ECS Meeting Abstracts最新文献

{"title":"(Invited) Green Ammonia-Mediated CO₂ Capture and Direct Electrochemical Reduction to Formate","authors":"Yifu Chen, Hengzhou Liu, Jungkuk Lee, Shuang Gu, Wenzhen Li","doi":"10.1149/ma2023-01392307mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01392307mtgabs","url":null,"abstract":"Direct electrochemical conversion of CO 2 capture solutions (instead of gaseous CO 2 ) into valuable chemicals can circumvent the energy-intensive CO 2 regeneration and pressurization steps. While commonly used CO 2 capture agents include alkali and amine solutions, ammonia has been rarely investigated. In another aspect, mismanagement of reactive nitrogen (Nr) in waste has emerged as a major problem in water pollution to our ecosystems, causing severe eutrophication and health concerns. Sustainably recovering Nr [such as nitrate (NO 3 − )-N] and converting it into green ammonia (NH 3 ) could mitigate the environmental impacts of Nr and reduce the NH 3 demand from the carbon-intensive Haber-Bosch process, as well as a possible CO 2 capture agent due to its alkaline nature. In this talk, we will present our rencet research on integration of electrodialysis and electrocatalysis for ammonia synthesis from dilute waste Nr sources, and green ammonia-mediated CO 2 capture (to ammonium bicarbonate, NH 4 HCO 3 ) and subsequent reduction to ammonium formate (NH 4 HCO 2 ) as a new approach to CO 2 capture and utilization (CCU). We have demonstrated a record-high NO 3 − -to-NH 3 performance in a scalable, versatile, and cost-effective membrane-free alkaline electrolyzer (MFAEL): an unprecedented NH 3 partial current density of 4.22 ± 0.25 A cm −2 with a faradaic efficiency of 84.5 ± 4.9%. We also discovered that an ammonium bicarbonate (NH 4 HCO 3 )-fed electrolyzer with an anion exchange membrane (AEM) outperforms the state-of-the-art KHCO 3 electrolyzer with a bipolar membrane (BPM) owing to its favorable thermal decomposition property, which allows for a 3-fold increase in the in situ CO 2 concentration, a maximum 23% increase in formate faradaic efficiency, and a 35% reduction in cell voltage by substituting BPM with the AEM. Our integrated process by combining NH 4 HCO 3 electrolysis with CO 2 capturing by on-site generated green ammonia from the electro-reduction of nitrate in MFAEL has shown a remarkable 99.8% utilization of CO 2 capturing agent. Such a multi-purpose process may offer a sustainable route for the simultaneous removal of N r wastes and streamlined CO 2 capturing and upgrading to valuable chemicals.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Structural Model for Transient Pt Oxidation during Fuel Cell Start-up Using Electrochemical X-Ray Photoelectron Spectroscopy","authors":"Hassan Nagra, Rik Mom, Axel Knop-Gericke","doi":"10.1149/ma2023-01382205mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01382205mtgabs","url":null,"abstract":"Potential spikes during the start-up (SU) and shutdown (SD) of fuel cells are a major cause of platinum (Pt) electrocatalyst degradation, which limits the lifetime of the device. The electrochemical oxidation of Pt that occurs on the cathode during the potential spikes plays a key role in this degradation process. However, the composition of the oxide species formed, as well as their role in catalyst dissolution remains unclear. In this study, we employ a special arrangement of XPS (X-ray Photoelectron Spectroscopy), in which the Pt electrocatalyst is covered by graphene, making the in situ examination of the Pt oxidation/reduction under wet conditions possible. We use this assembly to investigate oxidation state changes of Pt within fuel cell relevant potential window. We show that above 1.1 V RHE , a mixed Pt δ+ /Pt 2+ /Pt 4+ surface oxide is formed, with an average oxidation state that gradually increases as the potential is increased. By comparing a model based on the XPS data to the oxidation charge measured during potential spikes, we show that our description of Pt oxidation is also valid during the transient conditions of fuel cell SU/SD. This is due to the rapid Pt oxidation kinetics during the pulses. As a result of the irreversibility of Pt oxidation, some remnants of oxidized Pt remain at typical fuel cell operating potentials after a pulse. Figure 1","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"(Keynote) Electrochemical CO₂ Reduction on NiNC Single Metal Atom Catalysts Under Alkaline to Acidic pH Conditions","authors":"Peter Strasser","doi":"10.1149/ma2023-01492557mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01492557mtgabs","url":null,"abstract":"The science and technology of the direct electrochemical CO 2 reduction reaction on both model electrodes in liquid-electrolyte H-cells and Gas Diffusion Electrodes (GDEs) in flow electrolyzers