ECS Meeting Abstracts最新文献

{"title":"Effects of Bifunctional Oxygen Catalyst Layer Composition on Unitized Regenerative Fuel Cell Performance","authors":"Christopher P. Rhodes, Jose Fernando Godinez Salomon, Michael E. Urena","doi":"10.1149/ma2023-01362118mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01362118mtgabs","url":null,"abstract":"Proton exchange membrane unitized regenerative fuel cells (PEM-URFCs) can generate storable fuel (hydrogen) and oxidant (oxygen) which can then be used to produce power from the same cell. Combining electrolysis and fuel cell modes within the same cell allows PEM-URFCs to have the potential for lower mass, volume, and cost compared with discrete fuel cell and electrolyzer systems. The bifunctional oxygen catalyst layer (BOCL) catalyzes the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) at the same electrode, and there are wide potential differences and opposing mass transport phenomena involved within the BOCL when operating in electrolyzer or fuel cell mode. The BOCL composition, structure and morphology significantly affect performance and stability of PEM-URFCs. In our prior work, we showed bimetallic nanoframes provide bifunctional oxygen electrocatalysts with significantly higher activity compared with monometallic structures, evaluated using a rotating disk electrode configuration. 1 We will present our investigation of the effects of the BOCL composition, structure and morphology on URFC membrane electrode assemblies (MEAs) prepared using ultrasonic spraying. Catalyst composition and loading were determined to influence URFC performance, and there are tradeoffs between fuel cell performance, electrolyzer performance, and catalyst cost. In addition to the effects of the active catalyst (either Pt for ORR or IrO 2 for OER), our work supports the non-catalytically active component influences MEA performance, which is in agreement with our finding of synergistic effects of Pt and IrO 2 within rotating disk electrode measurements. 1 We are also evaluating the effects of porous transport layers and different operating conditions on URFC MEA performance and durability over repeated cycling. References Godínez-Salomón, F.; Albiter, L.; Mendoza-Cruz, R.; Rhodes, C.P. Bimetallic Two-dimensional Nanoframes: High Activity Acidic Bifunctional Oxygen Reduction and Evolution Electrocatalysts. ACS Appl. Energy Mater. 2020, 3 , 2404-2421 .","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":"135089192","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":"Techno-Economic Analysis of Electrochemical Refineries Using Solid Oxide Cells for Oxidative Coupling of Methane","authors":"Fabian Rosner, Mike C Tucker, Boxun Hu, Hanna Breunig","doi":"10.1149/ma2023-0154322mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-0154322mtgabs","url":null,"abstract":"With the shift away from fossil resources, there is a need for alternative pathways to carbon-based commodities such as ethylene. The electrochemical oxidative coupling of methane (OCM) enables the synthesis of higher hydrocarbons from simple organic molecules i.e., methane and has the potential to replace conventional ethylene production in the future. However, current solid oxide OCM cell development is still in an early stage and more comprehensive system-level analyses are needed to better understand operating conditions and economics to guide research and development. For this purpose, process models and new integration strategies for the electrochemical OCM process were developed. The integration of the electrochemical OCM unit into the plant revealed to be challenging based on current solid oxide cell designs and will be discussed as part of this presentation. The performance of the OCM plant is benchmarked against current state-of-the-art ethane steam cracker plants. In this context, key performance metrics are efficiency, direct and indirect carbon dioxide emissions, power consumption, plant cost and cost of ethylene. Of particular interest are aspects of hydrogen co-production and carbon dioxide utilization as well as the impact of carbon dioxide emission factors from the grid, which have shown to be of particular importance for electrochemical processes. Moreover, critical aspects of heat integration will be discussed including fuel pre-heating, carbon deposition and thermal cell management. The analysis will provide new insights into economic cost driving factors and the impact of cell cost, current density, overpotentials and Faraday efficiency upon the cost of ethylene. Based upon this information, performance targets will be recommended that will allow electrochemical OCM to become economically competitive in a free market environment.