bluuebunny/crossref_metadata_2025 huggingface dataset:
Phototropic Growth of Semiconductor Mesostructures Exhibits Auto-Optimizing Interfacial Light Absorption
Authors: Carim Azhar I , Batara Nicolas A. , Premkumar Anjali , Meier Madeline Claire , Hamann Kathryn R , Atwater Harry A. , Lewis Nathan S
Published: May 2020

Inorganic phototropic growth of chalcogen semiconductors wherein a uniform, incoherent, uncorrelated beam of light enables control over the morphology and growth direction of an evolving deposit in three-dimensional space at the nanoscale is explored. Such evolution is similar to natural phototropism exhibited by many photosynthetic plants wherein the physical extension of the biological system proceeds preferentially towards the time-averaged position of the sun. In analogy, during inorganic phototropic growth, a semiconductor material is electrodeposited under illumination and mass is addition is correlated with the spatial distribution of the light absorption. Highly periodic nanostructured films can be generated over macroscopic square centimeter areas in this manner. No laser source, photomask nor structure light field is necessary nor utilized. Additionally, no chemical templating agents (ligands, surfactants) are used. Isotropic morphologies consisting of ordered arrays of nanopores were generated using unpolarized illumination whereas linearly polarized light resulted in highly-anisotropic nanoridge/trough morphologies with the in-plane orientation of the patterns controlled by the direction of the light polarization. The pattern periodicity was encoded by the illumination spectral profile. A single periodicity in single spatial direction was only generated even with the use of broadband and multimodal spectral profiles and multiple polarization inputs and the periodicity was found to be sensitive to all investigated tuning of such profiles. Structures with nonequal periodicities in the two orthogonal in-plane directions could also be generated and both periodicities could be independently controlled. Structural complexity correlated with the complexity of optical inputs. Modeling of the growth using a combination of full-wave electromagnetic simulations of light absorption and scattering coupled with Monte Carlo simulations of mass addition successfully reproduced the experimentally observed morphologies and indicated that morphology development was in fact directed by evolution of the growth interface to maximize anisotropic light collection. This work may be useful for the high-throughput generation of light-trapping absorbers films, photonic elements, and platforms for (photo)electrocatalysts.
Electrode Stimulation
Authors: Scherson Daniel , Han Qi
Published: May 2020

According to Newman[1], the rates of heterogeneous redox reactions can be written in terms of the surface overpotential, η
s
, i = io{exp(aanFηs/RT)- exp(-acnFηs/RT)}, where η
s
is defined as “the potential of the working electrode, relative to a reference electrode of the same kind placed in the solution adjacent to the surface of the working electrode.” On this basis, η
s
can significantly alter the current flowing across the electrode-electrolyte interface. Due to its intrinsic resistive character, the flow of electricity through the electrolyte will elicit changes in the electrostatic potential within that phase, which can be conveniently measured using reference electrodes, as has been implemented in this[2-4] and other laboratories[5]. To be described in this presentation is a novel means of inducing local changes in η
s
by passing current between a
stimulating
electrode, SE, and a distant counter electrode in the same solution. The overall tactic was demonstrated using a redox active self-assembled monolayer of N-ethyl-N’-octadecyl-4,4’-bipyridinium dibromide (EOB) adsorbed on a Au(poly) disk electrode as the WE and a Au(poly) disk of larger diameter placed parallel to the WE with its normal axis aligned along the corresponding axis of the WE, as the SE. The potential of the WE, EWE, was set at EWE= -0.35 V, i.e. the layer was polarized in its fully oxidized state (See the cyclic voltammogram in the Insert, Fig 1), while the SE placed at a distance d = 0.5 mm from the WE was scanned from 0.65 V up to 0.8 V, and back at ν = 1 V/s, yielding a iSE vs time curve shown in red dots in Fig. 1. The response of the WE is shown in blue in Fig. 1. As clearly indicated, iSE > 0 elicits a corresponding iWE < 0 due to the change in the electrostatic potential in the vicinity of the WE. Once iSE is reversed, the previously reduced fraction of EOB is oxidized returning the redox layer to its original fully oxidized state. This explanation is also consistent with the increase in iWE induced by a decrease in d (See black, green and magenta curves in Fig. 1). Implementation of this tactic will enable application of a local potential in a region next to a working electrode and thus promote electrochemical processes in that region without the need of a mask.

Acknowledgements

This work was supported by NSF, CHE-1808592.

References

[1] J. Newman, K.E. Thomas-Alyea. Electrochemical Systems, 3rd Edition, Wiley-Interscience, 2004.

[2] Y. Chen, A. Belianinov, D.A. Scherson. J. Phys. Chem. C, 112 (2008), 8754-8758.

[3] C. A. Cartier, D. Kumsa, Z. Feng, H. Zhu, D. A. Scherson, Anal. Chem., 84 (2012), 7080-7084.

[4] Z. Feng, N. S. Georgescu, D. A. Scherson, Russian Journal of Electrochemistry, 53 (2017),1003-1010.

[5] I. Plettenberg, G. Wittstock, Energy Technology, 4 (2016), 1-8.

