bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermodynamic and Kinetic Control of Photoelectrochemical CO2 Reduction into Liquid Fuels
Authors: Kang Young Soo
Published: February 2020

In the photoelectrochemical CO2 reduction reaction, water oxidation reaction is performed on 040-BVO and chemical fuels is obtained on Cu cathode in the CO2-saturated NaCl electrolyte under AM 1.5 G. C1 chemical fuel is evolved through reduction potential depending multistep process from CO2 molecule. 040-BVO(photoanode)/NaCl(electrolyte)/Cu(cathode) system is illuminated with solar light under the external bias that is tailored to reduce CO2 via reduction potential tuning. Integrating applied bias potential into conduction band minimum of 040-BVO enables CO2 molecules to be converted into valuable chemical fuels. We observe that the selectivity and yield of the products depend on CO2 reduction potential tuning. With water oxidation reaction of 040-BVO photoanode which has 42.1% of the absorbed photon-to-current conversion efficiency at 1.23 V (vs RHE), chemical products were observed as faradaic efficiency of 30% formic acid, 60% formaldehyde, 12% MeOH and 3% EtOH by reduction potential tuning. For this study, the correlation between the production of solar chemical fuels and CO2 reduction potential tuning via external bias potential on 040-BVO photoanode/Cu photocathode is systematically investigated.

Keywords: Artificial photosynthesis; Multi-electron shuttling; CO2 reduction potential tuning
Decentralized Electrochemical Production of H2O2: A Focus on Catalysis and Single-Atom Catalysts
Authors: Yang Sungeun , Xi Jiangbo , Colic Viktor , Stephens Ifan , Silvioli Luca , Rossmeisl Jan , Kibsgaard Jakob , Wang Shuai , Chorkendorff Ib
Published: February 2020

Electrochemical production of hydrogen peroxide, H2O2, holds promise for small-scale, on spot, and safe production of green oxidizer. Electrochemical process requires small electrochemical device that can replace large and centralized current infrastructure using anthraquinone method. Optimizing cathode catalyst that can reduce oxygen to hydrogen peroxide with high activity and high selectivity will make such a system reality.

We focus on the catalysis of electrochemical oxygen reduction to hydrogen peroxide. Electronic effect and geometric effect are the two important factors determining activity and selectivity of catalysts. Beyond these well-known effects, pH and mass transport of product can profoundly change the activity and the selectivity of catalyst. Activity and selectivity of Pt-Hg, Ag-Hg, Ag, and glassy carbon electrode abruptly changed by pH of reaction environment. We also highlight the importance of mass transport on benchmarking the selectivity by comparing three different systems with different mass transport phenomena, rotating ring disk electrode, stagnant electrode, and membrane electrode assembly.

We propose single-atom catalyst as a promising type of catalyst for H2O2 production. Single-atom catalysts exhibit intriguing catalytic properties due to its geometric arrangement where active atoms are well separated with each other, and each individual atom directly interact with support atoms. Single-atom catalyst can satisfy both electronic and geometric effect for the optimized performance. Near hundred percent noble metal utilization led to high mass activity for electrochemical H2O2 production.
Kinetic Analysis of the Oscillatory Electrodeposition of Cu/Sn Multilayers: Activation and Diffusion Control
Authors: Menezes Laura , Parma Eduardo , Machado Eduardo Giangrossi , Nagao Raphael
Published: February 2020

The systematic study of the nonlinear dynamics of different systems can yield important scientific advances. Examples range from the better understanding of living systems, remarkably nonlinear, to the development of new, self-organized materials. In this work, for the first time, quasiperiodic oscillations were observed during the electro-deposition of Cu/Sn multilayers (Figure 1a). Return maps were used to characterize the quasiperiodicity, and the continuous wavelet transform was employed to isolate and determine the oscillation frequencies (Figure 1b and c). To further study the mechanism in play, it was determined the apparent activation energy, by tracking the oscillation frequencies and the currents in the cyclic voltammetry experiments under different temperatures. Two different energy intervals are showed, and those are mainly attributed to: activation barriers (~50 kJ.mol-1) closely related to a fast time scale of the feedback loops responsible for the current oscillations and, diffusional processes (~20 kJ.mol-1) connected with the slow modulations of the oscillation amplitude, giving rise to the quasiperiodic dynamics. As self-organization in chemical systems is quickly developing into a powerful strategy for designing new functional materials, available kinetic parameters become of major interest in a rational design approach. In fact, the quasiperiodic behavior observed during the oscillatory deposition of Cu/Sn yields a material with unique properties and opens the perspective for the synthesis of more intricate morphologies. This work is ready for publication and will be submitted within few days.

