bluuebunny/crossref_metadata_2025 huggingface dataset:
(Keynote) Detecting the Elusive Adsorbed CO2
·- Intermediate on a Copper Electrode Using Operando Raman Spectroscopy and Pyridine As a Promoter: Implication for CO2 Electroreduction
Authors: Chernyshova Irina , Somasundaran Ponisseril , Goldman Mark , Ponnurangam Sathish
Published: February 2020

Electrochemical conversion of the abundant CO2 to fuels, polymers, drugs, and other materials using renewable energy is one of the most promising approaches that can help deploy this energy and reduce our dependence on fossil fuels. However, the rational development of a viable CO2 electroreduction system is hampered by a daunting lacunae in the mechanistic knowledge of this reaction. This is especially true with respect to the knowledge derived from experimental (electrochemical and operando spectroscopic) data. The problem stems from the complexity of both CO2 electroreduction per se and the great technical challenges to detect and identify the key reaction intermediates in operandi
exactly on the same catalyst that is employed in the preparative electrolysis studies.

We address this technical challenge by employing advantages of the electrochemical surface-enhanced Raman scattering (SERS) method, which have been neglected in the earlier attempts to gain mechanistic insights into CO2 electroreduction. These advantages include the outstanding sensitivity of SERS to the species adsorbed on the ‘hot spots’ and the ability of this method to detect these species on real electrocatalysts in real time. Specifically, combining this method with Density Functional Theory (DFT) simulations and employing pyridine as the reaction promoter, we resolve the long-standing controversies about the mechanism of the formate and CO synthesis on a polycrystalline copper electrode in aqueous electrolytes, as well as on the promoting effects of pyridine. Correlating the microscopic results with the electrolysis and electrochemical data, we conclude that the formation of the CO2
•
d- intermediate is the rate-determining step of the formate synthesis on Cu, while formate and CO share the same route.
Hierarchical and Selective Systems for Photoelectrochemical and Electrocatalytic Reduction of Carbon Dioxide
Authors: Kulesza Pawel J , Rutkowska Iwona Agnieszka , Solarska Renata , Szaniawska Ewelina , Wadas Anna , Bienkowski Krzysztof
Published: February 2020

There has been growing interest in the photoelectrochemical conversion of carbon dioxide (a potent greenhouse gas and a contributor to global climate change) to useful carbon-based fuels or chemicals. The reaction products are of potential importance to energy technology, food research, medical applications and fabrication of plastic materials. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. It is often postulated that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate. In this respect, the proton availability and its mobility at the photo(electro)chemical interface has to be addressed. On the other hand, competition between such parallel processes as hydrogen evolution and carbon dioxide reduction has also to be considered.

Recently, we have concentrated on the development of hybrid materials by utilizing combination of metal oxide semiconductors thus capable of effective photoelectrochemical reduction of carbon dioxide. For example, the combination of titanium (IV) oxide and copper (I) oxide has been considered before and after sunlight illumination. Application of the hybrid system composed of both above-mentioned oxides resulted in high current densities originating from photoelectrochemical reduction of carbon dioxide mostly to methanol (CH3OH) as demonstrated upon identification of final products. Among important issue is intentional stabilization, activation, and functionalization of the mixed-metal-oxide-based photoelectrochemcal interface toward better long-term performance and selectivity production of small organic molecules (C1-C4) and other chemicals. In this respect, ultra-thin films of conducting polymers (simple or polyoxometallate-derivatized) and supramolecular complexes (with nitrogen containing ligands and certain transition metal sites), sub-monolayers of metals (Cu, Au), networks of noble metal (Au, Ag) nanoparticles or layers of robust bacterial biofilms have been considered.

The photo-biocathode with Cu-containing enzyme has induced the reduction of not only oxygen but carbon dioxide as well, under illuminations with photon energies higher than silicon band gap.

In the presentation, special attention will be paid to mechanistic aspects of electroreduction of carbon dioxide, fabrication and characterization of highly selective and durable semiconductor photoelectrode materials and to importance of the reaction conditions.
(Invited) Specific Metal-Metal Oxide Interactions in Efficient Electroreduction of Carbon Dioxide
Authors: Rutkowska Iwona Agnieszka , Kulesza Pawel J
Published: February 2020

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of carbon nanostructures and noble metal nanoparticles, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential attraction) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties (e.g. toward reduction of CO2). We explore here the ability of polynuclear inorganic systems to stabilize and derivatize metal and carbon nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, zinc or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ag, Au, Pd, Pt or Ru) thus affecting their chemisorptive and catalytic properties. Metal oxide nanospecies can generate –OH groups at low potentials that induce proton mobility at the photo(electro)chemical interface.

Our research interests concern development of systems for the reduction (conventional/electrocatalytic or photoelectrochemical) of carbon dioxide. For example, nanosized Cu or Au naoparticles immobilized within ultra-thin films of tungsten oxide or zirconia have been considered. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities.

When it comes to photoelectrochemical reduction, we are also going to demonstrate utility of zirconia or zinc oxide over-layers on copper(I) oxide photocathodes irradiated with visible light in aqueous solutions. The possibility of generation of localized surface plasmons with use of gold or silver nanoparticles, will also be considered. Special attention will be paid to stability and controlled reactivity of the proposed systems.
(Keynote) Oxide Semiconductors, Solid-State Chemistry, and Photoelectrochemistry: A Nexus
Authors: Rajeshwar Krishnan
Published: February 2020

Solid-state chemistry languished as an esoteric discipline till interest exploded on the so-called high-Tc superconductor materials; oxides were discovered to have unique properties in this regard. Paralleling this was the gradual realization that solid-state chemistry principles underpinned many technologically-important areas such as batteries, supercapacitors, and even solar cells. The culmination of this trend was in the application of solid-state chemistry to the preparation and characterization of electrode materials in photoelectrochemical (PEC) cells.

