bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Electrolyte Volume and Salt Concentration on SEI Stability and Cycling Performance of Lithium Metal Anodes
Authors: Wood Sean M. , Nagpure Shrikant C. , Dufek Eric J. , Sazhin Sergiy V.
Published: February 2020

In order to nearly triple the driving range of electric vehicles (EV), the US Department of Energy has set a goal of achieving an energy density of 500 Wh kg-1 in EV batteries, and the use of a lithium metal anode is essential to reaching this goal.(1) A key consideration in reducing the weight (and thereby increasing the energy density) of a lithium metal battery is its electrolyte, with the volume of electrolyte used and its salt concentration both affecting the overall battery weight. Unlike with the currently-used graphite anode, the highly reactive surface of a lithium anode varies widely from cycle to cycle, which irreversibly consumes the finite amount of electrolyte and causes lithium metal to suffer from low Coulombic efficiency. To account for Coulombic inefficiency caused by electrolyte depletion, many researchers "flood" their cells with electrolyte to prolong cycle life. However, commercial batteries will require smaller amounts of electrolyte in order to achieve weight and energy density goals.

Additionally, the components that make up the solid electrolyte interphase (SEI) layer on the surface of the lithium metal are soluble in the electrolyte to varying degrees. As the more soluble components selectively dissolve into the electrolyte, reparative SEI grows in its place. During non-uniform lithium plating, new SEI also forms over the freshly-exposed surface area. Both of these processes consume more of the limited electrolyte. Factors such as the volume of electrolyte used and its salt concentration affect the stability of the SEI against dissolution while also altering the composition of the SEI that forms, which can have further impacts on cell performance.

Here, three electrochemically-measurable factors are used to examine the stability of the SEI: formation rate (the rate at which the SEI forms or repairs itself each cycle), degradation rate (the rate at which the SEI dissolves or degrades during rest periods), and formation capacity (the total amount of charge dedicated to forming a stable SEI). Each of these factors will affect the consumption of electrolyte and ultimately dictate the amount of excess electrolyte needed to account for these losses.

Three electrolyte volumes and three salt concentrations were chosen to examine the impact that these parameters have on SEI stability and Coulombic efficiency in the standard 3:7 ethylene carbonate/ethyl methyl carbonate with 2 % vinylene carbonate electrolyte with LiPF6 salt. Higher volumes of electrolyte resulted in increased SEI formation rates and dissolution rates. Differences in these factors at low and high salt concentrations were found to result from a change in the type of SEI that formed.

References

Battery500 Consortium to Spark EV Innovations: Pacific Northwest National Laboratory-led, 5-year $50M effort seeks to almost triple energy stored in electric car batteries, in Office of Technology Transitions Energy.gov (2016).
Investigation of Pd and Pd-CeO2 Based Carbon-Supported Electrocatalysts for the Electrooxidation of Borohydride in Direct Borohydride Fuel Cell
Authors: Lafforgue Clémence , Chatenet Marian , Atkinson Robert W. , Swider-Lyons Karen , Miller Hamish , Dekel Dario R.
Published: February 2020

Direct borohydride fuel cells (DBFC) are considered high-energy density generators. The ideal case for the anodic reaction of a DBFC is the direct and complete borohydride oxidation reaction (BOR) that releases 8 electrons. However, the BOR is a very complex reaction that involves numerous intermediate species and suffers from competition with the heterogeneous hydrolysis of BH4
- that leads to molecular hydrogen, making full utilization of the fuel challenging [1]. Despite many studies of the BOR on several electrocatalysts (especially Au and Pt), this reaction is still poorly understood on most practical electrocatalysts and in relevant conditions to DBFC operation, and no ideal electrocatalyst fulfilling both high activity and high faradaic efficiency at low potential has been isolated, yet.

In this study, the BOR is investigated on Pd-based carbon-supported electrocatalysts. A set of four Pd/C electrocatalysts have been synthesized using Vulcan XC72 as substrate and loaded at 22, 33, 44 and 53 wt% Pd. These materials have been thoroughly characterized in terms of BOR activity in a rotating disk electrode setup. The experiments were performed for three NaBH4 concentrations (5, 50 and 500 mM) at 60°C. The electrochemical characterizations of Figure 1 (A) reveal that the onset potential (E
i=0) (see Figure 1 (B)) is lower than 0 V vs. RHE on all the Pd electrocatalysts, meaning that BH4
- anions can be valorized directly, albeit with slow kinetics. In contrast, Pt/C first decomposes BH4
- and utilizes hydrogen species, above 0 V vs. RHE. However, the kinetic is very slow. Similar experiments have been performed with advanced Pd electrocatalysts with a composite support made of Vulcan XC72 carbon and cerium oxide, which enhance hydrogen oxidation reaction (HOR) kinetics in alkaline media [2].

