Current Opinion Research Articles

Evolution and Perspectives of Anesthesia and Analgesia Techniques for Coronary Artery Bypass Grafting

For more than 60-year history of coronary artery bypass grafting, surgical techniques and specialists’ competence were improved as well as the safety of anesthesiological management. This analytical review discusses modern features of analgesia during coronary surgery and early postoperative period. We described current opinion on perioperative administration of opioids and modern methods of analgesia, taking into account possible complications of their use. Despite the low mortality and overall safety of coronary bypass grafting nowadays, the optimal strategy of analgesia for this surgery is not established yet. This review lists routinely used analgetics and some aspects of their use in cardiac anesthesiology, outlines trends and prospects for the introduction of new drugs and techniques for analgesia. Despite a number of restrictions on the use of opioids in intensive care in modern era, in cardiac anesthesiology their use remains justified and, under certain conditions, safe enough.

A Study on Animal Cellular Organization

Cells are comprised of highly organized assemblies of macromolecules, which undergo continuous dynamic rearrangements. Our contributors in this issue of Current Opinion in Cell Biology review some of the most exciting recent advances in our understanding of how various such dynamic assemblies function at the molecular level. As (to use the much-quoted phrase of Theodosius Dobzhansky) “nothing in biology makes sense except in the light of evolution”, Peroxisomes are vesicle-like packets containing specialized enzymes that rid cells of toxins and utilize fats as an energy source. They can be called into being or dismissed depending upon the metabolic needs of the cell, which may therefore have few or many peroxisomes at different times. Significant recent progress has been made in understanding peroxisomal biogenesis, and it turns out both fission and de novo assembly occur, depending on the cellular circumstances. The ER provides membranous materials for both processes, while the contents of the peroxisomes are imported by a long-mysterious mechanism that is only now being revealed. The coatomer family of vesicle coating complexes are shown to have significant structural relationships among themselves and, tellingly, to the nuclear pore complex; while the ESCRT system has been found to have a lineage that extends back into the Archea. Analyses of these factors indicate that a complex endomembrane system predates the initial radiation of eukaryotic lineages, and suggest new insights on the origins of eukaryotes. The biogenesis of cellular organelles represent another huge leap in complexity, generally involving either division of pre-existing organelles or de novo assembly from precursors generated by other organelles. With an insightful discussion of informational and algorithmic complexity, he argues persuasively that the problem is not as insurmountable as some had thought, and does not require the elaborate assumptions made by some previous theories. A mainstay of this review series has been the relentless and exciting progress made on the cytoskeleton. As several topics including septins, intermediate filaments, and the bacterial cytoskeleton were covered in excellent reviews in last year’s issue, this year we focused instead on recent progress on actin and microtubule function in cells.

Andexanet Alfa: What We Have Learned from Clinical Trials and Real-World Data.

Andexanet alfa is a specific reversal agent for factor Xa inhibitors with immediate reversal of their anticoagulant effect. Andexanet alfa is currently approved for use in patients treated with rivaroxaban and apixaban who have life-threatening or uncontrolled bleeding. New data from both controlled clinical trials and real-world experience are continuously being published, providing greater insight into the clinical characteristics of the drug, such as efficacy and safety. It is worth considering that andexanet alfa could be of benefit in a variety of different clinical scenarios where patients receiving treatment with apixaban and rivaroxaban (and endoxaban) have life-threatening conditions. These different clinical scenarios, which range from pre-treatment of urgent surgery, especially neurosurgical interventions, and concomitant use of andexanet alfa and prothrombin complex concentrate to onset of bleeding more than 6 h prior to admission, should be clarified as well as the issue of "low/high" dose of andexanet alfa and the need for baseline anti-Xa inhibitor levels measured by point-of-care testing. Finally, management of patients at high risk of thrombosis or recent arterial/venous thrombotic events needs to be further explored. In this current opinion, we address these urgent questions in the light of recent literature and clinical trial data.

Use of acenocoumarol in cardioembolic stroke: an evidence-based review

Stroke is the leading cause of long-term disability and the second most common cause of death worldwide. Nearly two-thirds of all strokes represent cerebral ischemia, of which about 15%-30% are of cardioembolic origin. Atrial fibrillation accounts for about 60% of all cardioembolic strokes. Current clinical evidence suggests that oral anticoagulant therapy can prevent around 70% of strokes in patients with atrial fibrillation. Oral anticoagulation therapy is preferred over antiplatelet therapy in patients with cardioembolic stroke. Vitamin K antagonists (VKAs) and nonvitamin K antagonist oral anticoagulants (NOACs) are routinely prescribed oral anticoagulants in patients at risk of stroke; however, there are specific indications where VKA use surpasses NOAC use or there are conditions where NOACs are contraindicated. A group of experts revisited the role of oral anticoagulants in the management of cardioembolic stroke in India with emphasis on VKA, specifically acenocoumarol. This article discusses various aspects of anticoagulation therapy, including the timing of initiation and patient monitoring, in patients with cardioembolic stroke with reference to current clinical evidence and expert opinion based on Indian clinical experience.

