bluuebunny/crossref_metadata_2025 huggingface dataset:
(Digital Presentation) Electrochemical Conversion of Cu Nanowires Synthesized By Electrodeposition in Track-Etched Templates to HKUST-1
Authors: Luo Jia , Wagner Michael Florian Peter , Ulrich Nils , Kopold Peter , Trautmann Christina , Toimil Molares Maria Eugenia
Published: November 2022

Metal-organic frameworks (MOFs) are a novel type of nanoporous materials that have attracted widespread attention over the past two decades [1]. Cu-based metal-organic frameworks such as Cu3(BTC)2 (also known as HKUST-1) are one of the most famous MOF representatives, which exhibit a huge open porosity and thus a remarkably capacity to store and uptake different gases [2, 3]. Recently, increasing efforts are devoted toward finding synthetic routes that enable downsizing MOF crystals to the nanoscale. Achieving control over the size and shape of nanoMOFs and finding ways to assemble them is essential for their exploitation in integrated devices such as sensors, gas separation membranes or photoelectrodes.

In this study we explore the conversion of free-standing arrays Cu nanowires with controlled diameter and length synthesized by electrodeposition in etched ion-track membranes into HKUST-1. In a first process step, free-standing Cu wires are produced by dissolving the ion-track polymer template. In a second step, the wires are converted into HKUST-1 structures by electrochemical oxidation. Applying 2.5 V versus a Cu counter electrode, the Cu nanowires are oxidatively dissolved and the MOF is built up as the as-formed Cu2+ ions bind to the BTC3− ligands in the electrolyte solution. The morphology and crystallinity of the samples at different transformation stages is investigated by scanning electron microscopy (Fig. 1) and transmission electron microscopy, respectively. X-ray diffraction spectra measured at different conversion times reveal the appearance of the characteristic reflections of HKUST-1. These results will be compared with previous studies of the transformation of Cu nanowires to HKUST-1 nanowires inside the polymer membrane [4].

Figure 1: SEM images of cylindrical Cu nanowires (a) before and (b) during the electrochemical conversion process, and (c) of a representative octahedral particle after complete conversion to HKUST-1.

References

[1] Freund R, Canossa S, Cohen SM, Yan W, Deng et al. Angewandte Chemie International Edition. (2021) 2: 23946-23974

[2] Chui SS-Y, Lo SM-F, Charmant JP, Orpen AG, Williams ID. Science. (1999) 283:1148-50.

[3] Li H, Li L, Lin R-B, Zhou W, Zhang Z, Xiang S, et al. EnergyChem. (2019) 1:100006.

[4] Caddeo F, Vogt R, Weil D, Sigle W, Toimil-Molares ME, Maijenburg AW. ACS applied materials & interfaces . (2019)11:25378-87.

Figure 1
Fabrication of Electroplated FeCo Nanowires in AAO Substrate for the Application to Inductor
Authors: Kim Dong Hyun , Kim In Yea , Lim Gi hwan , Kim Chae Yoon , Lee Min-Jeong , Kim Jaehun , Lim Jae-Hong
Published: November 2022

Recently, demand for inductors is increasing due to the development of IoT, automatic driving devices, and eco-friendly electric vehicles, and for this reason, efficient and miniaturized inductor manufacturing technology is becoming important. To miniaturize the inductor, it is necessary to miniaturize the core part, which is the center of the inductor. A typical method for manufacturing a core part of inductor is a multilayer ceramic capacitor (MLCC). This method cross-laminate silicon and metal in order to make patterns. After cross-laminating, it needs to be contracted to make it smaller in sintering process. This process causes imprecision of dimension thus there is a limitation in miniaturization of the inductor.

The diameter of AAO used in this study is 25mm and its pore size is 200nm. 3 electrode electroplating is selected for plating FeCo on AAO, counter elctrode as Pt electrode, and FeCo were deposited on –1 V vs. Ag/AgCl and on differed time for 6h, 7h, and 8h. The concentration of electrolytes used for FeCo plating is Fe 0.15 M/L, Co 0.2 M/L, and ascobic acid 0.01 M/L. For electrolytes, 47.4 g/L of cobalt chloride hexahydrate, 35.6 g/L of ion sulfate hepahydrate, and 1.769 g/L of L - ascobic acid were used. After the plating, SEM images and EDS were used to see the deposition rate of FeCo nanowires and composition variation via time.

FeCo nanowires were generated via time for 6h, 7h, and 8h to see the deposition rate. Figure 1 shows SEM image of FeCo nanowire plated for 8 hours and figure 2 shows length of the FeCo nanowire via time. After removing the AAO using 3M NaOH, we measured the saturation magnetization of FeCo nanowire and was 167.2269 emu/g and the coercivity was 120 Oe as shown in figure 3. The saturation magnetization was different from theoretical value of FeCo, 245 emu/g, probably due to the poor crystallinity. The more details will be presented.