Figure 1
(Invited) Tune Materials Structure and Chemistry for the Use of Micron Sized Silicon for Lithium-Ion Batteries
Authors: Zhou Xiao-Dong , Mishra Kuber
Published: February 2020

The aim of this talk is to illustrate the strategies for the development of high capacity Si-based electrodes in order to increase the energy density of the current state of art lithium ion batteries by using scalable synthesis techniques while investigating the structure-property-performance relations for different materials. The strategies include: (1) development of porous structures (2) incorporation of core-shell architectures and (3) modification of chemistry of the active materials.
Dimethyl Substituted Polyaromatic Alkaline Ionomers for Better Alkaline Hydrogen Oxidation
Authors: Park Eun Joo , Maurya Sandip , Bae Chulsung , Kim Yu Seung
Published: February 2020

Development of new ionomeric binding materials for the fabrication of fuel cell electrode is important to enhance performance and durability of alkaline membrane fuel cells.1 Recently we reported that adsorption of benzene groups in the polymer electrolytes on Pt-based electrocatalyst may cause an adversary impact on the activity of the hydrogen oxidation reaction under alkaline condition.2 In order to mitigate such adverse impact and further improve the fuel cell durability, here we report a new design of polyaromatic ionomers with dimethyl substituted aromatic backbone from acid-catalyzed Friedel-Crafts polycondensation3 using 2,2’-dimethylbiphenyl as a monomer. The backbone of the ionomer does not contain alkaline-labile aryl-ether linkage for chemical durability in high temperature alkaline condition.4

The hydroxide form of the ionomers with ion exchange capacity of 2.5 meq./g showed good solubility in a wide range of solvents including methanol, ethanol, isopropanol and polar aprotic solvents, which eases the fabrication of materials as electrode binders. The performance of the dimethylated ionomeric binders was tested in membrane electrode assembly using Pt-based catalysts under H2/O2 conditions and compared to that of poly(biphenyl alkylene) without methyl substituents. The membrane electrode assembly using the dimethylated ionomers showed good performance (peak power density up to 600 mW/cm2) with stable short-term stability. In this presentation, further structural effect of the polyaromatic ionomers will be discussed with other critical fuel cell operation factors that link with fuel cell performance.

Acknowledgments

This work is supported by the US Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technology Office (Program Manager: David Peterson).

References

Gottesfeld, D. R. Dekel, M. Page, C. Bae, Y. Yan, P. Zelenay, Y. S. Kim. J. Power Sources, doi:10.1016/j.jpowsour.2017.08.010 (2017).

Matanovic, H. T. Chung, Y. S. Kim. J. Phys. Chem. Lett.
8, 4918 (2017).

W.H. Lee, Y. S. Kim, and C. Bae. ACS Macro Lett.
4, 814 (2015).

Fujimoto, D. S. Kim, M. Hibbs, D. Wrobleski, Y. S. Kim. J. Memb. Sci.
423, 438 (2012).
Oxygen Electro-Adsorption Measurements on IrO2(110) and RuO2(110): Evidence for Scaling Relations and Design Insights for Oxygen-Evolution Catalysts
Authors: Kuo Ding-Yuan , Paik Hanjong , Nelson Jocienne N. , Kloppenburg Jan , Hautier Geoffroy , Shen Kyle M. , Schlom Darrell G. , Suntivich Jin
Published: February 2020

A catalyst operates by stabilizing reaction intermediates through surface adsorption. In the oxygen evolution reaction (OER), the surface electro-adsorptions stabilize the oxygen-containing intermediates as the catalyst breaks and connects the oxygen-hydrogen and oxygen-oxygen bonds. While this concept has led to many new OER-catalyst discoveries, the experimental relationship between the electro-adsorption energetics and the OER kinetics remains to be established. We present our measurements of the electro-adsorption energetics on IrO2(110) and RuO2(110) epitaxially grown on TiO2(110) substrates. The high quality of the oxide films grown using molecular-beam epitaxy affords the ability to extract the oxygen electro-adsorption energetics, consequently enabling us to quantify the relationship between the electro-adsorption and the OER. Putting together the adsorption energetics allows us to examine the validity of the scaling relation, an idea that the surface binding energy can be approximated by the first bond to the surface. Our measurement experimentally supports the scaling relation concept, thereby suggesting that the volcano relationship, the consequence of the scaling relation, could be valid on average. However, we also note some deviations, which do not impact the overall trend of the scaling relation but are sufficiently present that they could lead to superior OER catalysts if these deviations can be successfully understood and utilized.
Principles and Control of Electron Transfer through Conductive Proteins: The Role of Metal Doping and Charged Amino Acids
Authors: Lebedev Nikolai , Griva Igor , Blom Anders , Tender Leonard M
Published: February 2020

Protein electronics is a relatively new branch of molecular electronics which goal is to analyze the mechanism and utilize the gained knowledge for the construction of robust super small flexible protein- and biological cell-based electronic materials for bioinorganic hybrids, including sensors, actuators, electrochemical cell, and catalytic devices. Though widely discussed, the mechanism and the structural components controlling ET through multi-atomic proteins, which calculation requires unique software and high-performance computers, are not completely understood. In the present work, we calculate from first principles ET through two proteins, (a) helical region of PilA, an extracellular proteinaceous filament of Geobacter sulfurreducens with was reported to conduct electrons over long distances (>1 micron) and (b) through bacterial FeS protein, rubredoxin, a small non-heme protein widely used by biological cells as a soluble redox mediator. For comparison, we also calculate ET through an artificially designed carbon nanotube (CNT)-histidine-heme-histidine-CNT conjugate that mimics bacterial cytochromes. Our calculations show that iron atom incorporated into protein structure as a heme or an iron-sulfur cluster opens up a transmission path at the energy corresponding to the Fermi energy level of the electrodes that substantially (by several folds) increases efficiency of ET through the protein. Neither aromatic Tyr, nor Phe at any ring orientation can get the compatible effect, though bipolar Asn might participate in ET at high bias voltages. The conductivity of the proteins substantially depends on the polarity of applied electric field allowing for the protein operation of as a molecular rectifier. These data explain the origin of experimentally observed high conductivity of iron-containing native proteins and can be used for wise de novo construction of new proteins for molecular electronics and bio-inspired energy converting devices.
Sensitizing the Photocatalytic Ability of Dawson-Wells Polyoxometalates in Solution and Thin Films
Authors: Keyes Tia E
Published: February 2020

Heteropolyoxomolybdate anions exhibit rich redox and photochemistry enabled by the capacity of polyoxomolybdate to act as both electron and proton relays. They are widely investigated for application across domains involving photooxidation and photocatalysis. A key limitation though is that polyoxometallates such as [S2M18O62]4-, where M is W or Mo, are not signifantly activated by visible light.