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"15 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":"135089215","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":"Use of Boron Doped Diamond Corrosion Free Supports to Evaluate Fuel Cell Electrocatalyst Stability Under Accelerated Stress Testing","authors":"Daniel Houghton, Pei Zhao, Yisong Han, Richard Beanland, Julie V. Macpherson, Louis Godeffroy, Viacheslav Shkirskiy, Frederic Kanoufi, Jonathan Sharman","doi":"10.1149/ma2023-01382232mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01382232mtgabs","url":null,"abstract":"Proton exchange membrane fuel cell (PEMFC) electrocatalysts are typically Pt or Pt alloy nanoparticles (NPs) supported on high surface area carbon black powders, the latter which contain a significant sp 2 carbon component. One of the barriers to PEMFC commercialisation is the lifetime of the catalyst-support system, which should be at least 5,000 hours for automotive applications. [1] During the start-up and shut-down of the PEMFC, the cathode is subjected to significant oxidative potentials (greater than 1 V vs RHE) which can lead to corrosion of the predominantly sp2 bonded carbon support, a key factor which can limit the lifetime of PEMFCs. [2] High quality boron doped diamond (BDD) is an sp 3 bonded network with above 1:1000 B:C ratio, which is required for metal-like electronic conductivity. BDD has many favourable properties for electrochemical experiments, most notably: higher electrochemical corrosion resistance with respect to sp 2 carbons, low background currents, and a wide aqueous solvent window. [3] In this work we first explore the electrochemical corrosion stability of BDD when undergoing electrochemical cycling in acid solutions. To achieve this BDD substrates (BDD TEM grid) suitable for both electrochemical experiments and high magnification (single atom resolution) transmission electron microscopy (TEM) experiments were produced using precision ion polishing (Gatan PIPS-II). The surface was characterised using X-ray photoelectron spectroscopy to ensure the polishing process did not significantly alter the diamond substrate. Under aggressive electrochemical potential cycling in perchloric acid and sulfuric acid solutions, both TEM morphological analysis and Electron Energy Loss Spectroscopy (EELS) thickness measurements showed no evidence of BDD corrosion. [4] The BDD-TEM substrate was then used as a platform for investigating the degradation of a PEMFC electrocatalyst (Pt NPs) under accelerated stress testing (AST) [1] conditions on an atomic level, using the corrosion free carbon support. This enables the influence of other degradation pathways [2] (such as aggregation, Ostwald Ripening & direct dissolution) to be explored in more detail, free from issues associated with corrosion of the support. Pt NPs, in the size range 1 – 4 nm, were sputter coated onto the BDD TEM grid. Identical location ex-situ TEM (IL-TEM) [5] in combination with image analysis was used to probe NP changes e.g. size, shape, position, on an individual basis before, and after, AST (Fig. 1, which contains c.a. 200 NPs for analysis). Such measurements were complemented by Inductively Coupled Plasma – Optical Emission Spectroscopy analysis for any dissolved Pt, and electrochemical cyclic voltammetry measurements of the Pt to highlight changes in electrocatalytic behaviour (hydrogen evolution reaction and oxygen reduction reaction) due to AST cycling. Figure 1 – High magnification annular dark field (ADF) identical location images of Pt NPs, a) Pt/BDD bef","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":"135089237","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) Solid State Hybrid Inorganic Organic Polymer Electrolytes for Advanced Sodium Secondary Batteries","authors":"Gioele Pagot, Federico Brombin, Keti Vezzu, Enrico Negro, Vito Di Noto","doi":"10.1149/ma2023-01492563mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01492563mtgabs","url":null,"abstract":"The large-scale rollout of electric vehicles, smart grids and portable electronics is expected to require an amount of energy storage devices that the Li-ion technology alone will not be able to satisfy. In this concern, a quest for novel electrochemical energy storage technologies has started [1]. Sodium secondary batteries appear to be a good choice due to: (i) the high availability of raw materials; (ii) the low cost of sodium; (iii) the low sodium standard reduction potential; and (iv) the similarity between the chemistries of sodium and lithium, which facilitates the transition between the two technologies. Up to date, the best-performing electrolytes for the reversible deposition of sodium are based on organic solvents, which suffer from safety concerns and a poor stability towards sodium metal. Thus, research activities in this field are devoted to the development of safe and stable solid state electrolytes able to efficiently transport Na + ions. Inspired by the pioneering work done by Di Noto and co-workers [2-4], herein we present a family of hybrid inorganic-organic polymer electrolytes (HIOPEs) for advanced solid state sodium secondary batteries. The initial HIOPE is obtained by means