Figure 1
High Performance Thermoelectric Films with Nanoengineered Electrochemical Process for Micro Thermoelectric Power Generators
Authors: Ono Takahito , Van Toan Nguyen , Bin Samat Khairul Fadzli
Published: May 2020

Novel electrochemical processes of Bi2Te3 nanocomposites been developed for micro thermoelectric power generators (micro TEG) with a high figure of merit (ZT) at room temperature. Nanoparticles or/and carbon nanomatrials are dispersed in an electrolyte for electrodeposition, and co-electrodeposition is performed to make a thin or thick film. The small grained nanocomposite film is formed by the inclusion of the nanoparticles or/and carbon nanomaterials. Reduction of thermoelectric properties can be observed because of the phonon scattering with the nanostructures. In addition, nanomaterials inclusion can change the carrier density of the composite films, thus, appropriate density of inclusion can improve the performances of the electrical conductance and Seebeck coefficient. Maximum ZT ~1 is obtained by optimization of the deposition condition, which is 6 times higher than that of reported pristine Bi2Te3 deposited by electrodeposition also higher value than that of bulk Bi2Te3 (0.7~0.8). Those results show that this deposition methods have a high potential ability to manufacture the micro TEG for energy harvesting devices.

Figure 1
Electrodeposition of Grop Ⅳ Semiconductor Thin Film
Authors: Maldonado Stephen , Downes Nathanael
Published: May 2020

This presentation describes our latest work in the growth of Si films by electrochemical liquid phase epitaxy (ec-LPE). This method is an advanced form of the electrochemical liquid-liquid-solid crystal growth process, where a liquid metal serves both as a cathode for electrodeposition and as a solvent for crystal growth. Using tailored thin liquid metal film electrodes and non-aqueous electrolytes, it is possible to electrodeposit crystalline Si at unusually low temperatures. Data will first be presented that describes suitable electrolytes for Si ec-LPE. Results will then be presented that describe how the liquid metal identity impacts material quality. Finally, the attainable material quality and the requirements for solar grade crystalline Si will be discussed.
Electrolyte Additives for Controlling Roughness of Copper Electrodeposits Formed in Deep Eutectic Solvents
Authors: Shaheen Nora A. , Ijjada Mahesh , Vukmirovic Miomir B , Akolkar Rohan
Published: May 2020

Due to their wide electrochemical stability window, non-toxicity, and highly solubility for metal salts, deep eutectic solvents (DESs) are attracting attention as new class of electrolytes for electrodeposition and energy storage applications. However, due to their viscous nature, DESs impose transport limitations implying rough or dendritic morphology of electrodeposits formed in them. In the present work, we investigated roughness evolution during copper electrodeposition in a DES containing choline chloride and ethylene glycol in a 1:2 molar ratio (ethaline). Cuprous chloride was added to the DES as the metal precursor. Further, polyethyleneimine (PEI) – a common electrolyte additive used in electrodeposition from aqueous media – was added to ethaline and its effects on roughness evolution were investigated. Steady-state polarization measurements confirmed that PEI suppresses copper electrodeposition kinetics. This manifests into micro-scale leveling of deposits and thus suppression of roughness amplification during electrodeposition, which was confirmed electrochemically as well as using optical profilometry. Effects of PEI concentration on electrochemical behavior and roughness suppression were investigated. Specifically, hysteretic response during cyclic voltammetry was observed under certain conditions. Implications of the PEI-induced hysteresis on suppression of roughness in high-efficiency rechargeable batteries will be discussed.
Revisiting Electrodeposited Inverse Opals: New Insights into Magnetic Frustration
Authors: Kansal Chahat , Zeissler Katharina , Illy Benoit , Walton Stephanie , Cruickshank Amy , Felton Solveig , Branford Will R , Ryan Mary P.
Published: May 2020

Electrochemical deposition into templated architectures has been shown to increase the observed saturation magnetization of a range of magnetic materials (e.g. 1). Here we have created monolayer (2D) and 3D opal-type structures of NiFe (permalloy) and Co by electrodeposition into self-assembled polymer templates. The microstructure and thickness of the resultant macroporous structures is controlled by the electrochemical parameters during nucleation and diffusion-controlled growth. Preferential crystallographic texture is observed – resulting in magnetic anisotropy for Co. The magnetic behaviour is assessed by both conventional bulk magnetometry, and locally using high-resolution Lorentz microscopy in the transmission electron microscope (TEM) - providing new insights into the functional properties of these materials.

Hao, F. Q. Zhu, C. L. Chien & P. C. Searson. Fabrication and magnetic properties of ordered macroporous nickel structures. J. Electrochem. Soc. 154, D65-D69, (2007)
Direct Conversion of Low-Grade Heat to Electricity Based on Transition Metal Coordination Complexes
Authors: Yin Yichun , Li Kangkang , Jones Timothy , Feron Paul
Published: May 2020

Thermo-electrochemical cells (or thermocells), which could convert thermal energy to electrical power, are promising for waste heat utilization. Steady and continuous electricity can be generated through thermocells as long as there is a temperature gradient. The commercialization of thermocells is presently limited by low power output, energy conversion efficiency and high capital investment.