Figure 1
DFT Analysis of Amino Acid Functionalization of Hematite for Electroreduction Catalysis
Authors: Maheshwari Sharad , Janik Michael John , Li Yawei
Published: February 2020

In a future with plentiful renewable electricity, electro-chemical systems to carry out chemical transformations can provide an efficient and sustainable alternative to fossil-fuel based energy consumption. Several important chemical reactions, such as CO2 and N2 reduction, have electro-chemical counterparts to form useful products through a series of proton-coupled electron transfer (PCET) reactions. The activity and selectivity of PCET reactions can significantly be impacted by the electrode-electrolyte interfacial properties, and tuning this near-surface environment can be used as a control towards developing active and selective electrochemical conversions. Surface-bound amino acid chains can be used to alter the electrocatalytic performance by altering the active site structure and local environment. We used Density Functional Theory (DFT) to study the surface binding of short amino acid chains on Fe2O3 surfaces to understand how they alter the interfacial environment through surface-ligand interactions. We examine the effects of small amino acid binding on the stability of different Fe2O3
terminations in the electrochemical environment. We consider how presence of continuum solvation affects the binding preferences of the amino acid. Coverage effects on binding energies are also evaluated. We then examine how these amino acid or peptide chain can act as shuttling agents to alter the energetics and kinetic barriers of PCET reactions.
In Situ Raman Microscopy for Redox Mechanism of Cathode Materials
Authors: Ri Vitalii , Jeon Cheolho , Kim Chunjoong , Moon Joonhee
Published: February 2020

Raman spectroscopy has been used to study structural information is a vibrational technique which is very sensitive to the metallic oxidation state, and it is very suitable for electrode materials due to several characteristics; fast, nondestructive method, measurement of the same electrode and even on the same spot with various laser, and analysis using another techniques. Moreover, the Raman imaging technique is powerful tool to study the charge of structure, surface morphology, and phase transition accompanying crack propagation.

Here, we introduce Raman micro-spectroscopy installed at Advanced Nano-Surface Research Group in KBSI which is especially set up in glove box to measure various materials without air exposure, which can exhibit a sample from another surface contamination when exposure to atmosphere. Additionally, we designed and fabricated two types of electrochemical cells (plane cell and cross cell) developed for in situ Raman micro-spectroscopy for studying electrode materials in operating battery during battery operation. This approach simultaneously characterizes phase transition and facilitates uncovering the relationships between surface structure and activity during battery operation. This result provides a method for visualizing chemical structure of phase transition and the changed surface morphology.
Nano-Scale Confinement for Efficient Multi-Step Reaction Cascades
Authors: Chavan Kanchan Suklal , Calabrese Barton Scott
Published: February 2020

Strategic operation of multi-step reaction cascades for energy conversion/storage applications such as biofuel cells is a necessary step to increase process efficiency [1]. Beyond maximizing catalytic activity, efficient transport of reaction intermediates between active sites with minimal diffusion loss into the bulk is critical. Therefore, implementation of intermediate channeling mechanisms, many of which exist in nature, to multi-step energy cascades is a critical aspect of an overall design strategy.

Molecular tunneling is one mechanism of substrate channeling that minimizes intermediate diffusional losses into the bulk by confining intermediate pathway [2].In this work, we studied intermediate transport between two active sites confined by single-walled carbon nanotube (SWCNT) using continuum and molecular dynamics (MD) approaches [3]. MD was performed using model intermediates (oxalate and ethanol) inside SWCNTs with diameter 1 nm to 4 nm. Due to water molecule orientation inside the SWCNT, the intermediates experienced a constrained environment that resulted in Knudsen diffusion and decreased diffusion coefficient [4].

In order to increase intermediate residence time inside the nanotube, SWCNT termini were modified with varying numbers of negatively-charged carboxylate groups. Due to attractive-repulsive electrostatic interactions, ethanol, which is uncharged but polar, was retained for a longer time inside the SWCNT. Like-charged intermediates such as oxalate were less affected. This approach represents one possible technique to enhance confinement and therefore increase reaction efficiency.

References:

(1) Wheeldon, I. et al., Nat. Chem. 2016 p299.

(2) Dunn, M. F. et al., Trends Biochem. Sci. 2008 p254.

(4) Chavan, K. S. and Calabrese Barton, S., J. Phys. Chem. C 2018, p14474.

(3) Striolo, A., Nano Lett. 2006, p633.
Spontaneous Formation of Diazonium Salts Thin Films on Silicon Electrodes
Authors: Peiris Malwattage Chandramalika Rukmali , Ciampi Simone , Darwish Nadim
Published: February 2020

Future of electronics will require using single molecule as the active component in electric circuitry. In that vein our group and others have developed single molecule switches1,2, single molecular diodes3, single molecular resistors and transistors4. All these previous studies utilized alkynes, amines, thiols as anchoring groups to metals (mostly on gold (Au)). Despite the popularity of the S-Au linkers, they are mechanically unstable and their contact resistance is variable which complicates device fabrication. To realize molecular electronics devices a change towards more robust contacts is needed. In this study, we show that molecular contacts of o-Dianisidine bis(diazotized) zinc double salt (bis diazo) on silicon (Si) can be made electrochemically and also spontaneously without the need of external electric field (Figure 1a) and can be potentially extended to other types of electrodes. The thin films were characterized electrochemically by spontaneously attaching ferreocene to the distal end of the bis diazo molecule and by using X-ray Photoelectron Spectroscopy (XPS), X-ray Reflectometry (XRR), Atomic Force Microscopy (AFM). Furthermore, electrochemical reduction of bis diazo molecule on different crystalline faces of Si were studied (Figure 1b). We found that Si <111> reduction wave occurs at more positive potential then that observed for Si <100>. To confirm these assignments we have created Si <111> pyramids on Si <100> surface by anisotropic etching in 20% KOH solution. By doing so, we have created a mixed <111/100> surface that can probe in-situ the difference in the electrochemical reduction between the two crystal faces (Figure 1 c). These types of diazonium salts could be used as molecular diodes, devices since they can spontaneously attach to both gold and silicon.

