bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust and Efficient Mechanical Model of High-Volume-Change Silicon Electrodes for Li-Ion Batteries
Authors: Wheeler Dean , Hamedi Amir Sina , Shumway Edmund McKay
Published: December 2024

This work develops an efficient and accurate pseudo-2D (P2D or Newman-type) model capable of describing the relevant mechanical and electrochemical aspects of porous electrodes where the active material undergoes significant volume change. The model is applied to silicon-based anodes for high-capacity Li-ion batteries. While the standard electrochemical equations in a P2D model are well-known, the mechanical equations are less well-established. This presentation will describe the development of mechanical principles and corresponding equations suitable for use in a P2D model.

While it is common in previous modeling work for much attention to be spent on the mechanics of the active particles themselves, relatively little attention has been spent on understanding the mechanics of the porous composite electrode. As an example, it is common to treat the expansion of the active material as if it affects only electrode thickness and not electrode porosity. Or it is common to neglect plastic deformation and even elastic deformation of the electrode. And yet both are pervasive in the electrode film under the large chemical strains of lithiation and delithiation.

We discuss these and other issues to show complex electrode performance behavior is derived from simple mechanical principles and experimentally derived properties. Shown in the figure below is an example calculation for one set of input parameters, showing how (a,b) porosity, (c,d) film thickness (total strain), and (e,f) tangential (in-plane) stress can change under imposed conditions of external normal stress or lithiation of a pristine electrode. Arrows show direction on a hysteresis loop for a full cycle, caused by plastic deformation of the electrode. Comparison with experiment, where feasible, will also be done.

Figure 1
(Invited) Electrode Blending Simulations Using the Mechanistic Degradation Modes Modeling Approach
Authors: Beck David , Dubarry Matthieu
Published: December 2024

Blended electrodes are becoming increasingly more popular in lithium-ion batteries, yet most modeling approaches are still lacking the ability to separate the blend components. This is problematic because the different components are not likely to degrade at the same pace. In this work, we investigated a new approach towards the simulation of blended electrodes by replicating the complex current distributions within the electrodes using a paralleling model rather than the traditional constant current method.

We first investigated the impact of using a paralleling model within the mechanistic degradation modes modeling approach to replicate the current distribution more accurately within blended electrodes. Using three exemplary chemistries with electrochemical response that covers all the possible scenarios (separated, overlapping, or only partially overlapping), we demonstrated that, although the paralleling approach enhances accuracy and better replicates experimentally observed current distributions, the actual effect on the voltage response of the full cell, whether pristine or aged, was close to negligible at low rates while the computational cost was increased by two orders of magnitude and resulted in noisier results. While it might be better to use the paralleling model for simulation at higher rates or when the loss of active material on the PE is significant, the computational limitations could hinder the application of the paralleling approach in scenarios where simulation speed is crucial because of the two order of magnitude increase.

Recognizing that the constant current approach is accurate enough to provide data representative of the behavior of the individual components within a blend, we generated three publicly available synthetic datasets covering more than 260,000 different degradations to enable the development of new diagnosis techniques for blended electrodes. Such techniques must enable component specific diagnosis since we showcased a significant impact of the composition of the loss of active material on the positive electrode on the cell electrochemical response. Because these variations could be confused with the one induced by other degradation modes, overlooking them could lead to false diagnosis, potentially compromising the safety of deployed systems.
(Invited) Gradients and Instabilities in Solid-State Battery Architectures
Authors: Mukherjee Partha P. , Vishnugopi Bairav Sabarish , Ayyaswamy Abhinand
Published: December 2024

Solid-state batteries (SSBs), consisting of a lithium metal anode and an inorganic solid electrolyte, promise high energy and power density amenable to long-range electric vehicles and electric aviation. However, the complex nature of solid-solid interfaces in SSBs poses challenges associated with morphological evolution, heterogeneities, and electrochemical, thermal, and mechanical interactions. The intrinsic heterogeneities at the solid-solid interfaces result in spatiotemporally varying electrochemical and thermal signatures and gradients in the solid-state battery architecture. This presentation will discuss the dynamic evolution of thermo-electrochemical gradients in SSBs and their implications on the solid-state porous cathode response, anode interface stability, and cathode-anode crosstalk. The critical role of the solid-state cathode architecture, including attributes such as the solid/solid contact distribution and transport pathways, on the self-heating and electrochemical behavior will be analyzed. This work aims to elicit mechanistic insights into the evolution of thermal gradients and potential approaches to modulate them in SSBs.
Economic Feasibility Study of Deploying Green H2 Infrastructure at Los Angeles International Airport (LAX)
Authors: Rezaei Sajjad , Alsamri Khaled , Simeoni Elio , Huynh Jacqueline , Brouwer Jack
Published: December 2024