Interactive effects of low-volume interval exercise and nutrition on glycemic control.

Low-volume interval training has been demonstrated to improve indices of 24 h glycemic control using continuous glucose monitoring in individuals with or at risk for metabolic diseases. Nonetheless, there are inconsistencies in the literature with respect to the effects of interval exercise on 24 h glycemia, which may partly result from different nutritional conditions and/or controls adopted across various studies. This current opinion aims to provide a concise overview of the effects of acute and chronic interval exercise on 24 h glycemic control, while also describing how nutrition can influence and modify these responses. Given the distinct impact of dietary intake on blood glucose regulation, the adoption of diverse dietary control strategies during measurement of 24 h glycemia-spanning from using the participant's habitual diet to providing standardized meals customized to individual energy requirements-may contribute to varying conclusions across studies regarding the influence of interval exercise on 24 h glycemia. In addition, nutritional manipulations surrounding exercise, including whether interval exercise commences in the fasted or fed state, the macronutrient composition of post-exercise meals, and the presence of an energy and/or carbohydrate deficit among participants, offer important context when considering the effects of interval exercise on 24 h glycemia. Additional well-controlled studies are warranted to explore the interactive effects of interval exercise and nutrition on 24 h glycemia. These efforts will assist in refining exercise and nutrition recommendations aimed at improving glycemic control.

Current clinical opinion on surgical approaches and rehabilitation of hand flexor tendon injury-a questionnaire study.

The management of flexor tendon injury has seen many iterations over the years, but more substantial innovations in practice have been sadly lacking. The aim of this study was to investigate the current practice of flexor tendon injury management, and variation in practice from the previous reports, most troublesome complications, and whether there was a clinical interest in potential innovative tendon repair technologies. An online survey was distributed via the British Society for Surgery of the Hand (BSSH) and a total of 132 responses were collected anonymously. Results showed that although most surgeons followed the current medical recommendation based on the literature, a significant number of surgeons still employed more conventional treatments in clinic, such as general anesthesia, ineffective tendon retrieval techniques, and passive rehabilitation. Complications including adhesion formation and re-rupture remained persistent. The interest in new approaches such as use of minimally invasive instruments, biodegradable materials and additive manufactured devices was not strong, however the surgeons were potentially open to more effective and economic solutions.

What's the big IDEA? Incorporating inclusion, diversity, equity, and access (IDEA) in population health nutrition research and practice.

Historically, the constructs of inclusion, diversity, equity, and access (IDEA) have not been sufficiently considered or included in population health nutrition research and practice. Consequently, current nutrition assessment benchmarks and knowledge translation tools may not accurately or adequately reflect diversity in the Canadian population or produce meaningful dietary guidance. The purpose of this current opinion paper is to introduce the population health nutrition research and practice framework and explore the current application of IDEA within this framework. Recommendations are offered to incorporate the constructs of IDEA along the continuum of future nutrition research and services to improve population nutritional health.

Current Opinion in Hematology.

Current Opinion in Hematology.

Editorial introductions

Current Opinion in Supportive and Palliative Care was launched in 2007. It is one of a successful series of review journals whose unique format is designed to provide a systematic and critical assessment of the literature as presented in the many primary journals. The fields of supportive and palliative care are divided into 12 sections that are reviewed once a year. Each section is assigned a Section Editor, a leading authority in the area, who identifies the most important topics at that time. Here we are pleased to introduce the Journal’s Section Editors for this issue.

A neural probabilistic bounded confidence model for opinion dynamics on social networks

Opinion dynamics (OD) models simulate the evolution of personal opinions using computer science, social dynamics, physics, and complexity science tools on social networks. However, current opinion dynamics models mainly utilize agent-based models to simulate user interactions but still need to leverage large-scale data fully. Social networks typically involve a vast number of users and information, making it difficult for models to capture the complex interactions in real social networks. Additionally, many models overlook the specific mechanisms of user interactions, such as how network individuals influence and interact with one another, resulting in inaccuracies in modeling individual opinion evolution. This paper proposes a novel approach that integrates the probabilistic bounded confidence model (PBC) with deep learning, i.e., Neural Probabilistic Bounded Confidence (NPBC), to tackle these challenges. The NPBC model adopts an attention network, a long short-term memory (LSTM) network, and a feedforward neural network to approximate the evolution of individual opinions within networks. It satisfies the data approximation and the users’ opinion update rule that conforms to the PBC model. This model enhances the understanding of opinion dynamics, helping to develop effective strategies for opinion guidance in social networks. Finally, the proposed NPBC model is evaluated on three synthetic and Twitter datasets. The results demonstrate that the proposed NPBC model performs better than the six baseline methods in predicting user opinions. Compared to baseline models, the model’s accuracy (ACC) and comprehensive evaluation (F1) scores improve by up to 18% and 7%, respectively.

Current Opinion in Organ Transplantation welcomes a new Editor-in-Chief.

Current Opinion in Organ Transplantation welcomes a new Editor-in-Chief.

