bluuebunny/crossref_metadata_2025 huggingface dataset:
Cu-Based Nanoneedle Array for Electrochemical Detection of Nitrate
Authors: Yang Zhengyang , Che Fanglin , Gu Zhiyong
Published: September 2023

The extensive usage of nitrogen-based fertilizers, food preservatives and explosive chemicals in various industries has led to the accumulation of nitrate in the ecosystems, especially in soil and water bodies. Several severe environmental and human health issues, including eutrophication, diseases related to N-nitroso compounds (such as Cancer, Parkinson and Gastritis) and blue-baby syndrome (methemoglobinemia), have arisen from the excessive nitrate concentration in the environment. Consequently, various government and regulatory agencies, such as the U.S. Environmental Protection Agency (EPA), have established the maximum nitrate ion concentration in drinkable water at 44 mg/L (0.71 mM). In this context, an accurate monitoring of the level of nitrate becomes important in environmental pollution control, food, clinical analysis, and other industries. While the spectroscopy techniques are of the most use due to its high precision and low limit of detection (LOD), these methods frequently require skilled workforces and specific instrumentations to operate. The electrochemical sensors benefit from recent developments of new nanomaterials to detect nitrate with a quick response, ability of continuously monitoring, small and simple instrumentation as well as easy to use. Several studies have utilized different strategies to fabricate Cu-based nanostructures (such as nanoparticles, nanoclusters, nanowires, and single-crystals) to achieve a low LOD. However, the sensitivity that has been achieved so far is still relatively low compared to the requirements for the real sampling applications.

In this work, we utilized a one-step electrodeposition method to prepare Cu-based nano-array electrodes with high active surface sites, aiming for a fast and sensitive electrochemical detection of nitrate. The morphology of the array can be fine-tuned between nanoneedle and nanowire structures (Figure 1a and 1b). The x-ray diffraction (XRD) measurements indicate that the Cu-based nanoneedle array exhibited an abundant Cu(220) facet than the nanowire systems, which is usually associated with the active edge sites on copper (Figure 1c). The nanoneedle array was used for nitrate sensing via Cyclic Voltammetry methods which showed a sensitivity of 2.8 μA/μM*cm2, about 5-fold higher than the Cu foil control electrode (Figure 1d). The main reason of the sensitivity enhancement is that the nanoneedle structure resulted in a 30 times enrichment in the surface area compared to the Cu foil as shown in the electrochemical surface area (ECSA) measurement. Overall, our study provides a novel and convenient design of highly ordered Cu nanoneedle array structure for the sensitive electrochemical detection of nitrate.

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Reveal the Electrical Double Layer (EDL) in Zinc Battery Electrolytes with Electrocapillarity
Authors: Shi Feifei
Published: September 2023

The electrified interface between electrodes and electrolytes, aka, electrical double layer (EDL), resides at the heart of electrochemistry and exists universally in all electrochemical devices. It governs the kinetics and reversibility of all electrochemical processes, and predicts the interphase chemistries in advanced batteries. However, despite such importance, its understanding remains insufficient. While many theoretical models have been developed to predict EDL structure and to correlate key properties to the structures, so far there have been very rare direct experimental characterization, due to the limitations of existing techniques and the extreme elusiveness and sensitivity of the electrified interfaces.

In this talk, I will discuss a modernized high-resolution electrocapillarity method, developed in my group. Applying this reborn electrocapillarity on a bivalent electrolyte of ZnCl2 and ZnSO4, we reveal the interfacial structure of Zn ion battery electrolytes in the absence and presence of anion specific adsorption and established the abnormal potential distribution across the interface due to anion adsorption and its effect on the kinetics of Zn ion deposition chemistry.
(Invited) Translational Applications of Nanostructured Biosensors: Diagnostics at the Point of Care
Authors: Mahshid Sara
Published: September 2023

Development of diagnostic devices with clinically relevant sensitivity and rapidity is highly desirable for decreasing the delay between diagnosis and treatment. Diagnostic inefficiency permeates multiple medical fields including infectious diseases and antimicrobial resistance (both recognized by WHO among paramount threats and research priorities). Molecular detection is also central to cancer, where therapies are often out of step with disease complexity and progression. The respective challenges may be addressed through the application of nanomaterial and high-throughput devices that offer unique advantages. In Mahshid Lab, we develop novel paradigms in point of care diagnosis via synergistically combining innovative nanostructured sensors with fluidic sample delivery systems and biomolecular assay capabilities (Nano/Bio diagnostic devices).From an engineering perspective, the lab seeks to use the remarkable intrinsic properties of novel nanomaterials, to render them capable of sensing the specific biomolecules. Such miniaturized sensors could be integrated with automated lab-chip devices and deployed to diagnose molecular changes in biological systems and in disease such as cancer (by targeting new cancer biomarkers) or to detect infectious agents in biological samples, e.g. in blood, saliva and urine. From a health industry perspective, we target the advancement of the automated and portable tools for in-field testing, remote locations and hospitals in close collaboration with clinicians to validate the devices with clinical samples. In particular and in the context of infectious disease, Mahshid lab has developed SALIVERA analogous to a qPCR, and NFluidEX analogous to a glucometer, that enabled rapid portable automated monitoring of SARS-CoV-2 infection in patient saliva and antibodies in patient blood, respectively. In the context of cancer, Mahshid lab has developed MoSERS, anon-chip approach for molecular profiling of extracellular vesicles (a new cancer biomarker)on-chip approach for molecular profiling of extracellular vesicles (a new cancer biomarker)in plasma and cerebrospinal fluid of glioblastoma patients. The proposed hybrid devices are capable of working with small sample volumes and precise dosing of reagents, enabling the transition to a portable diagnostic tool.
(Invited) Next-Generation Enabling Technologies for Disease Diagnosis and Therapeutic Monitoring
Authors: Poudineh Mahla
Published: September 2023