Air transportation is among the critically debated subjects, contributing to approximately 2.5% of global CO2 emissions 1. The main strategy for addressing environmental concerns related to aviation emissions is the shift to low-carbon propulsion technologies for aircraft. Hydrogen could be introduced to the aviation sector as a fuel for fuel cell-powered aircraft or for direct combustion jet engines, with anticipated zero- to low-carbon emissions 2. Moreover, the universe lightest element possesses a very high gravimetric energy density of 120 MJ/kg, which will be higher when stored in cryogenic hydrogen form3, making it an ideal alternative to conventional aviation fuels (for example, jet fuel). This study provides a techno-economic analysis of introducing green hydrogen infrastructure to Los Angeles International Airport (LAX) to promote its transition towards sustainability. Preliminary research showed that the largest uncertainty in economic projections for H2-powered aviation hinges on future H2 supply costs, rather than aircraft modifications4. Therefore, the costs of potential hydrogen implementation routes, including off-site production supplied by road tankers or pipelines to the airport, and on-site production, will be assessed. In summary, the implementation of a hydrogen infrastructure at LAX is not only an initiative to reduce its associated carbon footprint but also suggests a practical and environmentally sustainable paradigm for future upgrades to aviation fuel infrastructure.

References:

H. Ritchie and M. Roser, Our World in Data (2023).

T. Yusaf et al., Int J Hydrogen Energy (2023).

T. Zhang et al., Renewable and Sustainable Energy Reviews, 176, 113204 (2023).

J. Hoelzen et al., Energy Conversion and Management: X, 20, 100442 (2023).

Figure 1
(Invited) Understanding Macroscopic Battery Degradation Observations through Ab Initio Theory, Atomistic and Coarse-Grained Simulations, and Experiments
Authors: Balbuena Perla B. , Perez Beltran Saul , Kuai Dacheng , Marshall Simone , Seminario Jorge M.
Published: December 2024

In the era of vehicle electrification, automation is also an important component, and this requires simulations able to reproduce experimental observables with maximum fidelity and a minimum of experimental data. This means prediction. However, how far or how close are we from prediction? In this talk, I will focus on battery degradation phenomena, certainly associated with materials evolution, and illustrate methodologies able to generate useful predictions of dynamic changes in battery materials and components during cycling. The methods cover a wide range of scales and phenomena, from atomistic effects of electrochemical and chemical reactions to transport and phase nucleation processes. In our analysis, we find that such abundance of coexistent events goes along with environment richness: multiple dissimilar materials, and complex phases and interfaces. We will show the development of a new coarse-grained algorithm that follows the physical events receiving input from ab initio methods and providing a realistic description of plating and stripping processes coexisting with chemical, electrochemical, and nucleation reactions in complex electrolytes reducing on the Li metal surface during cycling of Li metal batteries.
Lithiation-Induced Volume Change of NCM-Type Battery Cathode Materials from First Principles
Authors: Lowe Jeffrey , Hafiz Hasnain , Hector, Jr. Louis
Published: December 2024

Volume change during lithiation of battery cathode materials is a critical input parameter for battery cell performance predictions. Here, our focus was on seven LiNixCoyMn1-x-yO2 (NCM)-type battery cathode materials: NCM811, NCM721, NCM622, NCM523, NCM111, NCM361, and NCM271. Lithium (Li) concentration was varied from 0 to 1 in a range of structures for each material. The convex hull was computed with the VASP plane wave density functional code from which was determined the lowest energy structure for each Li concentration. Using two different functionals, viz. the optB86b-vdW (an optimized van der Waals functional based upon the Becke 86 functional) and the SCAN+rVV10 (combines the strongly constrained and appropriately normed meta-GGA for short- and intermediate-range interactions with the long-range van der Waals interaction from rVV10, the revised Vydrov-van Voorhis nonlocal correlation functional), the following were computed: DV (volume change) vs. state of charge (SOC) (0 ≤ x ≤ 1), ΔV vs. open circuit voltage (OCV), and OCV vs. SOC (0 ≤ x ≤ 1), where x is Li concentration. Qualitative comparisons with room temperature experimental data revealed closer accord from the SCAN+rVV10 functional. Noted disparities for lower values of x are explained in terms of structural phase transitions and loss of oxygen during lithiation/de-lithiation with incorporation of these effects as next steps.
(Invited) Voltage Controlled First-Principles Simulations of Li Ion Transport at Battery Interfaces Using the Quantum Continuum Approximation (QCA)
Authors: Campbell Quinn
Published: December 2024

Voltage has traditionally been difficult to include in Density Functional Theory (DFT) calculations of electrochemical interfaces which include large semiconducting/insulating sections, as is common in battery applications with the Solid Electrolyte Interface (SEI). This is due to the limited length scale available for full atomistic treatment with DFT. In this talk, I will outline a novel approach, the Quantum Continuum Approximation (QCA), which self-consistently pairs explicit DFT calculations of relevant interfaces with analytic treatment of the electrostatics within bulk semiconducting/insulating regions such as the SEI. This approach enables electronic voltage to be included within DFT calculations of battery interfaces. I demonstrate this methodology by examining potential barriers to Li transport within the Solid Electrolyte Interphase (SEI) in Li-ion batteries, demonstrating that changing voltages can lead to shifts in diffusion barriers, which make certain paths and SEI chemistries more favorable than would be expected under typically simulated neutral conditions.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525
(Invited) Dynamic Impedance Spectroscopy on Batteries: From Materials to Cells
Authors: La Mantia Fabio
Published: December 2024