offer as many formidable challenges as intriguing opportunities. Controlling the selectivity (faradaic efficiency), while maximizing the energy efficiency by lowering the kinetic overpotentials remains key to turn this complex reaction into a practical process embedded in a process chain. In this talk, I will highlight some of our recent advances in the design and characterization of NiNC single site electrocatalysts for the electrochemical reduction of CO 2 to CO and CO 2 /CO mixed feeds into value-added fuels and chemicals in H-cell and Gas Diffusion Electrode (GDE) single cell electrolyzers. Further focus will be placed on the diagnosis of carbonate transport processes during electrolyzer cell operation using the experimentally accessible carbon crossover coefficient, CCC. Performance and its limitations of cell operation in alkaline and acid conditions will be contrasted and discussed.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure and Dynamics of the Electrical Double Layer during the Rapid Alternating Polarity Electro-Synthesis","authors":"Chaoxuan Gu, Yue Qi","doi":"10.1149/ma2023-01452457mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01452457mtgabs","url":null,"abstract":"Conventional electrochemical organic synthesis uses direct current (DC) condition, where the electrode polarity is not changed during the operation. Unlike DC, alternating current (AC) introduces two more tunable parameters into the potential or current profile: frequency and waveform, allowing new possibilities for modulating reaction efficiency and selectivity. Several very recent AC electrosynthesis examples have shown that the AC can lead to enhanced chemoselectivity that cannot be reproduced by their DC counterparts 1–3 . For instance, Hayashi et al. presented a highly selective and easily scalable Birch-type reduction of heteroarenes by rapid alternating polarity (rAP) waveform 3 . AC voltage transforms the reaction kinetics presumably by affecting the mass transfer of reactive species both in the bulk solution and the electrical double layers (EDL). However, the mechanistic origin of the unique reactivity in AC electrosynthesis is underexplored. Molecular-level details are still in lack to possibly guide the rational design of AC reaction parameters. In this study, we have chosen the rAP heteroarene reduction as the example system and employed classical molecular dynamics (MD) simulations to reveal the liquid structure and dynamics in bulk and interfacial electrolyte. To capture the electrode-electrolyte interfaces, a slab-geometry simulation cell was used, where a 10 nm thick liquid electrolyte is sandwiched between two oppositely charged graphene surfaces. The multicomponent electrolyte was composed of ethanol and tetrahydrofuran (THF) as the co-solvent, [(CH 3 ) 4 N] + [(BF 4 )] - as the salt, and a heteroarene substrate. Based on the charge distribution function statistics, the EDL layer was about 1 nm thick, so if any of the oxygen atom in the ethanol or THF is within 6 Å to the electrode surface, they are considered to be within the EDL. Under both AC and DC, the ethanol to THF ratio was higher than that in the bulk electrolyte due to stronger ion-ethanol attraction. The EDL structure responded to electric field polarity change at different time scales. First, the molecule orientation would flip also within the picosecond time scale after the polarity switch. By tracking the number of molecules in the EDL, we have found that the compositional fluctuation in the EDL converges in about 40 ps. Although it is the ion migration that gets directly affected by the alternating electric field, diffusion of charge-neutral molecules was also found to be accelerated under AC, according to the higher mean squared displacement calculated from the movement of all molecules of each species in the simulation box. This accelerated diffusion spans a larger length and longer time scales. A multi-scale model is proposed to describe both reaction kinetics and liquid structure dynamics simultaneously. References: (1) Rodrigo, S.; Gunasekera, D.; Mahajan, J. P.; Luo, L. Alternating Current Electrolysis for Organic Synthesis. Current Opinion in Electrochemis","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advancement of Proton Conducting Solid Oxide Electrolysis Cells (p-SOEC) for Hydrogen Production at Idaho National Laboratory","authors":"Dong Ding","doi":"10.1149/ma2023-0154203mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-0154203mtgabs","url":null,"abstract":"Proton Conducting Solid Oxide Electrolysis Cells (p-SOEC) is an emerging and attractive technology for hydrogen production through water electrolysis at intermediate temperatures. Economically competitive p-SOEC systems have distinct advantages over conventional oxygen-ion conducting ceramic electrochemical cells, but further technology development and widespread market acceptance will require continuous innovation of materials and structures in order to improve cell performance, enhance system lifetime and reduce cost. Herein, we report the advancement of p-SOEC with materials R&D, interface engineering, as well as cell fabrication and manufacturing in INL. We highlight how DOE support through HydroGEN accelerates move up the technology readiness level.