyclizations have focused on the generation of a N-radical intermediate.2 Yet while these efforts have been very successful, they require the presence of a phenyl ring on the amide nitrogen in order to lower its pKa. This is essential for the formation of an amide anion that is in turn oxidized to the desired N-radical. Such a plan is not compatible with the synthesis of the Chrysosporazines that simply do not have a phenyl ring on the nitrogen of the amide. Placing one there would prevent the intramolecular cyclization. So, how can this problem be resolved?

There are two possible answers to this question. One involves a change in the overall strategy that converts the amide into an electron-rich olefin equivalent that can be oxidized to from a radical cation. The second involves finding an alternative method for dropping the pKa of the amide so that the anion and subsequent N-radical can still be made. In the chemistry to be discussed, both strategies will be examined and the propensity for the cyclic product to undergo over-oxidation shown to be the determining factor for which pathway is preferred; a preference that has led to a new approach to N-based radical cyclizations.

1. Elbanna, A. H., Khalil, Z. G., Bernhardt, P., V., Capon, R. J. Org. Lett.
2019,
21, 8097–8100.

2. Xiong, P.; Xu, H-C. Acc. Chem. Res. 2019, 52, 3339-3350.

Figure 1
Electrochemical and Spectroscopic Investigations of Bismuth(III) Pharmaceuticals with L-Glutathione
Authors: Cheek Graham , Dierickx Abram
Published: August 2024

Due to the importance of L-cysteine in the human system, the interaction of metals with this amino acid are worthy of investigation by various methods. In this laboratory1, we have investigated the interaction of bismuth(III) compounds with L-cysteine by both cyclic voltammetry and UV-VIS spectroscopy in an attempt to understand the role of bismuth in treating gastrointestinal maladies.2 The addition of bismuth(III) compounds to solutions of L-cysteine causes a negative potential shift for bismuth(III) reduction as an indication of complex formation between bismuth(III) and L-cysteine. This interaction is also evident by the appearance of a UV-VIS spectroscopic band at 340 nm (Bi-sulfur bond). Even at low pH values (pH 1.0), electrochemical studies show evidence of some kind of interaction even when there is no 340 nm band. These investigations have been conducted at pH 1.00 and 3.00 to simulate conditions in the human stomach and at pH 7.40 MOPS [(3-N-morpholino)propanesulfonic acid] to simulate general physiological conditions, in particular the intestinal tract. Recent work has involved extension of this work to L-glutathione, a tripeptide incorporating L-cysteine, under similar conditions. As might be expected, these interactions are considerably more complicated than those involving L-cysteine. As an example, there is a considerable positive potential shift for the reduction of bismuth(III) citrate in the presence of L-glutathione on the first and second voltammetric sweeps at gold and glassy carbon electrodes. This behavior evidently reflects the rather long (several seconds) time required for the re-formation of the bismuth complex with L-glutathione after its reductive ligand (L-glutathione) loss during bismuth(III) reduction on the first sweep. In addition, there is evidence of a film buildup on the electrode surface as observed by peak current increases during multiple potential sweeps. These observations are planned for inclusion in this symposium presentation.

References

T. Cheek and D. Peña, J. Electrochem. Soc.,
167, 155522 (2020)

Li, R. Wang, and H. Sun, Acc. Chem. Res.,
52, 216 (2019).
Electrochemical Quantification of Tobramycin Retention in Pseudomonas Aeruginosa as Antimicrobial Susceptibility Indicator
Authors: Lopes Luma Clarindo , Lima Dhésmon , Hayat Muhammad , Li Yanqi , Kumar Ayush , Kuss Sabine
Published: August 2024

The emergence and spread of bacterial resistance to antibiotics has developed into one of the most challenging threats to public health. Antibiotic susceptibility tests (ASTs) for bacterial infections are now essential, because they provide guidance for physicians in the selection of antibiotics, to which bacteria will respond. Most current AST methods require long periods of time, because of bacterial growth and incubation, leading to a prolonged and overuse of broad-spectrum antibiotics. Thus, there is a growing demand for methods and technologies that enable rapid antibiotic susceptibility assessment. Due to advantages related to cost-effectiveness, rapid response time and high sensitivity,

electrochemical detection methods are promising analytical tools that can successfully quantify antibiotic uptake and retention in clinically relevant bacterial strains. This study presents the electroanalytical quantification of tobramycin (TOB) retention in susceptible and resistant bacterial strains of Pseudomonas aeruginosa. The electrochemical behavior of TOB was characterized by voltammetry, identifying redox potentials, the current dependence on pH conditions, and the detection limit at unmodified glassy carbon electrodes. The presented methodology was able to distinguish between susceptible and resistant bacterial strains, and is also capable of identifying varying degrees of resistance against TOB. The presented approach detects the immediate interaction of bacteria with an antibiotic, without the need of complex and cost-intense equipment related to genomic testing methods
The Differential Impact of Resorcinarenes on Ferrocene Redox Couple: Towards Electroactive Host-Guest Systems
Authors: Quintero Carlos , Martic Sanela , Beyeh Ngong Kodiah
Published: August 2024