Electrochemical impedance spectroscopy (EIS) is a powerful technique for analyzing and understanding electrochemical systems, which is crucial in order to improve the performance and reliability of batteries. However, it is often necessary to investigate the materials and cells under the operating conditions, i.e. outside the stationary condition. In order to do so, dynamic multifrequency analysis (DMFA) can be used to acquire dynamic impedance spectra in a large range of frequencies and with high time-resolved precision [1,2]. Starting from the physical definition of impedance and admittance, and using the concept of Volterra series, it has been shown how the concept of dynamic impedance can be interpreted as a non-stationary extension of the concept of classic impedance [3]. Here, it will be shown how the DMFA can be applied to the study of the reactions occuring at the active materials for batteries and supercapacitors, as well as its application for the investigation of full battery cells of different kind.

On one side, when investigating the reaction mechanism occuring on active materials, it is possible to fit the impedance data with physical models describing the processes occurring at the interface. The effect of the non-stationarity is manifested in the dynamic spectra only in the low frequency range and introduces a deviation from the classic behavior, which appears as an additional parallel resistance.

On the other side, when investigating full battery cells it is important to develop tools in order to analyze the impedance spectra statistically, as physical models are often too complex (overparametrized). In this case, the development of measurement models, such as the Pade’ approximants, as well as the use of statistical concepts such as the “maximum description length” or "akaike information criterion" [4], are necessary in order to obtain meaningful information. As perspective, it will be shown how the Pade’ approximants can be further used to obtain information on the complexity of the system by analyzing the extracted parameters through the concept of mutual information.

Literature:

A. Battistel, G. Du and F. La Mantia, Electroanal. 28 (2016) 2346

D. Koster, G. Du, A. Battistel, and F. La Mantia, Electrochim. Acta 246 (2017) 553

A. Battistel, and F. La Mantia, Electrochim. Acta (2019) 513

R. Chukwu, J. Mugisa, D. Brogioli, and F. La Mantia, ChemElectroChem 9 (2022) e202200109

Figure 1
Physicochemical Impedance Modelling of Porous Electrodes in All-Solid-State Electrochemical Devices
Authors: Kullmann Felix , Hauck Benjamin , Lindner Adrian , Dierickx Sebastian , Weber Andre
Published: December 2024

Fundamental knowledge about performance limiting processes in electrochemical devices like battery-, fuel- and electrolyzer-cells is mandatory for a model-aided development. The method of choice to analyze these processes is electrochemical impedance spectroscopy, enabling a separation of electrochemical processes differing in their relaxation frequencies. In order to improve the deconvolution of these processes in the impedance spectrum, the distribution of relaxation times (DRT) analysis is a well-established method [1].

In case of porous, multiphase electrodes, the DRT usually doesn’t enable a simple correlation of a peak in the DRT with a single polarization process in an electrode. The complex coupling of electronic and ionic charge transport via charge transfer reactions, often described by a transmission line model (TLM) [2-4], induces a number of peaks in the DRT. TLM parametrization just by operating and/or electrode parameter variations is often insufficient. Since different parameter sets can result in identical spectra [3], a straightforward CNLS-fit is insufficient and a pre-parameterization by determining at least a few model parameters independently is required.

In this study, impedance spectra of two all-solid-state electrochemical devices, an all-solid-state battery and a solid oxide cell, are analyzed by the distribution of relaxation times. Physicochemically motivated impedance models based on the TLM-approach were derived, pre-parameterized and applied to quantify different loss processes in the cells. The pre-parameterization included microstructural parameters obtained by focus ion beam tomography and conductivity data. The model development and areas of application will be discussed in detail within this contribution, focusing on the differences between the two investigated all-solid-state electrochemical devices.

References:

[1] H. Schichlein, A.C. Müller, M. Voigts, A. Krügel and E. Ivers-Tiffée, J. Appl. Electrochem., 32, 875 (2002).

[2] S. Hori, R. Kanno, X. Sun, S. Song, M. Hirayama, B. Hauck, M. Dippon, S. Dierickx and E. Ivers-Tiffée, J. Power Sources, 556, 232450 (2023).

[3] F. Kullmann, M. Mueller, A. Lindner, S. Dierickx, E. Mueller and A. Weber, J. Power Sources, 587, 233706 (2023).