Current Opinion on Food Sustainability for Liver Associated Health Problems: Facts and Myths with Case Study

The liver is the second-largest organ in our body which separates the nutrients and waste as they move through our biological process system and it additionally produces bile, a substance that carries toxins out of your body and aids in digestion. There are several myths associated with liver spread amongst masses. It is a vital necessity to make society devoid of such myths and aware of the real scenario. This review aimed to summarize the different facts and myths associated with health problems of liver and highlight the importance of food sustainability approach with the help of some case studies. A comprehensive literature search was conducted using various databases between 2006 and 2022 that focused on the various facts and myths associated with liver related health issues. Myths create nothing but false notions and fear amongst people. Some case studies were summarized to clear all the conflict statements commonly related with liver diseases in the society. Myths like nothing other than water is considered a good beverage for the liver, but recent studies have proven that measured quantities of coffee and herbal tea intake is healthy for the body. Additionally, coffee has a protective effect on the organ liver. Similarly, hepatitis can spread through casual contacts. Although it is proven that hepatitis B, C and autoimmune hepatitis, do not spread on having casual contact or sharing food and drink. A substantial myth states that blood tests can detect problems associated with the liver, but doctors rarely suggest blood tests for liver functioning. This review is focused to resolve several myths associated with the liver which are often considered true by masses.

Current Evidence and Expert Opinion on Thromboprophylaxis After Total Knee and Hip Replacement.

An effective anticoagulant provides a balance between the risk for venous thromboembolism (VTE) and bleeding and is crucial in achieving optimal clinical outcomes in patients undergoing total hip replacement (THR) and total knee replacement (TKR) surgeries. We performed a review of the literature on thromboprophylaxis for patients undergoing total hip or knee replacement. This review article summarizes current guidelines and evidence for anticoagulation along with the expert opinion about pharmacological VTE prophylaxis, particularlynon-Vitamin K antagonist oral anticoagulants (NOACs), for patients after total hip or knee replacement. Aspirin for VTE prophylaxis after TKR/THR has been controversial and most of the evidence is reported from observational research. Although the guidelines do not recommend any specific thromboprophylaxis agent, available evidence suggests that NOACs are as effective as low molecular weight heparins (LMWHs) in preventing VTE. Oral administration and the lack of dose monitoring make NOACs easy to use in outpatient settings in cases with challenging treatment compliances. They can be used for two weeks after TKR and five weeks after THR - six weeks after TKR and THR to cover the at-risk period for VTE post-discharge. Owing to the lack of evidence for a head-to-head comparison of NOACs, an anticoagulant with better efficacy and safety may be suggested in special patient populations (elderly, obese patients, or those with renal dysfunction). The expert opinion on pharmacological VTE prophylaxis provided in this article could address some gaps in the management of anticoagulation in patients with total hip or knee replacement.

Integrating Micro-Patterned Flow Fields into Electrode Architecture Via Non-Solvent Induced Phase Separation for High Performance Redox Flow Batteries