of a reaction between zirconium ethoxide and polyethylene glycol (PEG400). The resulting material is doped with sodium perchlorate as source of Na + ions. In this system a 3D network is obtained, where inorganic zirconium metal nodes are interconnected by means of organic PEO chains. The latter ensure flexibility to the overall structure. Na + ions are coordinated by and exchanged between the oxygen atoms of the ethereal functionalities of PEO chains. In addition, to guarantee a good structural stability, positively charged Zr nodes partially coordinate perchlorate anions, thus raising the sodium transference number. After doping with the poly(ethylene glycol) dimethyl ether (PEGDME250) plasticizer, a room temperature conductivity higher than 10 -4 S cm -1 is demonstrated. An advanced study of the thermal and structural properties of the proposed materials is presented, with a particular focus on the interactions established between the different chemical species and complexes composing the HIOPEs. The conduction mechanism is elucidated starting from the results obtained in a wide range of temperatures from broadband electrical spectroscopy studies. Taking all together, this study offers insights on the application of non-traditional solid state electrochemical functional components as replacements for conventional solvents in the emerging field of sodium secondary batteries. Acknowledgments The project “Interplay between structure, properties, relaxations and conductivity mechanism in new electrolytes for secondary Magnesium batteries” (Grant Agreement W911NF-21-1-0347-(78622-CH-INT)) of the U.S. Army Research Office. The project “ACHILLES” (prot. BIRD219831) of the University of Padua. The project “VIDICAT” (Grant Agreement 829145) of the FET-Open call","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"21 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":"135089242","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":"Capture and Electrochemical Conversion of CO₂ into Carbon Nanotubes Using Molten Alkali Metal Borates","authors":"Michael Philip Nitzsche, Lev Bromberg, T. Alan Hatton","doi":"10.1149/ma2023-01492558mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01492558mtgabs","url":null,"abstract":"Molten alkali metal borates have recently shown promise as high-temperature sorbents for capture of CO 2 and acid gases. These molten salt sorbents enable realization of thermodynamic enhancements offered by conventional solid high temperature sorbents while resolving practical challenges such as morphological degradation. Prior studies have focused on regeneration of alkali borates through steam sweeping and thermal cycling. In this work, we demonstrate that mixed sodium-lithium borate salts as CO 2 sorbents can also be regenerated electrochemically, producing valuable multiwalled carbon nanotubes (MWCNT) via electroreduction of captured CO 2 . Effects of cathode materials and operating conditions in CO 2 electroreduction in molten sodium-lithium borate are quantified. By varying relative starting compositions of alkali borates and alkali carbonates, an optimal composition of borates and carbonates is determined, achieving high coulombic efficiencies and significantly higher CO 2 uptake capacities than traditionally employed carbonate salts used for conversion of CO 2 into CNTs in the desirable 550-650°C range.","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"6 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":"135089250","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":"Integration of Photoelectrochemical Signal Transduction with RNA-Cleaving Dnazymes for Culture-Free Detection of Bacteria","authors":"Sadman Sakib, Zijie Zhang, Enas Osman, Farhaan Kanji, Fatemeh Bahkshandeh, Yingfu Li, Igor Zhitomirsky, Leyla Soleymani","doi":"10.1149/ma2023-01532635mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01532635mtgabs","url":null,"abstract":"There is a growing interest in developing ultrasensitive biological sensors that can be used for rapid testing at the point-of-need. 1 A major hurdle in developing such sensors for detecting pathogens such as bacteria is that they require target enrichment or amplification to deliver the required limit-of-detection. 2 Among signal transduction strategies, photoelectrochemical (PEC) signal readout, built on the use of light for enhancing electrochemical reactions, is emerging as an ultrasensitive signal transduction mechanism. 3 However, the existing PEC platforms fail to deliver single step testing due to the existence of multiple manual steps, including the addition of biological materials labelled with inorganic photoactive nanoparticles, for signal transduction. 3 RNA-cleaving DNAzymes (RCDs), a class of synthetic nucleic acids, have been selected for precisely identifying specific bacterial species without the need for sample processing. 