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection of H₂O₂using Carbon Nanotubes Covalently Attached to Nanostructured Au Electrode","authors":"Artur Huseinov, Chaminda P Nawarathne, Noe T Alvarez","doi":"10.1149/ma2023-01482528mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01482528mtgabs","url":null,"abstract":"Detection of hydrogen peroxide (H 2 O 2 ) has practical significance in various fields, including pharmaceutical, clinical and food industries. The enzyme based H 2 O 2 biosensors allow for the detection at lower potentials, thus avoiding possible interference from reducing agents. However, this type of sensors is inherently less stable, difficult to fabricate and more expensive. Due to high electroactive surface area and electrocatalytic properties, gold nanoparticles and their combination with carbon nanotubes (CNTs) are commonly used in H 2 O 2 sensor design. To avoid fabrication inconveniences and improve stability of a H 2 O 2 sensor, we designed a new hybrid material in which CNTs are covalently attached to a gold surface. First, a highly homogeneous nanostructured gold surface was formed on top of the SiO 2 substrate with an intermediate layer of Ti, using E-beam evaporation technique. The average height of the gold nanostructures was 3.9 nm. The gold surface was then electrochemically grafted with aminophenyl groups. Further, plasma-functionalized densified CNT film made from CNT array was attached to the gold surface via amide formation reaction. An introduction of CNTs led to a 40-fold increase in current response. Formation of nanostructured gold surface without actual attachment of nanoparticles to the substrate, as well as covalent bonding of CNTs to the surface, provide a very high stability of the fabricated material, which, in turn, improves the repeatability of measurements. A designed electrode was used for non-enzymatic H 2 O 2 detection. Under optimized parameters of square wave voltammetry and optimum pH, analysis of H 2 O 2 can be performed using 5 independent oxidation peaks. The presence of multiple peaks is due to oxidation of gold, CNTs and H 2 O 2 itself. All peaks increase when H 2 O 2 is added in solution, because of chemical reduction of CNT and gold surfaces, and their consecutive electrochemical oxidation. Using the peak at -0.6 V allows for the H 2 O 2 detection at very low potential, that can minimize interference from various reducing agents. For the -0.6 V peak, the limit of detection was 1.4 mM. Using the peak at -0.05 V allows for much higher sensitivity with the limit of detection of 500 nM. Almost no signal deterioration was observed after 200 measurements, proving high stability of the fabricated electrodes.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metal-Oxygen Hybridization of Bi/Bife(oxy)Hydroxide for Sustainable Lattice Oxygen Mechanism at High Current Density","authors":"Seunghwan Jo, Woon Bae Park, Docheon Ahn, Kee-Sun Sohn, Ki Hoon Shin, John Hong, Jung Inn Sohn","doi":"10.1149/ma2023-01372155mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01372155mtgabs","url":null,"abstract":"Hydrogen energy production through the electricity-driven water electrolysis has been broadly studied to deal with growing energy demands and environment pollutions. Oxygen evolution reaction (OER) which is the half anodic reaction of water electrolysis determines overall water electrolysis due to OOH* coordination with high energy barrier. Recently, alternative reaction kinetics detouring sluggish OOH intermediate in OER pathway has been proposed as breakthrough for efficient water electrolysis. That is the strategy which directly conjugates activated lattice oxygen species to form O-O coupling instead of OOH intermediate. However, absence of facile method to realize lattice oxygen activation and structural instability during OER cycles remain as challenge, hindering practical applications of water electrolysis. In this work, metal-oxygen hybridization method has been demonstrated as not only a simple and facile strategy to activate lattice oxygen species but also sustain lattice oxygen mechanism (LOM) during OER cycles at a practical current density (> 1000 mA cm -2 ). Using redox potential difference between bismuth (Bi) and iron (Fe) as driving force, galvanic replacement and Kirkendall effect take place