Liquid-based thermo-electrochemical cells have great potential for large-scale industrialization. Transition metal (Fe, Ni, Co, Ru, Cr etc.) redox pairs, as well as their coordination complexes, have shown excellent thermo-electrochemical properties. The corresponding electromotive force is linked to the entropy changes of the redox reactions. Further, the thermodynamic and kinetics of the redox reactions are significantly influenced by the type of coordinating ligands, solvents and electrodes materials. Therefore, the design of an efficient thermo-electrochemical cell with outstanding thermal-to-electrical power output requires careful design and consideration of all components within the cell.

In this study, transition metal coordination redox couples have been investigated for thermo-electrochemical energy conversion. Iron and cobalt are screened out for their spin states and low cost. By tuning the chelating ligands of transition metals in various solvents, increased Seebeck coefficient and fast ion diffusion were obtained, resulting in significant improvement of the performances in cell voltage and power density.

Figure 1
Enhancement of Ion Diffusion By Targeted Phonon Excitation
Authors: Gordiz Kiarash , Muy Sokseiha , Shao-Horn Yang , Henry Asegun
Published: May 2020

We introduce two formalisms that determine the individual contributions of normal modes of vibration (phonons) to the diffusion of atoms/ions through a solid, based on (i) Nudge Elastic Band (NEB) calculations (ii) molecular dynamics (MD) simulations. The combination of the MD and NEB based modal decomposition methods presented herein provide a detailed picture for the atomic/ionic diffusion. MD samples the dominant mechanisms that are present in a natural simulation of the material, while NEB can be used to study specific mechanisms, regardless of the likelihood that they would occur at a given temperature. The results for an example material of Ge-doped Li3PO4 revealed that >87% of the Li-ion diffusion in the lattice originates from a subset of less than 10% of the vibrational modes in the system, which have frequencies between 8-20 THz. By deliberately exciting a very small targeted subset of these contributing modes we observe an increase in diffusion by several orders of magnitude, consistent with what would be observed if the entire material (i.e., all modes) were excited to the same level. This suggests that an entire material need not be heated to elevated temperatures to increase diffusivity, but instead only the modes that contribute need to be excited to elevated temperatures. This new understanding identifies new avenues for increasing diffusivity by engineering the vibrations in a material, and/or increasing diffusivity by external stimuli/excitation of phonons (e.g., via photons or other interactions).
Safety of Li-Ion Cells and Batteries at Various States-of-Charge
Authors: Jeevarajan Judith , Azam Saad , Kinyon S. E. , Lopez Carlos
Published: May 2020

With the increase in demand for li-ion batteries in the wide variety of applications they are used in today, billions of cells and thousands of batteries are manufactured every month. The challenge arises when every single cell and battery should be tested before they are shipped out to assure that the cells are manufactured with a high quality and the batteries were assembled and tested to high standards and that they were not subjected to any off-nominal conditions during the manufacturing or testing process. This challenge has led to concerns in several sectors such as the shipping and transportation industry. This led the ICAO to set temporary bans on the shipment of Li-based cells and batteries as cargo in passenger and cargo aircraft, with a restriction of the state of charge of a li-ion cell or battery to not exceed 30%. The safety of li-ion cells and batteries at various states of charge have not been studied comprehensively in the past and hence the goal of this study was to determine if the result of an off-nominal condition would vary with varying SOC. Cells of different form factors (18650, 26650, and pouch), cathode chemistries (NCA, NMC, and LFP), capacities (2.5-10Ah), and quality (based on nominal price and inexpensive) were studied under this program. Battery designs were also studied. To characterize the behavior under off-nominal conditions, cells and batteries were subjected to two types of tests: heating method using a heating tape, and low impedance external short. In addition to that, the stability of charge retention was studied at the various SOCs. The results of this comprehensive study will be presented.
Alloy Plating for Improved Molten Salt Reactor Performance
Authors: Hall Timothy D. , Radhakrishnan Rajeswaran , Ahmadi Kamyar , Raiman Stephen S
Published: May 2020

The use of molten fluoride salts as a primary coolant within next generation nuclear reactors has the potential to improve efficiency and nuclear reactor safety by operating at low pressures and high temperatures without boiling. However, these coolants will require the development of new corrosion resistant material systems that will have to meet or supersede existing standard codes for these systems. Therefore, state of the art reactors require validation and testing of new material systems that can produce robust component structures and enable them to withstand these corrosive environments. Furthermore, any next generation process to apply protective coatings must allow for a conformal, thick, dense, and bonded materials to be formed onto any low cost ASME material (like 316H SS) that comprises the structure of heat exchanger and containment vessel components.

Within this context, Faraday Technology Inc. is working on developing low cost and high value corrosion-resistant alloy coatings for next generation molten salt reactors with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of functionally graded NiMo alloys onto ASME certified substrates and subsequent high temperature corrosion evaluation in molten fluoride salt electrolytes. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, we demonstrated the potential to apply graded NiMo coating to the 316H SS surface (Figure 1) and found that a coating composition of ~25% Mo has the potential to improve the components lifetime.

Figure 1: Top) show a cross-sectional image of a NiMo coated 316HSS component. Bottom) shows composition of Ni (Left/Dashed) and Mo (Right/Solid) as measured by EDX trace from the SEM along the red line (Top image).

Acknowledgements: The financial support of DOE Contract No. DE-SC0019602 is acknowledged.