Alternative to complex labelling of resorcinarene hosts with redox-active probes, non-covalent complex formation offers a unique avenue towards the design of dynamic electro-active host-guest systems towards application in sensors and functional materials. Here, resorcinarene hosts were evaluated with a well-known redox probe, ferrocene (Fc). Specifically, hosts were designed based on tuning the resorcinarene rim with functional groups to allow for hydrogen bonding, pi-pi stacking, hydrophobic and electrostatic interactions. Cyclic voltammetry was used with glassy carbon electrode as a working electrode in organic solvent to evaluate interactions between hosts and Fc. Specifically, the electrochemical properties of Fc, hosts, and host-Fc mixtures were evaluated with respect to the ferrocene/ferrocenium redox couple (reversibility, current and potential). Depending on the host structure, all hosts induced a potential shift of ferrocene/ferrocenium redox couple. The reversibility of the redox couple was maintained with certain hosts, while others resulted in surface fouling. The electrochemical studies were further supplemented by non-electrochemical methods, such as nuclear magnetic resonance, spectroscopy, mass spectrometry as well as theoretical calculations using density functional theory. Data show that controlled and tunable redox host-guest systems with well-defined redox properties may be achieved through chemical modifications of hosts, which may be used to inform functional sensors and devices with a wide range of applications such as phosphate analogue detection.
Study on Meat Discoloration Based on Storage Effect and pH Factor Using Square Wave Voltammetry
Authors: Bhandari Silan , Kasthuri Dias Sandun Bogahawaththa , Ayabadda Devage Sachinthani , Kumar Rishav , Ramanathan Ranjith , Krishnan Sadagopan
Published: August 2024

The overarching objective of this project is to discover the electrochemical features of meat discoloration under various point-of-sale meat conditions. The bright red color of meat plays a key role in influencing consumers to purchase meat. The discoloration of meat is causing high economic loss around the globe. Here, we used a square wave technique to observe redox peaks in beef sarcoplasm with the incubation time to diagnose discoloration focusing on the point of sale. The first investigation was centered on the storage effect on discoloration where normal pH beef sarcoplasm (post mortem) showed a rising trend of peaks that correspond with a growing accumulation of metmyoglobin and decumulation of oxymyoglobin intensifying the rate of discoloration. The second study was done by comparing discoloration of beef meat at two pH conditions, pH 7.4 (physiological state) and pH 6.4 (stressed animal muscle). Notably, a substantial elevation in the oxidation peak signal was observed from the pH 6.4 sample compared to the pH 7.4 counterpart, with discoloration. Furthermore, the UV spectral absorbance of meat samples was used to calculate the percentage of oxy- and metmyoglobin contents to gain independent insights. From these studies, we can gain a fundamental understanding of the redox processes of beef upon discoloration and thus develop novel tools to detect meat spoilage and discoloration rates.

Keywords: Beef sarcoplasm, square wave voltammetry, metmyoglobin, oxymyoglobin
Origin of Electrochemical Ozone Activity on Tin-Oxide Based Electrodes
Authors: Alaufey Rayan , Tang Maureen H.
Published: August 2024

Electrochemical ozone production (EOP) is a promising green alternative route for ozone generation with applications in advanced oxidation processes and electro-organic synthesis. Nickel and antimony doped tin oxide (NATO) is a promising EOP active catalyst due to its high selectivity, low cost, and relative lack of toxicity. The origin of high EOP selectivity on NATO is disputed, given that the competing oxygen evolution reaction (OER) is thermodynamically favored due to its lower thermodynamic potential. In this work, we build on previous reports to establish the mechanism of EOP on NATO electrodes and explain the role of dopants in the anode. Additionally, we attribute the lack of electrode stability to the corrosion of the catalyst. Finally, based on our results, we introduce and verify a design framework for inducing EOP activity in tin oxide electrodes.
Microelectrode-Based Diffusivity Measurements of Hydrogen in Molten 2LiF-BeF2
Authors: Pickarski Timothy Ryan , Chen Claire Tianyi , Smith Eric David , Scarlat Raluca O. , Su Guanyu
Published: August 2024

Detailed knowledge of the mass transport behavior of hydrogen isotopes in molten 2LiF-BeF2 salt (FLiBe) is essential to the design of new nuclear fusion technologies that make use of this molten salt to breed tritium to fuel the fusion reaction. However, typical studies of hydrogen transport using macroelectrodes are limited to solely measuring the permeability of an analyte—a property defined as the product of concentration squared and diffusivity. This challenge necessitates the development of microelectrodes capable of dynamically measuring diffusion coefficients when concentrations are variable. Unlike macroelectrodes, microelectrodes can measure diffusivity and concentration independently due to a steady-state current proportional to the product of diffusivity and concentration captured in addition to the Cottrellian current response.