4 RCDs are molecular switches that cleave a segment of themselves in response to a particular bacterial target, combining biological recognition with signal transduction. 4 We developed photoactive RCDs by tagging them with TiO 2 nanomaterials for combining these molecular switches with PEC signal readout. We designed these molecular switches to make and then break semiconductive heterostructures in response to bacterial targets. These photoactive RCDs were the foundational basis for the design novel and highly sensitive PEC bacterial sensor. We developed two photoactive materials for use in the PEC bacterial assay: TiO 2 nanorod clusters (rutile) that form high surface area photoelectrodes and sub-nanometer sized TiO 2 -nanoparticles (anatase) that link to RCDs to create photoactive reporter probes. Combining TiO 2 -assemblies and TiO 2 -nanoparticles gives rise to a semiconductor heterostructure that massively improves the photoexcitation efficiency of the combined material system and improves photocurrent generation. Our PEC bacterial sensor makes use of this phenomenon for bacterial detection by utilizing photoactive RCDs to modulate photocurrent by breaking and then rebuilding the TiO 2 heterostructures, as a signaling mechanism. The assay consists of a release electrode – modified with photoactive RCDs and a capture electrode – modified with single-stranded DNA probes. Upon target interaction, RCDs release photoactive reporters which are captured by the probes, decreasing the release electrode signal while raising the capture electrode signal. The resulting biosensor can detect E. coli bacterial contamination with high specificity and has achieved a very low limit of detection of 21 CFU/mL in buffer and 18 CFU/mL in lake water samples. These results have set a new record for amplification-free detection of bacteria, that does not rely on target enrichment, reagent addition, or sample processing. This presents a new tool for rapid and in-field water testing. References Nat. Microbiol. , 1 , 16089 (2016).","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":"135089252","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":"Predicting Oxygen Release and Surface Reconstructions in Li-Ion Battery Cathodes Via Automated Construction of Computational Surface Phase Diagrams and Machine Learning","authors":"Xinhao Li, Wing-Chi Ashley Lam, In Won Yeu, Abhiroop Mishra, Joaquin Rodriguez Lopez, Alexander Urban","doi":"10.1149/ma2023-01452470mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01452470mtgabs","url":null,"abstract":"Although LiNiO 2 (LNO) is chemically very similar to LiCoO 2 (LCO), LNO and related Co-free Ni-rich cathodes suffer from continuing surface degradation via oxygen gas release during electrochemical cycling that leads to the formation of surface phases with high impedance. While the surface degradation of LNO and related cathode compositions have been characterized experimentally on a phenomenological level, an understanding of the surface reconstructions that form on the atomic scale and the intrinsic surface instability of LNO compared with other related cathode compositions is still lacking. To shed light on surface reactivity, we developed a thermodynamic methodology for the prediction of voltage and temperature-dependent surface electrode reconstructions [1] and a computational framework to automate the time-consuming enumeration of surface reconstructions, the construction of symmetric surface-slab models, and the analysis of surface phase diagrams [2]. By applying first-principles atomistic modeling, we determined the self-reduction mechanism of LNO and compared the stable surface reconstructions with those of LCO. To further assess the surface stability of more complicated NMC/NCA cathodes with the help of our own generated LNO and LCO databases, we developed a supervised machine learning (ML) model to train on geometrical and electronic fingerprints from surface and bulk models, respectively. Our results provide insight into the initial stages of surface degradation in Ni-rich cathodes and lay the foundation for the computational design of stable cathode materials against oxygen release. Li, X.; Wang, Q.; Guo, H.; Artrith, N.; Urban, A. ACS Appl. Energy Mater. 2022, 5 (5), 5730–5741. Li, X.; Qu, J.; Yeu, I.; Li, Z.; Rodríguez-López, J.; Urban, A., in preparation , 2023","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"81 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":"135089256","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":"Accelerated Stress Testing of Solid Oxide Electrolysis Cells in a Symmetric Steam-Rich Atmosphere","authors":"Christian Rose, Luca Mastropasqua, Jack Brouwer","doi":"10.1149/ma2023-0154187mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-0154187mtgabs","url":null,"abstract":"Temperature, current density, steam utilization variability, and local steam starvation or excess may cause diverse degradation processes to occur in solid oxide electrolysis cells. Typical degradation mechanisms for SOEC