To facilitate increasing penetration of intermittent renewables in the energy mix, there is a growing need for energy storage technologies. Redox flow batteries (RFBs) have attracted significant attention in recent years due to their suitable characteristics for long-duration stationary energy storage applications. However, the wider adoption of RFB systems is still limited by the capital cost, to which the reactor stack is a large contributor[1]. Further cost reduction can be achieved by reducing kinetic, mass-transfer, and ohmic losses to improve the stack performance. Porous electrodes are key components within the battery stack, providing active sites for electrochemical reactions, and transport pathways for active species. Commercially available carbon-fiber electrode architectures include carbon paper, carbon felt, and carbon cloth. They have a highly porous structure, but their relatively low surface area and low hierarchical fiber orientation increase both electrochemical and pumping losses[2]. There is still a need to develop a low-cost porous electrode that meets the requirements of high active surface area and facile electrolyte transport to enhance battery performance and system efficiency.Non-solvent induced phase separation (NIPS) is a manufacturing route in the field of membrane technology, which is widely used to fabricate asymmetric membranes[3]. Recently this route has also been used to fabricate non-fibrous porous electrodes[4]. The microstructure of NIPS electrodes is largely influenced and controlled by the solvent/non-solvent exchange rate at the interface between a polymer solution and a coagulation bath. When the phase exchange process is slow, segregation is delayed. This type of segregation generally results in a sponge-like, relatively dense structure[5]. This sponge-like structure has the advantage of small pore size and high surface area, but also has poor hydraulic permeability and high mass-transfer losses. The trade-off between surface area and permeability needs to be further optimized.In the present study, inspired by the flow field designs widely used in RFBs to guide the electrolyte flow paths for low pressure drop, uniform electrolyte distribution, and high electrochemical performance[6], we propose a strategy to imprint micro-patterned flow fields directly into the electrode architecture during NIPS processing to improve mass transfer properties. NIPS polymer films were cast onto molds with specific micro-patterns, and the resulting micro-channels can be preserved in the electrodes after carbonization. To verify the effectiveness of the micro-patterned electrodes, here, we investigate two selected micro-patterned designs. The groove-patterned electrodes were combined with flow-through flow fields (FT-FFs) for in-plane mass transport optimization, and the pillar-patterned electrodes were combined with interdigitated flow fields (IDFFs) for through-plane flow optimizations[7]. Two geometric sizes of the micro-patterns were considered in each design. The pore sizes and distributions of the micro-patterned electrodes were determined by mercury intrusion porosimetry. The hydraulic permeability of the electrodes was evaluated by half-cell pressure drop measurements, and the electrochemical specific surface area was determined through electrochemical impedance spectroscopy under non-faradaic conditions. In addition, we performed electrochemical battery tests with symmetric iron RFB (0.5 M Fe2+/Fe3+, 2 M HCl) cells and vanadium full-cells (1.6 M V active species at 50% state-of-charge). It was found that due to the small pore size (e.g., ~1 μm) and narrow pore size distribution of the sponge-like NIPS structure, the main contribution to the total losses in electrodes without micro-patterns in electrochemical performance comes from mass-transfer. Electrodes with groove and pillar patterns can help reduce the pressure drop and improve mass transfer properties. Pillar-patterned electrodes with the combination of IDFF show high overall electrochemical performance with greatly reduced mass transport resistances. At an electrolyte velocity of 10 cm/s, the total resistances for kinetic and mass transfer are less than 0.1 Ω·cm2 in symmetric iron cell tests. Compared to the activated commercial electrode (e.g., 2-layer Freudenberg H23 carbon paper, thermally treated at 450 oC for 12 h), the total resistances for kinetic and mass transfer are reduced by ~60%, which shows great potential for adoption in next generation high-performance RFB systems. References J. Noack, L. Wietschel, N. Roznyatovskaya, K. Pinkwart, J. Tübke, Energies, 9, 627 (2016).A. Forner-Cuenca, F.Brushett, Current Opinion in Electrochemistry, 18, 113-122 (2019).H. Wang, J. Jung, J. Kim, S. Kim, E. Drioli, Y. Lee, Journal of Membrane Science, 574, 44-54 (2019).C. Wan, R. Jacquemond, Y. Chiang, K. Nijmeijer, F. Brushett, A. Forner-Cuenca, Advanced Materials, 33, 2006716 (2021).D. Wang, J. Lai, Current Opinion in Chemical Engineering, 2, 229-237 (2013).X. Ke, J. Prahl, J. Alexander, J. Wainright, T. Zawodzinski, R. Savinell, Chemical Society Reviews, 23, 8721-8743 (2018).V. Muñoz-Perales, P. García-Salaberri, A. Mularczyk, S. Ibáñez, M. Vera, A. Forner-Cuenca, ChemRxiv, (2023).

Scaling up Electrode Manufacturing with Non-Solvent Induced Phase Separation Technology

Grid-scale energy storage technologies must be deployed at a massive scale to balance the mismatch between energy generation using renewable technologies and demand. Redox flow batteries are an emerging technological option for large-scale and multi-hour electrochemical energy storage thanks to their ability to decouple energy and power1. Despite their intrinsic advantages, the current elevated costs of this technology hinders commercialization2. To improve cost competitiveness, research efforts have focused on developing novel electrolyte chemistries and optimized reactor concepts. To the latter, optimizing the porous electrode microstructure and surface chemistry offers a promising pathway to increase the performance of flow batteries. However, porous electrodes design is challenging as they must fulfil contradictory requirements such as providing high surface area for electrochemical reactions, facilitating mass transport of reactive species, and maintaining low operational pressure drop. Furthermore, state-of-the-art porous electrodes have been repurposed from other mature electrochemical technologies but have not been tailored for the unique requirements of redox flow batteries3.Non-solvent induced phase separation (NIPS) has been recently introduced as a versatile method to synthesize porous structures suitable for RFBs with unique properties, which are unattainable with current fibrous materials4,5. Drawing inspiration from membrane fabrication techniques, we reengineered the method for the synthesis of porous electrodes for use in redox flow batteries. The porous electrodes synthesized with NIPS were tested in a single-electrolyte cell configuration and then in an all-vanadium redox flow battery, showing promising electrochemical performance in comparison with existing commercial fibrous carbon materials. In this presentation, I will discuss our current efforts to scale up the NIPS method to manufacture electrodes at industrial scale. We believe that non-solvent induced phase separation is a cost-effective alternative to traditional carbon fibrous materials thanks to the few simpler steps required for the electrode preparation. Based on technoeconomic modeling, we estimate that the production cost of the NIPS electrodes can be less than half of the production costs of traditional carbon fibrous electrodes6. Moreover, the phase separated electrodes do not require post-manufacturing heat treatment to increase the surface area and wettability, which further translates into savings on energy costs. In this project, we aspire to scale-up the NIPS materials to a final size, after carbonization, of 30·30 cm2 while retaining similar microstructural and electrochemical performance properties as in laboratory scale. We perform a suite of microscopy, spectroscopic and flow cell diagnostics to correlate the electrode microstructure, surface chemistry and device performance. In this presentation, I will discuss the scalability of the method, reproducibility based on statistical analysis of sample properties and performance, and finally electrochemical performance on two flow battery chemistries.References Markard, J. (2018). The next phase of the energy transition and its implications for research and policy. Nature Energy, 3(8), 628-633.Darling, R. M. (2022). Techno-economic analyses of several redox flow batteries using levelized cost of energy storage. Current Opinion in Chemical Engineering, 37, 100855.Forner-Cuenca, A., and Brushett, F. R. (2019). Engineering porous electrodes for next-generation redox flow batteries: recent progress and opportunities. Current Opinion in Electrochemistry, 18, 113-122.Wan, C. T. C., Jacquemond, R. R., Chiang, Y. M., Nijmeijer, K., Brushett, F. R., & Forner‐Cuenca, A. (2021). Non‐Solvent Induced Phase Separation Enables Designer Redox Flow Battery Electrodes. Advanced Materials, 33(16), 2006716.Jacquemond, R. R., Wan, C. T. C., Chiang, Y. M., Borneman, Z., Brushett, F. R., Nijmeijer, K., & Forner-Cuenca, A. (2022). Microstructural engineering of high-power redox flow battery electrodes via non-solvent induced phase separation. Cell Reports Physical Science, 3(7), 100943.Minke, Christine, Ulrich Kunz, and Thomas Turek. "Carbon felt and carbon fiber-A techno-economic assessment of felt electrodes for redox flow battery applications." Journal of Power Sources342 (2017): 116-124.