[4] P. Braun, C. Uhlmann, M. Weiss, A. Weber and E. Ivers-Tiffée, J. Power Sources, 393, 119 (2018).
Nicup Catalyst with the Synergistic Effect of Ni and Cu for Hydrogen Production Using Ammonia Electrolysis
Authors: Jo Chanmin , Jeon Minseo , Moon Dae Jun , Jeong Gyoung Hwa , Kim Joon Young , Sim Uk
Published: December 2024

Carbon neutrality using cleaner energy sources to replace fossil fuels is essential for climate change and a sustainable future. There are many candidates, including renewable energy, but hydrogen energy is gaining the most attention. Hydrogen energy is the most attractive alternative due to its abundance, renewability, and eco-friendliness as an energy source, however, its utilization is limited by transportation challenges. To solve this issue, various hydrogen carriers have been studied. Among them, ammonia is considered the closest to commercialization because it has an existing transportation infrastructure and does not contain carbon. In addition, ammonia can be electrochemically hydrogenated, and the theoretical reaction potential for this is 0.07 V vs. RHE, which is significantly lower than water electrolysis (1.23 V vs. RHE). Nevertheless, the actual reaction occurs at a potential between 1 and 2 V due to the high overpotential generated by the adsorption of NHx species on the surface during the reaction. Pt also has weaknesses like toxicity due to high nitrogen adsorption capacity, and its high price. To improve this, developing effective catalysts based on non-precious metal materials is important. In this study, a catalyst was synthesized using Ni, which has excellent nitrogen adsorption and ammonia oxidation reaction (AOR) properties, and Cu, which has desorption and dimerization properties of NHX species. Moreover, its phosphorylation improves catalyst durability and provides additional reaction sites. The as-prepared catalysts were characterized by physicochemical properties and electrochemical analysis along with the comparator, and the potential at 100 mA for AOR was 1.45 V vs. RHE. The catalysts were also evaluated for stability and hydrogen generation.
Polarization Electric Field of Tourmaline Promotes Formic Acid Oxidation on Palladium
Authors: Zhang Xinsheng , Hu Shuozhen , Luo Guoming
Published: December 2024

Direct formic acid fuel cells (DFAFC) use formic acid that is easy to store and transport as fuel, which has the advantages of high energy density and low operating temperature, and has shown broad application prospects in mobile power and other fields. Palladium is recognized as the most effective electrocatalyst for formic acid oxidation (FAO). Unfortunately, palladium nanoparticles are easily dissolved in the acidic environment during fuel cell operation. In addition, the d-band center of Pd is close to the Fermi level, resulting in forming a strong bond between Pd and adsorbed species (e.g., COad-like species). As a direct consequence of the above issues, Pd nanoparticles are continuously lost and poisoned, causing unsatisfactory cycling performance. However, all these previous approaches can only alleviate the issues of Pd poisoning and Pd dissolution, respectively.

In this work, by utilizing the polarization electric field of tourmaline minerals to change the adsorption state and energy of formic acid molecules, the electrocatalytic performance of palladium in FAO reactions can be improved. Tourmaline nanoparticles (TNP) are coated with resorcinol-formaldehyde (RF) resin to obtain TNP@RF support (Fig.1a), and Pd nanoparticles are uniformly and partially embedded in the RF carbon layer to generate TNP@RFC@Pd catalysts by in situ carbothermal reduction (Fig.1b). The polarized-electric field from tourmaline (Fig.1c) induces charge transfer from Pd to tourmaline, causing the d-band center to shift away from the Fermi level (Fig.1d). Both the strain effect and ligand effect cause the electron-deficient state of Pd. Consequently, breaking the O-H bond in formic acid is enhanced and the bond strength between Pd and COad is weakened. The polarized-electric field of tourmaline promotes the generation of OHad on Pd to convert COad into CO2 and release the active sites of Pd. The embedded structure of Pd nanoparticles in the carbon layer prevents the dissolution and agglomeration. Benefiting from these results, TNP6.67@RFC@Pd1 catalyst exhibits 3.9 times higher mass activity, greater CO-tolerance and better durability than those of electric-field-free catalysts (Fig.1e).

Figure 1
Pulsed Electrolysis for Enhanced Nitrate Reduction Reaction to Ammonia at Low Concentrations
Authors: Boppella Rami Reddy , Ahmadi Maryam , Arndt Brenden , Nazemi Mohammadreza (Reza)
Published: December 2024

Electrochemical nitrate (NO3
-) reduction reaction (NO3
-RR) could offer a transformative pathway to generate ammonia in a sustainable, electrified, and decentralized manner. Improving the selectivity of the electrochemical process toward desired products and minimizing competing reactions (e.g., hydrogen evolution reaction) are the major bottlenecks before widespread adoption of the technology at an industrial scale. In this talk, we present our recent efforts in leveraging various electrochemical techniques, including pulsed electrolysis, to enhance the selectivity of the process toward ammonia at low nitrate concentrations (e.g., 10 mM). We use computational and experimental techniques to pinpoint the mechanism for the improved performance of nitrate reduction reaction to ammonia under pulse electrolysis in flow-cell electrochemical systems. We characterize the catalysts and local microenvironment under pulsed electrolysis and potentiostatic conditions to understand their impacts on ammonia yield and energy efficiency of the electrochemical process. This work provides foundational knowledge and understanding of materials and processes to demonstrate electrochemical NO3
-RR to ammonia at low nitrate concentrations, enabling a paradigm shift toward green and sustainable fuel synthesis from nitrogen source and water under more realistic nitrate concentrations in various wastewater sources.
Biohybrid CO2 Electrolysis for the Direct Synthesis of Biomass from CO2
Authors: Lee Jae Won , Lee Hyunjoo
Published: December 2024

Converting anthropogenic CO2 into value-added products using renewable energy has garnered significant attention in pursuit of a sustainable carbon cycle. While CO2 electrolysis has been extensively explored, the resulting products have typically been limited to simple C1-3 compounds like CO, formate, ethylene, and small alcohols. Despite their simplicity, these products can serve as feedstocks for fermenters to produce more complex chemicals. Combining electrochemical CO2 reduction with microbial fermentation has been an active area of research, albeit often hindered by low production rates.