Figure 1
Electrodeposition of Functionally Graded Brazing Interlayers for Enhanced Joint Strength between Fusion Plasma-Facing Materials and Heat Sinks
Authors: Lee Katherine , Garich Holly , Snyder Stephen , Skinn Brian , Inman Maria
Published: November 2022

In response to the significant plasma science and engineering breakthroughs witnessed over the past decade, the fusion research community has developed an ambitious roadmap to achieve large-scale, energy-positive fusion reactors that will enable economically competitive fusion electricity. Critical to the success of commercial fusion energy is the development of materials able to serve as plasma facing components (PFCs) that can withstand the unprecedented high heat, particle, and neutron fluxes within the fusion reactor. Tungsten is a leading candidate for the plasma-facing portion of these PFCs because of its high melting point, high sputtering resistance, and low tritium retention. Copper or copper-based alloys (e.g., copper-chromium-zirconium alloy C18150) and reduced activation ferritic/martensitic (RAFM) steels have been proposed for the heat sink materials behind the tungsten armor due to their high thermal conductivity. Brazing is considered a promising method for joining the tungsten armor and heat sink layer. However, the extreme mismatch in the coefficient of thermal expansion (CTE) between tungsten and these potential heat sink materials makes directly joining these two layers challenging. This thermal stress can be reduced by incorporating a joining layer of functionally graded materials between the tungsten and heat sink that imparts gradual changes in CTE. Copper/tungsten or copper/tungsten carbide composites are leading candidates for these functionally graded materials. For these composites, gradual changes in the CTE are achieved by varying the volume fraction of tungsten/tungsten carbide in the composite, from tungsten-rich at the tungsten armor to tungsten-poor at the heat sink.

This talk will discuss the development of a scalable, electrochemical approach for fabricating interlayers with functionally graded CTE that can decrease the thermal mismatch between tungsten PFCs and copper or RAFM-based heat sinks. In this approach, the copper/tungsten or copper/tungsten carbide composite are electrodeposited onto the tungsten PFC. This component is then bonded to the heat sink via brazing. A key objective of the work is to achieve compositional control during electrodeposition through the use of highly tunable pulse and pulse-reverse electric fields. Engineering of the electric field enables control of the mass transport and crystallization phenomena in the deposition process and thus enables control of composite properties such as composition, porosity, and surface roughness. Results from electrodeposition trials and mechanical testing of brazed joints under ambient conditions as an initial screen for interlayer performance will be discussed, in anticipation of high-heat flux testing of joint performance under fusion-relevant conditions.
Perspectives and Impact of in-Situ X-Ray Techniques for Electrodeposition
Authors: Grunder Yvonne
Published: November 2022

In-situ surface x-ray diffraction has enabled an atomic/molecular-level understanding of the electrochemical interface, including its potential and time dependence, to be developed. [1] Specifically, for electrodeposition the influence of additives and adsorbates onto growth and nucleation behaviour could be established. Halogens on metal surfaces are prototypic adsorbate systems but the adsorption of halide ions especially on copper is also of major importance for on-chip metallization in ULSI microchip production. Halide ions on Cu surfaces form an inhibiting adsorbate layer with polyethylene glycol (PEG). Even though the influence of the additives combination on the shape evolution of the Cu deposit was subject of numerous studies, their precise role during the elementary steps of the deposition with regards to altering the charge distribution and dipole moment at the interface is largely not understood. [1] While information about the atomic structure of the electrode surface in electrochemical in-situ cells has been widely investigated, insight into the charge distribution and the structure of the electrolyte at the interface is still lacking. Combining x-ray spectroscopy and x-ray diffraction to gain site-specific information about the charge distribution at buried interfaces is a promising tool. [2,3,4]

Studies on the metal-halide interface and how the use of surface x-ray scattering techniques can help to characterise electrochemical interfaces in-situ in order to link, structure and stability and morphology changes will be presented. [1, 4] Advances in these directions offer possibilities in elucidating atomic scale models of the electrochemical interface and thus will help to establish structure-stability-reactivity relationships which will help to understand growth kinetics and nucleation behaviour.

References:

[1] In-Situ Surface X-ray Diffraction Studies of Copper Electrodes: Atomic-Scale Interface Structure and Growth Behavior. Gruender, Y., Stettner, J., & Magnussen, O. M. (2018). Journal of the Electrochemical Society; 166(1), D3049-D3057. doi:10.1149/2.0071901jes

[2] Probing the charge distribution at the electrochemical interface; Y. Gründer and C. A. Lucas, Physical Chemistry Chemical Physics, 2017, 19, 8416

[3] Simulation of Surface Resonant X-ray Diffraction; Y. Joly et al., J. Chem. Theory Comput,. 2018, 14, 973−980

[4] Charge Reorganization at the Adsorbate Covered Electrode Surface Probed through in Situ Resonant X-ray Diffraction Combined with ab Initio Modeling;Y. Grunder, C. A. Lucas, P. B. J. Thompson, Y. Joly, Y. Soldo-OlivierJ. Phys. Chem. C 2022, 126, 9, 4612–4619
Challenges in Understanding Electrochemical Growth
Authors: Magnussen Olaf M.
Published: November 2022

Over the past 100 years, electrodeposition has matured to an important method with numerous industrial applications, up to processes in micro- and nanofabrication. Knowledge on electrochemical processes on the atomic scale is still limited, however. While for vapor deposition under vacuum conditions the evolution of the deposit morphology can nowadays be predicted with high precision, a similar predictive understanding of electrodeposition is missing so far. A key issue here is the electrochemical interface where this growth occurs. The structural complexity of this interface on the one hand makes understanding of the elemental processes in nucleation and growth difficult. On the other hand, it is just this complexity that allows to tune electrodeposition processes in ways that are not possible for deposition in vacuum and thus make them attractive for many applications.