Figure 1
Electrochemical Deposition of Sn-Cu Alloys for Applications in 3D Stacking in Microelectronics Industry
Authors: Inoue Fumihiro , El-Mekki Zaid , Struyf Herbert , Hou Lin , Derakhshandeh Jaber , Beyne Eric , Radisic Aleksandar , Hsia Chih-Hao , Chang Iris , Kuttner Elisabeth , Flügel Alexander , Arnold Marco
Published: May 2020

The use of eutectic Sn-Cu alloys in packaging applications in microelectronics industry is not something entirely new. However, this alloy was mostly used in large features and fabricated using metal powders and metallurgical deposition techniques. The diameter of an individual grain of the eutectic Sn-Cu powder is typically similar in size to the diameter of pillars or bumps currently used in 3D stacking, and if we were to check its usefulness as a solder on this scale, an alternative manufacturing technique had to be used.

We have electrochemically deposited Sn-Cu alloys having up to 10 wt.% Cu and explored its possible benefits when used as a solder in combination with different Under bump metallization (UBM) materials. Sn-Cu alloys were deposited on blanket and patterned coupons, and promising experiments then transferred to a wafer-scale, i.e. Sn-Cu alloys were deposited on 300 mm wafers in an industrial-type plating tool. A typical sample/wafer had a Cu seed with a diffusion barrier (e.g. TiW) underneath and patterned features defined with a photoresist mask. Characteristic dimensions of the patterned features were on the order of mm and cm (lines), (diameter, d)50µm × (height, H)60µm (pillars), and (d)8µm × (H)15µm (bumps). Cu, Ni, or Co were used as UBM layers.

Chemical composition of deposited alloys has been examined by using X-ray fluorescence (XRF), Micro X-ray fluorescence (Micro-XRF), Inductively coupled plasma mass spectrometry (ICP-MS), and Electron probe microanalysis (EPMA). Surface morphology and the shape of deposited features have been examined using Scanning electron microscopy (SEM) and Laser scanning microscopy (LSM), while thermodynamic properties have been studied using Differential scanning calorimetry (DSC). Within-wafer (WIW) and within-die (WID) height uniformity of the pillars has been analyzed using Falcon 630 Plus tool (Camtek Ltd), capable of capturing heights of all the structures on the wafer simultaneously. The kinetics of Intermetallic compound (IMC) formation have been studied in the number of selected samples by combining ex-situ Focused ion beam (FIB) and in-situ measurements of resistance change of the features during anneal/thermal ageing [1].

We will discuss possible benefits and drawbacks for use of electrochemically deposited Sn-Cu alloy solders in combination with different UBM layers based on these results.

References:

[1] Lin Hou, Jaber Derakhshandeh, Eric Beyne, and Ingrid De Wolf, “A Novel Resistance Measurement Methodology for in-situ UBM/Solder Interfacial Reaction Monitoring”, DOI 10.1109/TCPMT.2019.2950448, IEEE Transactions on Components, Packaging and Manufacturing Technology.

Figure 1
Formation of Mo Metal Powder By Electrochemical Reduction of CaMoO4 and MoS2 Compounds
Authors: Akpinar Bengisu , Erdogan Metehan , Karakaya Ishak
Published: May 2020

Molybdenum (Mo) is a transition element and improves strength, toughness, hardenability and weldability of cast iron and steel. Commercially molybdenum production involves two staged hydrogen reduction which has some disadvantages. An alternative way to produce Mo metal powder is electrochemical production process, however, molten salt electrolysis is not suitable to produce Mo powder due to its high melting point. Moreover, FFC Cambridge process is also not applicable for production of molybdenum because of Mo loss during the process. An alternative electrochemical process was searched to produce Mo metal powder in this study. CaMoO4 (calcium molybdate) and MoS2 (molybdenum disulphide) were used as raw materials for reduction process. CaMoO4 was not successfully reduced, because solubility of CaMoO4 was observed during experiments. Complete reduction of MoS2 to Mo was achieved and CaS was observed as a by-product at 750oC under argon gas flow. CaS was removed by a dilute acid washing to obtain Mo metal powder.
Electrochemical Separation and Recovery of Metallic Zr from KCl-LiCl-K2ZrF6-PrCl3 Molten Salt System
Authors: Wang Wei , Han Wei , Li Mei
Published: May 2020

The electrochemical behavior of Zr(IV) and Pr(III) in LiCl-KCl melt on W and Sn electrodes was studied by various electrochemical methods. Electrochemical results indicated that the deposition potentials of Pr and Zr on Sn electrode shifted towards more positive value than that on W electrode due to forming different Sn-Zr and Sn-Pr intermetallic compounds. By means of cyclic voltammetry, square wave voltammetry, the deposited potentials of Pr and Zr on the Sn electrode were confirmed at -1.18 V and -0.8 V, respectively. Thus the selective potential range for separating Zr(IV) and Pr(III) was approximately -0.8 V to -1.1 V. The effects of applied potentials on separation were also studied and the optimal separation conditions were confirmed. The results of XRD and SEM-EDS indicated that the product consisted of Sn and Sn2Zr phases, and the separation of Zr and Pr could be achieved by potential electrolysis.