This steady-state current is established due to a continuously expanding diffusion layer from the electrode that cannot expand indefinitely within finite experimental setups. Therefore, COMSOL Multiphysics simulations mirroring experimental conditions were performed to validate the analytical mass transport model based on the solution of Fick’s Second Law in radial coordinates. These simulations employed a 2D axisymmetric model to examine the conditions under which the infinite bulk solution approximation is valid, confirming that our electrode design would yield true steady-state current responses indicative of radial diffusion.

Platinum microelectrodes developed in this study served a dual purpose: they not only addressed previous limitations in high-temperature molten salt experimentation but also enabled dynamic measurements of both the diffusion coefficient and concentration of hydrogen in molten FLiBe introduced by lithium hydride. Square wave voltammetry and chronoamperometry were performed on a three-electrode cell using a platinum working microelectrode, a tungsten counter electrode, and a Ni/Ni2+ thermodynamic reference electrode. The successful measurement of hydrogen diffusivity in these experiments not only offers essential insights into molten FLiBe behavior but also sets the stage for future investigations into the effects of redox conditions, impurities, and equilibration time on tritium within nuclear fusion reactors.
Unveiling the Role of Dopants in the Electrochemical Ozone Production Reaction Using Tin Oxide Electrodes
Authors: Alaufey Rayan , Tang Maureen H.
Published: August 2024

Ozone is a strong oxidizer with promising environmentally friendly applications in water disinfection, air purification, and organic synthesis. The 6-e- electrochemical ozone production (EOP) reaction offers great potential for ozone generation while curbing the formation of harmful by-products compared to other ozone production methods. However, the development of electrochemical ozone production (EOP) catalysts is limited by significant hurdles dictated by thermodynamic limitations. In this work, we develop and validate a comprehensive guideline that outlines a strategic and rational design approach to induce EOP activity in tin oxide. We propose that two things are needed for tin oxide to produce ozone: increased conductivity, achieved with donor dopants, and first-row transition metal (TM) dopants to facilitate hydroperoxyl radical generation through Fenton-like processes. To validate our approach, we picked tantalum, antimony, and tungsten as donor dopants and nickel and cobalt as transition metals. Our results suggest that all combinations of TMs, oxidizable to a cationic state capable of producing hydroperoxyl radicals from hydrogen peroxide, and donor dopants lead to EOP activity in tin oxide.
In-Situ Spectroelectrochemistry for Elucidating the Stable Mars-Van Krevelen Catalytic Cycle for Green Ammonia Production on Nitride MXene
Authors: Johnson Denis , Djire Abdoulaye
Published: August 2024

The electrochemical nitrogen reduction reaction (NRR) provides an opportunity to convert nitrogen (N2) to ammonia (NH3) at ambient conditions. Protons (H+), which stem from water oxidation, are necessary for this process, but result in the hydrogen evolution reaction (HER) reducing overall selectivity. Another cause for low selectivity in the NRR is the high energy required to activate the N≡N bond during typical adsorption-desorption mechanisms. An avenue to mitigate these challenges altogether is available on transition metal nitride materials through the Mars-van Krevelen (MvK) mechanism, where sub-lattice nitrogen atoms are protonated to form NH3, which then desorb to form nitrogen vacancies that require less energy to weaken the N≡N. Recently, we have provided preliminary evidence that the Ti2NTx MXene operates through this MvK mechanism. To further corroborate this mechanism, a series of electrochemical and in-situ spectroscopic techniques, including X-ray absorption spectroscopy (XAS) and Fourier-transform infrared (FTIR) spectroscopy, were utilized. We use XAS to track the Ti oxidation state shift as a function of applied potential to understand the role of the Ti in the MvK mechanism and to understand the dynamic change in the Ti-N-Ti bond network. Furthermore, we use FTIR to elucidate in real-time the adsorption of NRR reactive species and intermediates on the MXene surface, especially with regards to the periodicity of the -NH2 and N-N spectroscopic intensities, which allows for the MvK mechanism to be differentiated from the typical adsorption-desorption mechanisms. Finally, we use DFT to corroborate the experimental work and further enhance our understanding of the mechanisms of NRR. These findings serve as the foundation to produce green ammonia using earth abundant resources.