with nickel-based fuel electrode materials include nickel migration/evaporation and agglomeration, which may lead to reduced active sites at the triple-phase boundary. However, the phenomenological cause of such degradation mechanisms is still actively debated, making the selection of a durable fuel electrode material challenging. It is desirable to understand the process by which these phenomena occur not only to minimize it, but to intentionally induce it to develop accelerated stress test protocols for cell lifetime prognostics. The degradation of solid oxide electrolyzers has been reported to be accelerated by certain stressful operating conditions. Brisse and Mocotuguy conducted a review of the degradation mechanisms of solid oxide button cells; they reported that high steam partial pressures can lead to the formation of nickel hydroxide at the cathode, which then diffuse to the surface of YSZ 1 . Sun et al. hypothesize that this is the main mechanism for nickel migration, due to the positive oxidation state of nickel and the direction of the electric potential 2 . Changes in the surface morphology of the fuel electrode due to redox cycle-induced degradation has been reported, showing the dynamics of nickel migration and agglomeration under these conditions 3 . Redox cycling was found to be a destructive test protocol; efforts are currently being made by the group of Daria Vladikova to prevent fracturing of the electrodes and electrolyte during such stressful testing 4 . Königshofer et al. have reported through multiple investigations that protocols inducing operation at high steam conversion rates (>90%) and large current densities (0.8 A/cm 2 ) have been effective at reproducing long-term SOEC voltage degradation 5,6 . The objective of this research is to establish a protocol that will help determine the causes that trigger Ni migration or evaporation, and that will mimic the electrode degradation mechanism to standardize the procedure for comparing the long-term performance of solid oxide electrolysis cells. Symmetric button cells of various fuel electrode chemistries with a diameter of 20 mm (active area 1.23 cm 2 ) are tested under symmetric atmospheres with steam/H 2 blends. The following two accelerated stress tests (AST) protocols are employed: cycling of steam partial pressure and cycling of current density. In the former, the steam molar fraction is varied from 75% to 95% in a 20-minute cycle for at least 400 cycles (i.e., 1,176 h). In the latter protocol, current density is controlled using a galvanodynamic 10-minute long cyclic ramp profile between 0.8 A/cm 2 and 1.5 A/cm 2 at a constant steam molar fraction between 75-95% for at least 800 cycles (i.e., 1,176 h). For all tests, the cells are operated at a con","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"127 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":"135089268","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":"Size-Controlled Synthesis of IrO₂nanoparticles at High Temperatures for the Oxygen Evolution Reaction","authors":"Marko Malinovic, Paul Paciok, Ezra Shanli Koh, Moritz Geuß, Jisik Choi, Philipp Pfeifer, Jan Philipp Hofmann, Daniel Göhl, Marc Heggen, Serhiy Cherevko, Marc Ledendecker","doi":"10.1149/ma2023-01362023mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-01362023mtgabs","url":null,"abstract":"Polymer electrolyte membrane (PEM) electrolysis is considered to play a vital role in the sustainable energy transition. The efficient generation of hydrogen is largely influenced by the slow rate of the anodic oxygen evolution reaction (OER). Iridium oxide represents one of the most promising catalysts for the electrochemical oxidation of water in an acidic environment. Under harsh operating conditions at the anode, iridium oxide is found to be among the most dissolution-resistant catalysts while offering acceptable OER activity. However, iridium’s limited availability dictates high costs centralizing the research in direction of reducing noble metal content while maintaining favorable electrochemical properties. [1] Designing nanostructured catalyst with an increased surface-to-volume ratio improves the application-oriented mass-specific activity. [2] Hydrous iridium oxide is known for superior OER activity, but for a successful application, drastic dissolution of the catalyst must be addressed by stabilization. This can be achieved by heat treatment to temperatures ≥400ºC with the formation of crystalline order. However, managing to avoid agglomeration of nanoparticles at high temperatures is not trivial, thus, temperature studies on electrochemical stability and activity on similar particle sizes are missing. [3] . Here, we demonstrate how nanoparticles below 10 nm can be obtained at high preparation temperatures up to 800 °C with unprecedented control over particle size and morphology. A detailed understanding of the structural evolution during heating was obtained by in-situ scanning