Acknowledgement

The work was financially supported by the National Natural Science foundation of China (11675044, 21790373, 21876034 and 11875116), and the International Exchange Program of Harbin Engineering University for Innovation−oriented Talents Cultivation.
Electrodeposited TiB2 Coating on Graphite As Wettable Cathode for Al Production
Authors: Yvenou Etienne , Guay Daniel , Roué Lionel
Published: May 2020

Greenhouse gas (GHG) emission from the Canadian aluminum industry was about 6 Mt of CO2 eq in 2017, an amount equivalent to the GHG emitted by about 1.3 million cars [1-2]. The use of inert anodes, like Ni-Fe-Cu alloys [3], instead of carbon anodes to produce O2 rather than CO2 during aluminum electrolysis is paramount to curb GHG emissions from that industry. However, to maintain the energy efficiency of the process, the opposite cathode material must be wetted by molten aluminum to decrease the anode-to-cathode distance and thus reduce the overall cell voltage. TiB2 presents a good wettability by molten Al. Also, it has good electrical conductivity and good chemical stability under Al electrolysis. Accordingly, TiB2 is considered as an interesting cathode material to use in conjunction with inert anodes. However, its production as dense bulk cathode is challenging.

In this work, the electrodeposition of TiB2 on graphite substrate was performed by periodically interrupted current method in a molten LiF-NaF-KF salt at 600°C containing K2TiF6 and KBF4 as titanium and boron precursors, respectively [4]. The impact of the electrodeposition parameters on the crystalline structure, morphology, adhesion strength, Al wettability and Al penetration resistance of the TiB2 deposits will be presented.

[1] 2017 sustainable development report. Aluminium Association of Canada.

[2] Greenhouse Gas Emissions from a Typical Passenger Vehicle. United States Environnemental Protection Agency, 2018

[3] S. Helle, M. Pedron, B. Assouli, B. Davis, D. Guay, L. Roué, Structure and high-temperature oxidation behaviour of Cu–Ni–Fe alloys prepared by high-energy ball milling for application as inert anodes in aluminium electrolysis. Corros. Sci. 52 (2010) 3348.

[4] G. Ett, E.J. Pessine, Electrochim. Acta. 44 (1999) 2859.

Figure 1: (A) SEM cross-section image of electrodeposited TiB2 coating on graphite substrate. Optical images of Al droplet at 1000 °C on (B) TiB2-coated and (C) pure graphite substrates.Fig

Figure 1
Recovery of Ammonia during Food Waste Anaerobic Digestion Using a pH-Swing Electrochemical Process
Authors: Chen Weikun , Grimberg Stefan , Rogers Shane , Kim Taeyoung
Published: May 2020

Anaerobic digestion (AD) is a biological process for breaking down organic materials in an oxygen-free environment by microorganisms. This process has been proposed as a promising solution for diverting food waste from landfills as well as producing biogas and recovering nutrients from food waste to use as a fertilizer. A major challenge during AD is that ammonia created by microorganisms inhibits microbial methane production. Therefore, ammonia removal during AD can improve the overall performance, and yield high-quality ammonia for fertilizer reblending or other uses. Previous ammonia recovery systems have relied on the use of high amounts of base to elevate the solution pH for converting ammonium into ammonia. While electrodialysis (ED) is a promising alternative to increase pH by electrochemical reaction without the need for chemical, a high voltage (>2.5 V) is required for electrochemical water splitting. To enable energy-efficient recovery of ammonia, a proton-mediated electrochemical reaction was implemented using hydroquinone (HQ)/benzoquinone (BQ) as a model redox couple. The proton-mediated redox couple undergoes electrochemical reduction with H+ uptake (increase the pH) and oxidation with H+ release (decrease the pH). A three-channel flow cell separated by cation exchange membranes was constructed and the channel located at the middle was fed by synthetic digestate while applying a constant current of 10 A m-2. Ammonia flux achieved was 132 g N m-2 d-1 with a solution pH of 9.5. The resulting energy consumption of 1.6 kWh (kg N)-1 was less than a half of that needed in ED due to the low cell voltage requirement (<1 V). The separated ammonium was captured in an acidic solution (0.05 M H2SO4) using a membrane contactor at a flux of 49 g N m-2 d-1, resulting in 4.3 kWh kg N-1 based on the energy consumed for the electrochemical separation. These results support that the use of proton-mediated redox couple can enable energy-efficient recovery of ammonia during food waste AD.
TiB2-Coated Graphite As Wettable Cathode for Al Production
Authors: Yvenou Etienne , Bily Alexandre , Dolatabadi Ali , Moreau Christian , Davis Boyd , Guay Daniel , Roué Lionel
Published: May 2020

A significant reduction in greenhouse gas emissions from aluminum smelters will only be achieved with the emergence of new technologies. The most effective way to decrease significantly CO2 emissions from this industry is to replace the consumable carbon anodes that are used nowadays with so-called inert anodes that emit O2 instead of CO2 during Al electrolysis [1]. However, the implementation of inert anodes in Al smelters will induce an increase of the cell voltage, which could be compensated by reducing the cell ohmic drop by decreasing the anode-to-cathode distance. For that purpose, the thickness of the molten Al layer presents on the surface of the cathode must be minimized, which requires a high wettability of molten Al on the cathode. To date, the most promising cathode material is TiB2, which has an excellent Al wettability, good electrical conductivity and good chemical stability under Al electrolysis conditions. However, the manufacturing of bulk TiB2 electrodes at the industrial scale poses challenges. Sintering of TiB2 must be performed at high temperature (~2000°C), which induces significant crystal growth that has dramatic consequences on the mechanical properties of the electrode. Faced with these constraints, various consolidation methods operating at lower temperatures have been evaluated (sintering under pressure, spark plasma sintering...), but they are expensive and/or poorly adapted to the production of large electrodes of complex shape as required for Al electrolysis application.