References

N. Darwish, M. N. Paddon-Row and J. J. Gooding, Acc. Chem. Res., 47, 385 (2013).

N. Darwish, A. C. Aragonès, T. Darwish, S. Ciampi and I. Díez-Pérez, Nano Lett., 14, 7064 (2014).

A. C. Aragonès, N. Darwish, S. Ciampi, F. Sanz, J. J. Gooding and I. Diéz-Pérez, Nat. Commun., 8 (2017).

M. L. Perrin, E. Burzurí and H. S. J. van der Zant, Chem. Soc. Rev., 44, 902 (2015).

Figure 1. a) Cyclic voltammogram of a thin film of bis diazo spontaneously grafted on n-type Si <111> (resting in a solution of bis diazo for 2 h on Si <111> surface and then exposed to a solution of ferreocene, scan at 0.2 V/s) b) Cyclic voltammetry of a the reduction of bis diazo on n-type Si <111> (red line (a)) and <100> (black line (b)) at scan rate 0.05 V/ s c) Potential difference in the electrochemical reduction between the two crystal faces on the pyramid surface .

Figure 1
Functionalized GaAs Photocathodes for Spin-Dependent Charge Transfer Studies
Authors: Tamski Mika , Blumenschein Felix , Roussel Christophe , Ansermet Jean-Philippe
Published: February 2020

Chiral-Induced Spin Selectivity (CISS) is a well-documented phenomenon occurring at electrochemical interfaces, where chiral functional groups can hinder the transfer of electrons with a specific spin state, while allowing the electrons with an opposite spin state to be transferred to the electroactive species in the solution.1,2

Spin dependent electron transfer has also been observed at p-GaAs/electrolyte interface without chiral functionalities, relying on the spin selectivity between polarised electrons in the conduction band (CB) of the p-GaAs and spin-oriented radical species in the solution.3,4

Here we report spin-dependent charge transfer in electrochemistry, where the spin selectivity is achieved by manipulating the electron spins of a radical redox mediator in the sample solution using microwaves (MW) under resonance conditions. This work has required us to characterise the photocathodic behaviour of p-GaAs in contact with methyl viologen radical cation (MV+•) in organic solvents under very low light intensities, a domain not traditionally covered in semiconductor electrochemistry.

We have also contrasted the behaviour of the bare p-GaAs to biphenyl- and peptide-functionalised surfaces, showing that the parasitic valence band (VB) and surface state (SS) mediated processes can be completely avoided. In the future, we hope that these functionalised surfaces allow us to increase the spin-dependent signal intensity, as the probability of electron’s spin state relaxing due to parasitic processes can be minimised.

Figure 1
Recent Progresses in Ionic Liquid-Based Electrolytes for Hybrid Multivalent Metals Secondary Batteries
Authors: Pagot Gioele , Vezzù Keti , Nale Angeloclaudio , Negro Enrico , Greenbaum Steven , Di Noto Vito
Published: February 2020

The seeking of stable and high-performing electrolytes is the major bottleneck to the development of future secondary batteries belonging to the so-called beyond Li-ion technology. In particular, electrolytes able to reversibly deposit and strip multivalent metals seem to be the answer to the growing energy demand requested by the Electric Vehicles market. Indeed, the multi-electron chemistry could ensure a higher energy value per moles of active material.

In this concern, Ionic Liquids (ILs) are considered attractive materials thanks to their low volatility, negligible flammability and good electrochemical performance in the metal reversible deposition processes [1-3]. Indeed, it was recently demonstrated that these electrolytes are able to deposit and strip magnesium/metal alloys with Coulombic efficiencies higher than 99%, overpotentials lower than 50 mV vs. Mg/Mg2+ and remarkable current densities (Fig. 1).

In this report, an overview on the most recent progresses in IL-based electrolytes for hybrid multivalent metals secondary batteries will be given. A detailed description of the interplay between structure and conductivity of ionic species will be presented. Finally, the relationships existing among metal ion speciation, long-range charge migration processes and electrochemical performances of these materials will be elucidated.

References:

[1] G. Pagot, F. Bertasi, K. Vezzù, E. Negro, S. Greenbaum and V. Di Noto, under submission.

[2] G. Pagot, F. Bertasi, K. Vezzù, F. Sepehr, X. Luo, G. Nawn, E. Negro, S.J. Paddison and V. Di Noto, Electrochim. Acta 2017, 246, 914-923.

[3] F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, E. Negro, S.J. Paddison, S.G. Greenbaum, M. Vittadello and V. Di Noto ChemSusChem 2015, 8, 3069-3076.