In our study, we integrated CO2 electrolysis with microbial fermentation to directly produce biomass from gaseous CO2. Firstly, we established a biohybrid system where the electrolyte solution containing formate was continuously circulated through both the CO2 electrolyzer and fermenter. This approach facilitated efficient accumulation of poly-3-hydroxybutyrate in Cupriavidus necator cells, achieving a PHB content of 83% of dry cell weight and producing 1.38 g PHB. The biohybrid system involved the electrochemical conversion of CO2 to formate on Sn catalysts deposited on a gas diffusion electrode, with careful optimization of the electrolyzer and electrolyte solution. Subsequently, we modified the system to enable continuous PHB production at a steady state by introducing fresh cells and removing PHB.

Secondly, we developed electrochemical biohybrid system with metabolically engineered Escherichia coli (E. coli) capable of producing lactic acid solely from CO2 and formic acid. By constructing a biohybrid system comprising a CO2 electrolyzer that generates formic acid from CO2 and a fermenter housing the engineered E. coli, we achieved direct electrochemical production of lactic acid from gaseous CO2. The catholyte was optimized to support the engineered E. coli within the biohybrid system, and the formic acid production rate was controlled to ensure stable lactic acid production. These strategies employed in developing our biohybrid system hold promise for establishing other electrochemical biohybrid systems capable of producing chemicals and materials directly from gaseous CO2.
Development of a Photoelectrochemical Process for the Elimination of Trace Substances in Wastewater Treatment with an Integrated 200% Electrolysis Cell
Authors: Schanz Tobias , Bloh Jonathan Z.
Published: December 2024

Access to clean water is one of the UN’s strategic development goals. Though often seen to target mostly the developing counties or rural regions with low infrastructure, this is an important topic even in modern industrialized countries. Here, drinking water is certainly clean by most standards, yet it is often still contaminated with micropollutants with known adverse effects even at minute concentrations which are difficult to mitigate with conventional technology. Promising technologies to tackle this challenge include electrochemical or photoelectrochemical wastewater treatment, which can effectively completely mineralize organic pollutants using in-situ generated reactive oxygen species (ROS) like hydroxyl radicals.

Photoelectrochemical wastewater treatment is an emerging technology for the removal of organic and inorganic pollutants from wastewater using sunlight as an additional or sole energy source and thereby saving on electricity costs. Since the water quality should not be subject to the intermittency of solar energy, we employ an additional conventional “dark” electrode which will operate with supplied external current in the absence of sufficient light energy. In particular, we use a BDD (boron-doped diamond) as anode in combination with a bismuth vanadate (BiVO4) based photoanode. In case of light illumination, this photoanode generates a photovoltage and current on its own without an external power supply. In both cases, ROS like hydroxyl radicals and hydrogen peroxide are formed from water oxidation. These two anodes are used in conjunction with a carbon-based gas diffusion electrode (GDE) as cathode. Here, atmospheric oxygen is reduced to form hydrogen peroxide also serving as oxidant.

In addition to the described reactions, the electrolyte ions may also play an important role. These may form other peroxo-species at the electrodes themselves or indirectly via hydrogen peroxide and hydroxyl radicals. Recently, we could show that bicarbonate in particular plays a very important role, forming the highly potent peroxomonocarbonate which was shown about 200 times as active as hydrogen peroxide itself.[1]

Overall, we show that the photoelectrochemical process can efficiently remove a wide range of recalcitrant pollutants from wastewater, including organic dyes, pesticides and pharmaceuticals. It has the advantage of being a sustainable and energy-efficient technology, as it uses sunlight as the primary energy source, meaning that a smaller amount of electricity needs to be fed in. We will further discuss the influence of the reaction parameters (light intensity, voltage, current density, pollutant concentration, flow rate) as well as the role the supporting electrolyte plays.

[1] Schanz, T.; Burek, B. O.; Bloh, J. Z. ACS Energy Lett.
2023, 8, 1463–1467.