In the present study, new avenues based on the elaboration of TiB2 coated graphite cathodes by electrochemical and thermal spray methods are evaluated. The influence of the deposition conditions on the crystalline structure, morphology, mechanical resistance and Al wettability of TiB2 coatings will be presented in this communication.
Electrocatalytic Effect of IrO2 / Ta2O5 || Ti and RuO2 / Ta2O5 || Ti in the Oxidation of Amoxicillin in Aqueous Medium
Authors: Bustos Erika , León Itzel , Manríquez Juan , Sepúlveda-Guzmán Selene , Gomes Helena
Published: May 2020

Titanium electrodes coated by transition metal oxides have been used in many applications, thus they remain the subject of constant research and improvement. One of the most important applications for this type of electrode is the electro-generation of hydroxyl radicals (•OH), via catalytic water oxidation, during the electrochemical degradation of organic compounds. In this sense, the intention of this study was the development of modified surfaces by transition metal oxides (IrO2/Ta2O5||Ti with Ir:Ta 70:30 and 30:70; and RuO2/Ta2O5||Ti with Ru:Ta 70:30 and 30:70) for electrochemical advanced oxidation processes (AOP) to degrade organic micropollutants, specifically amoxicillin (AMX). The characterization of the surface morphology and composition of the different anodes used in this study was made by Scanning Electron Microscopy (SEM) – Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Photoelectron Spectroscopy (XPS) and electrochemical characterization; the last one was carried out by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Additionally, the indirect detection of •OH generated on the surface of the electrode was done by UV-Vis spectrophotometry using coumarin. The corresponding degradation was carried out by electrolysis of AMX in an aqueous medium applying a current of 15 mA, where the amoxicillin concentration was measured throughout by High Performance Liquid Chromatography (HPLC) - UV-Vis, obtaining efficiencies of more than 90 % AMX degradation in 0.1 M Na2SO4 after 400 min. The Carbon Organic Demand (COD) removal was also measured, obtaining up to 80% removal using the same experimental conditions in presence of IrO2/Ta2O5||Ti 70:30 by the major generation of •OH than using RuO2/Ta2O5||Ti 30:70.
Electrocatalytic Reduction of Lignin Model Compounds in a Stirred Slurry Reactor: Mild Approach for Synthesis of Renewable Chemicals
Authors: Wijaya Yanuar Philip , Smith Kevin J. , Kim Chang Soo , Gyenge Elod
Published: May 2020

Electrocatalytic hydrogenation-hydrogenolysis (ECH) is a promising approach for synthesis of bio-based chemicals. The advantages of this process over the classic thermocatalytic routes are mainly attributed to the mild operating conditions with in-situ H2 generation and the feasibility of product selectivity control by synergistic interactions between the electrode potential, current density, and temperature. In this work, a mild electrosynthesis of value-added chemicals from lignin model compounds (e.g., phenol, guaiacol, and creosol) is presented using a stirred slurry electrochemical reactor (SSER). Cyclohexanol and cyclohexanone are among the main target products, which represent important chemicals for the industrial synthesis of Nylon polymers. The effects of different electrolyte pairs, electrolyte compositions (aqueous and organic mixtures), and electrocatalysts (Pt/C, Ru/C, and Pd/C) were investigated under benign reaction conditions (1 atm, ~60 oC). The primary source of protons for ECH was identified by pairing the diverse electrolytes (H2SO4, NaCl, and NaOH), showing the importance of acidic anolyte for an effective ECH. Methanesulfonic acid was also successfully employed in the ECH of guaiacol with low Pt/C loading, resulting in high guaiacol conversion (~90%) and cyclohexanol selectivity (~50%) at high Faradaic efficiency (>70%) and at low operating temperatures (35–40 oC). The electrocatalytic activity is strongly dependent on the adsorbed hydrogen radical surface coverage, which in turn is a complex function of active sites, electrolyte (pH and composition), and electrode potential. By pairing neutral catholyte (NaCl) and acid anolyte (H2SO4), anodic protons transported through the cation exchange membrane may be effectively utilized for ECH reactions. Pt/C shows superior activity in the acid-acid pairs, while the activity of Ru/C and Pd/C were significantly improved in the neutral-acid pairs. The most obvious example was found in the guaiacol ECH, where Ru/C, which was least active in the acid-acid pair, resulted in in significant conversion (>70%) and Faradaic efficiency (~76%) in the neutral-acid pair after 4 h. Overall, this work demonstrates that the efficient reductive upgrading of lignin monomers can be achieved under mild conditions via electrocatalysis in a stirred slurry electrochemical reactor at high cathode superficial current densities (i.e. above 100 mA cm-2).