In this talk, I will discuss current challenges in developing a true microscopic picture of electrodeposition processes, using examples from us and other groups. The focus will be on puzzling experimental observations and fundamental aspects that we do not yet understand and thus provide a rich field for future research. These include the mechanisms of elemental steps in electrochemical growth processes, such as ion transfer, intra- and interlayer surface diffusion, and the resulting development of the deposit morphology. Of particular interest is how these events are influenced by the electric field and electrolyte species in the electrochemical double layer, which is of key relevance for understanding the effects of overpotential and additives. A further challenge is to extend the insights obtained for electrodeposition of metals to the electrochemical growth of compound materials, such as oxides.
Examples, Perspectives, and Impact of in-Operando Electrochemistry & Electrodeposition
Authors: Rost Marcel J.
Published: November 2022

In order to leave our children not with a huge problem in the future, we quickly have to realize the energy transition to renewable and CO2 neutral sources and circuits, which implies the introduction of the complete H2 economy. In addition, the ever ongoing demand and progress in electronics requires new and smart steps from the semiconducting industry pushing the border for device fabrication and thus material science and nanotechnology.

Both extremely important topics crucially depend on the complete understanding of the fundamental atomic processes for device or catalyst manufacturing by electrodeposition as well as their stability during operation under (electrochemical) application.

The general problem, however, has been formulated nicely already by Wolfgang Pauli:

„God made the bulk; surfaces were invented by the devil.“

It took around two decades, before most of the basic concepts and atomic effects have been observed and understood in standard, ultra-high vacuum (UHV) surface science and nanotechnology. Now, it is surely time to open a similar book and start from scratch, as atoms and surfaces in electrochemical environment clearly behave differently than in UHV. Moreover, this time it is not enough to measure after the deposition, after the growth, after the nucleation, or after a reaction!

Both electrochemical data clearly show that many surfaces change during application and the complex understanding during electrodepostion, which involves a huge parameter space of tunable variables, can surely only be addressed adequately by in operando measurements.

In this talk, I will show examples from in operando measurements ranging from STM over TEM to SXRD and X-ray photoelectron spectroscopy that all demonstrate the power and perspective for gaining new insight.

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(Digital Presentation) Electrodeposition of Free-Standing Porous Cu Frameworks for Energy Applications
Authors: Kurniawan Mario , Calmbach Jasmin , Zullufi Kosovare , Stich Michael , Bund Andreas
Published: November 2022

Recently, a convenient method has been suggested to produce a highly porous metal structure such as Cu using a single-step electrodeposition method [1]. In this approach, hydrogen bubbles are used as dynamic templates during the metal electrodeposition process to create the micro-porous structure. However, the pore walls of the porous layers often grow in ramified dendritic structure, which results in limited mechanical stability and creates challenged for applications in compact devices.

In this contribution, a novel approach will be discussed to improve the mechanical stability of these porous structures by employing a second electrodeposition step. This process greatly reduces the number of dendrites within the pore walls making the porous layer more compact and thus improving the mechanical stability significantly. Furthermore, a complete separation of the porous layer from the flat substrate can be achieved by ultrasonication to obtain a free-standing porous Cu framework. Some parameters such as the layer thicknesses and pore sizes can be tuned easily by changing the current density and the electrodeposition time, respectively.

The use of thus prepared free-standing porous Cu frameworks will be discussed for photoelectrochemical (PEC) water splitting and CO2 reduction. For the PEC water splitting application, a photoactive Cu2O layer is electrodeposited on the free-standing porous Cu framework. A homogenous coating of the Cu2O can be achieved and the PEC performance shows a significant increase of photocurrents by more than 80 % at 0 V vs. RHE in comparison to the Cu2O planar substrate [2]. For the CO2 reduction application, a large sample with10 cm2 geometric surface area was successfully prepared. The sample was used in a custom-made electrochemical cell with a cation exchange membrane as a separator. CO2 gas in a high humidity environment is transported to the free-standing porous Cu working electrode via a membrane pump in a closed-loop system. Our preliminary results show formation of ethylene and ethane gas using gas chromatography which indicates a successful reduction reaction of the CO2.