This presentation describes investigations into the sensitization of Dawson polyoxometallates photochemistry [S2Mo18O62]4- and [S2W18O62]4- by ruthenium(II)polypyridine complexes in solution and at modified electrodes. Electrostatically associated supramolecular structures comprising of ruthenium polypyridyl cations and polyoxoanions can be readily isolated as charge neutral adducts by combining the cation and anion in solution. For [Ru(bpy)3]2+ with [S2Mo18O62]4- or [S2W18O62]4-
the polyoxometallate adducts are remarkably photostable. And [Ru(bpy)3]2+ the resulting clusters sensitises the very efficient photooxidation of organic substrates such as DMF and benzylalcohol by the polyoxometalates under visible irradiation, between 355 and 490 nm.. Resonance Raman spectroscopy was used to identify a charge transfer transition between Ru and polyoxometallate which suggests significant electronic communication in these cluster complex. Exploiting resonance Raman spectroscopy to identify the presence of the CT transition we took a combinatorial approach to identifying potentially sensitized Ru(II)-POM pairs and assemble the resulting pairs into layer by layer electrostatic assemblies at electrodes. The photoelectrochemical response of these systems, with a range of organic donors, including persistent pollutants diclofenac and ibuprofen is described.

References

Nigel Fay, Victoria M. Hultgren, Anthony G. Wedd, Tia E. Keyes, Deirdre Leane, Alan M. Bond, Dalton Trans, 2006, 4218 - 4227.

Visible Light Sensitized Photocurrent Generation from Electrostatically Assembled Thin Films of [Ru(bpy)3]2+ and the polyoxometalate [W18O54(SO4)2]4-; Optimizing Performance in a low electrolyte media, James J Walsh; Jie Zhu; Alan M Bond; Robert J Forster, Tia E Keyes, 2013, Journal of Electroanal. Chem., 2013, 706, 93-101

Hybrid Polyoxometalate Materials for Photo(electro-) chemical Applications., J. Walsh, A.M. Bond, R.J. Forster, T.E. Keyes, Coord. Chem Rev., Volume 306, Part 1, 1 January 2016, Pages 217–234

Figure 1
Field-Driven Odor Mitigation in Sanitation Facilities
Authors: Vasquez Mariana Madelen , Ngaboyamahina Edgard , De March Claire A , Do Matthew , Matsunami Hiroaki , Glass Jeffrey T.
Published: February 2020

There is an urgent need to increase access to appropriate sanitation of human waste in developing countries. However, malodor nuisance is a major risk factor in the adoption of effective sanitation technologies. Foul-smelling sanitation facilities encourage people to practice open defecation in developing countries. Our work focuses on the mitigation of the most common and prevalent odorant molecules in human waste. These molecules consist mainly of carbon backbone endings with functional groups such as aldehydes, alcohols, or ketones. The odorant perception of these molecules can be changed to more pleasant smells by simply applying an electrical signal to the offending liquid/gas source.

We propose to demonstrate the capability to modulate malodor and generate a pleasant olfactory perception. This is achieved simply by applying an electrical signal to the offending liquid/gas source to induce an electrochemical reaction. Results suggest that butyric acid, which has a rancid smell and is used as a case study, can be selectively modified to lead to a more pleasant odorous composition, thanks in part to the production of butanal, a molecule with a fruity-strawberry like smell.
Spectroscopic Evidence of Size-Dependent Buffering of Interfacial pH By Cation Hydrolysis during CO2 Electroreduction
Authors: Ayemoba Onagie , Cuesta Angel
Published: February 2020

The nature of the electrolyte cation is known to affect the Faradaic efficiency and selectivity of CO2 electroreduction. Singh et al. (J. Am. Chem. Soc. 2016, 138, 13006–13012) recently attributed this effect to the buffering ability of cation hydrolysis at the electrical double layer. According to them, the pKa of hydrolysis decreases close to the cathode due to the polarization of the solvation water molecules between the cation’s positive charge and the negative charge on the electrode surface. We have tested this hypothesis experimentally, by probing the pH at the gold-electrolyte interface in situ using ATR-SEIRAS. The ratio between the integrated intensity of the CO2 and HCO3
- bands, which has to be inversely proportional to the pH, provided a means to determining the pH change in-situ during the electroreduction of CO2. Our results confirm that the magnitude of the pH increase at the interface follows the trend Li+ > Na+ > K+ > Cs+, adding strong experimental support to Singh’s et al.’s hypothesis. We show, however, that the pH buffering effect was overestimated by Singh et al., their overestimation being larger the larger the cation.

Figure 1
(Keynote) Modification of the Electrocatalyst Surface Composition By the Electrode Potential and the Substantial Resulting Effects on the Cell Characteristic
Authors: Gottesfeld Shimshon
Published: February 2020

This talk addresses a fundamental aspect of electrocatalysis: the dependence of the rate of the electrocatalytic process on electrode potential. Discussions with Ratko Adzic related to this subject, starting back in the early 1990’s, are appreciatively recognized.