Figure 1
Investigation on the Pseudo-Reference Electrodes for Electrochemical Measurements in Molten Li2o/LiCl
Authors: Shi Meng , Li Shelly , Zhao Haiyan
Published: May 2020

Electrolytic reduction is an integral step in pyroprocessing to treat used oxide fuels, and also applicable for transition metal productions. During the electrochemical reduction process, oxides fuels are loaded at the cathode basket in molten Li2O–LiCl salt and electrochemically reduced to the metal form. In electrochemical studies within the molten salts, reference electrode is essential to understand the electrode reaction and reaction mechanism. However, a wide range of reference electrodes have been employed for electrolytic reduction studies such as molybdenum, Pt, Li-Pb and Ni/NiO etc. It is challenging to compare and understand different results from different literature and research groups. In this work, glassy carbon, tungsten (W), molybdenum (Mo) and Ni/NiO were tested as reference electrodes within the same system under the same conditions which forms a direct comparison base for understanding the different behavior due to the reference electrodes.
Investigation of the Effect of Bath Ageing on Electropolishing Efficiency
Authors: Krishna Bivi , Manoharan Gobinath Vellapalayam , Wüthrich Rolf
Published: May 2020

The bath age poses a serious challenge during prolonged electropolishing processes. It is a general practice in electropolishing industry to reuse the bath to cut down the cost and to minimize the harmful effects on the environment. It is well known in the electropolishing industry that the final polishing quality declines over time due to the increased dissolved metal ions. The present study aims to quantify this effect.

Various sets of experiments were conducted to investigate the effect of bath aging during prolonged electropolishing on polishing quality. The experiments were performed in a bath with an initial composition of 50% phosphoric acid (H3PO4), 35% sulfuric acid (H2SO4) and remaining water. The variations in the properties of the bath (conductivity, viscosity and specific gravity) were measured over prolonged polishing (Electropolishing tests were conducted up to passing 72000 C/ L of the bath). Variation of quality (in term of surface roughness and gloss) of standard workpieces polished under identical conditions (constant voltage, inter-electrode distance and time) were determined at various bath ages. Further bath composition (in term of the relative amount of acids) was determined periodically by titration.

It was observed that as the bath properties change throughout the electropolishing experiments with bath aging, significant variation was seen in roughness and gloss of the polished workpiece. The roughness result for the workpiece polished in the most-aged bath was ~12 times higher than the workpiece polished in the fresh bath. Also, the first few polished workpieces had a shiny, mirror finish whereas the workpieces polished for the prolonged bath usage had a dull, matte finish.

Bath composition varied from the initial composition of 50:35:15 (phosphoric acid: sulfuric acid: water) to 31:22:47 as the bath aged. Recovering initial bath composition (by adding an adequate amount of acids to the aged bath) allowed to recover the similar quality of polished samples (very similar surface roughness but less bright surface finish). Correlation between measured bath properties and composition with polishing achieved under standard conditions can be considered for further studies to develop strategies to make polishing parameters adaptable to given bath states.
New Method for Characterization of the Open Circuit Potential Curve for Battery Cathode Materials
Authors: Usubelli Camille , Kimura Kevin Wayne , Klein Reinhardt , Christensen Jake , Gorlin Yelena
Published: May 2020

Battery management system (BMS) is a key component of the battery for electric vehicles and portable electronics, as it guaranties reliable and safe operation of the battery, while ensuring its longevity and optimal performance. State-of-the-art BMS relies on an equivalent circuit model, while an important research topic is the development of BMS, which is based on an electrochemical model.[1] The main task of BMS is to accurately estimate the available energy and power of the battery by tracking its current state of charge (SOC). The open circuit voltage (OCV) of a cell is often used for estimation of the SOC of a battery. It depends on the open circuit potential (OCP) of the anode and the cathode materials, which give the potential associated with a certain amount of lithium stored in each structure. The accuracy of the OCP curves of each electrode material is critical for use with BMS based on electrochemical models, as in addition to tracking the bulk SOC of a battery, it also tracks the surface SOC.[1] As a result, BMS based on electrochemical models can offer improved prediction for both instantaneous and pulse power relative to systems based on an equivalent circuit model.

In this contribution, we propose a novel method for characterization of the open circuit potential vs. state of lithiation (OCP) curves for active materials commonly used in lithium-ion batteries. Our method offers increased accuracy over existing electrochemical procedures [1-3]by providing a standardized mapping process from the measured gravimetric capacity to state of lithiation and improving characterization in the region of the curve that is close to the lithium content of 1. We demonstrate the strengths of the method on two different cathode materials: LiCoO2 and LiNi1/3Mn1/3Co1/3O2, which are widely used in commercial cells for portable electronics and electric vehicles. [2-3]

1. Chaturvedi, N. A., Klein, R., Christensen, J., Ahmed, J. & Kojic, A. Algorithms for Advanced battery-Management Systems. IEEE Control Syst. Mag. 49–68 (2010).