in binary metal system, resulting in heterostructure composed of amorphous BiFe(oxy)hydroxides and molecular bismuth (Bi) metal nanoparticles (BM/BiFeO x H y ) with abundant oxygen non-bonding states. In 1 M KOH solution, the BM/BiFeO x H y electrocatalyst requires low overpotential of 232 and 359 mV at the current densities of 10 and 1,000 mA cm -2 , respectively. Moreover, long-term catalytic stability is demonstrated up to 1,000 hours at a practically high current density of 1,000 mA cm -2 without significant degradation by virtue of the balanced hybridization of Bi/Fe-O. Electrochemical/physicochemical analysis and density functional theory (DFT) calculation reveal that the excellent OER performance and stability of BM/BiFeO x H y electrocatalyst are attributed to the optimized Fe/Bi-O hybridization and resulting heterostructure with increased oxygen non-bonding states.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights into the Structure - Composition - Activity Relationship of PtCo Alloy Nanoparticles towards Oxygen Reduction Reaction (ORR)","authors":"Marek Janssen, Jochen Klein, Alexandra Dworzak, Sonja Blaseio, Mehtap Oezaslan","doi":"10.1149/ma2023-01382222mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01382222mtgabs","url":null,"abstract":"PtCo alloy nanoparticles (NPs) are widely used as highly active oxygen reduction reaction (ORR) catalysts for polymer electrolyte membrane fuel cells (PEMFCs). Despite large efforts, the critical relationships between structure, composition and ORR performance of catalyst materials are not fully understood to date. In this study, we prepared two PtCo alloy NP catalysts with an atomic ratio of 1:1 using wet-impregnation route by varying the annealing parameters under reductive conditions. The as-prepared PtCo alloy catalysts were structurally characterized using ex-situ HR-TEM, EDX, XRD, and EXAFS. We show that the annealing temperature and holding time affect the particle size, composition and homogeneity of the PtCo NPs. With higher annealing temperature and longer holding time, the particle size grows from 3.1 ± 0.7 nm (400 °C, 4 h) to 4.4 ± 0.6 nm (800 °C, 6 h) and simultaneously, the alloy formation within the NPs improves. After electrochemical activation in 0.1 M HClO 4 , the electrochemically active Pt surface area (ECSA) for activated PtCo T400 (65 ± 8 m 2 g Pt -1 ) is slightly lower than that for pure Pt/C (70 ± 11 m 2 g Pt -1 ), but significantly higher than that for the activated PtCo T800 (50 ± 4 m 2 g Pt -1 ). However, the activated PtCo T800 shows the highest ORR mass activity (0.56 ± 0.14 A mg Pt -1 at 0.9 V RHE, iR-free ) than the activated PtCo T400 (0.43 ± 0.03 A mg Pt -1 ) and Pt/C (0.24 ± 0.04 A mg Pt -1 ). Altogether, we provide deeper understanding of the structure - composition - ORR activity relationships for two differently annealed PtCo alloy catalyst materials.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recycling and Reuse Strategies for Ceramic Components of Solid Oxide Cells","authors":"Stephan Sarner, Norbert H. Menzler, Andrea Hilgers, Olivier Guillon","doi":"10.1149/ma2023-0154210mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-0154210mtgabs","url":null,"abstract":"Fuel Cell and Hydrogen (FCH) applications will become crucial to enable the transition towards decarbonatization and meet the EU's zero net greenhouse gas emission targets to be achieved by 2050 (The European Green Deal, European Commission, 2019). As one part of novel FCH technologies, Solid Oxide Cells (SOCs) can be used as fuel cells and electrolyzers, enabling a fuel-flexible and adaptable range of applications. However, the Technology Readiness Level (TRL) of SOCs is currently assessed at 5–7 (H2-international, October 2022), which is lower compared to most of the technologies mentioned above. In order to achieve their market breakthrough, SOCs require scalable and cost-efficient manufacturing trails. This involves an adequate End-of-Life (EoL) material treatment, minimizing environmental impact, and avoiding landfill disposals. EoL strategies for FCH applications (including the SOC) are currently in the early stages and have not been adequately addressed. Until now, existing novel technologies and their materials are reviewed based on hazardousness, scarcity and cost. Initial considerations directly for SOC material recovery are given in two very recent publications. In these two studies, the focus was on the ceramic cell part of an SOC, aiming for the recovery of the most valuable cell fractions in a (semi-) closed loop scenario. Challenges in cell recycling arise from the diversity of structures and materials of established stack and cell designs. For industrial applications, planar stack geometry is likely to prevail, further subdivided based on the mechanical