In a complete description of the dependence of the rate of an electrocatalytic process on electrode potential, the effect of the potential has to include two components: acceleration of the electrode reaction by lowering the activation energy of any step involving electronic charge transfer and, modification of the composition of the catalyst/electrolyte interface by the change in electrode potential. The latter effect has only rarely been included rigorously in quantitative descriptions of the rate dependence on electrode potential, thereby missing in the description an important factor determining the dependence of the rate on overpotential and , consequently, determining the power output and conversion efficiency observed in a fuel cell or electrolyzer given some combination of electrocatalyst and electrolyte.

This talk will cover examples of ORR , OER and HOR processes taking place at electrocatalysts which undergo significant changes in surface composition with change of the potential within the window of relevance to fuel cells or water electrolyzers. The examples cover several types of effects on the rate of the faradaic process as result of the dependence of the interfacial composition on overpotential, including:

* rate acceleration by potential-induced generation of active surface sites

* rate decay by potential-induced deactivation of surface sites

* rate effects by potential-induced electrolyte layer formation

Complete quantitative description of these effects in mathematical form, is, in many cases, not straightforward. Nevertheless, recognition of such effects in the general expression for the rate of the electrocatalytic process can and should be reflected by a pre-exponential factor which is potential dependent [1,2]. Assuming a potential independent pre-exponential factor, as typically done, results in misinterpretation of fundamental aspects of the kinetics of electrocatalytic process, for example the reason for commonly observed increase in "Tafel slope" with the increase in overpotential.

Finally, the argument made frequently that electrocatalytic processes can be fully understood using a single “descriptor”, e.g., a M-O or M-H bond strength (where M stands for an active metal surface site) , does not recognize the change of the number of active M sites with overpotential as result of a potential-induced surface modification process. This dependence of the number of active sites on potential has to be covered by , at least, a second “descriptor” , for a full description of the electrocatalytic process.

References:

1. S.Gottesfeld, ECS Trans. 2014 61(31): 1-13

2. S.Gottesfeld, ECS Trans. 2015 66(29): 13-30
The Impact of Adsorbates on Metal Deposition through the Curvature Enhanced Accelerator Coverage Mechanism
Authors: Josell Daniel , Moffat Thomas P.
Published: February 2020

Superconformal electrodeposition utilizing deposition accelerating additives enabled the implementation of damascene interconnects in microelectronics using copper “superfill” in the late 1990’s. The underlying Curvature Enhanced Accelerator Coverage (CEAC) mechanism was defined in 2001. Since then, superconformal deposition of copper, silver and gold in fine features as well as the formation of optically smooth, soft deposits has been successfully predicted by CEAC-based models that capture the interplay of deposition-rate accelerating adsorbate coverage and metal deposition through area change on nonplanar surfaces. Void-free filling of high aspect ratio, submicrometer trenches and vias with silver and gold has been quantitatively predicted and demonstrated using additives selected from the literature on catalysis of metal deposition by additive adsorption. These additives also provide, through the same CEAC mechanism, a means of obtaining optically smooth deposits without relying on deposit-hardening grain refinement through additive incorporation. I will summarize results to date, including what we believe we understand as well as what we don’t.
(Invited) Structure and Reactivity of Hybrid Functional Materials in Electrocatalysis
Authors: Kulesza Pawel J
Published: February 2020

Our research interests aim at establishing structure/property relations leading to rational designs of functionalized materials for efficient electrocatalysis and electrochemical energy conversion and storage. There has been growing interest in the electrochemical reduction of carbon dioxide, a potent greenhouse gas and a contributor to global climate change. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials. To optimize the hydrogenation-type electrocatalytic approach, we have proposed to utilize nanostructured metallic centers (e.g. Pd, Pt or Ru) in a form of highly dispersed and reactive nanoparticles generated within supramolecular network of distinct nitrogen, sulfur or oxygen-coordination complexes. Among important issues are the mutual completion between hydrogen evolution and carbon dioxide reduction and specific interactions between coordinating centers and metallic sites. We have also explored the ability of biofilms to form hydro-gel-type aggregates of microorganisms attached to various surfaces including those of carbon electrode materials. Upon incorporation of various noble metal nanostructures and/or conducting polymer ultra-thin films, highly reactive and selective systems toward CO2-reduction have been obtained. Another possibility to enhance electroreduction of carbon dioxide is to explore direct transformation of solar energy to chemical energy using transition metal oxide semiconductor materials. We show here that, by intentional and controlled combination of metal oxide semiconductors (titanium (IV) oxide and copper (I) oxide), we have been able to drive effectively photoelectrochemical reduction of carbon dioxide mostly to methanol.

Application of mixed-metal oxides as active matrices is also of particular importance to electrocatalytic oxidations of small organic molecules in low-temperature fuel cell technologies. The hydrous behavior, which favors proton mobility and affects overall reactivity, reflects not only the oxide’s chemical properties but its texture and morphology as well. For example, during oxidation of ethanol (e.g. at PtRu), when rhodium nanoparticles have been dispersed in between WO3 and ZrO2 layers, significant current enhancements are observed. The result can be rationalized in terms of the formation of nanoreactors in which Rh induces splitting of C-C bonds in C2H5OH molecules before the actual electrooxidtion steps.