Figure 1
Bipolar Membrane Polarization Governed By Interfacial Ionic Species
Authors: George Thomas Young , Brimley Paige N , Smith Wilson A , Aziz Michael J.
Published: December 2024

Bipolar membranes (BPMs), consisting of an anion exchange polymer membrane layer, a cation exchange polymer membrane layer, with a catalytic interfacial layer in between, enable electrolysis cells with large difference of pH between adjacent chambers. This pH gradient is a working principle of a number of devices for energy and sustainability: acid/base batteries store and release energy by building and depleting a pH difference; BPM electrodialysis reactors capture CO2 in alkaline electrolytes and release CO2 by acidifying; CO2 and H2O electrolysis devices may employ pH-decoupled electrodes to avoid precious metal electrocatalysts while maintaining low electrode overpotentials. For all of these devices the most efficient operation - in terms of extracting maximum voltage from a battery or driving electrolysis with minimum overpotentials - is achieved when the BPM selectively transports H+ and OH- ions in the cation and anion exchange layers respectively. But in practical devices, salt impurities may be present in the electrolytes, or supporting salt may be intentionally added to improve electrolyte conductivity. In this work, we explore how ion exchange processes in bipolar membranes in impure electrolytes affect the ion composition at the bipolar junction - the interfacial layer where the two membrane layers meet. We propose that the ion composition at this interface determines the voltage measured across the membrane at open-circuit, as well as the polarization behavior of the membrane under applied current.

We investigate the proposed mechanism using a model system comprising electrolytes with KOH, HCl, and KCl at various relative concentrations with a commercially available BPM (Fumasep FBM). We combine analysis of polarization experiments in a four-electrode setup with a 1D continuum model of water dissociation and multi-ion transport. We report that increased relative salt concentration in the electrolytes erodes the open-circuit voltage across the membrane, yielding voltages significantly lower than expected based on the measured pH difference, indicating that H+ and OH- ions within the BPM exchange with ions from the added salt to occupy membrane fixed charges at the bipolar junction. This phenomenon penalizes the energy efficiency of BPM acid/base batteries. Additionally, we find that during polarization, impure electrolytes exhibit salt crossover at low current density and that the magnitude of this crossover depends on the relative concentration of the salt versus H+ and OH- ions. We utilize the 1D continuum model to visualize concentration profiles of ions in the BPM at both open-circuit and applied current conditions.

This work illustrates the importance of electrolyte species on interfacial BPM phenomena and provides guidance both for designing new BPM materials and for choosing electrolytes and operating conditions in electrochemical cells.

Figure 1
Selective Reduction of Bicarbonate to Formate Via in-Situ Generated CO2 on a Hydrophilic Membrane Filter
Authors: Nomoto Kohta , Okazaki Takuya , Amano Fumiaki
Published: December 2024

Formate (HCOO−) production by electrochemical CO2 reduction reaction (CO2RR) has been paid much attention. To mitigate the energy loss associated with the purification and compression of CO2 gas, electrochemical conversion of in-situ generated CO2 from liquid bicarbonate (HCO3
−) feedstock has been developed instead of supplying CO2 gas. However, the Faradaic efficiency (FE) for formate production was low, necessitating the suppression of competing hydrogen evolution reactions. In this study, the configuration of the electrolyzer was optimized for highly efficient formate synthesis by bicarbonate electrolysis. We used electrodeposited bismuth crystallites as a cathode catalyst for CO2RR. FE was improved by using a hydrophilic membrane filter to reduce the H+ concentration on the cathode catalyst surface, thereby decreasing hydrogen evolution capability. Increasing the flow rate of 3 M KHCO3 solution further enhanced the FE by promoting efficient H+ consumption with bicarbonate to generate CO2. At a high flow rate condition (32 mL/min), the FE was over 90% at 100 mA/cm2 at 1.60 V (vs. RHE), comparable to conventional gas-fed CO2 electrolyzer performance. High selectivity at 100 mA/cm2 with low cell voltage (3.1 V without iR compensation) was achieved over 30 hours when using an IrO2 anode catalyst for oxygen evolution reaction. This work presents a simple and effective approach for highly selective formate synthesis at a high current density by improving the efficiency of H+ consumption and CO2 generation inside the bicarbonate electrolyzer.

Figure 1
Life Cycle Assessment of Liquid Alkaline Electrolyzers Comparing Environmental Performance across Various Design, Operation, and End-of-Life Scenarios
Authors: Zaki Mohammed Tamim , Breunig Hanna
Published: December 2024

Alkaline water electrolysis (ALK) is a demonstrated technology, used for over 100 years primarily for ammonia production, and later advanced for oxygen production for nuclear submarine applications. With a new focus on the expansion of renewably-powered hydrogen production, ALK systems hold great promise for commercialization. Recent research may further drive-down costs by addressing challenges related to electrodes, electrolytes, bubble formation, and impact of operation patterns. However, literature studies on ALK often lack a comprehensive model that can capture the impact of such deployment nuances on overall greenhouse gas emissions and environmental impacts. For example, an analysis of the effect of hourly or sub-hourly operation of ALK based on electricity generation profiles on required heat management, shutdowns, hydrogen leakage, safety, and cell degradation are lacking. Additionally, details on the manufacturing of critical components of the ALK cell stack are missing, although material contributions by weight are available. Materials at their end-of-life may have unique requirements for recycling or disposal, and these factors are also not well understood.

