bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Optimization of Novel Alkali Superionic Conductors
Authors: Zhu Zhuoying , Chu Iek-Heng , Ong Shyue Ping
Published: February 2020

All solid-state rechargeable alkali-ion batteries are a safer, potentially more energy dense architecture for energy storage. The crucial enabling component is the non-flammable alkali superionic conductor solid electrolyte, which must possess high alkali ionic conductivity, excellent phase stability, electrochemical and mechanical compatibility with the electrodes, and ideally, stability under ambient air. Despite recent advances, the total number of known alkali superionic conductors remain relatively small, and most have significant compromises. In this talk, we will propose several promising novel alkali superionic conductor solid electrolytes - Li3Y(PS4)2 and Li5PS4Cl2 - identified using an efficiently-tiered first principles screening approach. These candidates are inspired by the observation that many known alkali superionic conductors have analogues in the silver thiophosphate chemical space (e.g., Li7P3S11, the Li6PS5X argyrodites, etc.). We will also present evidence that these candidates may potentially have a better balance of properties, especially with regards to phase and electrochemical stability, compared to current state-of-the-art superionic conductors such as Li10GeP2S12, Li9.54Si1.74P1.44S 11.7Cl0.3 and Li7P3S11.
Universal Design Strategy for Li Super-Ionic Conductors in All-Solid-State Li-Ion Batteries : A First-Principles Study
Authors: He Xingfeng , Zhu Yizhou , Mo Yifei
Published: February 2020

Lithium super-ionic conductor (SIC) materials are the key component in enabling all solid-state Li-ion batteries. However, it has not yet been understood why only a few materials as super-ionic conductors can achieve exceptionally higher ionic conductivity than typical solids and how one can design fast ion conductors following simple principles. Using ab initio modeling, we show that fast diffusion in super-ionic conductors happens through unique concerted migration mechanism of multiple ions with low energy barrier in contrast to typical solids. We elucidate that low energy barriers of the concerted ionic diffusion are a result of unique mobile ion configurations and strong mobile ion interactions in super-ionic conductor materials, such as Li10GeP2S12, lithium garnet, NASICON, etc. Our theory provides a conceptually simple framework for guiding the design of super-ionic conductor materials. We demonstrate this strategy by designing a number of novel fast ion conducting materials to activate concerted migration with reduced diffusion barrier. The novel materials are predicted to have comparable Li+ ionic conductivity at room temperature to the known Li SIC materials. In summary, our proposed theory and identified mechanism are universally for fast diffusion in a broad range of ionic conducting materials, and provide a general framework and a universal strategy to design solid materials with fast ionic diffusion.
Molecular Dynamics Simulations on Li-Ion Conduction in Nasicon-Type Solid Electrolytes
Authors: Noda Yusuke , Nakayama Masanobu
Published: February 2020

As a promising solid electrolyte material for all-solid-state Li-ion batteries (LIBs), Na super ionic conductor (NASICON)-type material is considered to be comparable to perovskite-type or garnet-type ionic conductors. Since the discovery of the fast Na-ion conducting NASICON-type material of Na1+xZr2SixP3-xO12 in 1976 [1], many kinds of Li-ion conducting NASICON-type solid electrolytes have been investigated. One of the most popular among them is Li1+xAlxTi2-x(PO4)3 (LATP), which can be generated by partially substituting Ti4+ with Al3+ in LiTi2(PO4)3 (LTP). Especially, LATP with x = 0.3 exhibits enhanced bulk Li-ion conductivity in the order of 10-3 S/cm at room temperature [2,3]. However, it is also well known that LTP-based materials react with Li metal at around 2.5 V vs. Li+/Li due to the Ti4+/Ti3+ redox reaction [4,5]. Recently, another NASICON-type solid electrolyte LiZr2(PO4)3 (LZP) has been well studied, then it is known to be stable in contact with Li metal due to no redox reaction up to 5.5 V [6]. Therefore, NASICON-type materials would be alternative solid electrolytes for all-solid-state LIBs.

In this study, we estimate Li-ion conductivity and activation energy in NASICON-type solid electrolytes using molecular dynamics simulations. The Li-ion trajectory is also analyzed and discussed. The results and discussions will be shown in more detail in our presentation.