To enable personalized and precision medicine, it is crucial to monitor patient health status and bring information on disease-related agents and therapeutic drug molecules into the clinic. This requires new technologies to interrogate different body fluids that are rich sources of biomarkers, such as whole blood and interstitial fluid (ISF). Such technologies enable rapid, sensitive and - ultimately - real-time and continuous analysis of the clinically important biomarkers. Micro and nanofabrication and nanomaterials as well as materials chemistry and polymer and molecular engineering are crucial tools in this endeavor.

At IDEATION Lab, we apply innovative engineering solutions to advance patient health monitoring using two main technologies: Microneedles and Microfluidics. Our new transdermal biosensing technologies powered by engineered hydrogel microneedles (HMNs), aptamer probes, and in-situ metallic nanoparticle synthesis enable minimally invasive, on-needle, and real-time measurement of clinically important biomarkers in ISF. Our HMN assays expect to pave the way for the next-generation of polymeric-based wearable biosensors. We developed a real-time biosensor driven by microfluidic techniques that continuously updates specific biomolecules’ fluctuating concentration levels with picomolar sensitivity directly in whole blood. For the first time, our microfluidic assay enables measuring the dynamic changes in blood insulin which is an important knowledge gap in diabetes management. Another microfluidic technology integrated with electrochemical biosensor has been recently developed in our lab that enables cervical cancer screening at point-of-care setting.

These new advances enrich the level of information that can be collected from different body fluids and provide new means and potentials for highly accurate patient health status monitoring, thus transforming the field of personalized and precision medicine.

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Broadband Microwave Microfluidic Spectroscopy to Capture Product Evolution in Electrosynthesis Reactions
Authors: Pawlik Jacob , Miller Samantha , Evans Sarah , Schwarz Kathleen , Orloff Nathan , Long Christian , Booth James C. , Stelson Angela
Published: September 2023

Electrosynthesis plays an important role in chemical manufacturing with over 2 billion dollars in annual sales worldwide of products such as chlor-alkali and aluminum. Synthesis with an electrochemical driving force can afford unique chemical products that are difficult to achieve with conventional synthesis techniques. Electrosynthesis can also provide a more sustainable alternative to energy-intensive processes. For example, the most profitable electro-organic synthesis in industry is adiponitrile production, a precursor to Nylon 6,6, and the electrochemical route consumes less energy than conventional thermochemical methods. However, electrosynthesis reaction mechanisms are often complex and involve multiple biproducts that are difficult to distinguish, limiting product yield and cost efficiency. Prior work involves characterization with techniques such as NMR spectroscopy, mass spectrometry, and optical spectroscopy to understand product evolution during the reaction. These methods tend not to capture intermolecular interactions between substances, which is important for understanding the influence of the dielectric environment on reaction outcomes.

Here, we propose to analyze the dielectric environment of electrosynthesis reaction mixtures with on-chip broadband microwave microfluidic spectroscopy (MMS) from 40 kHz – 110 GHz (see attached figure). MMS has been implemented previously for capturing broadband fluid effects such as electric double layer formation, ionic conduction, ion pairing, and dipole relaxations in a single measurement. We want to use MMS to diagnose the interactions between species during an electrolysis reaction and correlate these interactions with specific electrochemical mechanisms. We plan to test our idea by analyzing a model reaction, namely the Shono oxidation of N-Boc pyrrolidine, which is a well-studied electrosynthesis reaction. The goal is to validate our method with a known electrosynthesis reaction mechanism, then extend the technique to systems with an unknown mechanism.

We performed broadband MMS of the reaction mixture at different time points to capture product evolution during the electrolysis. Then, we calibrated the resulting S-parameters and fit the data to equivalent circuit models. The equivalent circuit parameters were correlated to signatures from specific entities in the product mixture and used to develop a picture of the evolving dielectric environment. After validating our models with known literature about the Shono oxidation mechanism, we plan to extend our technique to other electrolysis reactions with unknown mechanisms. The goal is to provide a high-throughput technique for identifying key species and interactions that influence the outcome of electrolysis reactions.