This perspective talk will examine how solid-state chemistry principles have contributed both to the design and synthesis of photoelectrode materials for PEC applications related to water splitting, CO2 reduction, and environmental remediation. The design of new-generation oxide semiconductors with the correct optoelectronic and bulk/interfacial chemistry characteristics needed to efficiently drive the above reactions will be addressed. The list of material pre-requisites for efficient solar fuels generation or photocatalytic degradation is daunting and it is hardly surprising that a “magic bullet” material has not emerged even after 4 decades of R&D effort. However, these same challenges have attracted researchers drawn from diverse communities including solid-state/device physics, photophysics/photochemistry, colloid chemistry, ultra-fast spectroscopy, classical inorganic chemistry, environmental chemistry and organometallics.

To keep the discussion coherent, only a very limited subset of topics will be addressed in this talk. The progression from binary to ternary, and even quaternary oxides will be examined from the perspective of “band-gap engineering” (a much-maligned word!) and tuning of the interfacial semiconductor surface/fluid energetics. Examples will be drawn from recent research in the speaker’s laboratory and with collaborators.1-4

Acknowledgements

The author thanks his collaborators, particularly, Prof. Csaba Janaky (University of Szeged, Hungary) and the National Science Foundation (CHE- 1303803) for partial funding support.

References

1. K. Rajeshwar, C. Janaky, W-Y. Lin, D. A. Roberts and W. A. Wampler, “Photocatalytically Prepared Metal Nanocluster-Oxide Semiconductor-Carbon Nanocomposite Electrodes for Driving Multielectron Transfer,” J. Phys. Chem. Lett.
4. 3468-3478 (2013) (Perspective).

2. K. Rajeshwar, C. Janaky and A. Thomas, “Photocatalytic Activity of Inorganic Semiconductor Surfaces: Myths, Hype, and Reality,” J. Phys. Chem. Lett.
6, 139-147 (2015) (Viewpoint).

3. C. Janaky and K. Rajeshwar, “The Role of (Photo)Electrochemistry in the Rational Design of Hybrid Conducting Polymer/Semiconductor Assemblies: From Fundamental Concepts to Practical Applications,” Prog. Poly. Sci.
43, 96-135 (2015).

4. K. Rajeshwar, C. Janaky and E. Kescenovity, “Electrodeposition of Inorganic Oxide/Nanocarbon Composites: Opportunities and Challenges,” ChemElectroChem
3, 181-192 (2016).
Highly Active and Selective Au Thin Layer on Cu Polycrystalline Surface Prepared By Galvanic Displacement for the Electrochemical Reduction of CO2 to CO
Authors: Guo Wen , Woo Hyunje , Kim Yong-tae
Published: February 2020

An electrochemical reduction of CO2 to CO has become a challenging issue in CO2 utilization in order to mitigate the climate change. In this study, we report a promising approach to prepare Au-based electrocatalysts for the electrochemical reduction of CO2 to CO having the maximized activity/selectivity and the minimized Au usage. It was clearly confirmed that the Au thin layer formed by the electrochemical galvanic displacement on polycrystalline Cu surface resulted in a markedly enhanced performance for the electrochemical reduction of CO2 to CO. The CO Faradaic efficiency for the Au thin layer on Cu was 10.6 and 3.4 times higher than that for the polycrystalline Cu and Au, respectively. It was revealed from the photoemission spectroscopy (PES) studies that the increase of electron population in s-band and the upshift of d-band center position of Au in Au/Cu increased the bond strength with reaction intermediates leading to the enhancement of activity and the selectivity. Along with the electronic effect, the geometric effect like the increased the electrochemical surface area (ECSA) and proportion of low coordinated sites also played a substantial role in the performance enhancement.
Interplay of Mass Transfer and Local pH Effects in CO2 Reduction Electrocatalysis
Authors: Raciti David , Wang Chao
Published: February 2020

Here we report on the study of mass transfer and local pH effects on CO2 reduction by using Cu nanowires as the electrocatalysts. Highly dense Cu nanowires were synthesized by first thermal oxidation of Cu mesh in air, and then reduction by applying a cathodic electrochemical potential or thermal annealing in a reducing atmosphere (see the Methods). Our previous report has shown that the electrochemically reduced (ECR) Cu nanowires are highly active for CO2 reduction, with favorable production of CO and formate at potentials more positive than ‒0.5 V (versus reversible hydrogen electrode; the same potential scale is used in the following discussion) and C2 species (ethanol, ethylene, and ethane) at more negative potentials. In this work, we performed more systematic studies in the high-overpotential region, i.e., potentials more negative than ‒0.5 V, where the mass transport of CO2 and high local pH near the electrode surface are believed to play a significant role in determining the electrocatalytic performance. We aimed to examine the interplay between the mass transfer and local pH effects in the electrocatalysis for CO2 reduction and elucidate their roles in the structure-performance relationships of the high-surface-area nanowire catalysts. The ultimate goal is to explore the optimal electrochemical conditions for CO2 reduction to produce valuable C2 products.
Nanoporous Cu Thin Films for Electrochemical CO2 Reduction
Authors: Pounds Tyler D. , Benn Ellen , Wang Chao , Erlebacher Jonah
Published: February 2020

Copper catalysts have been extensively researched as catalysts for electrochemical reduction of CO2 (CO2RR) due to their capability to catalyze production of hydrocarbons. The selectivity and activity of Cu catalysts for CO2RR are greatly dependent on the surface structure of the catalysts, and due to this dependence, many forms of Cu (ranging from high quality single crystals to densely populated arrays of supported nanostructures) have been investigated as CO2RR catalysts.