[1] H.C. Shin., M. Liu. Chem Mater 16:5460–5464 2004. Doi:10.1021/cm048887b

[2] M. Kurniawan, M. Stich, M. Marimon, M. Camargo, R. Peipmann, T. Hannappel, A. Bund, J. Mater. Sci.
2021, Doi:10.1007/s10853-021-06058-y
A Room Temperature Electrodeposition Method to Develop High Performance Metal-Chalcogenide Nanowire Array-Based Photoelectrochemical (PEC) Device for Solar Hydrogen Production
Authors: Vijay Shiljashree , Cheng Wei , Jawahar Hussaini Syed Mubeen
Published: November 2022

Photoelectrochemical (PEC) water splitting has emerged as a significant and promising technique for the generation of low-cost, highly efficient, and sustainable hydrogen(H2) fuel. Currently, PEC hydrogen production has been successfully demonstrated on a laboratory scale. However, the commercial viability of PECs depends critically on the cost of H2 produced by the PECs, which is affected by the cost of PEC construction. Here we consider electrodeposition as a promising method to fabricate multijunction PEC cells because this is an inexpensive solvent-based technique operated at low temperature with the ability to control the film thickness by varying the deposition potential and charge passed which can be optimized to perform like other matured and expensive vapor-based deposition techniques functioning at high temperatures.

In this research work, we report a room temperature, low-cost electrodeposition method to synthesize metal chalcogenide semiconductor thin films and nanowire arrays in superstrate configuration and demonstrate its applicability for solar hydrogen production. Specifically, the talk will address the effect of electrodeposition parameters and post-treatment on observed photocurrent and photovoltage responses. By optimizing the deposition potential and deposition charge we were able to achieve photocurrent densities exceeding 15 mA cm-2 for thin films and nanowire arrays when tested using regenerative redox couples.

Finally, the talk will cover the aspects of developing a buried junction PV/PEC using electrodeposited chalcogenide semiconductors for solar hydrogen production.
Optimization and Kinetic Study of the Electrochemical-Assisted Leaching of Valuable Metals in Lithium-Ion Batteries
Authors: Molina Montes de Oca Daniel E , Shi Meng , Klaehn John , Diaz Aldana Luis , Lister Tedd
Published: November 2022

Efficient recycling of lithium-ion batteries (LIB) is required to meeting future demand of materials and support sustainable decarbonized energy systems. At the center of the recycling process is the recovery of valuable active metals in LIBs. Hydrometallurgical recovery processes are considered cleaner and less expensive than pyrometallurgical processes, and we previously reported a hydrometallurgical process for the leaching of valuable metals in mixed shredded LIBs. [1] In this process the reductant Fe2+, at low concentration, is electrochemically regenerated to complete the leaching of metals of interest Co, Ni, Li, Mn, and removal of Cu from LIB black mass, eliminating the need of H2O2. To accelerate this process and reduce chemical and energy consumption, the effect of process variables needs to be better understood. In this work, we study the effect of added electrochemical mediator concentration (Fe), total current and agitation level on the kinetics and leaching efficiency the EC-leaching process. Moreover, we propose a new multi-stage leaching scheme for the adjustment of final pH and recirculation of iron in the system.

References

1. Diaz, L.A., et al., Electrochemical-assisted leaching of active materials from lithium ion batteries. Resources, Conservation and Recycling, 2020. 161: p. 104900.
Improved Adhesion Strength for Electrodeposited Nickel Onto Titanium Alloys Via the Brush Plating Method
Authors: Thomas Joshua , Milosevic Danijela
Published: November 2022

Titanium and titanium alloys are attractive materials in a variety of industries such as aerospace due to a high strength to weight ratio and a surface which is naturally resistance to many forms of corrosion. However, tribological properties such as poor abrasion resistance and high friction during metal-to-metal contact have proven difficult to handle without additional treatments. Application of coatings onto the material’s surface is one means of protecting it from those poor tribological properties.

Electroplated nickel coatings retain much of the corrosion resistance desired of titanium alloys while also exhibiting better abrasion and wear resistance. Electroplating onto titanium and its alloys is prohibitively difficult due to the propensity of the material to form a tenacious oxide coating on any fresh surface instantaneously after its exposure. The oxide surface acts as a barrier between the solution and the titanium surface reducing the adhesion strength of the resulting deposit. The oxide layer is most commonly removed and the surface modified by hydrofluoric acid (HF) based treatments. HF is considered highly dangerous to workers and to the environment and work is being done to heavily limit its use.

For this work, a proprietary chloride-based solution was used during the preparatory steps. Brush or selective plating was chosen as the application technique due to its ability to perform the entire operation with the substrate exposed to solution and under potential control. In most applications of electroplating, the surface/part to be plated must be transferred between multiple tanks containing each preparatory solution used to etch and activate the surface which would involve exposure to air at several points. In addition, the brushing action inherent in brush or selective plating creates a surface environment which can be optimized to promote strong adhesion at the nickel/titanium interface.

This presentation will discuss how SIFCO’s brush plating process technology and automation capabilities were used to achieve strong adhesion to the titanium surface without the use of HF. Focus was specifically placed on achieving strong adhesion of a nickel pre-plate onto the titanium surface which allows for a multitude of other coatings to be applied thereafter. The method was performed using a single anode through which the solutions for each step flowed. The samples were under applied potential and immersed in solution throughout the entire process. Applied potential and solution delivery were automated to maximize process consistency.