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Fuel-Flexible Ceramic Fuel Cells at Reduced Operating Temperatures
Authors: Liu Fan , Fang Liyang , Duan Chuancheng
Published: September 2023

Ceramic fuel cells are uniquely capable of generating power using a wide range of fuels, including hydrogen, hydrocarbons, and ammonia. One of the primary issues of ceramic fuel cells for large-scale power generation originates from the high operating temperature, which leads to limited material choices for interconnects and sealants, expensive balance of plants, slow start-up and shutdown cycles, and high degradation rates, inevitably limiting their scaleup and commercialization. Reducing the temperature to <600 °C could transform the architecture and operation of ceramic fuel cells. However, the internal reforming of hydrocarbons is endothermic, which is thermodynamically and kinetically unfavorable at lowered operating temperatures, necessitating the development of internal reforming catalysts to enhance the anode catalytic activity. This talk will first focus on presenting the approaches that have been validated for designing and synthesizing internal reforming catalysts, with a particular focus on internal steam reforming and dry reforming of methane. Additionally, the characterization of high-performance ceramic fuel cells equipped with these catalysts will also be discussed. The associated challenges and proposing strategies from different perspectives will also be provided in this talk.
Highly Connected Oxygen Ion Conduction Pathways for Solid Oxide Fuel Cells Operating in Intermediate Temperatures with Fuel Flexibility
Authors: Bang Sehee , Lee Jongseo , Lee Wonyoung
Published: September 2023

Solid oxide fuel cells are promising eco-friendly power generating devices directly utilizing various fuels such as hydrogen, methane, and carbon dioxide. However, a technical breakthrough is required for further commercialization by lowering the high operating temperature to the intermediate temperature regime. Introducing the anode functional layer (AFL) between the electrolyte and anode is one of the crucial methods in the development of high performance solid oxide fuel cells by maximizing the triple phase boundary (TPB) sites. To activate the TPB sites, ensuring the continuous oxygen ion conduction from the electrolyte to the TPB sites is essential to maximize their utilization for hydrogen oxidation reactions (HORs). In this study, we modify the connectivity of oxygen ion conduction pathways in the AFL by controlling the microstructure in AFLs. We calculated active reaction site using image processing of cross-sectional scanning electron microscopy (SEM) image and the strong correlation between the electrochemical performance and calculated active reaction site is revealed. The modified AFL with highly connected oxygen ion conduction pathways exhibits substantially higher maximum power density (MPD) compared with conventional AFL: ~1.7-fold higher MPD of 1.51 Wcm-2 at 550 ℃ with hydrogen and ~3.5-fold higher MPD of 1.11 Wcm-2 at 550 ℃ with methane and carbon dioxide, surpassing previously reported values. Moreover, excellent carbon tolerance is observed in the modified AFL, exhibiting nearly no degradation at 550 ℃ for 130 h. This result substantiates the role of connectivity of the oxygen ion conduction pathways in the HOR and carbon tolerance in AFLs.

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Fabrication of Low-Temperature Solid Oxide Fuel Cells via Development of Magnetron Sputtering Process
Authors: Ryu Sangbong , Yu Wonjong , Tran Quang Tuyen , Thieu Cam Anh , Lee Sanghoon , Sreenarayanan Bhagath , Feng Shijie , Meng Shirley , Fullerton Eric E. , Liu Ping , Minh Nguyen Q.
Published: September 2023

We herein report the development of the sputtering process for the fabrication of thin film low-temperature solid oxide fuell cells (LT-SOFCs) supported by anodized aluminum oxide (AAO). The process development has been conducted for each component, anode, electrolyte, electrolyte/cathode interlayer, and cathode to achieve not only high performance but also durability. In order to fabricate catalyst-ion conducting anode cermet, Ni and GdCe co-sputtering is utilized. Since the AAO is an electrical insulator, the electrons produced from the anode requires to pass through the thin anode layer to be collected which can lead to high current collecting resistance. Therefore, sputtering conditions such as power, pressure, and time are adjusted to produce the anode with minimal ohmic loss stemming from current collection. For the electrolyte (YSZ) and interlayer (GDC), a ceramic sputtering recipe has been developed to achieve high density and uniformity, which are the most critical requirement for these components. Through optimization of the gun angle, power, pressure, and the target to substrate distance (TSD), a highly dense and uniform ceramic electrolyte can be deposited on various AAO substrate sizes. For the cathode, a mixed ionic electronic conducting cathode sputtering recipe has been developed to enhance oxygen reduction reaction (ORR) at low operating temperatures. We have been developing the sputtering process to fabricate a nanocrystalline and highly porous LSC-GDC cathode with desired microstructure to enhance the ORR activity. Through the integration of the aforementioned sputtering process development, durable and high performance LT-SOFCs have been successfully fabricated on AAO substrates up to 15cm x 15cm size. Suppered thin film cells have shown superior performance at low operating temperatures, e.g., peak power density of 1.5W/cm2 at 550oC with hydrogen fuel.
Strong Metal-Support Interactions Stabilize Pt Nanocatalysts for Ceramic Fuel Cells
Authors: Jung WooChul , Seo Jongsu , Jeon SungHyun
Published: September 2023

Nano-sized metal particles are widely used in various chemical/electrochemical fields due to their excellent catalytic activity, but they still suffer from deactivation by sintering, and this leads to serious issues regarding the price and lifespan of catalysts. In this study, we demonstrate that the introduction of nanoscale amorphous TiOx
via atomic layer deposition can significantly improve the dispersion and durability of supported Pt nanocatalysts. An ultrathin TiOx layer (< 1 nm) deposited on a conductive Pr0.5Ba0.5MnO3 electrode, with a deposition time of less than 1 min, provides nucleation sites for the Pt nanocrystals impregnated thereon and promotes the migration of TiOx to the Pt surface, creating a metal-oxide interface. As a result, when applied to ceramic fuel cells, the TiOx undercoat achieves remarkable power density increases of over 100% and 400%, respectively, for wet (3% H2O) H2 and CH4 fuels without degradation at 700 °C for 120 h. These observations provide an innovative direction for the design of supported metal catalysts for high-temperature applications.
Scenarios for Hydrogen Production from a Full-Scale Reversible Solid Oxide System with Electrolyte-Supported Stacks
Authors: Parashar Aadarsh , Braun Rob J
Published: September 2023