Nanoporous (np) metals, which are produced through selective dissolution of an element from a parent alloy or compound, have inherent properties not typically present in other nanostructured materials that can strongly affect their catalytic properties, including concave surfaces with unique surface structures and open porosity that can cause mass transport effects during catalysis. Nanoporous Au and Ag, have been demonstrated as efficient and selective catalysts for oxidation of CO and reduction of CO2 to CO relative to their bulk metals. However, np-Cu has yet to be comprehensively studied as a CO2RR catalyst. To date, np-Cu has been primarily produced from homogeneous bulk materials which are not well suited for practical use as a potential CO2RR catalyst due to long dealloying treatments required to produce np-Cu that remains stable, without continued dealloying of the non-noble metal, at low CO2RR overpotentials.

In this work, we demonstrate new electrochemical methods for producing fully dealloyed thin films of high-quality, crack-free np-Cu on inert substrates in significantly shorter processing times compared to bulk samples. We examine the activity and selectivity of np-Cu film catalysts produced by several dealloying methods for CO2RR. These results are presented in relation to other Cu catalysts with focus on the catalytic effects of the unique structural properties of np-Cu and the effects of post dealloying treatments to tune pore and ligament sizes of the np-Cu films. In addition to np-Cu films, we discuss how the presented techniques offer a path for production of stable thin films of other nanoporous metals on complex geometries.

This work is supported by the Department of Energy award number DE-SC0008686.
Oxygen Reduction Reaction Catalytic Sites on Carbon-Coated Fe3C Catalyst
Authors: Reda Mateusz , Hansen Heine A. , Vegge Tejs
Published: February 2020

Proton-exchange membrane fuel cells (PEMFC) are promising chemical-to-electrical energy conversion devices which can potentially replace combustion engine in automobiles. Their commercialization is currently suppressed primarily due to the price of the platinum catalyst for the cathodic oxygen reduction reaction (ORR). Required platinum loading per fuel-cell car is about 10 times higher than for the conventional one [1], which results in a significant contribution to the car price. Therefore, either the platinum loading needs to be drastically decreased, or a stable and active non-precious metal catalyst has to be developed.

Recently, a new type of ORR catalyst composed of carbon-coated iron carbide nanoparticles has been synthesized [2]. It exhibits only slightly lower activity than, and comparable durability to platinum in acidic solutions. It has been suggested that a new ORR catalytic site may have been discovered [3]. In this work we study the catalyst by means of the Density Functional Theory to identify its active sites.

Spin-polarized DFT calculations are performed using the Vienna Ab Initio Simulation Package (VASP) with PAW potentials, BEEF-vdW exchange-correlation functional [4], plane wave cutoff of 400 eV and vacuum layer of 14 Å. The model system consists of Fe3C/carbon interface and a few explicit water molecules to model the liquid environment. The following factors influencing the activity are taken into account: (i) thickness of the carbon layer (single- or multilayer graphene), (ii) defects in the carbon structure, (iii) nitrogen doping, (iv) adsorbate coverage, (v) presence of spectator adsorbates. A few other catalyst structures, which are independent of the presence of iron carbide, but still may exist in the real system, are also studied. These include catalysts with porphyrin-iron moiety embedded in the graphene structure and defective graphene with or without nitrogen doping. As a result, a few possible structures of catalytic sites in the carbon-coated Fe3C catalyst are proposed.

[1] H.A. Gasteiger, D.R. Baker, R.N. Carter, W. Gu, Y. Liu, F.T. Wagner, P.T. Yu, in Hydrogen and Fuel Cells: Fundamentals, Technologies and Applications (D. Stolten, Ed.) Ch. 1 p. 3, Wiley-VCH, Weinheim, 2010.

[2] Y. Hu, J. O. Jensen, W. Zhang, L. N. Cleemann, W. Xing, N. J. Bjerrum, Q. Li, Angew. Chem. Int. Ed., 2014, 53, 3675.

[3] J.-P. Dodelet, R. Chenitz, L. Yang, M. Lefèvre, ChemCatChem, 2014, 6, 1866.

[4] J. Wellendorff, K.T. Lundgaard, A. Møgelhøj, V. Petzold, D.D. Landis, J.K. Nørskov, T. Bligaard, K.W. Jacobsen, Phys. Rev. B, 2012, 85, 235149.
(Invited) Fick's II Law and Deploying Spatially Varying Diffusion Coefficients on Electrodes
Authors: Knoche Krysti L. , Landgren Jeffrey , Leddy Johna
Published: February 2020

In typical applications of electrochemistry, Fick's second law for diffusion is established with spatially invariant diffusion coefficients. However, when the diffusion coefficient is spatially dependent, D(x), Fick's second law in one dimension, as shown below, introduces opportunities to control transport.

When the diffusion coefficient varies spatially and the solution is quiescent, steady state flux of the diffusant is possible. Films of nonuniform density and viscosity on electrodes provide a matrix to establish domains with spatially varying diffusion coefficients. To explore impacts of D(x) on probe transport through films under voltammetric perturbation, several inquiries were undertaken.

The impact of spatially varying diffusion coefficients is simulated by explicit finite difference for a redox probe moving through a graded film on an electrode. Voltammetric morphologies vary with the structucture of the gradient. Sigmoidal voltammograms result as cyclic voltammetric scan rate slows.