Samples were measured for tensile adhesion strength via the specification ASTM C633. Several variables related to the preparatory procedure were optimized during the study including the flow rate of the solution, the voltage/current conditions, and the evaluation of preparatory steps taken before the electrochemical procedure.
Electrochemical Dewatering of Cellulosic Nanomaterials
Authors: Vijapur Santosh Hanamant , More Santosh R , Le Huong , Hall Timothy , Taylor E. Jennings , Inman Maria , Snyder Stephen , Nelson Kim , Handler Robert M
Published: November 2022

Renewable cellulosic nanomaterials exhibit great potential in various applications due to unique properties. Abundant availability of feedstock has led to industrialization of production. A significant cost-limiting factor to utilize cellulosic nanomaterials is dewatering/drying as cellulosic nanomaterials are not economical to ship long distances while containing significant water content (>95 wt.%). This represents a critical driver for increased costs of nanocellulose products.

Accordingly, Faraday Technology in collaboration with GranBio USA, manufacturers of cellulosic nanomaterials, is addressing this need by developing electrochemical based dewatering system and process to dewater cellulosic nanomaterials while maintaining material properties when dried and re-dispersed. Energy-efficient (70% reduction in energy requirements compared to thermal dewatering), environmentally beneficial (51% reduction in greenhouse gas emissions), economical (31% reduction in cost/ton of dried material), and industrially viable electrochemical based dewatering approach to process up to 2 tons/year of dried nanocellulose at alpha-scale has been demonstrated. The approach is capable of achieving >50 wt.% final solids and 18 wt.% final solids, that could be rehydrated under vortex and confirmed for re-dispersibility. Material properties (structure, particle size) were maintained by the dewatered cellulosic nanomaterials. Specifically, this talk will discuss the results of these advancements.

Acknowledgements: The financial support of DOE Contract No. DE-SC0018787 is acknowledged.
Fouling of Cu Catalysts during Electrochemical Hydrogenation and Hydrogenolysis of Furfural in Acidic Media
Authors: May Andrew S. , Biddinger Elizabeth J.
Published: November 2022

Electrochemical processes offer sustainable means of production when coupled with renewable energy. While thermocatalytic processes require external hydrogen gas for reduction reactions, which generates copious amounts of CO2 in the generation of the hydrogen gas, electrochemical processes have the ability to use protons from the electrolyte in lieu of external hydrogen gas as a reactant. In addition to eliminating the hydrogen gas reactant, electrochemical processes can operate at room temperature and pressure. The development of electrochemical reactors for transformation of biomass derived species is of growing interest for the sustainable production routes it enables of various fine chemicals and fuels. Furfural (FF), one such biomass derived species can be electrochemically reduced to furfuryl alcohol (FA), a resin, and 2-methylfuran (MF), a potential fuel. To produce both FA and MF, acidic electrolytes and Cu catalysts can be used. While Cu electrodes allow for high selectivity to furfuryl alcohol or 2-methylfuran, the Cu electrodes suffer from stability issues caused by things such as fouling over longer durations of electrolysis.

In this work, we intentionally operated FF ECH under conditions to promote fouling so that the impact of fouling could be investigated. This consisted of 200mM FF in the catholyte with pH 0 electrolyte in 20:80 acetonitrile:water. We used a Cu flag working electrode of 6cm2. We then recycled the Cu electrode for 3 runs of ECH at 3 hours, refreshing the catholyte after each run. A polymeric substance was observed on the Cu electrode surface after multiple uses which had identical IR spectroscopic features to poly(furfuryl alcohol). The impact of the polymeric coating was investigated further using electrochemical impedance spectroscopy, the chemical characterization was determined using x-ray photoelectron spectroscopy, and morphology was imaged using scanning electron microscopy.
Electrochemical Immobilization of Rare Earth Elements
Authors: Engmann Eugene , Diaz Aldana Luis , Lister Tedd , Atifi Abderrahman , Orme Kennalee
Published: November 2022

The reduction of rare earth elements (REE) such as Nd, Pr, and Dy to a stable metallic phase at low temperature is difficult due to the high reactivity of REEs. Non-aqueous electrolytes have been investigated due to their wider electrochemical window. While most work has focused on the cathodic reduction of REEs, little attention has been directed to the anode reaction. While not a focus of studies, the anticipated anode reaction is oxidation of the non-aqueous electrolyte. In this work, options for developing alternate anode reactions which do not degrade the electrolyte are being pursued as an alternate pathway of introducing REEs into non-aqueous electrolytes through an anodic reaction that could avoid degradation of the electrolyte. Investigations using electrochemical techniques such as cyclic voltammetry and chronoamperometry permit evaluation of various materials options.
Modeling Electrochemical Direct Air Capture of CO2 using Redox-Functionalized Electrodes
Authors: Ali Fawaz , Kwabi David G.
Published: November 2022

Increasing research attention is being devoted to designing electrochemical systems that can capture CO2 from air and thus mitigate climate change, as decarbonization of the energy sector is occurring very slowly. The low concentration of CO2 in air however makes large scale, energy-efficient and rapid CO2 capture challenging. Understanding how the energetic cost of CO2 capture depends on operational and material parameters that describe electrochemical systems is important for designing practical and cost-effective devices.