Reversible solid oxide cell technology is of increasing interest and is emerging as a promising grid-flexible support system [1] with storage [2]. Among the types of cell architecture available, electrolyte-supported cells have proven to be better in terms of long-term stability and degradation of the cell, albeit sacrificing on performance as compared to anode-supported cells [3]. This makes electrolyte-supported cells better suited architecture to be used in reversible systems where higher stability is required due to the changing operating conditions in each mode. In the present work, validated cell and stack models of Nexceris electrolyte-supported cells are used to model a full-scale reversible solid oxide system designed for hydrogen production.

EIS data from symmetric button cells and polarization curves from 5cm×5cm full cells are used to validate the stack model. A net 100 kWe system in fuel cell mode is modelled with electrolyte-supported stacks from Nexceris operating at a nominal temperature of 800 oC. The system is run at thermoneutral conditions in electrolysis mode and at 0.5 A/cm2 in fuel cell mode to balance between efficiency and hydrogen production. The levelized cost of hydrogen production is calculated using a price-taker model with the system pumping the produced hydrogen into a natural gas/hydrogen pipeline. The effect of various parameters, such as the capacity factor of the system, the operating pressure, grid-electricity pricing, etc. - are investigated on the levelized cost of hydrogen.

[1] Guenther Glenk and Stefan Reichelstein, “Reversible Power-to-Gas systems for energy conversion and storage”, Nature Communications
13, 2010 (2022).

[2] Evan Reznicek and Robert J. Braun, “Techno-economic and off-design analysis of stand-alone, distributed-scale reversible solid oxide cell energy storage systems”, Energy Conversion and Management
175, 2018.

[3] Marco A. Buccheri, Anand Singh, and Josephine M. Hill, “Anode- versus electrolyte-supported Ni-YSZ/YSZ/Pt SOFCs: Effect of cell design on OCV, performance and carbon formation for the direct utilization of dry methane”, Journal of Power Sources 196, 2011.

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A High Performance Tubular Solid Oxide Fuel Cell for Unmanned Autonomous Systems
Authors: Chu Deryn
Published: September 2023

Small unmanned aerial systems (SUASs) have a great potential for numerous applications. The SUASs are light-weight, man-portable, and capable of delivering commercial products. Currently, small UASs are powered by lithium-ion batteries, however, flight endurance is limited and requires frequent charging battery due to low capacity and energy density. Numerous research and development efforts have focused on alternative power sources. These alternative power sources include technologies such as solar cells and hydrogen based polymer electrolyte membrane fuel cells. Additionally, polymer electrolyte membrane fuel cells still have the same technical constraints, the source of hydrogen, as it did many years ago. We have developed and examined the operational capabilities of propane fueled solid oxide fuel cell (SOFC) technology can power an sUAS. A self-sustaining miniature tubular SOFC stack provides a unique high power and high energy density for UAS. The SOFC has great potential for commercial and civilian applications, ranging from small scale systems (e.g. small unmanned air vehicle, wireless sensor networks) to large scale system (e.g. electric vehicle, wireless sensor networks, electric vehicles).
Analysis of Interfacial Capacitance of Ni-YSZ Anode By Transient Simulation
Authors: Yashiro Keiji , Watanabe Kota , Budiman Riyan Achmad , Sato Masami , Muramatsu Mayu , Kawada Tatsuya
Published: September 2023

An electrochemical impedance and equivalent circuit analysis are frequently used for electrochemical evaluation of SOFC cells. The impedance analysis enables to obtain the resistance and the capacitance components of the electrode reaction. The electrode resistance is directly related to the cell performance. The electrode capacitance can be sometimes give information about the active electrode reaction site. As to Ni-YSZ electrode, we've tried to elucidate the physical meaning of the capacitance [1]. However, it is not easy to clarify the physical origin of the electrode capacitance. Thus, the capacitance has not been used to evaluate the active reaction zone so far. In this study, the capacitance of Ni-YSZ interface will be simulated by calculating the chemical capacitance derived from YSZ. Then, the origin of the capacitance will be discussed through comparison with the previous studies [1].

The structural model to simulate the Ni-YSZ model cell [1] are shown in Fig. 1., which shows simplified model according to symmetry of the cell. In order to limit the electrochemical reaction zone (triple phase boundary), a virtual reaction zone was introduced. Cell conditions for the calculation are following: temperature: 765ºC; oxygen partial pressure of the air electrode: 0.21 bar;hydrogen partial pressure: 1.00 bar, and water vapor partial pressure: 0.03 bar for fuel electrode. Transient simulation was performed to obtain the chemical capacitance by an in-house code, SIMUDEL, where mixed ionic electronic conduction and oxygen nonstoichiometry were taken into consideration [2,3] using the reported conductivity data of YSZ [4].