Characterization of Fuel Cell Catalyst Layers in a Gas Diffusion Electrode Setup (GDE)

Although the performance of new catalyst materials for proton exchange membrane fuel cells (PEMFC) often show very promising results in ideal rotating disc electrode (RDE) environment, these results cannot always be transferred to applicable conditions in membrane electrode assemblies (MEAs). This is mainly attributed to differences in the catalyst layer (CL) structure, which hinders the transport of reactants and products for the oxygen reduction reaction (ORR). Therefore, the chemical structure and morphology of the CL have to be considered to improve the performance of these systems in fuel cells. However, due to the various possibilities in producing CLs, many experiments must be carried out until the optimum is reached. The interaction of Pt nanoparticles, carbon support, and ionomer creates a complex triple phase interface dependent on numerous parameters. Characteristics of the carbon support,[1] the Pt loading[2] or the ionomer content[3-5] leads to intensive research efforts and a considerable amount of time as many MEA experiments have to be performed for such studies.[6] To accelerate the screening of catalyst layers, the gas diffusion electrode (GDE) was recently proposed as a half-cell to study real catalyst layers.[7] As a proof of concept study, our group recently shown that catalyst layers with different Pt loading in GDE demonstrate similar ORR trends to MEA experiments.[7] Subsequently, GDEs from different laboratories were benchmarked with standardized electrochemical protocols obtaining reproducible results.[8] Most recently, advanced electrochemical characterization methods developed for MEA technique were established as a GDE method.[9] In the present work, we focus on main aspects of catalyst development, such as the morphology of catalyst layer formation and different catalyst materials, to gain fundamental insights into catalyst layer development. We tuned the porosity of real catalyst layers using different solvent compositions. The results show that low macroporosity leads to severe O2 mass transport limitations, whereas a better performance could be achieved for higher porosity. This allows a critical consideration of key parameters in MEA manufacturing, which has hot pressing as an indispensable step.This work demonstrates the importance of morphology and treatment of the catalyst layer and how substantially it affects the performance and mass transport in GDE setups to elucidate the optimal conditions for the accessibility of the triple phase interface.Literature[1] V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson and A. Kongkanand, ACS Energy Lett. 2018, 3, 618-621.[2] J. P. Owejan, J. E. Owejan and W. Gu, J. Electrochem. Soc. 2013, 160, F824.[3] E. Antolini, L. Giorgi, A. Pozio and E. Passalacqua, J. Power Sources 1999, 77, 136-142.[4] K.-H. Kim, K.-Y. Lee, H.-J. Kim, E. Cho, S.-Y. Lee, T.-H. Lim, S. P. Yoon, I. C. Hwang and J. H. Jang, Int. J. Hydrogen Energy 2010, 35, 2119-2126.[5] G. Sasikumar, J. W. Ihm and H. Ryu, J. Power Sources 2004, 132, 11-17.[6] K. Ehelebe, D. Escalera-López and S. Cherevko, Current Opinion in Electrochemistry 2021, 29, 100832.[7] K. Ehelebe, D. Seeberger, M. T. Y. Paul, S. Thiele, K. J. J. Mayrhofer and S. Cherevko, J. Electrochem. Soc. 2019, 166, F1259-F1268.[8] K. Ehelebe, N. Schmitt, G. Sievers, A. W. Jensen, A. Hrnjić, P. Collantes Jiménez, P. Kaiser, M. Geuß, Y.-P. Ku, P. Jovanovič, K. J. J. Mayrhofer, B. Etzold, N. Hodnik, M. Escudero-Escribano, M. Arenz and S. Cherevko, ACS Energy Lett. 2022, 7, 816-826.[9] P. Kaiser, V. Lloret Segura, K. Ehelebe and S. Cherevko, ECS Meeting s 2022, MA2022-01, 2071.