We also consider nanoelectrocatalytic systems permitting effective operation of the iodine-based charge relays in dye sensitized solar cells. The ability of palladium or platinum nanostructures to induce splitting of I-I bonds in the iodine (triiodide) molecules is explored here to enhance electron transfers in the triiodide/iodide-containing 1,3-dialkylimidazolium room-temperature ionic liquids.
(Invited) Nickel-Based Anode Electrocatalysts for Alkaline Exchange Membrane Fuel Cells
Authors: Atanassov Plamen , Serov Alexey
Published: February 2020

Over the last decade UNM has been involved in the design of Platinum Group Metal-free (PGM-free) anode catalysts for the emerging field of Alkaline Membrane Fuel Cells (AMFC). Initial effort was directed towards catalysts for selective hydrazine oxidation.1-3 These series materials were based on allowing Ni with oxophillic metal (Zn, La, etc.) to enhance hydrazine dehydrogenation step in contrast to N-N bond splitting as a base for much desired catalyst selectivity.4, 5 These Ni-based electrocatalysts were further designed to include Ni alloys with refractive metals6 (Mo, W, Cr) and demonstrated exceptional dehydrogenation selectivity, thus creating the base for the development hydrogen oxidation catalysts in alkaline media. The nickel-based electrocatalysts were synthesized as nanoparticles supported on various carbon blacks and modified carbon blacks with loadings of up to 50 % wt. (see Figure A & B). Synthesized martials were comprehensively characterized by physical-chemical methods: XRD, BET, SEM, TEM and XPS. Electrochemical activity of the catalysts was studied with Rotating Disk Electrode (RDE) technique and in a single membrane electrode assembly (MEA) AMFC. MEA design was optimized with respect to critical fabrication parameters such as: catalyst layer thickness (loading), catalyst-to-ionomer ratio, and catalyst deposition as Catalyst Coated Membrane (CCM) vs. gas-diffusion electrode (GDE). It was found that NiMo/C electrocatalyst has a mass activity similar to palladium supported on carbon.7 The MEA performance obtained in H2/O2 single MEA fuel cell tests using Tokuyama membrane and ionomer reached a peak power density higher than 120 mW.cm-2 at relative humidity (RH) of 70 %. When Ni0.9Cu0.1 supported on Ketjen Black catalysts was used (see Figure C), a record high peak power density was demonstrated: up to 350 mW.cm-2. These new nickel-transition metal alloy catalysts are being studied in detail by spectroscopy and modeled by DFT to establish relevant structure-to-property correlation and demonstrate their utility in H2/O2 AEMFC.

Acknowledgement: DOE-EERE FCTO, Incubator Program DE-EE0006962 “Development of PGM-free Catalysts for Hydrogen Oxidation Reaction in Alkaline Media” (Alexey Serov, PI).

U. Martinez, et al., Physical Chemistry and Chemical Physics, 14 (2012) 5512-5517

T. Sakamoto, et al., Journal of Power Sources, 234 (2013) 252-259

A. Serov et al., Angewandte Chemie, Int. Ed., 126 (2014) 10419-10715

T. Sakamoto, et al., Journal of Power Sources, 247 (2014) 605-611

T. Sakamoto, et al., Electrochimica Acta, 163 (2015) 116-122

T. Asset et al., Electrochimica Acta, 215 (2016) 420-426

S. Kabir et al., Journal of Materials Chemistry A, (2017) DOI:10.1039/C7TA08718G

Figure 1
(Invited) Difficulties in Synthesis of Effective Ternary Catalysts for Ethanol Oxidation
Authors: Kowal Andrzej , Gruzeł Grzegorz , Parlinska-Wojtan Magdalena
Published: February 2020

The synthesis of ternary catalysts is difficult because it is necessary to obtain a good mixture of the three elements, which are distributed in a designed way within a nanoparticle having the size in the range of 10 nm [1, 2]. Catalysts, which effectively oxidize ethanol to CO2, contain PtRh nanoparticles (NPs) connected to SnO2 NPs [3-6]. Such catalyst must also assure an effective electron transfer from the catalyst grain to the carbon support. Thus it is necessary to take into account the electron transport through the SnO2 part of the PtRh/SnO2 catalyst. The conductivity of the SnO2 NPs can be improved by doping. The synthesis and morphology of SnO2 NPs doped by F and Sb was described in [7]. PtRh NPs and SnO2 NPs were synthesized separately using the polyol method. Dynamic light scattering (DLS), XRD and TEM techniques were used to obtain the global and local information about the size of the obtained NPs. Ternary PtRh/SnO2 NPs were produced using previously synthesized and characterized SnO2 colloid, to which Pt and Rh salts were added and reduced by ethylene glycol. All the obtained catalysts were deposited on amorphous carbon and then characterized by high-resolution electron microscopy, Figure 1. Electrocatalytic activity towards ethanol oxidation (EOR) was assessed by cyclic voltammetry. The relation between the structure of the nanocatalysts grains and their activity towards EOR at room temperature was discussed.

References

Pryadchenko V.V. Srabionyan, E.B. Mikheykina, L.A. Avakyan, V.Y. Murzin, Y.V. Zubavichus, I. Zizak, V.E. Guterman and L.A. Bugaev, J. Phys. Chem. C, (2015) 119.

Casado-Rivera, D.J. Volpe, L. Alden, C. Lind, C. Downie, T. Vazquez-Alvarez, A.C.D. Angelo, F.J. DiSalvo and H.D. Abruna, J. Am. Chem. Soc. (2004) 126, 4043.

Kowal, M. Li, M. Shao, K. Sasaki, M.B. Vukmirovic, J. Zhang, N. S. Marinkovic, P. Liu, A. Frenkel, R.R. Adzic, Nature Materials (2009) 9, 325.