We have previously shown that electrochemical CO2 capture is possible using a pH swing cycle that is driven by proton-coupled electron transfer (PCET) involving organic molecules [1]. More recently, we have begun to consider a new design for electrochemical CO2 capture in which PCET-active species are conformally attached to the internal surface area of a highly porous electrode, and effect a reversible pH swing in an adjacent layer of aqueous electrolyte upon redox cycling. We develop a continuum reaction-transport model that simulates reactive CO2 capture into and release from the electrolyte layer, as well as transport of (bi)carbonate species, and protons, in response to an applied current or voltage. The model permits an assessment of the energetic cost of CO2 separation under various current densities and concentration gradients, and decomposition of that cost into thermodynamic, kinetic, mass transport-related and Ohmic contributions. We then highlight potential pathways to achieving an energetic cost of CO2 capture from air of 100 kJ/molCO2, and discuss preliminary results from an experimental prototype.

[1] Jin. S, Wu M., Gordon R., Aziz M., Kwabi D., pH Swing Cycle for CO2 Capture Electrochemically Driven through Proton-Coupled Electron Transfer
(Digital Presentation) The Role of Iron in the Zinc Electrodeposition from Chloride Media for Recovering Zinc from Spent Pickling Liquors
Authors: Zakiyya Hanna , Kekesi Tamas
Published: November 2022

Electrodeposition of Zn from chloride media had been studied by potentiodynamic method to understand the characteristics of Zn recovery from spent pickling liquor (SPL). Various concentration, pH, agitation speed and impurities contamination were examined in the series of experiments. The influence of Zn concentration in the range of 30-150 g/dm3 relevant to the real SPL were studied along with acidity level change (pH 1.5-5.5). It was found that the cathodic deposition started with the uniform patern followed by sponge-like deposit and as the concentration of the electrolyte near the cathode surface decreased, the dendritic deposition start to grow, especially at the edge of the cathodes.

It was found that the effect of iron concentration on the polarization curves of zinc from SPL is complex. Initially it has a negative effect on the generated cathodic current because of the enhancement of hydrogen bubble formation. At a higher concentration range, however, iron deposits at a relatively higher rate. Further increased iron concentrations may make the composition of the Zn-Fe deposit dominantly in favor of iron, resulting in a hydrogen dominated cathodic mechanism. It is also characterised by the loss of the dendritic structure – attributed mostly of zinc deposition when hydrogen bubbles are not blocking the cathode. As the gas evolution becomes more characteristic, the deposit tends to become more powdery. Under such conditions the cathode becomes smoother and the active surface is reduced. Increasing the stirring speed, the powder was easily detached from the cathode surface. Iron, however can enhance the cathodic deposition process of zinc. With 30 – 60 g/dm3 iron in the 90 g/dm3 Zn solution, an increased iron concentration resulted in a significant increase in the mass of the deposited zinc. This may be interpreted by a beneficial effect of the increased hydrogen evolution enhancing the zinc ion transport to the electrode surface. However further increments of iron had a contrary effect, possibly by the locally increased – and generally detected – pH of the solution indirectly causing a superficial precipitation of hydroxides. Technically pure zinc could be deposited from only low-iron (< < 30 g/dm3) zinc solutions (of 90 g/dm3 Zn) at relatively vigorous stirring speeds. High iron concentration in the solution is definitely unsuitable for obtaining the aimed quality of cathode zinc.
Analysis of Boron Removal By Capacitive Deionization
Authors: Shocron Amit N. , Guyes Eric N. , Dykstra Jouke E. , Suss Matthew E.
Published: November 2022

Climate change and water overextraction are some of the reasons for a growing global water stress, with seawater desalination being the leading solution worldwide. The state-of-the-art technology for seawater desalination is reverse osmosis (RO), utilizing mechanical pressure to push seawater through membranes, leaving the dissolved species in the brine. However, boron, which is considered toxic in high concentrations, is poorly removed by RO. This is because under normal conditions boron is present as boric acid, a small neutrally-charged compound. The most common technique to overcome this problem includes multiple RO stages combined with chemical dosage of the effluent, ensuring boron is present as borate, a charged species, present in high pH conditions.

Capacitive deionization (CDI) is an emerging membraneless technique for water treatment and desalination, based on electrosorption of salt ions into microporous electrodes. Large internally-generated pH gradients develop during CDI operation, and thus CDI can potentially remove boron without chemically adjusting the feed pH. Here, we present a novel theoretical framework predicting the adsorption of boron in micropores, while considering pH-dependent chemical surface groups in the micropores, ion transport in the macropores, and local electrolyte pH. Moreover, we account for association and dissociation reactions of boron-consisting compounds in the electrolyte[1].

We analyzed the effects electrodes order have on pH dynamics, where panels a. and b. in the attached figure present spatiotemporal plots of the pH for the case where cathode is placed upstream (panel a., cat-an) and the anode placed upstream (panel b., an-cat). This analysis shows that higher pH in the anode are expected for the an-cat configuration, counter to common-wisdom in the field. Panel c. follows this trend, by presenting the removed boron as a function of scaled flow velocity for both configurations. The results show, both experimentally and theoretically, that an-cat configuration should be preferred. Similarly, we found that an optimum charging voltage exists, even without accounting for parasitic reactions. Moreover, we found that also the discharging voltage significantly affects boron removal. Overall, CDI is a promising technology for boron removal, but a deep theoretical understanding of the problem is crucial towards future optimization.