The measured capacitance of the model cell [1] was 5×10-4 Fcm-2. On the other hand, the calculated chemical capacitance of YSZ was 2×10-3 Fcm-2. Even though the oxygen nonstoichiometry of YSZ was small, calculated chemical capacitance was much larger than the observed interfacial capacitance. These difference implies there was unknown factors to promote the response of electron in the actual Ni-YSZ interface. If a thin resistive layer was inserted between Ni and YSZ interface, the calculated chemical capacitance became smaller than that of observed. Sasaki et al. observed an incoherent interface between Ni and YSZ by TEM [5]. This kind of interface structure may be the potential cause of the complicated capacitance.

This study was partially supported by NEDO, Japan.

[1] M. Takeda, et. al., submitted to J. Electrochem. Soc.

[2] K. Terada, et. al., ECS Trans. 35(1), 923 (2011).

[3] M. Sato, et. al., Trans. Jpn. Soc. Comp. Eng. Sci. 2017, 14 (2017).

[4] J.H. Park, et. al., J. Am. Ceram.Soc.,72[8],1485-87(1989).

[5] T. Sasaki, et. al., Mater. Trans. 45(7), 2137 (2004).

Fig. 1 Schematic diagrams of the structural model to simulate the chemical capacitance of Ni-YSZ.

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Development of Novel 3D Cell Structure and Manufacturing Processes for Highly Efficient, Durable, and Redox Resistant Solid Oxide Electrolysis Cells
Authors: Lee Sanghoon , Lin Haichen , Kahn Bruce E. , Malakhov Arkady , Kovach Bobby , Tran Quang Tuyen , Ghosh Sam , Liu Ping , Cormier Denis , Minh Nguyen Q.
Published: September 2023

A novel cell design and its corresponding manufacturing processes are being evaluated to demonstrate a highly efficient, durable, and reduction-oxidation (redox) resistant solid oxide electrolysis cell (SOEC) technology for hydrogen production. The cell design includes a unique 3D hydrogen electrode configuration composed of two layers ‒ a 3D hydrogen electrode support layer (for improved cell redox resistance) and an exsolved perovskite hydrogen electrode active layer (for enhanced cell performance and increased durability). The hydrogen electrode support layer consists of specifically designed 3D networks of electrode materials; tetragonal zirconia (TZ) and Ni-yttria stabilized zirconia (YSZ). Each phase is topologically connected throughout the electrode with controlled geometry and connectivity. The TZ component plays a role as an outer frame to provide structural support, while the Ni-YSZ component inside the TZ frame imparts electrical conductivity for the hydrogen electrode support layer. The hydrogen electrode active layer, which primarily supports electrochemical reaction, is a nickel-substituted perovskite that will exsolve nickel nanoparticles on the oxide surface when exposed to a reducing environment and is redox-reversible. A fabrication scheme being developed for this cell design incorporates a printing-based additive manufacturing (AM) process for producing the 3D hydrogen electrode. This paper presents the progress to date in developing the printing fabrication process for the 3D hydrogen electrode support and evaluating exsolved nickel-substituted perovskite for the hydrogen electrode active layer.
Efficiency Optimization of SOFC Subject to Degradation and Minimum Power Constraint
Authors: Li Hangyue , Han Minfang
Published: September 2023

Solid Oxide Fuel Cell (SOFC) is a developing energy conversion technology featuring high efficiency, power density, durability, and fuel compatibility. With these advantages, SOFCs are combined frequently with heat engines such as gas turbines, for higher system efficiency and power density.

In practice, SOFCs are often required to deliver certain power. Considering economical aspects, power generation efficiency is critical to the running cost of energy conversion systems. However, high power and high efficiency are likely reached under different operating conditions. For example, to meet peak power demands, higher operating currents and fuel flowrates are necessary, while SOFCs are generally more energy efficient at lower current densities and fuel flowrates. Hence, the ideal operating condition is the solution to a power-constrained efficiency optimization problem. Moreover, SOFCs degrade as they operate, introducing gradual changes to SOFC characteristics. Thus, the optimization needs to be solved dynamically.

To analyze the above-mentioned problem, a 10 cm by 10 cm planar SOFC was repeatedly tested for polarization characterizations and electrochemical impedance spectra. A 2-dimentional multi-physics model was developed and calibrated using both polarization and impedance data. To account for the lower open circuit voltage at lower fuel flowrates, an equivalent leakage current is included in the model. The model was thereafter employed for efficiency optimization given power constraints. At each required power output, the optimal fuel flowrate and the corresponding voltage, current, and efficiency was calculated. The electrical efficiency peaks globally at around 0.1 Standard Liter per Minute (SLM) hydrogen flowrate, while at higher power, the optimal efficiency is reached at fuel utilizations between 65% and 90%. Accounting for degradation in terms of growing ohmic resistance and decreasing electrode exchange current densities, the optimal efficiency is reached at lowering fuel utilization and lowering voltage, which may result in local oxidization of the anode.

Moreover, an easy and straight-forward way was proposed to estimate the optimal fuel flowrate given polarization data. Further studies involving the safety constraints will be carried out in the future.