Figure 1
Proton Dissociation and Transfer in Protic Ionic Liquids (PILs)
Authors: Zhu Zhenghao , Luo Xubo , Paddison Stephen J.
Published: February 2020

Protic ionic liquids (PILs) have attracted significant attention due to their promising properties and potential use in various applications. Recent studies revealed exceptionally strong decoupling of proton conductivity from structure relaxation in a mixture of lidocaine with phosphoric acid.1 Proton conductivity in this mixture even exceeds that of phosphoric acid at the same viscosity. Both lidocaine and phosphoric acid have proton donor and acceptor sites that facilitates the formation of a well-connected hydrogen bond network contributing to their high proton diffusivity. Thus, it is necessary to study the effects of the molecular geometry of both the acid and base, the number of the proton donating and accepting sites on the acid and base, and the solvation on the proton dissociation and transfer.

In this study, fully optimized structures of pairs and clusters of the phosphoric acids (PAs) with different bases (lidocaine, imidazole, creatinine, and trimethylammonium) were determined through ab initio electronic structure calculations at the B3LYP/6-311G** level of theory in both the gas phase and the SMD model. The molecular binding energies of PA and the base molecules were calculated from both the uncorrected and zero point energies (ZPEs) corrected total electronic energies based on the same level of theory. Subsequently, potential energy surface (PES) scans for the transfer of a proton for pairs and clusters of the acids with various bases were performed at the same level of theory to study the effects of different bases and the number of PAs on the dissociation of PA and the proton transfer energetics. The results reveal that dissociated protons are generally more favorable in the SMD model since the continuum solvation model stabilizes the charge separation.

Reference:

1. Z. Wojnarowska, Y. Wang, K. J. Paluch, A. P. Sokolov, M. Paluch, Observation of highly decoupled conductivity in protic ionic conductors. Phys.Chem.Chem.Phys
2014
, 16, 9123-9127.
Photoluminescence Spectroelectrochemistry Study of CVD-2D MoS2monolayers Transferred Onto a Conductive Transparent Electrode
Authors: Strange Lyndi , Garg Sourav , Yadav Jeetika , Kung Patrick , Kim Seongsin M , Pan Shanlin
Published: February 2020

Two-dimensional transition metal dichalcogenides (2D-TMDs) have been the focus of much research study in a variety of different fields such as sensing, supercapacitors, batteries, hydrogen evolution reactions, and catalysts. Monolayer 2D TMDs of MoS2have attracted particular attention in optoelectronics due to the transition of indirect to direct bandgaps with decreasing number of layers. Furthermore, the photoluminescence (PL) of monolayer MoS2can be tuned by increasing the ratio of excitons (electron and hole) to trions (two electrons and a hole) via chemical doping and localized surface plasmon resonance (LSPR). Electron withdrawing groups also have been used to produce p-type doping effects on the MoS2, which cause the ratio of trions to excitons to increase thereby increasing the PL. In this study, the effect of an electrochemical potential bias on PL from 2D MoS2synthesized by Chemical Vapor Deposition (CVD) and transferred onto a Indium-Tin-Oxide (ITO) electrode is examined. It was observed that a positive external bias caused an increase in the PL by three-fold at 0.8 V vs. Ag/AgCl in PBS buffer accompanied by a red shift in its peak position. The PL intensity and peak shift dependencies on scan rate, maximum oxidation potential, and spatial distribution of initial PL intensity and upon electrochemical potential bias and possible mechanism will be discussed in this presentation.
Understanding Electrochemical Interface Using Atom-By-Atom Metal Substitution of Redox Species
Authors: Prabhakaran Venkateshkumar , Lang Zhongling , Clotet Anna , Poblet Josep M. , Johnson Grant , Laskin Julia
Published: February 2020

Molecular-level understanding of electrochemical processes at nanostructured electrode-electrolyte interfaces (EEI) is key to the development of clean and sustainable electrochemical technologies in energy generation and storage as well as water and chemical separation and purification. Herein, we introduced a novel in situ electrochemical cell coupled with ion soft landing to study the precisely defined operating EEI. Ion soft landing is a mass spectrometry based deposition technique which enables to land uniform layers of redox-active ions onto electrode surfaces with precise control over the charge state, composition, and kinetic energy. In this work, we used ion soft landing to study (i) the multi-electron redox activity of Keggin polyoxometalate anions (POMs) to design high-performance EEIs for energy storage (ii) examined how “atom-by-atom” metal substitution affects the redox activity of well-defined mixed addenda POM anions, PMoxW12-xO40
3- (x = 0,1,2,3,6,9,12) at ionic liquid based in situ electrochemical cell. We made a striking observation in in situ experiment and well-supported by theoretical calculation, which is that substantial increase in the first reduction potential obtained by substitution of only few tungsten by molybdenum atoms in the PW12O40
3- anions. More specifically, PMo3W9O40
3- showed the highest redox activity compared to all other mixed-addenda POM anions, which making it as a “super active redox anion” for this class of redox species. This presentation will also focus how these fundamental understanding on the activity of mixed addenda POMs was translated well into achieving device-level supercapacitor performance with superior capacity and capacity retention.
High Energy SAXS-Waxs Studies on the Fluid Structure of Molten LiCl-Li Solutions
Authors: Guo Jicheng , Merwin Augustus , Benmore Chris , Mei Zhi-Gang , Hoyt Nathaniel C. , Williamson Mark A.
Published: February 2020