Herein, we present an overview of life cycle assessments (LCA) of ALK, as well as novel modeling of environmental impacts associated with ALK supply chains in the United States. Details and impacts of component manufacturing is included, along with the uncertainties of the raw materials production. We will then present our dynamic ALK model that includes cell voltage degradation, effects of the input power load on the electrolyzer temperature, purity, and associated hydrogen leakage at the electrolyzer facility itself. Finally, we present findings on plausible recycling and landfilling of the raw materials. We use the NREL United States Life Cycle Inventory database supplemented by Ecoinvent in the OpenLCA platform to evaluate embodied emissions. We compare the environmental performance for different scenarios of stack design (baseline versus advanced based on reduced diaphragm thickness and improved catalyst material), operation (low versus high pressure and scales such as 50 versus 500 ton/day), end-of-life cases (landfilling versus combination of landfilling and recycling). Finally, we make a comparison of these different scenarios to identify environmental impact hotspots along the life cycle of a liquid alkaline electrolyzer and guide future research on cell stack development.
Influence of Electrodes Surface Area Ratio on Titanium Electrorefining Process
Authors: Woo Hwa-young , Ri Vladislav , Kim Ki-hong , Lee Byoung-gun , Kim Ga-min , Ryu Hong-youl
Published: December 2024

Most titanium is commercially produced by the Kroll process, which was developed in the 1960s. Recently, it has been criticized for its high energy consumption, toxicity, significant greenhouse gas emissions, and the generation of iron-contaminated titanium scrap. Consequently, numerous attempts to develop alternative methods for titanium production have been widely studied in the past few years, electrorefining is one of these methods.

The titanium electrorefining process is based on the transfer of titanium from an impure electrode (CuTi anode) to another electrode (cathode) in an electrolyte environment. The configuration of the electrodes is highly important for the electrorefining process, as it can limit conditions for efficient electrorefining and reduce the quality of the produced titanium deposits.

Titanium electrorefining tests were conducted in molten LiCl-KCl-NaCl with 7.5 mol.% of TiCl2, in an argon atmosphere at 600 °C. A CuTi ingot was used as the anode, and a steel electrode served as the cathode. The influence of the electrodes' surface area was studied to improve the efficiency of the electrorefining process and the quality of titanium deposits. The surface area ratio of the anode to cathode was varied from 2.28 to 7.84, and the current density applied to the cathode ranged from 12.5 to 104 mA/cm².

Electrode potentials, cell voltage, and maximum current density were measured using a data logger and DC power supply for experimental setups with various surface area ratios of the electrodes. The experimental results indicated that current efficiencies ranged from 69 to 82.5% based on weighing the leached titanium deposits. Typically, lower current densities resulted in higher current efficiencies and improved quality of titanium deposits. Higher cell voltages and potentials were observed in setups with lower surface area ratio.

Morphology and chemical analysis of titanium deposits were obtained through SEM/EDS analysis and N/O analysis. It was found that higher current densities resulted in finer titanium deposits and increased oxygen content in the deposits. The optimal surface area ratio was estimated to be 2.84 at a current density of 62.5 mA/cm² for producing large dendritic titanium with oxygen as low as 963 ppm, and as 5.21 at current density of 104 mA/cm2 for production of fine titanium powders with oxygen of 3163 ppm.
Resistivity Engineering of Atomic Layer Deposited Tungsten Carbonitride Thin Films Via Carbon Concentration Control for Cross-Point Memory Electrodes Applications
Authors: Na Seunggyu , Yoo Namkyu , Seo Jeongwoo , Kim Jaehyeok , Kim Tae Hyun , Park Seungwon , Lee Minkyu , Kim Myoungsub , Chung Seung-min , Kim Hyungjun
Published: December 2024

As the demand for data storage and processing continues to rise exponentially, the development of phase change memory (PCM) has gained significant attention. In particular, three-dimensional (3D) vertical cross-point (VXP) array architecture is one of the most promising solutions for PCM fabrication, offering increased integration density and cost-effectiveness compared to the conventional planar memory structures, realized by atomic layer deposition (ALD) due to its excellent controllability and conformality.1) However, the implementation of a 3D VXP structure necessitates selectors, such as an ovonic threshold switch (OTS), to suppress sneak current from unselected cells. The switching behavior of the OTS selector depends heavily on electrode materials, constituting an essential part of the OTS device.2) Thus, detailed engineering of electrode material is required to obtain desirable properties for 3D VXP. Electrodes for 3D VXP require moderate resistivity because of the trade-off between thermal efficiency and power consumption. Moreover, the resistivity of film can be shifted by carbon incorporation. In this regard, we controlled the resistivity of the electrode with varying carbon concentration of the film utilizing ALD technique.