References:

[1] Amit N. Shocron, Eric N. Guyes, Huub H. M. Rijnaarts, P. M. Bieshuvel, Matthew E. Suss, Jouke E. Dykstra, "Electrochemical removal of amphoteric ions", PNAS, 118, 40, e2108240118, 2021.

Figure 1
Charge Redistribution Reactions in Intercalation Electrodes Used for Capacitive Deionization
Authors: Pothanamkandathil Vineeth , Gorski Christopher A
Published: November 2022

Electrodes used for capacitive deionization (CDI) are prone to self-discharge reactions, in which their electrochemical potentials can drift over time under open-circuit conditions. These self-discharge reactions inhibit energy recovery during the cell discharge step when operating CDI cells, which increases the amount of energy required to deionize water. Self-discharge reactions for porous carbon electrodes are well-documented in the literature, where they have been attributed primarily to parasitic faradaic reactions and charge redistribution reactions in pore networks. Little work, however, has examined how and why self-discharge reactions occur for electrodes that intercalate cations into their structures. Here, we report that nickel hexacyanoferrate, a Prussian blue analog, undergoes significant self-discharge under open-circuit conditions in neutral saline solutions, which adversely impacts its use in deionization cells. We examined how the charging history, charging process, and electrolyte composition influenced self-discharge. Preliminary evidence indicates that self-discharge is largely a consequence of charge redistribution within the crystal lattice. Our findings provide insights into the feasibility of using Prussian blue analogs as electrode materials for deionization as well as caution in how salt absorption capacities of electrode materials are quantified.
(Invited) Surface Electrochemistry and Physicochemical Behaviors of Carbon and Compound Electrodes in Electrochemical Separation Systems
Authors: Kang Jin Soo
Published: November 2022

In recent years, electrochemical separation systems have received a great attention due to their excellent capabilities in environmental remediation, water desalination, and resource recovery. The performances of electrochemical separation systems are often interpreted in terms of capacity and selectivity, both of which are highly dependent on electrode materials. For instance, capacitive deionization (CDI) used for desalination of water employs activated carbon electrodes, as it enables capture and release of sodium chloride in large amounts. In addition, lithium-ion selective electrode such as delithiated LiMn2O4 (i.e. λ-MnO2) or LiFePO4 plays an essential role in selectivity of electrochemical lithium recovery systems. However, although the importance electrode materials cannot be overemphasized for such electrochemical separations, it is also true that we are yet to achieve a sufficient level of understanding on their behaviors in the systems, which is necessary to establish rational electrode-design strategies to enhance capacity and selectivity of the electrochemical separation systems. In this talk, our recent findings on surface electrochemistry of carbon electrodes in electrochemical desalination will be introduced, together with an overview on the non-favorable Faradaic reactions thoroughly characterized with the assistance of various X-ray and electrochemical techniques. Additionally, development of heteroatom-doped carbon material and how it resulted in a highly stable CDI performance will be presented. Moreover, I will talk about our efforts on characterization of physicochemical behavior of λ-MnO2 in electrochemical lithium recovery systems, based on which a significantly higher utilization rate of the electrode materials could be achieved.
Generating and Optimizing Hierarchical Porosity in Electrospun Capacitive Deionization Electrodes through Control of Mesopore Volume
Authors: Waugh John , Liu Min , Komini Babu Siddharth , Pintauro Peter N. , Kang Qinjun , Spendelow Jacob S.
Published: November 2022

Capacitive deionization (CDI) is a promising technology that has gained interest recently for the desalination of brackish water. Hierarchically porous carbons are commonly used for CDI due to their high surface areas and various pore size distributions that maximize ion adsorption capacity and rate.1 Electrospinning is an effective way of generating nanofibers with high inter-fiber macroporosity that can be converted to carbon fiber and modified to improve surface area, total pore volume, and pore size distribution. This work describes the usage of sacrificial mesopore formers in tandem with a micropore etching technique to induce hierarchical porosity. The combination of mesopores (2-50 nm) and micropores (<2 nm) enables fast ion adsorption rates and capacity.2 Mesopores will be formed via the dissolution of silica nanoparticles (10-20 nm) that are introduced into the fibers during the electrospinning step. Mesopore volume will be controlled by changing silica content in the fiber. An optimum mesopore contribution is found, at which point added mesoporosity maximizes ion transport. Further increasing mesoporosity is detrimental to fiber conductivity and surface area and results in decreased performance as reported in the literature. 3 After mesopore formation, micropores are etched on the surface of the fibers through KOH loading and thermal activation. Micropore formation is optimized to maximize specific surface area while maintaining physical integrity of the fibers. This sequential technique creates a hierarchical network of pores from the inherent microporosity of the fiber network, to the mesopores, and finally micropores to maximize usage of surface area. Fiber electrodes fabricated in this method achieve specific surface areas exceeding 1400 m2 g-1, with pore volumes exceeding 1.0 cc g-1. The pore size distributions are highly controlled, with 80% of total pore volume coming from pores less than 20 nm in radius. In 500 ppm constant voltage CDI tests, these fiber electrodes obtain a salt adsorption capacity of over 14 mg g-1, at a salt adsorption rate of ~3 mg g-1 min-1, showcasing the high capacity matched with high rate of these easily fabricated, inexpensive materials.