Graded diffusion coefficients are established on electrodes by modification of density gradient polymers such as Ficoll^{®}. Sigmoidal voltammograms with limiting currents independent of scan rate are observed at slow scan rates, consistent with steady state transport in a domain where the diffusion coefficient is spatially varying.

Ion exchange polymer Nafion cocast with a graded density polymer similarly impacts transport of a probe through the graded Nafion film and sigmoidal voltammograms are observed.

The interplay between Fick's second law with spatially varying diffusion coefficients; simulation of voltammetry with D(x); and implementation of graded diffusion coefficients on electrode modification by Ficoll and by Ficoll-Nafion composites will be presented.

Figure 1
(Invited) In Situ FTIR Reflection Spectroscopy and Its Applications
Authors: Zhou Zhi-You , Li Jun-Tao , Jiang Yan-Xia , Sun Shi-Gang
Published: February 2020

In situ FTIR reflection spectroscopy (in situ FTIRS) can probe both surface and solution species involved in electrochemical reactions, and is powerful in characterization of interfaces and studies of electrode reaction mechanism at a molecule level. This communication reviews our recent progresses in developing in situ FTIR reflection spectroscopy, including microscope FTIR reflection spectroscopy (MFTIRS), step-scan fast time-resolved FTIR reflection spectroscopy (SSTRFTIRS) and the surface combinatorial analysis method by combining the MFTIRS with an individually addressable array of microelectrodes. Selected examples of using these advanced techniques in studies of electrochemical reactions such as electroadsorption of different molecules, electrocatalytic reactions of different fuels and amino acids, as well as interfacial reactions involved in a lithium ion battery will be demonstrated. In addition, the first infrared free electron laser and spectroscopic facilities for energy chemistry studies built up in China will be briefly introduced.

Acknowledgement: The study was supported by NSFC (21621091, 21327901)

References:

Ye, J.Y., Jiang, Y.X., Sheng, T., Sun, S.G. Nano Energy, 2016, 29, 414.

Huang, L., Sun, J.Y., Cao, S.H., Zhan, M., Ni, Z.R., Sun, H.J., Chen, Z., Zhou, Z.Y., Sorte, E.G., Tong, Y.Y.J., Sun, S.G. ACS Catal., 2016, 6, 7686.

Liu, H.X., Tian, N., Ye, J.Y., Lu, B.A., Ren, J., Huangfu, Z.C., Zhou, Z.Y., Sun, S.G. Faraday Discus. 2014, 176, 409.

Lin, J.L., Ren, J., Tian, N., Zhou, Z.Y., Sun, S.G. J. Electroanal. Chem. 2013, 688, 165.

Li, J.T, Zhou, Z.Y.; Broadwell I., Sun, S.G. ACR, 2012, 45, 485.

Zhou, Z.Y., Huang, Z.Z., Chen, D.J., Wang, Q., Tian, N. and Sun, S.G. Angew
.
Chem
.
Int
.
Ed
., 2010, 49, 411.

Cheng, Q., Jiang, Y.X., Tian, N., Zhou, Z.Y. and Sun, S.G. Electrochim Acta, 2010, 55 , 8273.

Li, J.T., Chen, S.R., Ke, F.S., Wei, G.Z., Huang, L. and Sun, S.G. J Electroanal Chem, 2010, 649, 171.

Zhou, Z.Y., Chen, D.J., Li, H., Wang, Q., and Sun, S.G. J. Phys. Chem. C, 2008, 112: 19012.

Chen, Q. S., Sun, S.G., Zhou, Z.Y., Chen, Y.X., Deng, S.B. Phys. Chem. Chem. Phys., 2008, 10, 3645.

11. Li, J.T., Chen, S.R., Fan, X.Y., Huang, L., Sun, S.G. Langmuir, 2007, 23: 13174.
Operando Grazing Incidence X-Ray Diffraction and X-Ray Absorption Spectroscopy for Electrochemical CO2 Reduction on Aupd, Pd and Au Electrodes
Authors: Landers Alan Taylor , Feaster Jeremy T , Farmand Maryam , Lin John , Fackler Sean , Higgins Drew Christopher , Nishimura Yusaku , Davis Ryan C. , Mehta Apurva , Hahn Christopher , Yano Junko , Jaramillo Thomas F , Drisdell Walter
Published: February 2020

The electrochemical reduction of carbon dioxide to fuels and chemicals using electricity produced from renewable sources represents an appealing approach to creating a carbon neutral fuel cycle or carbon negative chemical production pathway. However, a lack of fundamental understanding of the surface of the catalyst during electrochemical experiments hinders the development of more active catalysts. Recent reports indicate that the surface of the catalyst can change drastically under reducing conditions, suggesting that the active form may differ from the catalyst as characterized ex situ. Consequently, accurately probing the surface of the catalyst under operando conditions is critical to observing structural and electronic changes in the catalyst, allowing key insights into the carbon dioxide reduction reaction. We report the design and development of such operando experiments at the Stanford Synchrotron Radiation Lightsource using grazing incidence x-ray diffraction and grazing incidence x-ray absorption spectroscopy. Using these techniques, we study changes in the surface physical and electronic structure of thin film Au, Pd, and AuPd catalysts during electrochemical carbon dioxide reduction.
In-Situ Gracing Incidence X-Ray Diffraction Cell for Electrochemically Formed Thin Films
Authors: Reither Sabine , Artner Werner , Eder Andreas , Larisegger Silvia , Nelhiebel Michael , Eisenmenger-Sittner Christoph , Fafilek Günter
Published: February 2020

Grazing incidence X-ray diffraction allows surface sensitive measurements of structural and phase properties of thin solid films. For the characterization of layers formed during electrochemical processes ex-situ techniques are usually employed which has the requirement of a stable structure and composition of the formed films even at atmospheric conditions. For cases where this requirement is not met, in-situ techniques have been developed. Existing designs of in-situ electrochemical cells normally have the disadvantage of high absorption of the beam in the setup and/or brittle window materials. The problem of high absorption of the X-ray in the setup is normally compensated by either using very thin electrolyte films or high intensity radiation as is provided by a synchrotron.