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Fabrication and Electrochemical Testing of Silver Pattern Cathodes for Proton Conducting It-SOFC
Authors: Sozal Md Shariful Islam , Li Wenhao , Das Suprabha , Jafarizadeh Borzooye , Chowdhury Azmal Huda , Durygin Andriy , Drozd Vadym , Wang Chunlei , Cheng Zhe
Published: September 2023

Dense silver (Ag) cathodes with different triple phase boundary (TPB; the interface of gas, electrolyte and electrode) length (LTPB) and electrode area (AELT) were fabricated by photolithography and E-beam evaporation over different proton-conducting electrolytes such as BaZr0.4Ce0.4Y0.1Yb0.1O3–
δ
(BZCYYb4411). A bi-layer lift-off resist method appears more versatile than single layer for successful pattern cathode fabrication. The electrochemical behaviors of Ag pattern cathodes over the BZCYYb4411 electrolyte were tested with counter electrode such as Ba0.5Sr0.5Co0.8Fe0.2O3-δ and correlated against geometric features such as LTPB and AELT to understand the oxygen reduction kinetics and mechanism for proton conducting solid oxide fuel cells.

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Mechanistic Details of CO2 Electroreduction on Ni and Ni{Cu}-YSZ Electrodes Using Operando Spectroscopy
Authors: Ranjan Chinmoy
Published: September 2023

Electroreduction of CO2 to fuels using renewable energy can significantly help in reducing emissions and dependence of fossil fuels. Electrochemical reduction of CO2 to hydrocarbon fuels (CHx) is energy inefficient owing to multistep-multielectron transfer process which posses many kinetic limitations. The selective conversion of CO2 to CO is energy efficient. CO as product can be directly used as a fuel or converted to hydrocarbon fuels by using green hydrogen via Fischer-Tropsch reactions.

Well known Ni/YSZ electrode architectures have both well-established lifetimes, performance benchmarks and optimised manufacturing protocols when it comes to use as SOFC. Unfortunately, using these electrodes as CO2 reduction electrodes requires use of H2 at the inlet. The reaction proceeds through a reverse water gas shift reaction (RWGS) (CO2 + H2 à CO + H2O) in conjunction with water electrolysis. Most of the CO originates from non-electrochemical RWGS reaction. Use of pure CO2 streams at currents exceeding 240mA/cm2 leads to catastrophic electrode failure. In the literature, it is believed that transformation of Ni metal to NiOx and carbon deposition via Bouduard reaction are the causes of electrode failure in pure CO2. We have adapted this well-known Ni/YSZ electrode by impregnation of Cu into the Ni architecture. The Ni{Cu}/YSZ electrode not only does not deactivate but also shows improved performance in every aspect compared to the pure Ni/YSZ electrode.

We have developed a unique setup for operando Raman Spectroscopy and online mass spectroscopy which can be used to study electrode reactions under both steady state and transient conditions. Using this setup, we have shown that Ni-YSZ and Ni{Cu}/YSZ electrodes go through an oxide mediated mechanism of CO2 reduction. Metal oxides such as NiOx and Ni{Cu}Ox are the active catalyst species and not the metals. Upon applying strongly reducing conditions (currents > 240mA/cm2), NiOx reduces to Ni metal which can no longer catalyse the reaction, whereas the oxide on Ni{Cu}Ox is much stronger and does not reduce under even the most reducing of conditions (reducing currents >480mA/cm2). Such an electrode remains active for reducing pure CO2. Supporting studies using SEM, TEM, XPS, operando EIS, TPR and DFT modelling were also carried out. We believe that enabling CO2 reduction Ni/YSZ architecture using Cu impregnation is a game changer as all aspects of electrode manufacturing and device compatibility for Ni/YSZ have been extensively tested and market proven. This will allow for quick adaptation for this electrode in the CO2-SOEC market. Besides this, such a mechanistic study remains unique in the field of solid oxide-based research.

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Modeling Delamination of Electrodes of Solid Oxide Electrolyzers with Fuel Electrode as a Support
Authors: Kupecki Jakub , Niemczyk Anna , Jagielski Stanisław
Published: September 2023

Solid oxide electrolyzers (SOE) are the most efficient yet not fully mature devices for electrochemical production of hydrogen. These devices offer a great advantage in applications which make it possible to utilize process heat or steam to feed SOE for direct conversion of steam instead of water. However, the technology is prone to a degradation, as it combines advanced materials, requires dedicated fabrication techniques and it operates at elevated temperature, typically above 650ºC. One of the biggest challenges is the mitigation of degradation of solid oxide electrolyzers due to the delamination of the electrode. Several measures can be proposed to limit the process, however full elimination of this type of degradation is not yet possible. The good understanding of the mechanisms and consecutive steps which lead to deterioration of the interface between the electrolyte and air electrode of SOE is based on thorough experimental studies supported by the numerical modeling.