support used (fuel electrode-supported cells, FESC; electrolyte-supported cells, ESCs; metal-supported cells, MSCs). As a part of the German government-funded technology platform “H2Giga”, we are working on the re-integration of EoL FESC-type SOCs into the cell manufacturing process. The concept for FESC-recycling (Figure 1.) is based on the separation of the air-side perovskite materials (air-side electrode and contact layer) from the remaining predominant cell fraction (mechanical support, fuel electrode, electrolyte, and diffusion barrier layer). [1] Separation can be achieved by exploiting the chemical resistance of NiO and YSZ to suitable leachants such as hydrochloric acid or nitric acid. In comparison, the structure of the conventional perovskites used is more vulnerable to acid corrosion. The remaining solid fraction then undergoes a re-dispersion step and is incorporated into newly manufactured substrate. The recycled substrate is characterized in terms of electrical conductivity, mechanical stability, and microstructure. Critical components (Co, La) in the separated perovskite liquid fraction are to be recovered from the solution by precipitation. The presentation will guide the audience through the concept of multi-step recovery of the predominant cell fraction Ni(O)/YSZ, and will provide insides of the experimental results, ranging from the hydrometallurgical separation","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"(Invited) Microelectrode-Based Diagnosis of Charge Propagation and Redox Transitions in Concentrated Polyoxometallate Electrolyte of Potential Utility for Redox Flow Battery","authors":"Iwona A. Rutkowska, Claudia Janiszewska, Keti Vezzu, Enrico Negro, Vito Di Noto, Pawel J. Kulesza","doi":"10.1149/ma2023-01492564mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01492564mtgabs","url":null,"abstract":"Concentrated solutions of Keggin-type silicotungstic acid, as well as the system’s single crystals (H 4 SiW 12 O 40 *31H 2 O) and their colloidal suspensions have been tested using the microelectrode methodology to determine mass-transport, electron self-exchange and apparent (effective) diffusion-type coefficients for charge propagation and homogeneous (electron self-exchange) rates of electron transfers. Silicotungstic acid facilitates proton conductivity, and undergoes fast, reversible, multi-electron electron transfers leading to the formation of highly conducting, mixed-valence (tungsten(VI,V) heteropoly blue) compounds. To develop useful electroanalytical diagnostic criteria, electroanalytical approaches utilizing microdisk electrodes have been adapted to characterize redox transitions of the system and to determine kinetic parameters. Combination of micoroelectrode-based experiments performed in two distinct diffusional regimes: radial (long-term experiment; e.g., slow scan rate voltammetry or long-pulse chronoamperometry) and linear (short-term experiment; e.g., fast scan rate voltammetry or short-pulse chronocoulometry) permits absolute determination of such parameters as effective concentration of redox centers ( C 0 ) and apparent transport (diffusion) coefficient ( D app ). The knowledge of these parameters, in particular of [ D app 1/2 C 0 ] seems to be of importance to the evaluation of utility of redox electrolytes for charge storage. While current densities which reflect dynamics of electrochemical processes have an influence on the systems’ current densities, the viscosity of the electrolyte and the mass transport dynamics are also affected by the nature of the redox-active material and its concentration. Trying to develop useful electroanalytical diagnostic approaches, we have successfully utilized microelectrode-based probes, as well as the historical concepts of charge propagation in semi-solid or semi-liquid systems developed for mixed-valence polynuclear materials in order to characterize concentrated redox electrolytes. Among important parameters are concentration of redox centers ( C 0 ) and apparent transport (diffusion) coefficient ( D app ). The knowledge of these parameters and, in particular of [ D app 1/2 C 0 ], are crucial when it comes to evaluation of the diffusional-type charge propagation dynamics in the concentrated electrolyte which may reflect both physical mass transport and electron self-exchange (electron-hopping) contributions. Both potential-step (chronocoulometry, chronoamperometry) and cyclic voltammetric experiments utilizing microdisk electrodes have been adapted to characterization (identification of redox transitions and determination of kinetic parameters) of model inorganic redox electrolytes, namely highly-concentrated solutions or colloidal suspensions of Keggin-type polyoxometallate, silicotungstic acid.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}