This work presents a novel solution for a grazing incidence X-ray diffraction setup. Backside-illumination of a thin film working electrode applied on a Mylar® foil by magnetron sputtering as support is used to eliminate the problem of high absorption of the X-ray in the setup. It can be used in a three electrode setup and tackles the common problems of gas evolution, voltage drop and non-constant electrolyte bulk solution in in-situ X-ray setups. The setup is tested on the anodic and cathodic formation of Cu2O on copper as an example for X-ray irradiation from a Lab-scale (not synchrotron) source.

Acknowledgement:

This work was jointly funded by the Austrian Research Promotion Agency (FFG, Project No. 854247) and the Carinthian Economic Promotion Fund (KWF, contract KWF-1521/28101/40388).
(Invited) Benefits of Borohydride- and Glyme-Containing Electrolytes for Improved Magnesium Anode Behavior
Authors: Buttry Daniel A , Kumar Ashok
Published: February 2020

Our group has been involved in studies of the complexation and speciation of Mg2+ in ionic liquids as a means to understand the influence of coordination environment on Mg anode electrochemical behavior.1,2 As part of those efforts, we showed the beneficial effects of borohydride and glyme electrolytes for improved magnesium anode behavior. In this presentation we will focus on the complexation of Mg2+ by glyme components in electrolytes and chemical reactivity of borohydride anion on the reversibility of Mg electrodeposition/dissolution. We show that the lessons learned from such studies of Mg2+ complexation allow the design of new chelating ionic liquids that show markedly improved Mg2+/Mg0 electrochemical behavior compared to the parent TFSI-based ionic liquids. Specifically, we describe reasonable coulombic efficiency and current densities that are achievable through judicious choice of the complexation environment and other chemical features of the electrolyte system.

We also discuss more generally the factors that act to suppress facile Mg electrodeposition/dissolution. We provide experimental verification of some of the means by which these various factors influence both chemical and electrochemical reversibility of Mg anode behavior.

Acknowledgment We acknowledge support from the Army Research Office grant number W911NF-11-1-0432.

References:

“Determination of Mg2+ Speciation in a TFSI--Based Ionic Liquid With and Without Chelating Ethers Using Raman Spectroscopy”, Watkins, T., Buttry, D. A.; J. Phys. Chem. B, 2015, 119(23), 7003-7014. (DOI: 10.1021/acs.jpcb.5b00339)

“Designer Ionic Liquids for Reversible Electrochemical Deposition/Dissolution of Magnesium”, Watkins, T.; Kumar, A.; Buttry, D.A.; J. Am. Chem. Soc.,
2016, 138(2), 641-650 (DOI: 10.1021/jacs.5b11031)
(Invited) Structure-Function Relationships in Electrolytes for Reversible Magnesium Batteries
Authors: Bartlett Bart M.
Published: February 2020

Despite the highly touted goals of moving beyond Li-ion batteries for electrochemical energy storage, lithium-based technology remains king of the hill. Moving to magnesium, which is similar in size but carries out two-electron chemistry, is hampered in part due to the paucity of suitable electrolytes. The most widely published reports on magnesium electrolytes are composed of air- and moisture sensitive Grignard reagents, which decompose to form electron-insulating layers on either platinum or glassy carbon electrodes. Recent work in our group has unfurled structure-activity relationships in a series of salts formed from ROMgCl (R = phenolate or t-butoxide) and AlCl3 in THF solvent. A transmetalation reaction gives rise to the cationic species [Mg2(μ-Cl)3(thf)3]+ and a series of chloro- and alkoxy-aluminate anions in equilibrium at room temperature. We find that adding fluorinated substituents maximizes the anodic stability, and adding steric bulk maximizes solution conductivity. Accordingly, our most promising candidate is the combination of 1.2 M (CF3)2(CH)3COMgCl with 0.2 M AlCl3, which shows anodic stability on to 3.2 V vs. Mg2+/0 on a platinum working electrode with a solution conductivity of 3.5 mS/cm, both of which are competitive with electrolytes used in lithium-ion chemistry. Not surprisingly, this electrolyte shows lowest Tafel slope for dendrite-free magnesium metal deposition, ~ 80 mV/dec. Moreover, it supports reversible cycling of Chevrel phase Mo3S4
vs. Mg metal in 2016-type coin cells.
(Invited) Electrodeposition and Development of Mg and Ca Metal Anodes
Authors: Ponrouch Alexandre
Published: February 2020