References:

Liu, T., Serrano, J., Elliott, J., Yang, X., Cathcart, W., Wang, Z., ... Liu, G. (2020). Exceptional capacitive deionization rate and capacity by block copolymer-based porous carbon fibers. Science Advances.

Baround, T., Giannelis, E. (2019). Role of Mesopore Structure of Hierarchical Porous Carbons on the Electrosorption Performance of Capacitive Deionization Electrodes. ACS Sustainable Chemistry & Engineering.

Pan, H., Yang, J., Wang, S., Xiong, Z., Cai, W., & Liu, J. (2015). Facile fabrication of porous carbon nanofibers by electrospun PAN/dimethyl sulfone for capacitive deionization. Journal of Materials Chemistry A.
Scalable Carbon Nanofoams for Faradaic Desalination of Brackish Water
Authors: Neale Zachary Garbe , DeBlock Ryan H. , Sassin Megan B. , Rolison Debra R. , Long Jeffrey W.
Published: November 2022

Water scarcity is becoming an increasing exigent humanitarian crisis which can be ameliorated with development of economical and practical water treatment systems. Present reverse-osmosis systems effectively desalinate seawater, but are energy and time-intensive, require regular maintenance due to membrane fouling, and are less adaptable to small scale uses. In contrast, capacitive deionization (CDI) technology shows promise for scalable, energy-efficient desalination of brackish waters, but its application has been limited by reliance on double-layer capacitance ion storage at carbon-only electrodes. Recent advances in electrochemical desalination have focused on exploiting Faradaic (redox-active) materials to increase ion-storage capacity. We design hybrid capacitive deionization (HCDI) flow-cells utilizing scalable, NRL-pioneered porous carbon nanofoam (CNF) architectures that also incorporate environmentally benign, faradaic active materials. Electrolessly deposited nanometric MnO2 on CNFs supports a 6-fold increase in sodium-ion adsorption capacity compared to bare-carbon CNFs, while solvothermally deposited BiOCl in CNFs renders a reversible, high-capacity chloride-ion adsorption electrode. We systematically explore architectural parameters such as the pore size distribution and electrode thickness of the CNF, and faradaic material loading with respect to their optimization for desalination performance in prototype flow-cells. Additionally, the performance of such electrode architectures may be further improved by constructing graded-pore, multilayer CNFs that optimize and balance ion transport to the electrode interior while maintaining high capacity. Continued progress in bench-top level HCDI flow-cells with faradaic materials will validate the promise of this technology en route to demonstrating larger-scale desalination devices.
Redox-Mediated Electrodialysis for Resource Recovery and Energy-Efficient Desalination
Authors: Kim Nayeong , Su Xiao
Published: November 2022

In the chemical and biochemical manufacturing industry, separation processes are amongst the most energy-demanding processes. Electrochemical separations have been growing in interest as promising candidates for both downstream processing for resource recovery and producing clean water due to their energy-efficient, environmentally benign, and modular features.1

Leveraging a sustainable redox reaction, we developed a redox-mediated electrodialysis system for energy-efficient desalination coupled with resource recovery of valuable resources such as lithium, and even biomolecules.2, 3 Our proposed redox-mediated electrodialysis system utilizes a reversible redox reaction as a driving force of salt removal at a much lower voltage than a water-splitting reaction (>1.2 V). As the redox materials are reduced or oxidized, all charged species migrate across the membranes to balance the charge in the electrolyte compartment. As the redox materials circulate in the cathode and anode compartments, they sustainably regenerated without additional regeneration steps, one of the major bottlenecks for industrializing the electrosorption system. We demonstrated the redox-mediated electrochemical system for resource recoveries such as simultaneous lithium recovery from brine3 and valorization of whey proteins and lactose from whey waste.2 Especially for the valorization of whey waste, our system treated 99% of salt from the whey solution within a single step and recovered > 98% of various whey proteins (e.g., valuable protein contents such as beta-lactoglobulin, alpha-lactalbumin, and lactose). The preliminary techno-economic analysis confirmed the economic potential of redox-mediated ED with 51−73% lower energy consumption compared to conventional ED. Overall. we envision the system can become a breakthrough in tackling the environmental challenges coupled with the limited resources.

Kim, N.; Jeon, J.; Chen, R.; Su, X., Electrochemical separation of organic acids and proteins for food and biomanufacturing. Chemical Engineering Research and Design
2022,
178, 267-288.

Kim, N.; Jeon, J.; Elbert, J.; Kim, C.; Su, X., Redox-mediated electrochemical desalination for waste valorization in dairy production. Chemical Engineering Journal
2022,
428, 131082.

Kim, N.; Su, X.; Kim, C., Electrochemical lithium recovery system through the simultaneous lithium enrichment via sustainable redox reaction. Chemical Engineering Journal
2021,
420, 127715.