Acknowledgements

This work was supported by the “Materials research by Information Integration” Initiative (MI2I) project of the Support Program for Starting Up Innovation Hub from Japan Science and Technology Agency (JST).

References

[1] J. B. Goodenough, H. Y.-P. Hong, and J. A. Kafalas, Mat. Res. Bull. 11, 203-220 (1976).

[2] H. Aono, E. Sugimoto, Y. Sadaoka, N. Imanaka, and G. Adachi, J. Electrochem. Soc. 136, 590-591 (1989).

[3] H. Aono, E. Sugimoto, Y. Sadaoka, N. Imanaka, and G. Adachi, J. Electrochem. Soc. 137, 1023-1027 (1990).

[4] C. Delmas and A. Nadiri, Mater. Res. Bull. 23, 65-72 (1988).

[5] S. Patoux and C. Masquelier, Chem. Mater. 14, 5057-5068 (2002).

[6] Y. Li, W. Zhou, X. Chen, X. Lü, Z. Cui, S. Xin, L. Xue, Q. Jia, and J. B. Goodenough, Proc. Natl. Acad. Sci. 113, 13313-13317 (2016).
(Invited) Resolving Sites for Catalysis in Amorphous Metal Oxide and Molecular Water-Oxidation Catalysts Using in-Situ X-Ray Techniques
Authors: Tiede David M , Kwon Gihan , Kim In Soo , Martinson Alex B. F. , Hoyoung Jang , Lee Jun-Sik , Kohlar Lars , Mulfort Karen
Published: February 2020

A key challenge for the development of materials and technologies for solar-to-fuels energy conversion lies in resolving structure, structural dynamics, and mechanisms underlying solar fuels catalysis, and measuring these structural parameters during functional conditions. This presentation will discuss the resolution of sites for solar-driven catalysis in amorphous cobalt oxide and molecular water-oxidation catalysts using a combination of in-situ high energy X-ray (60 keV) scattering with atomic pair distribution function (PDF) analysis, cobalt L3 edge X-ray absorption spectroscopy, and anomalous wide angle X-ray scattering (AWAXS), with a goal of resolving structure, "one electron at a time", following successive, single-electron, photo-initiated electron transfers. We have extended the in-situ PDF technique by developing 3-D porous electrode architectures that enable structural characterization of interfacial thin films during photo-electrochemistry with 0.2 Å spatial resolution. PDF-electrochemistry measurements for the cobalt borate OEC film, CoBi, poised across the potentials from 0.5 V and 1.4 V vs NHE show lattice contraction of the domains as a result of bond shortening by the accumulation of metal centers in high valence oxidation states. The structural change is associated with increased metal-oxo covalency and charge delocalization. Comparable in-situ PDF measurements for the cobalt phosphate, CoPi, OEC show that charge accumulation leads to similar domain lattice contraction. In addition, for CoPi the CoIICoIII to CoIIICoIII transition is found to be coupled to Co-O peak broadening and amplitude decreases for pairs involving edge O atoms, identifying these as the sites for redox activity. Corresponding changes are seen in the P-O peak. These results provide experimental evidence for a Pi edge-associated model with bond length disorder. The PDF data shows that Pi remains edge-bound at the onset of water oxidation, suggesting the possible positioning of Pi for function in proton-coupled electron transfer. The cobalt OEC are also distinguished by X-ray absorption at the L3 edge, with CoPi showing both octahedral and tetrahedral Co(II) assigned to lattice and edge or extra-domain connecting sites, respectively. Finally, we demonstrate new AWAXS measurements for structure resolution in molecular and mixed metal OEC.
3D/2D Nanocomposite Phtotocatalyst Martials for Phenolic Compounds Degradations
Authors: Al-Kandari Halema Ali , Abdullah Aboubakr Moustafa , Mohamed Ahmed meslam , Al-Kandari Shekhah Ali
Published: February 2020