Various metals have been used as battery anodes in electrochemical cells ever since the birth of batteries with Volta’s pile and also in the first commercialized primary (Zn/MnO2, Leclanché 1866) and secondary (Pb/acid, Planté 1859) batteries. The idea and prospects of building a technology based on lithium are much more recent, as it required moving away from aqueous electrolytes. However, the first Li-MoS2 cells with specific energy two or three times higher than the current Ni/Cd or Pb/acid cells were withdrawn from the market after safety difficulties were experienced with overheating on recharge related to dendrite growth. As an alternative, secondary Li-ion batteries avoiding the use of lithium metal anodes were commercialized by Sony in 1991. In contrast with Li metal anode, electrodeposition of Mg and Ca does not seem to be plagued with dendrite formation.1,2 In addition to the low cost of the raw materials ($5000/ton, $100/ton and $265/ton for Li2CO3, CaCO3 and MgO2, respectively), such alternative technologies would benefit from high standard reduction potentials (ca. -2.87 V and -2.37 V vs NHE for Ca and Mg, respectively, as compared to -3 V for Li) and high theoretical electrochemical capacities (both gravimetric and volumetric) for the metal electrode, while relying on the 5th (Ca) and 8th (Mg) most abundant elements on the Earth’s crust, respectively, whereas Li is the 25th. These metals are thus interesting candidates as anodes in rechargeable batteries.

Pioneering research work by Aurbach et al.3,4 allowed to conclude that the electrochemical behavior of Ca and Mg metal anodes in conventional organic electrolytes is surface-film controlled, as is the case for Li, but Ca and Mg plating is virtually impossible, which was attributed to the lack of divalent cation transport through the passivation layer (solid electrolyte interphase or SEI). Therefore, research has been focusing on electrolyte formulation in which no SEI is formed. Recently Ca plating and stripping through a stable SEI layer has been demonstrated, setting out the basis for the development of new electrolytes for divalent cation based batteries with high resilience upon oxidation.2 The effect of several factors influencing the Ca deposition/stripping will be presented. Also, the reliability of the so called half-cell configuration in which Mg or Ca pseudo reference and counterelectrodes are used will be discussed and a systematic evaluation of the non-polarizability and stability in the electrolytic environment will be presented for these metal electrodes.

Fig
ure 1. Theoretical gravimetric and volumetric capacities for different anodes: metals and Li-ion.

References:

[1] M. Matsui, J. Power Sources 196 (2011) 7048.

[2] A. Ponrouch, C. Frontera, F. Bardé, M.R. Palacín, Nat. Mater. 15 (2016) 169.

[3]. D. Aurbach, R. Skaletsky, Y. Gofer, J. Electrochem. Soc. 138 (1991) 3536.

[4]. Z. Lu, A. Schechter, M. Moshkovich, D. Aurbach, J. Electroanal. Chem. 466 (1999) 203.

Figure 1
(Invited) Effect of Ni:Fe Stoichiometry and Architectural Expression on the Bifunctional Activity of Nanoscale Ni
y
Fe1–Y
ox
Authors: Ko Jesse S. , Chervin Christopher N. , Vila Mallory , DeSario Paul A. , Parker Joseph F. , Long Jeffrey W. , Rolison Debra R.
Published: February 2020

The efficient electrocatalysis of reactions involving molecular oxygen determines the performance of many electrochemical energy-storage and -conversion systems. Electrocatalysis of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was assessed for a series of Ni-substituted ferrites (Ni
y
Fe1–y
Ox, where y=0.1–0.9) prepared as high surface area nanoarchitectures using epoxide-based sol–gel chemistry. Wet gels were processed using either ambient-pressure or supercritical-fluid drying to render ambigel or aerogel nanoarchitectures, respectively. For this series of Ni
y
Fe1–y
Ox materials, we correlate electrocatalytic activity with Ni:Fe stoichiometry and nanoarchitecture. In order to ensure in-series comparisons, calcining at 350°C in air was necessary to crystallize the respective Ni
y
Fe1–y
Ox nanoarchitectures, which index to the inverse spinel structure for Fe-rich materials (y ≤ 0.33), biphasic for intermediate stoichiometries (0.5 ≤ y ≤ 0.67), and rock-salt for the most Ni-rich material (y = 0.9). For the OER, Ni-rich nanoarchitectures (y > 0.5) exhibit high activity (low overpotential, η), while both the ambigel and aerogel series in the intermediate Ni:Fe stoichiometry range (0.33 ≤ y ≤ 0.67) exhibit a monotonic increase in current density with progressively higher specific surface area. The commensurate OER activity obtained for ambigel and aerogel expressions across a given Ni:Fe stoichiometry highlights the fact that competitive electrocatalytic performance can be achieved without the additional complexity of supercritical-fluid extraction. We also find improved OER performance (η decreases from 390 to 373 mV) for Ni0.67Fe0.33Ox aerogel when heated at 300°C under flowing Ar, owing to an increase in crystallite size (2.7 to 4.1 nm). For the ORR, electrocatalytic activity favors Fe-rich Ni
y
Fe1–y
Ox (y < 0.5) materials. As the Ni-content increases beyond y = 0.5, a two-electron reduction pathway is still exhibited, demonstrating that bifunctional OER and ORR activity may be possible by choosing a Ni
y
Fe1–y
Ox nanoarchitecture that provides high OER activity with decent ORR activity. We find that assessing catalytic activity requires an appreciation of the multivariate interplay between Ni:Fe stoichiometry, surface area, crystallographic phase, and crystallite size rather than basing electrocatalyst selection on Ni:Fe stoichiometry alone.
(Invited) Multivalent Metal/Sulfur Chemistries for High Energy Density Rechargeable Batteries
Authors: Gao Tao , Wang Chunsheng
Published: February 2020

The increasing demand for high energy density batteries urges the community to seek novel chemistries. Among them, Li/S and Li-O2 have received the most attentions due to their great potential and the community's extensive experience in Li chemistry. In contrast, multivalent chemistries (Mg and Al) attract less attention despite of their unique and remarkable advantages. Although their higher reduction potentials (Mg=-2.36V vs SHE; Al=-1.3V vs SHE) compromises battery voltages, their less reactive nature has enabled a better (elec)chemical compatibility at the metal/electrolyte interface, which eliminates any surface layer and leads to a high coulombic efficiency (100%) for metal deposition/striping. This is crucial for a rechargeable battery chemistry based on metal anode, because the formation of surface layer would cause continuous consumption of electrolyte during repeated cycling. Furthermore, the deposition of multivalent metal (Mg and Al) shows uniform morphology with no whiskers (‘dendrite’) below Sand’s time, which eliminates the possibility of whiskers penetrating through separators and internal short circuit of the battery. This feature allows multivalent metal batteries to function in a much safer manner than Li metal batteries.