In the study we present a delamination model, which can be used to identify the safe operating envelope of SOEs with a given structure and material composition. The mechanisms behind degradation through delamination are discussed with respect to the chemical and electrochemical potentials. This is complement by the discussion of criteria for the formation and propagation of cracks, taking into account the oxygen potential at the electrolyte-electrode interface. Moreover, the microstructural modifications of the electrodes, e.g. increase of its porosity, are discussed as one of the potential measures to substantially reduce the risk of delamination under design point and off-design operation of SOEs. The methodology of manipulating the porosity of the electrode by varying the content and type of pore forming agents was proposed in order to adjust the parameters of electrodes to the required microstructure. Results of the experimental characterization of cells fabricated in such a way are presented, and the guidelines for fine-tuning the microstructure are discussed with respect to the degradation mechanisms.
Long-Term Degradation Models for the Solid Oxide Electrolysis Cell
Authors: Wang Dewei , Bao Jie , Koeppel Brian , Meinhardt Kerry D , Marina Olga A
Published: September 2023

Solid oxide electrolysis cells (SOECs) have been recognized as offering high efficiency of water/steam splitting and having the potential to meet the huge energy storage demand created by sustainable energies (solar, wind electricity, etc.). However, cell degradation takes place during long-term operation and seriously influences the implementation of this technique. Various degradation mechanisms exist in high-temperature operating SOECs: carbon formation due to the boudouard reaction at the active area of the anode (e.g., Ni-YSZ electrode); sulfur poisoning in the cathode (e.g., LSCF electrode) due to a trace of SO2 in the feed air; SrZrO3 insulation phase formation at the interface of the cathode and the electrolyte (e.g., YSZ) even with the existence of the reaction barrier layer (e.g., GDC); Ni coarsening in the anode; chrome poisoning, etc. This study investigates these long-term degradation mechanisms qualitatively and quantitatively. Numerical models are then built, respectively. Experiments are conducted with 2 cm2 button cells to benchmark certain degradation mechanisms. After all, the above-developed numerical models are embedded into a simulation framework for SOECs to investigate the influences of cell degradations on cells’ electrochemical performance.
Tracking Localized Degradation of Solid Oxide Cells Via Multi-Physics Modelling of Impedance Spectroscopy
Authors: Taubmann Julian , Sun Xiufu , Chatzichristodoulou Christodoulos , Frandsen Henrik Lund
Published: September 2023

The global, macro-scale description of degradation phenomena in solid oxide cells (SOC) reaches limitations when dealing with localized, micro-scale processes. For example, it is established that carbon deposition and transformation of the active area in nickel containing electrodes in electrolysis mode depend strongly on the local overpotential and gas composition. The state-of-the-art long-term characterization of a full SOC however relies on macroscopic measurements of DC polarization and electrochemical impedance spectroscopy (EIS), which are capturing the average response of the entire cell. The deconvolution of impedance spectra allows to separate the electrolyte resistance from electrode electrochemistry, gas conversion, and diffusion contributions. Nonetheless, heterogeneous, and local degradation cannot be described deploying commonly used tools of EIS analysis, such as equivalent electric circuit models, transmission line models, or the analysis of distribution of relaxation times.

Multi-physics based numerical models on the other hand open new opportunities in gaining advanced insights into the complex degradation mechanisms in SOCs. In the model proposed here, combining simulations of transient and frequency domain into one framework allows the description of measured long-term durability of an SOC in terms of voltage-current and impedance characteristic. In addition, the framework enables a local, micro-scale description of the degradation process based upon physical properties confirmable in experiments.

The modelling framework is validated with the durability measurements of the SOC in Sun et al. [1]. In this study, a fuel electrode supported cell with an active area of 16 cm2 was tested in galvanostatic operating conditions as an electrolysis cell with the constant current of -1 A/cm2 over 4383 h. Simultaneously to the voltage measurements over the test duration, the impedance response of the cell was tracked every eight hours. The evolution of the measured impedance spectra of the cell can be seen in the attached figure.

Comparing the outcomes of the model to the experimental data showcases the benefits of the model in describing the degradation induced increase in voltage over time and the evolution of impedance spectra. In particular, the effect of higher activation overpotential at the fuel inlet to the outlet of the cell is analyzed enabling the generation of local insights concerning the observed degradation. The model establishes an improved validation of equations describing degradation of SOCs encompassing overpotential gradients and relating to postmortem observed micro-structural changes.

Reference

[1] Sun, X., et al. "Degradation in solid oxide electrolysis cells during long term testing." Fuel Cells 19.6 (2019): 740-747.

Figure 1
Progress of Solid Oxide Electrolysis and Fuel Cells for Hydrogen Generation, Power Generation, Grid Stabilization, and Power-to-X Applications
Authors: Horlick Samuel A , Swartz Scott , Kopechek David , Merchant Geoff , Cochran Taylor , Funk John
Published: September 2023

Over the past 25+ years, Nexceris has been developing solid oxide cell (SOC) technology for power generation, energy storage and hydrogen production applications. Nexceris is vertically integrated SOC technology provider that develops and manufactures solid oxide electrode materials, interconnect coatings, planar electrolyte supported cells, and solid oxide stacks. Nexceris stacks are designed for low-cost manufacture and pressurized operation, and stacks have large repeat unit area for efficient packaging into megawatt-scale systems. Nexceris’ stacks are being tested in fuel cell, electrolysis, and reversible modes, with a focus on optimizing performance, efficiency, and durability. Current work at Nexceris includes long-term electrolysis stack durability testing, breadboard system testing of reversible SOC stacks, third-party stack validation testing, and SOC system design and demonstration testing. Nexceris also is exploring solid oxide co-electrolysis for converting steam and CO2 to syngas and the conversion of this syngas to fuels and chemicals. This presentation will provide an update on Nexceris’ solid oxide cell technology development and commercialization activities.
Theoretical Prediction of the Vapor Pressure of Solid Oxide Fuel Cell Components
Authors: Hu Yang , Wang Kai , Spatschek Robert , Müller Michael , Wessel Egbert
Published: September 2023

Due to the high operation temperature solid oxide fuel cells, various chemical reactions can lead to degradation, e.g. based on Cr2O3 gas phase evaporation from the interconnect and subsequent reaction with SrO which originates from LSCF cathodes. Therefore, investigations of the potential chemical reactions and the sublimation process play an extremely important role to study the related chemical reactions in SOFCs.