In this study, we focus on the development of thermal ALD tungsten carbonitride electrodes for 3D VXP arrays. Tungsten nitride is mainly used as an electrode due to its high thermal stability and conductivity. We present a novel ALD process with intentional carbon control of tungsten nitride to change film properties, including resistivity, by adjusting process parameters. Through systematic control of ALD process parameters, we investigated the impact of carbon concentrations on film characteristics and subsequently analyzed how these variations influence the electrical properties of OTS devices. This research opens the possibility of tuning electrode characteristics in detail, ultimately enhancing the overall electrical performance of the next-generation cross-point memory devices.
(Invited) Atomic Layer Etching: Basics, New Developments & Applications
Authors: Lill Thorsten
Published: December 2024

Atomic layer etching (ALE) is becoming an important technology for patterning and shaping of electronic and photonic devices. This tutorial briefly recaps the fundamentals of thermal, directional and plasma assisted atomic layer etching. Performance benefits and limitations for ALE in comparison to the continuous processing analogues such as reactive ion etching, radical and vapor etching are the consequence of the cyclic self-limited structure of ALE processes. Selection criteria for the appropriate etching technology for a given task will be presented. The enormous progress in the development of new ALE process and chemistries will be illustrated using published and potential practical applications in the manufacturing of electronic and photonics devices. They include multi-patterning, advanced planar and 3D logic and memory devices, 2D materials, emerging memories comprised of hard to etch materials, power and optical devices and combinations of ALE and atomic layer deposition.
Ceramic Thin-Film Composite Membranes with Tunable Subnanometer Poresfor Molecular Sieving By Atomic Layer Deposition
Authors: Elam Jeffrey W. , Zhou Xuechen , Shevate Rahul , Mane Anil U. , Kim Jaehong , Elimelech Menachem
Published: December 2024

Membranes with tunable, sub-nanometer pores are needed for molecular separations in applications including water treatment, critical mineral extraction, and recycling. Ceramic membranes are a promising alternative to the polymeric membranes typically used in such applications due to their robust operation under harsh chemical conditions. However, current fabrication technologies fail to construct ceramic membranes suitable for selective molecular separations. In this presentation, we describe a ceramic thin film composite (TFC) membrane fabrication method that achieves sub-nm pore size control using atomic layer deposition (ALD) by incorporating a molecular-scale porogen. By co-dosing alkyl alcohols along with the H2O coreactant during Al2O3 ALD, we incorporate alkoxide species in the film which create a continuous network of pores upon calcination. Varying the alkyl alcohol (methanol, ethanol, isopropanol) tunes the pore size. We use Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy to elucidate the surface chemistry and growth during the alcohol-modulated ALD as well as the subsequent pore formation. We evaluate the transport and separations properties of the ALD TFC membranes using a two-chamber diffusion cell with aqueous salt solutions. We measured a remarkable enhancement in the transport of Cl- compared to SO4
2- (8.6 times faster) matching the selectivity of state-of-the-art polymer membranes. We attribute this selectivity to the dehydration of the large divalent ions within the subnanometer pores. In addition, permeation studies using neutral adsorbates revealed average pore sizes of ~7Å, 13Å, and 19Å for ALD TFC membranes prepared using methanol, ethanol, and isopropanol, respectively. This work provides the scientific basis for the design of ceramic membranes with subnanometer pores for molecular sieving using ALD.
(Invited) Recent Advancements and Emerging Applications in Atomic Layer Deposition (ALD) on High-Porosity Materials
Authors: Bechelany Mikhael
Published: December 2024

Atomic Layer Deposition (ALD) represents a state-of-the-art technology facilitating the production of thin films utilizing high-quality materials on substrates featuring high aspect ratios. This method delivers precise control over thickness, uniformity, and exceptional conformality, making it especially suitable for modifying the structure and tailoring the pores of highly porous materials like synthetic membranes. ALD coatings have found successful applications across a broad spectrum of membrane substrates, ranging from inorganic templated supports to porous polymers.

In this presentation, we seek to provide a comprehensive overview of the progress achieved in employing ALD on highly porous materials such as those used in membrane technology. Drawing upon a carefully curated selection of our research endeavors, we will demonstrate how ALD can be effectively harnessed to enhance the operational efficiency of various membrane types, including inorganic, organic, hybrid, or composite membranes. We will showcase examples illustrating how ALD plays a crucial role in designing membranes with precisely adjustable geometries, facilitating a systematic exploration of the relationship between physical-chemical properties and geometric parameters. This methodology enables thorough investigations into membrane performance across diverse applications such as renewable energy, encompassing tasks like gas separation and osmotic energy harvesting, as well as environmental applications like water treatment and sensor technologies.

Furthermore, we will delve into the challenges and prospects associated with employing ALD in membrane applications. This presentation aims to provide an exhaustive overview of the benefits of ALD and its applications across various aspects of membranes and related engineering processes. It endeavors to shed light on the myriad opportunities within this emerging and swiftly advancing field.

Selected References:

Chemistry of Materials 2018, 30, 7368-7390

Journal of Membrane Science, 2015, 475, 39–46

Journal of Membrane Science, 2020, 596, 117701

ACS Appl. Mater. Interfaces, 2017, 9, 16669–16678

Separation and Purification Technology, 2023, 312, 123377

Journal of Materials Chemistry A, 2019, 7, 8107-8116

Sensors and Actuators B: Chemical, 2021, 344, 130302