The success of multivalent battery chemistry relies on development of proper electrolytes and cathode materials. While great progress has been made regarding the former, few advance was seen in the latter. In this presentation, we will introduce our latest achievement in tackling the cathode challenges. Our study has focused on metal/sulfur chemistries, because 1) they provide close or even higher volumetric energy density than Li/S chemistry; 2) the potentially fast reaction kinetics of the non-topotactic reaction compared with intercalation reaction.
Towards Next Generation Body Worn Glucose Sensors
Authors: Salari Maryam , Fan Andy , Dennis Allison , Klapperich Catherine , Galagan James , Grinstaff Mark W
Published: February 2020

Wearable chemical sensor technologies enable the opportunity to continuously collect physiologically information on an individual’s health status. This is in contrast to traditional blood draws and subsequent analysis. Using glucose oxidase as a model enzyme we compare several fabrication methods and describe an optimized glucose monitoring sensor which works in open circuit potential with good selectivity and sensitivity over a glucose concentration range of 50 to 300 µM (Figure 1). The sensors maintain good sensitivity of more than 2000 nA/mM after two weeks. The current drifting is minimal and reproducible and device can be made. (Figure 1c). Key steps, procedural details, and findings will be discussed in this work.

Figure 1. (a) The open circuit potential amperometric monitoring the liberated hydrogen peroxide after (a) 1 day of fabrication and (b) 15 days of fabrication; along with the calibration curves on inset. (c) Drifting and calibration curve obtained for sensors made from different batches.

Figure 1
Label Free Detection of Gene Mutation by Applying a Ce2(Zr1-xTix)Oy Sensing Film Based Electrolyte – Insulator – Semiconductor (EIS) Biosensors Using Sol-Gel Method
Authors: Bag Sankar Prasad , Garu Prabir , Singh Kanishk , Lou Bih Show , Her Jim Long , Pan Tung Ming
Published: February 2020

In recent scenario, various kinds of high-k materials such as rare-earth (RE) oxide based film are the promising candidate for achieving pH response. These types of high-k materials have been used as gate oxide material to fabricate electrolyte–insulator–semiconductor (EIS) sensor devices as pH sensing membranes due to good sensing performance with their high dielectric constant, high resistivities, and large band gap energies]. Employing the Ce2(Zr1-xTix)Oy (CZT) oxide sensing membrane based EIS device has been rarely studied for biosensing applications. In this study, a bio-membrane/ Ce2(Zr1-xTix)Oy (CZT) /Si EIS structure was used as a disposable bio-chemical transducer for DNA mutation. The advantage of this structure is easy to fabricate and has greater performance than conventional devices. Zr 4+ rich content CZT based EIS devices exhibited the best sensing properties (sensitivity: 62.31 mV/pH, , lower hysteresis voltage : ~ 3.36 mV and lower drift rate : ~1.1 mV/hr). Being higher sensing properties of Zr 4+ rich content CZT is considered as a potential candidate for detection of DNA /protein due to change in the surface potential of CZT membrane. To apply the detection of ssDNA and cDNA hybridization was successfully observed in Zr 4+ rich content CZT based EIS devices

Figure 1
Alternative Approaches to Evaluating Multivalent Cathodes
Authors: Khalifah Peter
Published: February 2020

It is often difficult to assess the suitability of candidate multivalent cathodes since their electrochemical activity cannot be effectively evaluated until problems associated with the cell cathode, the cell anode, and the cell electrolyte are simultaneously resolved. In such cases, the use of alternative techniques to pre-screen candidate cathodes is important so that cell optimization efforts are focused on the most promising cathode systems. Some simple tools for pre-screening multivalent cathodes utilizing both experimental and computational methods developed in the course of our work will be discussed in the broader context of results that validate these approaches.
Electrolyte and Cathode Compatibility for Rechargeable Mg Ion Battery
Authors: Sa Niya , Ren Yang , Burrell Anthony , Vaughey John T.
Published: February 2020

Rechargeable Mg batteries have been one of the most well-studied polyvalent-metal storage batteries owing to several merits, namely non-dendrite formation for Mg electro-deposition, high volumetric capacity and low cost. However, there are still a number of challenges for the development of Mg battery. For instance, lack of appropriate Mg electrolytes, defined as the “roadblocks” for Mg battery development. Before the successful invention of a prototype Mg ion battery, optimization of the Mg electrolyte performance and exploration of its compatibility with beyond Chevrel phase cathodes is necessary. Work presented here includes work for developing and characterizing non-halogen contained Mg electrolyte that can plate and strip Mg reversibly. Specifically, electrochemical evaluation of such new non-aqueous Mg electrolyte and its compatibility with beyond Chevrel cathodes will be discussed.
An Advanced Separator for Li–O2 Batteries : Maximizing the Effect of Redox Mediators
Authors: Lee Seon-Hwa , Sun Yang-Kook
Published: February 2020