Structure and Activity-Durability Tradeoff of Coated Fe-N-C Catalysts for the Oxygen Reduction Reaction

Fe-based catalysts stand out for oxygen reduction reactions among the platinum group metal (PGM)-free catalysts for reducing the reliance on expensive and scarce platinum. With the endeavor of a PGM-free community, the state-of-the-art Fe-N-C catalysts have demonstrated encouraging initial activity in Proton Exchange Membrane Fuel Cell (PEMFC) 1-2. However, their long-term stability and durability remain a challenge, both in acidic liquid electrolyte cells and in single-cell PEMFCs3. Recently, a novel approach has demonstrated improved durability of Fe-N-C catalysts during ORR, which consisted of coating a pre-existing Fe-N-C with a thin carbon overlayer obtained via chemical vapor deposition of a metal-organic framework (ZIF-8), at 1100 °C4. However, the underlying mechanism for enhanced durability remains unclear. One of the keys to improved stability lies in the specific structure of the catalysts, including the coordination of the ORR-active iron atoms and the structure of the nitrogen-doped carbon matrix, especially the structure located at the top surface of catalysts. The CVD conditions that affect the structure of FeNC must be optimized, to achieve the optimal activity-durability trade-off.This presentation will report on the structure, activity, and durability trends of a suite of FeNC catalysts coated at different CVD conditions. The key parameters have been investigated, such as deposition temperature, overlayer thickness, and iron speciation on their ORR activity and durability. The coated Fe-N-C catalysts have been evaluated for their activity/durability (in oxygenated environments) both in liquid electrolyte cells and PEMFCs. The coated Fe-N-C demonstrated inferior initial activity and improved durability (Figure 1). The correlation between the structural information derived from multiple techniques (XRD, Mossbauer spectroscopy, TEM, Raman spectroscopy, N2 sorption, etc) and their electrochemical behaviors will be discussed.References Jiao, L.; Li, J.; Richard, L. L.; Sun, Q.; Stracensky, T.; Liu, E.; Sougrati, M. T.; Zhao, Z.; Yang, F.; Zhong, S.; Xu, H.; Mukerjee, S.; Huang, Y.; Cullen, D. A.; Park, J. H.; Ferrandon, M.; Myers, D. J.; Jaouen, F.; Jia, Q., Nature Materials 2021, 20 (10), 1385-1391.Mehmood, A.; Gong, M.; Jaouen, F.; Roy, A.; Zitolo, A.; Khan, A.; Sougrati, M.-T.; Primbs, M.; Bonastre, A. M.; Fongalland, D.; Drazic, G.; Strasser, P.; Kucernak, A., Nature Catalysis 2022, 5 (4), 311-323.Martinez, U.; Komini Babu, S.; Holby, E. F.; Zelenay, P., Current Opinion in Electrochemistry 2018, 9, 224-232.Liu, S.; Li, C.; Zachman, M. J.; Zeng, Y.; Yu, H.; Li, B.; Wang, M.; Braaten, J.; Liu, J.; Meyer, H. M.; Lucero, M.; Kropf, A. J.; Alp, E. E.; Gong, Q.; Shi, Q.; Feng, Z.; Xu, H.; Wang, G.; Myers, D. J.; Xie, J.; Cullen, D. A.; Litster, S.; Wu, G., Nature Energy 2022, 7 (7), 652-663. Figure 1

Investigating Enzyme-Based Electrode Processes Using Electrochemical Impedance Spectroscopy and Distribution of Relaxation Time Analysis