Molten mixtures of lithium chloride and metallic lithium (LiCl-Li) play an essential role in the electrolytic reduction of various metal oxides. These mixtures possess unique high temperature physical and chemical properties that have been researched for decades. However, due to their extreme chemical reactivity, no study to date has been capable of definitively proving the basic physical nature of Li dissolution in molten LiCl. In this study, the evolution of structures of the molten LiCl-Li, as metallic Li is electrochemically introduced into the melt, is investigated in situ using synchrotron radiation based high energy wide angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The scattering results indicate the presence of Cl- ion “cages” with size of approximately 7.9Å, which suggests the formation of Li nanoclusters as previous reported. The structure factor of the melt derived from the SAXS results is in agreement with that obtained from ab-initio molecular dynamics (AIMD) simulation of lithium nanoclusters (Li4, Li6 and Li8) in LiCl. A physical model based on the formation and suspension of metallic Li nanocluster in lithium chloride is proposed to explain various phenomena exhibited by these solutions that were previously unexplainable.

The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan
(Invited) Discovery of New Capacity Fade Mechanism in Lixsn Batteries with Derivative Operando (dOp) NMR Spectroscopy
Authors: Lorie Lopez Jose L. , Grandinetti Philip J. , Co Anne C.
Published: February 2020

Tin, silicon and other intermetallic forming electrodes have large volumetric lithium capacities—nearly 10 times that of graphite. Such a high capacity combined with their low cost make intermetallics promising materials for the next generation of rechargeable batteries. Unfortunately, severe capacity fade remains the greatest obstacle in their commercial use. For example, in 2005 Sony introduced their NEXELION battery technology using nanostructured SnCo electrodes but eventually had to pull these batteries from the market due to substantial capacity loss with cycling. While a major reason for capacity fade in these electrodes is thought to be cracking from large volume changes during transitions between intermetallic phases, little evidence for cracking in nanostructured electrodes has been found; and the mechanism for capacity fade in nanostructured intermetallic electrodes has remained a mystery.

Using derivative operando (dOp) 7Li NMR we have discovered a mechanism for capacity fade in LixSn nanoparticle electrodes that may solve this mystery. In short, the capacity fade in nanoparticle electrodes is the result of nanopar- ticles losing contact with the carbon/PVDF binder. Yet, it occurs in a peculiar way which causes the cell to reach full capacity at the end of every cycle on lithiation. In other words, capacity fade only occurs during delithiation. We present clear NMR evidence showing that particle disconnection occurs during the delithiation (volume contraction of the electrode particles) process. During lithiation (volume expansion of the electrode particles) our NMR data further reveals that connected particles are surprisingly pushed back into contact with the disconnected particles which then rejoin the circuit and allow the cell to reach full capacity on lithiation. Our dOp 7Li NMR spectra also reveal the structural transformation pathways between Li-Sn intermetallics during lithiation and delithiation of Sn nanoparticles. The disconnecting particles are associated with LixSn phases undergoing large decreases in diameters on delithiation, i.e., Sn, Li2Sn5, LiSn, and Li7Sn3. The Li–Sn phases observed are somewhat consistent with the structural evolution expected from the equilibrium binary phase diagram, but there are some notable exceptions with the observation of a metastable phase Li2Sn3, and two vacancy rich metastable phases, Li7−ζSn3, and Li13−δSn5 during delithiation.

Although this new capacity fade mechanism is simple, we know no in-situ microscopy method capable of detecting and following such a disconnection-connection mechanism. Our approach clearly show the power of operando NMR spectroscopy for revealing such fundamental processes. These results point the way for future efforts in both industrial and academic research labs to reduce capacity fade in a wider range of nano-structured intermetallic electrodes, involving Si, Ge and Sb.

Figure 1
Graduate Electrochemistry Course Projects
Authors: Cliffel David E.
Published: February 2020

Electrochemistry as a discipline is taught comprehensively as a graduate course throughout the United States. With the increasing movement towards active learning environments in classrooms, this talk will highlighted several past and current models of including laboratory and computational components to augment the classical lecture format in the graduate electrochemistry course and a related advanced analytical sensors course. Significant challenges occur in “flipping the classroom” or other in vogue “SCALEUP” course models when a working knowledge of the field is very difficult to obtain from reading even the most accepted texts. Hybrid models incorporating out of class projects have been adapted to increase the relevance of the field to particular students while building up a working knowledge and experimental experience. The nature of these projects has shifted over the years to specific assignments to independently designed projects to team projects and back to individual ideas plus team help.
The Effects of Ultrasound on the Electro-Oxidation of Sulfate Solutions
Authors: Wallace Alexander George , McHugh Patrick J , Symes Mark
Published: February 2020