Li–O2 batteries have a major obstacle regarding the large overpotential upon charging that results from the low conductivity of the discharge product.1-3 Thus, various redox mediators (RMs) have been widely studied to reduce the overpotential upon the charging process; this should help promote the oxidation of Li2O2. However, since RMs degrade the Li-metal anode through a parasitic reaction between the RM and the Li metal, a solution is needed to rectify this phenomenon. Here, we propose an effective method to prevent the migration of the RM toward the anode side of the lithium metal by using a modified separator with a negatively-charged polymer. When DMPZ (5,10-dihydro-5,10-dimethylphenazine) is used as the RM, we find that the modified separator suppressed the migration of DMPZ toward the counter electrode of the Li-metal anode; this is investigated by a visual redox couple diffusion test, morphological investigation, and X-ray diffraction study. This advanced separator effectively maximizes the catalytic activity of the redox mediator. Li–O2 batteries using both a high concentrated DMPZ and the modified separator exhibit improved performances and maintain 90% of the round-trip efficiency up to the 20th cycle.

 

References

1. B. D. McCloskey, R. Scheffler, A. Speidel, D. S. Bethune, R. M. Shelby, and A. C. Luntz, J. Am. Chem. Soc., 2011, 133, 18038–18041.`

2. S. A. Freunberger, Y. Chen, N. E. Drewett, L. J. Hardwick, F. Bardé, and P. G. Bruce, Angew. Chem. Int. Ed. Engl., 2011, 50, 8609–8613.

3. S. Meini, N. Tsiouvaras, K. U. Schwenke, M. Piana, H. Beyer, L. Lange, and H. A. Gasteiger, Phys. Chem. Chem. Phys., 2013, 15, 11478–11493
Solid State Electrolytes and Composite Cathodes for Li-S Batteries
Authors: Henslee Brian E , Kumar Jitendra , Bhattacharya Priyanka , Zalar Frank
Published: February 2020

Advanced lithium battery chemistries beyond lithium-ion have demonstrated high energy density (>300 Wh/kg) but need further work to improve and demonstrate cycle life, shelf life, rate capability, and safety matching or exceeding that of lithium-ion batteries. A lithium sulfur battery can theoretically reach energy densities of 2600 Wh/kg and has high potential to meet energy density needs for portable power including electric vehicles. Nevertheless, the Li-S system has not yet been implemented because of multiple obstacles: poor electrical conductivity of elemental sulfur, lack of a system that reduces the capacity robbing polysulfide shuttle (PS) effect, a suitable electrolyte that can suppress dendrite formation, and thicker cathode layers necessary to realize the energy density of a lithium sulfur couple.

Past research to improve sulfur cathode conductivity and eliminate the PS effect has included infusing sulfur within electrically conductive carbon micro- and nano-scale particles. This approach addresses both the PS shuttle and sulfur’s poor electrical conductivity; however it presents a barrier for lithium ions, which slows reaction, reduces power, and limits cathode thickness1. Effective sulfur encapsulation require both electronic and ionic conduction to build thicker cathode structures that retain battery power, capacity, and cycle life.

Typically liquid electrolytes facilitate high sulfur loadings and cathode capacity in a lithium sulfur battery however they also encourage the polysulfide shuttle through the porous polymer separator and don’t prevent dendrites. Excessive amounts of liquid electrolyte also reduces the practical energy density of a lithium sulfur cell. Solid-state electrolytes have the potential to play at least three significant roles in a lithium sulfur battery: (1) provide a barrier to stop PS shuttle effect, (2) prevent lithium dendrite formation, and (3) reduction of liquid electrolyte.

This presentation will discuss the development of a lithium sulfur battery based on combining a solid state electrolyte, entrapped sulfur cathode, and a lithium metal anode necessary to meet needs for high energy density, rechargeable energy storage. New processing methods that improve performance of sulfur carbon composites for cathodes will be discussed. The feasibility of low cost practical carbon materials for sulfur carbon composite cathodes will also be discussed in relation to the new processing methods. Methods and results of using solid state electrolytes in lithium sulfur cell design will also be discussed related to their impact on liquid electrolyte reduction and cathode capacity improvement. Finally optimization targets for a metallic lithium anode, solid electrolyte, and sulfur cathode materials will be discussed in relation to goals for cell specific energy.

1) Manthiram, Arumugam, et al. "Rechargeable lithium-sulfur batteries." Chem. Rev 114.23 (2014): 11751-11787.
Microstructural Limitations in Lithium-Sulfur Battery Performance
Authors: Mistry Aashutosh , Mukherjee Partha P
Published: February 2020

Lithium-sulfur batteries present a lucrative option in the beyond lithium-ion chemistry category due to higher theoretical specific capacity (e.g. 1675 mAh/g of sulfur) compared to Li-ion batteries. However, experimental evidence suggests that typical Li-S cells exhibit reduced capacity even for the first discharge over a wide range of operating rates. The electrochemical operation of Li-S batteries is complex having its roots in both materials as well as electrode microstructural limitations. Transport in the liquid electrolyte progressively evolves during operation with disparate reduction speciation. The precipitating discharge products, such as Li2S, are electronically insulating, giving rise to local reaction shutdown and may even lead to partial pore blockage. Precipitation in the cathode may also lead to leakage of the electrolyte and equivalent loss of the sulfur active material. This work discusses the implications of the underlying microstructure-transport-electrochemical evolution coupling in the sulfur cathode and resulting influence on the cell performance.