Enzymatic fuel cells (EFCs) are an emerging class of electrochemical devices that have the potential to harness renewable energy sources by converting the chemical energy of an organic substrate into electrical energy. Enzymes are responsible in an EFC for highly selective and efficient electrode processes under typically mild ambient conditions, such as the oxidation reaction at the anode and the reduction reaction at the cathode 1. In addition to more conventional techniques, electrochemical impedance spectroscopy (EIS) can be employed to characterize such systems. Electrochemical behavior of enzymatic electrodes, such as enzyme reaction kinetics, substrate mass transport, and electrode stability, can be studied by measuring the system's impedance over a wide frequency range and then performing a precise post-process analysis based on the distribution of relaxation time (DRT). DRT analysis is rarely used to interpret EIS spectra within the EFCs research field, despite the fact that it is widely acknowledged as relevant for properly understanding the EIS potential to improve power density in fuel cells 2,3. Glucose oxidase (GOx) and bilirubin oxidase (BOD) were immobilized on multi-walled carbon nanotubes (MWCNTs) to catalyze the bioelectrocatalytic oxidation of glucose at the anode and the bioelectrocatalytic reduction of oxygen at the cathode, respectively. This study presents a promising approach for the investigation of enzyme-based anodic and cathodic processes by measuring them with EIS and then interpreting the results with DRT analysis, as depicted in Figure 1. By varying different operating parameters, such as the enzymatic loading on the electrode surface or electrolyte conditions, this method can be used to identify three primary relaxation processes occurring at both electrodes. At the interface between the electrolyte and the electrode, it is possible to conclude that high-frequency processes are accountable for ionic conduction, intermediate-frequency processes are accountable for charge transfer, and low-frequency processes are accountable for oxygen surface exchange and diffusion.This method provides access to preliminary fundamental information about enzymatic bioelectrode processes, which can be used to optimize biofuel cell construction and compositions and increase their power output. Figure 1. Schematic representation of the characterization method used to characterize a GOx-CNT-modified anode consisting of EIS measurements and subsequent DRT analysis. Concentration of glucose 175 mM in 0.1 M HEPES Buffer, pH 7; EIS parameters: 20 mV sinusoidal excitation, 0.1 Hz-100 kHz. References K. Herkendell, A. Stemmer and R. Tel-Vered, Nano Res., 12(4), 767–775 (2019). H. Wang, X. Long, Y. Sun, D. Wang, Z. Wang, H. Meng, C. Jiang, W. Dong and N. Lu, Frontiers in microbiology, 13, 973501 (2022). F. Ciucci, Current Opinion in Electrochemistry, 13, 132–139 (2019). Figure 1

Accelerating Real-Time Analysis of Gas Diffusion Electrodes Using Different Coupled Mass Spectrometry Techniques

Due to the rapid development of new catalysts, simple electrochemical screening methods are needed to evaluate the activity and stability of catalyst layers. Setups for these applications already exist: the so-called Scanning Flow Cells (SFCs) unify real-time electrochemical activity and dissolution stability analysis in a high-throughput fashion and find applications in a broad range of topics, such as battery research, 1 oxygen evolution reaction catalysts performance,2 and photo-electrochemistry.3 Yet, the low current densities reached in the system hinder the direct comparison of the results to real devices.4 Gas diffusion electrode (GDE) based setups present a promising alternative to Aqueous Model Systems (AMS) due to their ability to achieve higher current densities. Compared to two electrode full cells (fuel cell or water electrolyser), GDE half-cells are operated in a three-electrode configuration with liquid electrolyte. However, as in fuel cells, gasses reach the catalyst layer through a flow field, achieving relevant current densities up to 2 A cm-2. The GDE half- cell offers the advantage of studying the isolated reaction of the working electrode by applying controlled potentials with a reference electrode. While the GDE offers a simplified approach, the assembly process can be time-consuming, and the overall catalyst throughput analysis could be further optimised.5,6 In this context, we present a novel setup that enables the rapid examination of catalyst layers for fuel cells, providing more realistic conditions while simultaneously investigating degradation processes. The setup consists of an optimised SFC based on lower internal resistance and an additional flow field to purge the catalyst layer with different gasses. As the common SFC, the presented Scanning Gas Diffusion Electrode half cell (S-GDE) can be connected to an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) to quantify the dissolution of metals in real-time. Furthermore, the gas-sensitive Mass Spectrometer can be connected to the gas stream of the cell, enabling the detection of volatile products via on-line electrochemical mass spectrometry (OLEMS). The simple replacement of catalyst layers in the S-GDE allows fast analysis of multiple catalysts consecutively. Still, as the aim is to facilitate high-throughput electrochemistry, developing the S-GDE is ongoing. Furthermore, the optimised cell can reach higher current densities than cells of a similar design, allowing accelerated stress tests (ASTs) and the performance of polarisation curves.The S-GDE will offer a new perspective on realistic catalyst layers, their performance, and catalyst/support degradation processes, e.g. Pt dissolution and carbon corrosion. The increasing demand for new catalyst materials highlights the need for their rapid evaluation under realistic conditions, taking into account not only their electrochemical performance but also their stability. Lüchtefeld J, Hemmelmann H, Wachs S, Mayrhofer KJ, Elm MT, Berkes BB. Effect of Water Contamination on the Transition Metal Dissolution in Water-Enriched Electrolyte: A Mechanistic Insight into a New Type of Dissolution. The Journal of Physical Chemistry C. 2022;126(40):17204–11.Zlatar M, Nater D, Escalera-López D, Joy RM, Pobedinskas P, Haenen K, et Evaluating the stability of Ir single atom and Ru atomic cluster oxygen evolution reaction electrocatalysts. Electrochimica Acta. 2023;444:141982.Jenewein KJ, Kormányos A, Knöppel J, Mayrhofer KJJ, Cherevko S. Accessing In Situ Photocorrosion under Realistic Light Conditions: Photoelectrochemical Scanning Flow Cell Coupled to Online ICP-MS. ACS Measurement Science Au. 2021;1(2):74–81.Ehelebe K, Escalera-López D, Cherevko S. Limitations of aqueous model systems in the stability assessment of electrocatalysts for oxygen reactions in fuel cell and Current Opinion in Electrochemistry. 2021;29:100832.Ehelebe K, Knöppel J, Bierling M, Mayerhöfer B, Böhm T, Kulyk N, et Platinum Dissolution in Realistic Fuel Cell Catalyst Layers. Angewandte Chemie (International ed in English). 2021;60(16):8882–8.Ehelebe K, Seeberger D, Paul MTY, Thiele S, Mayrhofer KJJ, Cherevko S. Evaluating Electrocatalysts at Relevant Currents in a Half-Cell: The Impact of Pt Loading on Oxygen Reduction Reaction. Journal of The Electrochemical Society. 2019;166(16):F1259-F68. Figure 1: The S-GDE unifies the real conditions approach of the GDE and the high throughput approach of the SFC and the connection to two mass spectrometer enables the real time detection of dissolved catalyst (ICP-MS) and volatile products (OLEMS). Figure 1