2. Daniel, C., Mohanty, D., Li, J. & Wood, D. L. Cathode materials review. AIP Conf. Proc.
1597, 26–43 (2014).

3. Cairns, E. J. & Albertus, P. Batteries for Electric and Hybrid-Electric Vehicles. Annu. Rev. Chem. Biomol. Eng.
1, 299–320 (2010).
Probing Dynamic Mass Transport at Multivalent Battery Interfaces
Authors: Sa Niya , Vaughey John T. , Cora Saida , Fan Shengqi
Published: May 2020

The integration of electrochemistry and materials has developed rapidly over the past decade and is now a key contributor in many important applications, one emerging area is to design efficient energy storage devices at low cost. Many of these savings are driven by utilizing the higher abundance chemical elements from the earth's crust, for instance Zn, Mg or Ca. Despite some successful research advances in recent decades, there is a lack of an in-depth analysis of the electrolyte/electrode interface for multivalent battery systems. One major difficulty is the lack of capability to provide direct in-situ interfacial information without perturbing its chemical environment. Efforts from the presented work aim to probe and quantify the solid electrolyte interface formation in-situ. We aim to understand at the interface, how parasitic reactions affects or disrupts the mass transport processes and shuts down the cycling of the multivalent electrode material.
Long Cycle Stability of Conversion Metal Fluoride Cathodes in Polymer Electrolytes
Authors: Turcheniuk Kostiantyn , Huang Qiao , Bondarev Dmitry , Yushin Gleb
Published: May 2020

The development of Li-ion batteries (LIBs) has been slowed down to a mere 1-2% per year. The skyrocketing price of Co (>30 $USD kg-1) and Ni (>15 $USD kg-1), their limited resources, and accompanying to that low energy density of intercalation-chemistry batteries make it difficult the pack cost to fall to $90-100 kWh-1 or even below. The improvements in LIB energy density (> 1.0 kWh/L) at a reduced cost (<$50-70 kWh-1) can be sought from conversion metal fluoride cathodes (FeF2(3), CuF2 or MFx), which exhibit 2-3 times higher energy density (in Si-/Li-anodes based cells) and low cost (6-9 USD cents for Fe and 6-7 $USD fro Cu per kg, respectively). To streamline these battery chemistries, intrinsically poor ionic conductivity of MFx, substantial volume (up to 30%) and morphological changes during cycling, active material dissolution, substantial resistance buildup, and irreversible growth of the cathode electrolyte interphase (CEI) need to be minimized. By utilizing strong and tough ionically conducting polymer electrolyte matrix and elevated temperature cycling conditions (50 °C), we demonstrated formation of thin conformal CEI, substantial mechanical resilience, decreased internal resistance, reducing of active material dissolution, and overall improvement in performance of FeF2 to 300 cycles at ~400 mAh g-1.

Figure 1
Diffusion Control of Organic Cathode Materials in Lithium Metal Battery Using a Graphite Modified Separator
Authors: L. Belanger Rachel , Commarieu Basile , Paolella Andrea , Daigle Jean-Christophe , Claverie Jerome P. , Zaghib Karim
Published: May 2020

Energy storage technology is a critical research area for the success of portable electronic devices and electrical transportation. Such applications need affordable, durable, safe and environmentally friendly battery materials with high energy density. Organic cathode materials are currently promising candidates because they fulfill most of these requirements for an active battery material1. However, they usually suffer from a major limitation, namely their solubility in organic electrolytes2. Even a very low solubility translates into a decreased capacity upon cycling due to the loss of active material. Among organic cathode materials, conjugated carbonyl compounds have been intensively scrutinized because of a combination of desirable properties, such as low cost, good theoretical capacity, reversible oxidative behavior, high discharge potential and commercial availability. For example, 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) is an inexpensive red pigment that is widely investigated as an active material for energy devices. However, Li-PTCDA batteries suffer from poor and irreversible cycling stability due to the dissolution in the electrolyte. Even more problematic, the dissolved PTCDA migrates through the porous separator and deposits on the anode surface causing irreversible damage3. In order to solve this problem, chemical modifications such as polymerisation, functionalization and immobilization on carbon materials have improved cycling stability. However, these modified cathode materials, which are often prepared by complex processes, contain considerable amounts of inactive mass that cause a decreases of the energy density. We developed a Janus membrane, which consists of two layers – a commercial polypropylene separator (CelgardTM) and a 300-600 nm layer of exfoliated graphite that was applied by a simple and environmentally friendly process. The submicron graphite layer is only permeable to Li+ and it drastically improves the battery performance, as measured by capacity retention and high coulombic efficiency, even at 2C rates. Post-mortem analysis of the battery indicates that the new membrane protects the anode against corrosion, and cathode dissolution is reduced. This graphite-based membrane is expected to greatly expedite the deployment of lithium batteries using organic moities as active materials.

References

[1] Armand, M. & Tarascon, J. M. Building better batteries. Nature
451, 652–657 (2008).

[2] Zhao, Q., Zhu, Z. & Chen, J. Molecular Engineering with Organic Carbonyl Electrode Materials for Advanced Stationary and Redox Flow Rechargeable Batteries. Adv. Mater.
29, 1–25 (2017).

[3] Wang, J., Wang, X., Li, H., Yang, X. & Zhang, Y. Intrinsic factors attenuate the performance of anhydride organic cathode materials of lithium battery. J. Electroanal. Chem.
773, 22–26 (2016).