Adzic, A. Kowal, (Brookhaven National Laboratory) „Electrocatalyst for Alcohol Oxidation at Fuel Cell Anodes”, Patent Application Publication, Pub. No. US2009/0068505 A1 (Mar. 12, 2009).

Li, A. Kowal, K. Sasaki, N. Marinkovic, D. Su, E. Korach, P. Liu, R. Adzic, Electrochim. Acta (2010) 55, 4331.

Kowal, S. Gojković, K.-S. Lee, P. Olszewski, Y.-E. Sung, Electrochem. Comm. (2009) 11, 724.

Parlinska-Wojtan, R. Sowa, M. Pokora, A. Martyła, K. S. Lee and A. Kowal, Surf. & Interfaces Anal. (2014) 46, 1090.

Acknowledgements

The authors thank the Center for Innovation and Technology Transfer of the Rzeszow University and the Institute of Engineering Materials and Biomaterials of the Silesian University of Technology for the use of the Osiris FEI TEM and the Titan FEI TEM instruments, respectively. Financial support from the Polish National Science Centre (NCN), grant UMO-2014/13/B/ST5/04497 is acknowledged. Partial financial support by Pik-Instruments is greatly acknowledged.

Figure 1
Tunable and Efficient Tin Modified Nitrogen-Doped Carbon Nanofibers for CO2 Electroreduction
Authors: Zhao Yong , Liang Jiaojiao , Ma Jianmin , Wang Caiyun , Wallace Gordon
Published: February 2020

Electrochemical reduction of CO2 (CO2ER) into value-added chemical feedstocks and liquid fuels using renewable energy is a promising route for CO2 recycling.[1] The major challenges are the large overpotential for CO2 activation and the competitive H2 evolution in aqueous mediums.[2] Although some nanostructured noble metal catalysts have demonstrated impressive electrocatalytic activity and selectivity for CO or formate production over CO2ER, the low abundance and high cost limit their large-scale applications.[3] Efficient and cost-effective electrocatalysts with high energy efficiency and product selectivity are highly desirable to drive the development of CO2ER.

In our study, we developed a low-cost Sn particle modified N-doped carbon nanofiber hybrid catalyst via a straightforward electrospinning technique coupled with a pyrolysis process.[4] Its electrocatalytic performance was tuned by the coverage of Sn nanoparticles and the structure of N species on the nanofiber surface. The pyridinic-N supported Sn nanodots drove efficient formate formation with a high current density of 11 mA cm-2 and a faradaic efficiency of 62% at a moderate overpotential of 690 mV. After a simple acidic leaching treatment, only atomically dispersed Sn species remained on the surface of pyridinic-N-doped carbon nanofibers. This catalyst dominantly promoted the CO2-to-CO conversion with a high faradaic efficiency of 91% at a low overpotential of 490 mV.

The change of product selectivity was attributed to the difference in local chemical and electronic environment (Sn-Sn or Sn-N) surrounding the Sn active sites, which facilitated different intermediate stabilization and reaction pathway. The abundance of Sn nanodots and the strong electronic interaction between Sn and pyridinic-N-doped carbon may promote the formate formation, while the efficient CO production over the Sn atoms modified nanofibers may arise from the intrinsically high activity and selectivity of the formed Sn-N moieties.

References

[1] J. Qiao, Y. Liu, F. Hong and J. Zhang, Chem. Soc. Rev., 631-675 (43) 2014.

[2] E. E. Benson, C. P. Kubiak, A. J. Sathrum, J. M. Smieja , Chem. Soc. Rev. 89-99(38) 2009.

[3] Q. Lu, Jonathan Rosen, F. Jiao, ChemCatChem, 38-47 (7) 2015.

[4] Y. Zhao, J.J. Liang, C.Y. Wang, J.M. Ma, G.G. Wallace, Tunable and efficient tin modified nitrogen-doped carbon nanofibers for electrochemical reduction of aqueous carbon dioxide, Adv. Energy Mater., accepted on 16/10/2017.
A Hybrid Multi-Catalyst Motif for Enhanced Electro-Oxidation of Glycerol
Authors: Macazo Florika C. , Hickey David P , Abdellaoui Sofiene , Sigman Matthew S , Minteer Shelley D.
Published: February 2020

Enzyme-based catalytic systems are common bioelectrocatalysts employed in biofuel cells, as a consequence of the inherently high volumetric catalytic activity towards oxidation of biofuels. Integration of these bioelectrocatalysts with organic oxidation catalysts extends their utility by enabling significant amplification of the electrocatalytic activity, which increases the rate of electrocatalytic oxidation of readily available biofuels. However, immobilization of organocatalysts is necessary for their use in biofuel cell applications. Herein, we describe the development of a hybrid catalytic architecture consisting of MWCNTs, TEMPO-modified linear poly(ethylenimine) (TEMPO-LPEI), and an enzyme, oxalate decarboxylase (OxDC) (MWCNT/TEMPO-LPEI/OxDC) to illustrate a synergistic enhancement in the electrochemical oxidation of glycerol. Specifically, we demonstrate that immobilized MWCNT/TEMPO-LPEI/OxDc permits enhanced electrocatalytic oxidation of glycerol by allowing the organic redox polymer, TEMPO-LPEI, to catalyze the oxidation of glycerol to mesoxalate, followed by cleavage of CO2 from mesoxalate by catalytically active MWCNTs - a crucial step in the complete oxidation of glycerol. Finally, conversion of oxalate to formate by OxDc, and subsequent oxidation of formate by TEMPO-LPEI generates CO2 while collecting up to 14 electrons per molecule of glycerol. This results in a synergistic enhancement of up to 3.3-fold. This study illustrates the promising potential of surface-immobilized, polymer hydrogel-based hybrid multicatalytic systems, and thus offers a simple methodology for fabricating bioanodes for enzymatic fuel cells.
Multiplexed 3D Paper Platform for Electrochemical and Enzymatic Catalytic Conversions in a Complex Cascade System
Authors: Andersen Nalin I , Artyushkova Kateryna , Gonzales Ivana , Atanassov Plamen
Published: February 2020