The electro-oxidation of sulfate solutions is a well-established route for the generation of powerful oxidants such as persulfate. Despite this, the effects of simultaneous ultrasound irradiation during this process has attracted little attention. In this talk, we investigate the effects of a low-intensity ultrasonic field on the generation of solution-phase oxidants during the electro-oxidation of sulfate solutions. Our results show that at high current densities and high sulfate concentrations, ultrasound has little effect on the Faradaic and absolute yields of solution-phase oxidants. However, at lower current densities and sulfate concentrations, the amount of these oxidants in solution appears to decrease under ultrasonic irradiation. A mechanism explaining these results is proposed, whereby anodically-generated sulfate and hydroxyl radicals are more effectively transported into bulk solution (where they are quenched) during sonication, whereas in the absence of an ultrasonic field these radicals combine with one another to form more persistent species (such as persulfate) that can be detected by iodometry.
Tripling the Energy Density of Insertion-Type Electrode Materials for Rechargeable Alkali-Ion Batteries By Introducing Carefully Selected Dopants
Authors: Ma Yanjiao , Passerini Stefano , Bresser Dominic
Published: February 2020

Targeting continuously increasing energy and power densities for the next generations of rechargeable alkali-ion batteries like lithium-ion and sodium-ion batteries (LIBs and SIBs), researchers worldwide are trying to develop new electrode materials which are capable of hosting more lithium/sodium ions per unit weight or volume.[1]–[4] Ideally, these new materials also allow for a fast delithiation/desodiation and, even more important, lithiation/sodiation, i.e., the charge step. This is a particular challenge for insertion-type materials, which are commonly used at present in commercial LIBs. In fact, it is frequently written that the insertion mechanism sets an intrinsic limit to the achievable lithium storage capacity.

Herein, we show that the introduction of carefully selected dopants provides the chance to double or even triple the capacity of insertion-type lithium- and sodium-ion anodes. Based on an in-depth characterization down to the atomic scale, we will moreover provide general guidelines for achieving such improvement and, eventually, present also their employment in high-performance lithium-ion and sodium-ion full-cells, offering an outstanding combination of high energy and high power, as shown in Figure 1 and Table 1.
[5]–[12]

References

[1] B. Scrosati, J. Garche, J. Power Sources
2010, 195, 2419.

[2] M.S. Whittingham, Chem. Rev.
2004, 104, 4271.

[3] N. Loeffler, D. Bresser, S. Passerini, M. Copley, Johns. Matthey Technol. Rev.
2015, 59, 34.

[4] J.-Y. Hwang, S.-T. Myung, Y.-K. Sun, Chem. Soc. Rev.
2017, 46, 3529.

[5] X. Su, J. Liu, C. Zhang, T. Huang, Y. Wang, A. Yu, RSC Adv.
2016, 6, 107355.

[6] X. Sun, X. Zhang, B. Huang, H. Zhang, D. Zhang, Y. Ma, J. Power Sources
2013, 243, 361.

[7] A. Varzi, D. Bresser, J. von Zamory, F. Müller, S. Passerini, Adv. Energy Mater.
2014, 4, 1400054.

[8] W. Wang, D. Choi, Z. Yang, Metall. Mater. Trans. A
2013, 44, 21.

[9] L. Shen, H. Lv, S. Chen, P. Kopold, P.A. van Aken, X. Wu, J. Maier, Y. Yu, Adv. Mater.
2017, 29, 1700142.

[10] H. Kim, M.-Y. Cho, M.-H. Kim, K.-Y. Park, H. Gwon, Y. Lee, K.C. Roh, K. Kang, Adv. Energy Mater.
2013, 3, 1500.

[11] V. Aravindan, J. Sundaramurthy, A. Jain, P.S. Kumar, W.C. Ling, S. Ramakrishna, M.P. Srinivasan, S. Madhavi, ChemSusChem
2014, 7, 1858.

[12] J. Xu, Y. Li, L. Wang, Q. Cai, Q. Li, B. Gao, X. Zhang, K. Huo, P.K. Chu, Nanoscale
2016, 8, 16761.

Figure 1
Dual-Functional Polymer Binders for Silicon Based Electrodes
Authors: Cao Pengfei , Li Bingrui , Sokolov Alexei P. , Nanda Jagjit , Saito Tomonori
Published: February 2020

As the “inert” materials in electrode, polymer binders play an important role in the long-term performance of silicon-based electrode. Several principles have been recognized to fabricate a “better” binder, there continues to be a lack of a rational design that would meet the robust criteria required for silicon (Si) anodes. Herein, we will present a synthetic polymer binder, i.e., catechol-functionalized chitosan cross-linked by glutaraldehyde (CS-CG+GA) that will serve both wetness-resistant adhesion capability via catechol grafting and mechanical robustness via in-situ formation of a three-dimensional (3D) network. The SiNPs based anode with the designed functional polymer network (CS-CG10%+6%GA) exhibits a capacity retention of 91.5% after 100 cycles (2144 ± 14 mAh/g). Properties which are traditionally considered to be advantageous, including stronger adhesion strength and higher mechanical robustness, do not always improve the binder performance. A semi-quantitative analysis on the main-chain scaling behavior and stiffness also demonstrated that both catechol grafting and crosslinking lead to the reduced flexibility of polymer backbone for the resultant binder system. It turns out that the end-to-end distance of the two adjacent crosslinking points (Re) should be no less than the persistence length (lp) of the chitosan backbone for an efficient binding performance. The relationship established between binder properties and electrochemical performance of consequent Si electrode is imperative for designing polymer binders with optimized electrochemical performance. The strategy of in-situ construction of a functional polymer network is instructive for the design of high-performance polymer binders not only for Si based anodes, but also for a wide variety of other types of alloy and conversion-based electrodes.