Here we propose a practical physical model based on density functional theory calculations and statistical mechanics, which is used to predict the vapor pressure of pure substances, which allows to extend thermodynamic database and to analyse the resulting chemical reactions inducing the new phase formation which leads to the degradation of SOFCs. These investigations serve as theoretical basis to understand and reduce degradation phenomena from a thermodynamic and kinetic perspective.
Perovskite-Based Materials As Alternative Fuel Electrodes for Solid Oxide Electrolysis Cells (SOECs)
Authors: Winterhalder Franziska Elisabeth , Alizad Farzin Yousef , Guillon Olivier , Weber Andre , Menzler Norbert H.
Published: September 2023

Enhancing the lifetime of SOECs is a challenge to overcome regarding their commercialization. A major impact on the lifetime of a cell during electrolysis operation, particularly under thermoneutral potential and high current densities, is the degradation of the currently used electrode materials, mainly the Ni-based fuel electrode. Among other things, nickel migration, as well as agglomeration, is leading to a significant performance loss after a certain operating time. Hence, preventing degradation mechanisms of the fuel electrode during operation is a necessity to be tackled for using it commercially. Therefore the development of alternative materials which combine sufficient performance with the lowest possible degradation rate is needed. Perovskite-based materials have been investigated in the last years as all-ceramic possible substitutes.

In this work, four perovskites (i.e., strontium-iron-niobate double perovskite (SFN), a strontium-iron-titanate material (STF), a lanthanum-strontium-titanate (LST) and a lanthanum-strontium-iron-manganese (LSFM)) were examined as alternative electrode materials. The aim is to substitute the active fuel electrode, at the moment commonly consisting of Ni cermets, with a perovskite-based electrode while at the same time using state-of-the-art materials for the remaining cell components.

The first task here was to look at the chemical stability between the new electrode material and the electrolyte under the standard conditions used to manufacture fuel electrode-supported SOECs.

Therefore, the compatibility between these perovskites with a yttria-stabilized-zirconia (8YSZ) electrolyte and how nickel inside the fuel electrode affected the chemical stability during sintering in air at 1400 °C for 5 h was investigated. At this point, SFN double perovskite shows the lowest interaction between the electrode and electrolyte after thermal treatment.

A thorough evaluation of all preliminary tests (including compatibility, stability in reducing atmospheres and redox stability tests) indicates that SFN shows so far the best results of the four materials in terms of application as fuel electrode material, followed directly by STF.

Thus SFN and STF were chosen to be evaluated in single cell tests. The tests of pure SFN and STF electrodes are carried out with electrolyte-supported single cells exhibiting an LSCF air electrode and symmetrical cells, respectively. CV-characteristics and impedance spectra are measured at varied operating conditions. Impedance spectra are evaluated by the distribution of relaxation times (DRT). These examinations are carried out to give an insight into the electrochemical properties of pure perovskite-based fuel electrodes in order to obtain a base for further optimization.
High-Performance Solid Oxide Electrochemical Cells with Ultrathin and Dense Double-Doped Ceria Interlayers
Authors: Yu Hyeongmin , Im Ha-Ni , Lee Kang Taek
Published: September 2023

To mitigate the drastic global climate change, which mainly originated from the indiscriminate use of fossil fuels, various alternative eco-friendly energy conversion technologies have been studied. Among them, solid oxide electrochemical cells (SOCs) are one of the most promising devices with superior power and energy densities and low environmental impact. The current main objective of the SOCs research field is lowering the operating temperature to secure thermal cycling stability and minimize system costs. To achieve a feasible performance for commercial usage at reduced temperatures, it is inevitable to use state-of-the-art cobalt-based oxygen electrode materials. However, cobalt-based materials inherently react with conventional zirconia-based electrolytes at high temperatures forming insulating phases at the interface. Thus, the ceria interlayer is essentially required to prevent unwanted chemical reactions.

In this study, we newly developed thin and dense doubly doped ceria interlayers (~250 nm) using a non-vacuum solution deposition process with gelatin. The SOCs with the thin-film ceria interlayers achieved superior electrochemical performance both in the fuel cell (FC) and the electrolysis cell (EC) mode (~3.5W/cm2 and ~2.1A/cm2 at 750°C for the FC and EC modes, respectively) compared to the SOC with a conventional porous and thick interlayer. The mechanistic analyses showed that the thin-film interlayer provides a much shorter route for oxygen ionic conduction and more active sites for oxygen reduction reaction (ORR) and oxygen evolution reaction (ORR) at the interface compared to the porous interlayer. Our results suggest that the thin-film doubly-doped ceria interlayer fabricated using the gelatin-assisted process has a high potential for development of high-performance SOCs.