A strategy is presented for studying multiple modalities of catalysts in a paper-based platform using stencil-printed electrodes and surface enhanced Raman spectroscopy (SERS). Microfluidic devices improve precision of experiments, shorten experiment times, and allow multiplexed analyses of catalytic reactions. By strategically configuring multiple modalities of catalysts, one can generate desired chemical conversions. As a proof of concept, the full oxidation of glycerol will be studied where three modalities of catalysts (biological, molecular, and inorganic) will be used in series. We report on a 3D paper-based platform for multiplexed characterization of catalysts and chemically converted analytes. The enzyme oxalate decarboxylase coupled with electrocatalysts will be demonstrated 1,2. The components within the device are modular and can be made by researchers using common laboratory tools. By strategically manipulating porous media, stencil-printing electrodes, and placing SERS detection zones, one can devise a customizable tool useful for understanding the interactions of different catalysts for complex chemical conversion reactions.

References:

Hickey, D. P., McCammant, M. S., Giroud, F., Sigman, M. S. & Minteer, S. D. Hybrid enzymatic and organic electrocatalytic cascade for the complete oxidation of glycerol. J. Am. Chem. Soc.
136, 15917–15920 (2014).

Abdellaoui, S., Hickey, D. P., Stephens, A. R. & Minteer, S. D. Recombinant oxalate decarboxylase: enhancement of a hybrid catalytic cascade for the complete electro-oxidation of glycerol. Chem. Commun.
51, 14330–14333 (2015).

Figure 1
Hybrid Energy Conversion and Storage (HECS) Cells of the Composite Materials between Visible-Light Active Co(OH)2 and UV-Light Active Ni(OH)2
Authors: Sawangphruk Montree , Kongsawatvoragul Ketsuda , Kalasina Saran
Published: February 2020

Cobalt hydroxide (Co(OH)2) and nickel hydroxide (Ni(OH)2) which have optical band gap energies of 2.85 eV and 3.31 eV, respectively are used as active electrode materials for hybrid energy conversion and storage (HECS) cells by following the principle of the solid semiconductor/liquid junction photovoltaic effect. Interestingly, Co(OH)2 can absorb the visible light while Ni(OH)2 can absorb the ultraviolet (UV) light. The weight ratio of Co(OH)2-to-Ni(OH)2 was finely tuned and electrochemically investigated by cyclic voltammetry, galvanostatic charge discharge, and electrochemical impedance spectroscopy. Both ionic liquid and aqueous electrolytes were used. The in-situ X-ray absorption spectroscopy was intensively used to investigate the charge storage mechanism.
Charge Transfer Characteristics of Diaza-Anthraquinones in Different Solvents and Their Application As Organic Active Material in Redox Flow Batteries
Authors: Hofmann Jonas D. , Janek Jürgen , Schröder Daniel
Published: February 2020

Redox flow batteries (RFBs), with their independent scalability of power and capacity and their versatility concerning applicable active materials and solvents, pose a promising technology to meet the challenges of cost efficient large scale stationary energy storage. This holds particularly for RFBs based on the redox active material class of quinones that can be derived from naturally abundant resources at low cost.

In this work, we electrochemically investigate the modified quinone 2,3-diaza-anthracenedione, and two of its derivatives, as promising active material for aqueous redox flow batteries. Interestingly, these anthraquinone derivatives exhibit varying charge transfer properties depending on their functionalization and the applied solvent and pH value. In general, a positive redox potential shift of about 300 mV is achieved by the incorporation of a diaza moiety into the anthraquinone base structure. Moreover, our experiments at low pH prove that the addition of a methoxy group to the base structure of the 2,3-diaza-anthracenedione strongly increases the electrochemical stability in aqueous acidic media. A functionalization with two hydroxyl groups in close vicinity to the carbonyl group evokes a negative redox potential shift of 54 mV in acidic and 264 mV in alkaline solution.

For this study the influence of protonation and hydrogen bonding on the charge transfer characteristics of diaza-anthraquinones was investigated specifically by comparison of measurements taken in non-aqueous solvents and in aqueous solutions at high and low pH. Whereas at low pH values solely one voltammetric anodic and cathodic wave can be observed for the occurring two-electron transfer, peak splitting takes place at high pH values for two of the derivatives, which is highly unusual for quinonoid compounds. Further, measurements in non-aqueous solvents reveal a greater potential difference between the two subsequent electron transfers compared to the pristine anthraquinone. This indicates a discrepancy in charge transfer kinetics evoked by the incorporation of a diaza-moiety into the anthraquinone base structure.

Our findings allow for a deeper understanding of the redox characteristics of diaza-functionalized quinonoid compounds that could lead up to efficient active materials for future redox flow batteries with organic active material.