Figure 1
X-Ray Photoelectron Study of the Binder/Electrode Interface on Silicon Anodes for Lithium Ion Batteries
Authors: Johnson Richard , Waller Gordon H. , Nadimpalli Siva
Published: February 2020

Polymeric binders are a critical component of all composite electrodes used in today's lithium ion batteries (LIB). Binders keep active material and conductive additive mixture together, while also adhering this mixture to the current collector. At the particle level the binder forms bridges between particles of active material. Failure of these bridges contributes to electrical isolation of active material and thus poor cyclic life. the mechanical strength of these binder bridges is of key interest to understand the failure mechanisms of LIBs. Failure of binder bridges is highlighted in LIBs that incorporate Li-alloy forming anode materials such as Si which are known to degrade due to expansion and contraction during cycling. Meanwhile, the formation of solid electrolyte interphase (SEI) can also exacerbate capacity loss in novel anode materials, however the contribution of the binder to SEI formation and stability of alloying anodes has not been emphasized. Favorable interface properties between binder and active material resulting in good adhesion is desirable for anodes which encounter larger stresses during cycling.

The objective of this study is to understand the effect different polymer binders have on the nature, formation, and location of the SEI layer of silicon based anodes. In this study crystalline Si wafers coated with thin films of CMC and PVDF binders were utilized. No conductive additives were used. Half cells containing either bare crystal Si or a wafer with a thin film of CMC or PVDF were cycled in a standard lithium-ion electrolyte (1 molar LiPF6 in 1:1:1 vol. ratio of EC:DC:DMC) to form a stable SEI. After cycling, the cells were opened in an inert atmosphere and x-ray photoelectron spectroscopy (XPS) was carried out to analyze and compare the surface chemistries. Depth profiling was then conducted utilizing C-60 fullerene ions opposed to the conventional Ar ion milling probe due to the known issue of chemical degradation caused by the Ar ion milling. In addition, the morphology of the substrates and binder films were characterized by SEM.

Preliminary results indicate that binder layers on the order of hundreds of nm thick do not impede the lithiation and delithiation of Si (Figure 1A) but do play a role in the SEI composition (Figure B-D). These results can help inform the optimization of current and advanced composite electrodes for commercial LIB.

Figure 1
(Invited) Towards the Realization of Sustainable High-Performance Lithium-Ion Batteries: Aqueous Processing of Cobalt-Free High-Energy Cathodes
Authors: Kuenzel Matthias , Kazzazi Arefeh , Kim Guk-Tae , Bresser Dominic , Passerini Stefano
Published: February 2020

The recently rising awareness for a more sustainable cell manufacturing can be expected to gain even more momentum in sight of the announcements from major car manufacturers across Europe and North America to entirely electrify their fleet within the next half-decade1,2. The implementation of aqueous electrode processing strategies for lithium-ion cathodes is a key step to realize the environmentally benign battery production. To achieve this ambitious goal, most studies focus on the development of non-toxic and abundant active materials and specifically, the implementation of nature-derived, inexpensive binders in combination with the use of water as dispersion agent and solvent provides the great possibility to spare energy-intensive drying procedures and costly dry-room conditions, and thus, will turn the whole battery fabrication more eco-efficient 3,4.

What could easily be established for graphite anodes – employing water-soluble natural polymers as binder, thus, abolishing the need of toxic and rather costly N-methyl-2-pyrrolidone (NMP) as processing solvent3,5 – appears more complicated for transition metal oxide-based and imperatively cobalt-free cathode materials, which suffer from lithium leaching and transition metal dissolution when getting in contact with water, which has, so far, rendered the use of aqueous binders very challenging6,7.

In our group we recently demonstrated the general feasibility for the aqueous processing of several lithium-ion cathode materials, such as high-voltage LiNi0.5Mn1.5O4, by introducing a complementary approach, of suitable processing additives to stabilize the active material surface as well as the electrode/electrolyte/current collector interface8. Moreover, we extended our investigations to various binder systems and cathode materials in order to advance the aqueous electrode preparation and move from the well-established lab-scale process towards the fabrication of commercial-scale lithium-ion batteries9.

References

C. J. Barnhart and S. M. Benson, Energy Environ. Sci., 6, 1083 (2013).

D. Larcher and J. M. Tarascon, Nat. Chem., 7, 19–29 (2015).

D. Bresser, D. Buchholz, A. Moretti, A. Varzi, and S. Passerini, Energy Environ.
Sci. (2018) http://xlink.rsc.org/?DOI=C8EE00640G.