A Study on Electrochemical Properties of Fuel-Electrode-Supported Reversible Solid Oxide Cells

Introduction Reversible solid oxide cells (r-SOCs) enable both power generation and steam electrolysis, and have attracted attention as a solid state electrochemical energy device for a decarbonized society (1). R-SOCs have the advantage of high efficiency due to high temperature operation, but there exist various technical issues remained in materials selection, start-up and shutdown, and long-term durability. Therefore, reducing operating temperature is desirable for practical applications (2,3). Electrode-supported cells, in which the electrode acts as a structural support, enable lower temperature operation by reducing the thickness of the electrolyte, which has certain electrical resistivity. Here in this study, the current-voltage characteristics and reversible cycle durability under r-SOC operating conditions are evaluated using fuel-electrode-supported cells, with the aim of developing r-SOCs capable of highly efficient fuel cell power generation and steam electrolysis. Experimental For the experiments, fuel-electrode-supported cells were fabricated using fuel electrode-supported half-cells (Japan Fine Ceramics, Japan), schematically shown in Fig. 1. The half-cell consists of scandia-stabilized zirconia (ScSZ: 10 mol%Sc2O3-1mol%CeO2-89 mol%ZrO2) or yttria-stabilized zirconia (YSZ: 8 mol%Y2O3-92 mol%ZrO2) electrolyte and a Ni-cermet fuel electrode, such as Ni-ScSZ or Ni-YSZ. (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF) was applied for the air electrode, and Gd0.1Ce0.9O2 (GDC) was inserted between the electrolyte and the air electrode to suppress interdiffusion and chemical reactions. Four types of cells were used with different combinations of the electrolyte component (YSZ or ScSZ) in the electrolyte layer or the supporting fuel electrode.In electrochemical tests, 50%-humidified hydrogen (100 ml min-1) was supplied to the fuel electrode, and air (150 ml min-1) was supplied to the air electrode. R-SOC initial performance tests were conducted using an electrochemical analyzer (1255B, Solartron). Cell voltage and impedance were measured at 700-800°C at current densities ranging from -0.5 A cm-2 to +0.5 A cm-2. Positive current density means the value in SOFC mode, while negative current density means the value in SOEC mode. In r-SOC 1,000 cycle durability tests, cycles of switching between SOFC and SOEC operation were repeated 1,000 times by varying current density. The range of current density in the cycle tests was between -0.2 A cm-2 and +0.2 A cm-2. The cell impedance was measured before the cycling test and every 100 cycles. After each test, the cells were analyzed by using a focused-ion beam scanning electron microscopy (FIB-SEM) to observe and evaluate the electrode microstructure. Results and discussion Figure 2 (a) shows the r-SOC initial performance of each fuel-electrode-supported cell. The cell with the Ni-YSZ fuel electrode and the YSZ electrolyte showed better current voltage characteristics than other cells. Figure 2 (b) shows the r-SOC 1000-cycle durability of the cell with the Ni-YSZ fuel electrode and the YSZ electrolyte. The results showed a decrease in power generation and electrolysis performance with increasing the number of cycles in both SOFC and SOEC modes. Possible degradation mechanisms will be discussed. Acknowledgments This paper is based on results obtained from a project (Research and Development Program for Promoting Innovative Clean Energy Technologies Through International Collaboration), JPNP20005, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Collaborative support by Prof. H. L. Tuller and Prof. B. Yildiz at Massachusetts Institute of Technology (MIT) is gratefully acknowledged. References (1) Venkataraman, M. Pérez-Fortes, L. Wang, Y. S. Hajimolana, C. Boigues-Muñoz, A. Agostini, S. J. Mcphail, F. Mar échal, J. V. Herle, and P. V. Aravind, J. Energy Storage, 24, 100782 (2019).(2) Subotić, S. Pofahl, V. Lawlor, N. H. Menzler, T. Thaller, and C. Hochenauer, Energy Proc., 158, 2329 (2019).(3) B. Mogensen, Current Opinion Electrochem., 21, 265 (2020). Figure 1