transmission electron microscopy ( in-situ STEM) with locally resolved nanoparticles, high spatial resolution, and chemical specificity. Additionally, changes in surface properties at different temperatures were tracked ex-situ by X-ray photoelectron spectroscopy (XPS), the crystal structure was investigated by X-ray diffraction analysis (XRD), size and morphology were characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The OER activities of synthesized iridium oxide nanoparticles were measured in half-cell measurements at forced convection. The stability was carefully studied by operando flow cell measurements that were coupled to online inductively coupled plasma mass spectrometry. [4] The iridium oxide catalyst calcined at the lowest temperature resulted in outstanding mass-specific activity outperforming the reference iridium oxide catalyst by a factor of 40. By gradual increase in calcination temperatures up to 800 °C, we observe improvement in the durability of the synthesized catalysts, being comparable to the reference catalyst, yet still with notable improvement in catalytic activity. This is the first report to synthesize iridium oxide nanoparticles at high temperatures with preserved size and morphology not exceeding 10 nm and allows for the determination of activity and durability of similarly sized","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"19 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":"135089300","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":"Improving Gas Diffusion in Solid Oxide Cells Through Laser-Ablated Electrode Supports","authors":"Saahir Ganti-Agrawal, Dalton Cox, Scott A Barnett","doi":"10.1149/ma2023-0154142mtgabs","DOIUrl":"https://doi.org/10.1149/ma2023-0154142mtgabs","url":null,"abstract":"Improving solid oxide cell power density will enable cheaper commercial-scale SOFCs and SOECs. In Ni-YSZ electrode-supported cells, gas diffusion through the electrode support layer can be a major limitation at high H 2 or H 2 O utilization and high temperature. Conventional methods of improving diffusion through the electrode support include increasing the support porosity and reducing the support thickness, but these can reduce the cell’s structural integrity. Freeze casting 1 and 3D printing 2 have also been explored to enhance diffusion. Here we explore cells in which the Ni-YSZ supports have macroscopic channels, produced by laser ablation, that reduce the average gas diffusion length. To test the difference in mass transport through patterned and pristine electrode supports, symmetric electrode-supported Ni-YSZ cells are patterned on one side, which enables comparison of the electrochemical performance of two otherwise identical electrodes (Figure 1a). Cells with varying pattern geometry, pore geometries, Ni/YSZ ratios, and Ni-YSZ particle sizes were created to fully understand how the support layer microstructure and macrostructure affects the cell performance. Patterned and pristine cells were tested together at three temperatures (600C, 700C, and 800C) in a 97%H 2 :3%H 2 O environment, chosen to produce a clear gas diffusion limitation in H 2 O electrolysis. j-V sweeps and electrochemical impedance spectroscopy (EIS) were carried out on each cell at each test condition, and the microstructure of patterned and control supports was characterized through SEM imaging. Upon removing the ohmic portion and fitting the j-V data to Equation 1 (see Figure 1), patterned electrodes consistently demonstrated higher limiting current density and lower mass transport losses than the control (Figure 1c-d). Three-point-bend mechanical testing revealed that the mean flexural fracture strengths of pristine cells and patterned cells are 36.0 ± 11.4 MPa and 33.0 ± 8.9 MPa respectively. Combining the equations for limiting current density with diffusion in a system with prismatic channels, we determined the ratio of the limiting current density for a patterned and pristine electrode using Equation 2 (see Figure). For the cell data shown in Figures 1c-1d, we expect an average 33% increase (with a standard deviation of 3.5%) in limiting current density based on microscopy measurements of channel and support layer thicknesses. In 1c, we see that the limiting current density of the patterned electrode is 32% higher than the pristine electrode, which matches our expectation. Furthermore, the Nyquist plot in Figure 1d demonstrates that patterned symmetric cells have similar impedance to pristine cells in the high-frequency regime with less impedance in the low-frequency regime, which is consistent with our expectations that the patterned cells have reduced mass transport losses with similar ohmic and activation losses. These j-V and EIS results suggest that macrosco","PeriodicalId":11461,"journal":{"name":"ECS Meeting Abstracts","volume":"10 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":"135089307","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}