A. Kwade et al., Nat.
Energy, 3, 290–300 (2018) http://www.nature.com/articles/s41560-018-0130-3.

S. F. Lux, F. Schappacher, A. Balducci, S. Passerini, and M. Winter, J. Electrochem. Soc., 157, A320 (2010).

M. M. Thackeray, J. Am. Ceram. Soc., 82, 3347–3354 (1999).

N. Loeffler et al., ChemSusChem, 9, 1112–1117 (2016).

M. Kuenzel et al., ChemSusChem, 11, 562–573 (2018).

A. Kazzazi et al., ACS Appl. Mater. Interfaces, 10, 17214–17222 (2018).
Understanding the Electrochemical Performance of Rechargeable LiFePO4/Li4Ti5O12 Design Using Mathematical Model
Authors: Ma Miaomiao , Hendricks Christopher E. , Mansour Azzam N. , Ko Jonathan K. , Waller Gordon H. , Fuentevilla Daphne A.
Published: February 2020

A lithium-ion cell utilizing LiFePO4/Li4Ti5O12 electrodes has attracted interest as a result of its safe and fast charging performance. A commercially available software package, Battery Design Studio, was utilized to simulate the electrochemical performance of an LFP/LTO cell at different rates and temperatures to understand the charge transfer and diffusion processes of this electrode pairing. Open circuit potential curves for each electrode were obtained using galvanostatic intermittent titration technique (GITT) as a base for modeling. Simulation of the High Pulse Power Characterization (HPPC) test data on a 26650 cell showed that the pulse discharge was affected by six parameters, including ohmic resistance, capacitance, SEI resistance, electrode conductivity, electrolyte diffusion, and electrode diffusion. These parameters were obtained by comparing the experimental data with the model predictions at various SOC and temperatures to demonstrate their SOC and temperature dependence. Sensitivity of parameters was evaluated within the range of the reference values.

To further evaluate the dependence of these parameters on SOC and temperature, AC impedance measurements were performed on the full cell at different SOC and temperatures during both charge and discharge processes as shown in Figure 1. Analyses of impedance results indicated the charge and discharge processes undergo different charge transfer processes and diffusion in both the electrolyte and solid phase. AC impedance on half-cell coin cells was performed to understand the contribution from each electrode.

Finally, the electrochemical model was utilized to understand the performance limitations and failure mechanisms of the LFP/LTO cell though the current and concentration distributions throughout the electrode thickness.

Figure 1. AC impedance measurement on LFP/LTO 26650 cell at different SOC during charge and discharge processes at room temperature.

Reference:

[1] M. Doyle, T. F. Fuller, and J. Newman, J Electrochem Soc, 140, 1526 (1993).

[2] V. Ramadesigan, P. Northrop, S. De, S. Santhanagopalan, R. Braatz, and V. Subramanian, J Electrochem Soc, 159, R31 (2012).

Acknowledgement:

This work is funded by the Office of Naval Research under award N0001419WX01258.

Figure 1
X-Ray Absorption Spectroscopy of SrTi0.65Fe0.35O3-Δ : Understanding Local Structure Evolution during Crystallization
Authors: Skiba Emily , Ma Qing , Perry Nicola H.
Published: February 2020

Mixed ionic and electronic conductors (MIECs) serve as active materials and electrodes in a variety of electrochemical energy conversion, storage, processing, and sensing devices. Compared to composites of an ionic conductor and electronic conductor, single phase perovskite-structured MIECs that conduct both oxide ions and electronic species extend the reaction site for surface oxygen exchange beyond the triple phase boundaries and can exhibit high efficiencies. There has been increasing interest in lower temperature processing and application of MIECs. Therefore, there is a significant need to understand the local structure of amorphous and crystallizing MIECs so that structure-property relationships pertaining to electrode function (surface exchange kinetics, conductivity) can be established. To this end, we have studied the model MIEC SrTi0.65Fe0.35O3-d (STF).

To better understand the role of crystallization on local structure evolution of STF films, X-ray absorption spectroscopy (XAS) studies at Argonne National Laboratory’s DND-CAT beamline were carried out on films at various stages of crystallization. Three films were deposited using PLD at several temperatures to control crystallinity: 1) room temperature (amorphous), 2) room temperature and subsequently annealed for 2h at 550 °C (semi-crystalline), and 3) at a substrate temperature of 700 °C (highly crystalline). Our experiments observed the Sr, Fe, and Ti K-edges using XAS to compare the local structure (valence states, coordination environment, and bond lengths) of amorphous, semi-crystalline, and crystalline STF thin films. Our results to date suggest significant differences in the first shell mean bond length and coordination environment of Fe and Ti polyhedra. Although it is widely assumed that the local environment of amorphous and crystalline materials is similar, with the main distinction being in the long-range ordering, our results show that the amorphous samples are significantly undercoordinated relative to their crystalline counterparts. Furthermore, we observe that the Ti-O and Fe-O coordination number increases with increasing crystallinity. However, it appears that even in the fully crystalline samples, there remain tetrahedrally coordinated cation centers with Fe atoms having, across all samples, more oxygen vacancies than Ti atoms within the same film.