Figure 1
In Situ Investigation of Au-Cu2o Core-Shell Nanoparticles Formation By Liquid Cell TEM
Authors: Chen Fu-Chun , Lin Ya-Hsuan , Chen Jui-Yuan , Wu Wen-Wei
Published: February 2020

Heterogeneous nanoparticle is wildly used in catalysis, sensors, biology, and semiconductor due to its versatile functions. Among various heterogeneous nanoparticle, Au-Cu2O core-shell nanoparticle shows high thermal stability and short response time for sensor, which attracted much attention. However, the behavior of forming heterostructure and its mechanism are not fully explored. In this work, we used Liquid cell transmission electron microscopy (TEM) to investigate the formation of Au-Cu2O nanoparticles. Liquid cell TEM is a burgeoning technique to study the dynamic process of nanostructures in fluid. First, we sealed Au nanoparticles, synthesized by reducing HAuCl4 with citrate acid, into the liquid cell. Next, we added the precursor containing Cu ions. Electron beam is an important parameter in in-situ TEM for reduction reaction. During the electron beam exposure, Cu2O can be reduced from Cu2+ without adding reducing agent. Finally, the Au-Cu2O core-shell nanoparticles could be synthesized. The growth kinetics and elements distribution have systematically studied. The in-situ experiment sheds light on mechanism of nanostructures and will improve the applicability and controllability of heterostructure synthesis.
(Invited) Ordered, Nanoporous Carbon Scaffolds (NCS) for Use in Energy Conversion and Related Applications
Authors: Birss Viola , Li Xiaoan , Atwa Marwa , Mayall Robert Matthew , Ai Chengying , El Sawy Ehab N
Published: February 2020

Nanoporous carbon materials are of significant interest for use in various electrochemical applications, including as catalyst supports in fuel cells, sensors, and as electrodes in supercapacitors, redox flow batteries, and lithium batteries. The nanoporous carbons under study in our group include both soft- and hard-templated ordered mesoporous carbons as well as colloid-imprinted carbons (CICs). While all of these carbons have well-controlled and narrow pore size distributions and high surface areas, they are all produced in the form of powders, which can cause problems when used in electrochemical devices. This is due to challenges in relation to reproducible powder packing and binders must normally be used to hold particles together. The binder may then block ions and electrons from passing through the pores and between particles, thus preventing full utilization of their surfaces. Furthermore, fine particulates may also cause health concerns (e.g., PM2.5).

In order to overcome these challenges, our research group has focussed on the development of a series of novel nanoporous carbon scaffolds (NCS membranes), possessing a fully ordered and monodisperse porous structure. The NCS materials have pore diameters in the range of 5 to 100’s of nm and contain a fully inter-connected nano/macro-porous network (porosity ~80%). These NCS membranes, which can be made to be 0.5 - 100’s of microns in thickness, also have a very good conductivity of 2-10 S/cm and are fully electrochemically accessible in aqueous solutions, exhibiting a capacitance of 40-100 F/g. The fabrication method used to form these novel NCS membranes is also environmentally friendly and has been demonstrated to be applicable for manufacturing at large scale.

Due to these exceptional properties, the NCS materials are of great interest for use in a wide range of clean energy and water remediation products. In this presentation, the preparation and properties of these materials will be discussed, including the successful loading of the NCS membranes with catalytic metal nanoparticles and internal surface functionalization. An overview of the application of the NCS material in PEM fuel cells, redox flow batteries, capacitors, and in nanofiltration applications will also be presented.
(Vittorio de Nora Award Address) New Tools for Brain Research
Authors: Deligianni Hariklia (Lili)
Published: February 2020

At the system level neuroscience is trying to understand how neural circuits work in learning, memory, multisensory integration, motor coordination and how the electrochemical function of these circuits is compromised in the case of disease. Diseases that involve the nervous system are highly complex and mostly not well understood. The Global Burden of Disease Study 2010 (GBD 2010), estimated that a substantial proportion of the world’s disease burden came from mental, neurological and substance use disorders. We need new tools and methods at the system level to effectively tackle these conditions and to better elucidate brain function and disease.

One such tool is a novel cognitive computing platform, IBM's TrueNorth chip, that enables the use of deep learning techniques in an ultra-low power environment. We have used deep learning with a convolutional neural network (CNN) and TrueNorth technologies for real-time analysis of brain-activity data at the point of sensing. This approach has the potential to create true closed-loop insights (analytics) and therapies for next generation of wearable and implantable devices at the intersection of neurobiology and artificial intelligence.

Neurotransmitters are small proteins secreted between neurons to facilitate neural communication. These compounds are key to information processing during behavior. However, until recently, this chemical communication had not been characterized because biosensors suitable to monitor sub-second chemical events in micron dimensions were unavailable. Cyclic voltammetry at carbon-fiber microelectrodes provides measurements with sub-second time resolution and has been used to examine the dynamics of neurotransmitter concentrations. To enhance the sensitivity and the selectivity of these measurements, we have developed polymeric coatings for bare carbon electrodes. Dopamine, serotonin and adenosine are neurotransmitters that were measured with this methodology.

Another tool that we have developed is a novel nanoscale electrode array with superior sensitivity and improved spatial resolution which can be used in the future to gain improved understanding of dopamine dysregulation. We report on the scalable fabrication of dopamine neurochemical probes of a nanostructured glassy carbon that is smaller than any existing dopamine sensor and arrays of more than 6000 nanorod probes. Compared with a flat glassy carbon surface, the nanostructured glassy carbon nanorods provide about 7X higher signal per unit area (current density) for dopamine sensing. The glassy carbon nanorods were fabricated by pyrolysis of a lithographically defined polymeric nanostructure with an industry standard semiconductor fabrication infrastructure. The scalable fabrication strategy offers the potential to integrate these nanoscale dopamine rods with an integrated circuit control system, with other sensors and with different modalities of neural activation.