Nanocomposite photocatalysts of carbon nitride loaded on TiO2 and graphene oxide loaded on TiO2 different mass ratios were prepared by a hydrothermal treatment method and characterized using X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), UV-Vis diffuse reflectance spectroscopy (DRS) and Transmission Electron Spectroscopy (TEM). UV-Vis diffuse spectrum showed that the both nanocomposits exhibited absorption in the visible light range. The kinetics of the phenolic degradation using the as-prepared nanocomposite photocatalysts compared to the bare TiO2 nanoparticles was tested using Xenon lamps (mainly a visible light source) as a photoexcitation source in presence and absence of H2O2 and/or O3. For example, The photodegradation of phenol was evaluated using UV spectrophotometer and total organic carbon (TOC). It was revealed that the photocatalytic activity of the CNTi composites significantly higher than TiO2 nanoparticles. Furthermore, 0.1CNTi composite showed the best phenol degradation when H2O2 and O3 were simultaneously used in which the degradation percentage of phenol was more than 90% within 30 min
(Keynote) Novel Computational Approaches in Practical Bioelectrocatalysis
Authors: Matanovic Ivana , Babanova Sofia , Chavez Madelaine Seow , Abdellaoui Sofiene , Minteer Shelley D. , Atanassov Plamen
Published: February 2020

Computational approaches and tools play a fundamental role in modern science and have had an enormous impact on both fundamental and applied research across different scientific fields. This paper will describe some of the computational tools that can be used in concert with experimental approaches to explore various aspects in practical bioelectrocatalysis. This includes application of molecular docking simulations to explore new substrates for biocatalysts, which can enable development of novel synthetic catalytic cascades. Furthermore, we will show how docking simulations and first principles calculations can be combined with experimental approaches for a rational design of electrode surface modifications in biofuel cells and biosensors with enhanced performances.

Molecular docking simulations based on semi-empirical free energy force fields have the ability to efficiently and rapidly predict the binding-conformation of different ligands to a biomolecule with a known structure. Here, the fundamentals of docking simulations based on AutoDock, a suite of automated docking tools, will be presented together with several examples of their application in bioelectrocatalysis. We will first show how computational docking simulations can be used to predict the unexpected activity of the enzymes. Molecular docking simulations were used to predict the promiscuity of formate dehydrogenase from Candida boidinii (cbFDH) with mesoxalate, which was also tested with spectroscopic assays and characterization by HPLC and GC/TCD. Based on this assessment cbFDH was used in a combination with a molecular catalyst to create a hybrid cascade for complete electro-oxidation of glycerol to carbon dioxide (1). Density Functional Theory and docking simulations were further used to gain a fundamental understanding of the role that different small molecules, which are used to increase the efficiency of biocatalysts’ immobilization, have in the design and operation of enzymatic electrodes. These approaches were first used to explain the role of 1,2-benzoquinone, 1,4-benzoquinone, and ubiquinone on the operation and mechanism of electron transfer in PQQ-dependent soluble glucose dehydrogenase anode (2). The same approach was also combined with electrochemical measurements to explore the interaction of bilirubin oxidase and bilirubin modified graphene support for a design of oxygen reducing bio-cathodes based on bilirubin oxidase (3).

(1) S. Abdellaoui, M. Seow Chavez, I. Matanovic, A.Stephens, P. Atanassov, and S. Minteer. Chem. Commun.,Accepted, DOI:10.1039/C7CC01027C (2017).

(2) S. Babanova, I. Matanovic, M. Seow Chavez, and P. Atanassov, J. Am. Chem. Soc., 137, 7754-7762 (2015).

(3) I. Matanovic, S. Babanova, M. Seow Chavez, and P. Atanassov, J. Phys. Chem. B, 120, 3634−3641 (2016).

Figure 1
(Invited) Novel Nanostructured Catalyst Approaches for CO2 Electroreduction
Authors: Baturina Olga A , Lu Qin , Dyatkin Boris , Padilla Monica , Serov Alexey , Gogotsi Yury
Published: February 2020

High-surface area catalysts are crucial for electrochemical devices that rely on kinetically-limited electrochemical reactions. Two commonly used approaches to increase catalyst surface area include (1) placement of catalyst nanoparticles on high surface area support and (2) synthesis of highly porous unsupported catalyst structures. In this presentation, we will discuss both approaches along with several previously unexpected phenomena that we had discovered and, eventually, used to highly selectively electrochemically reduce CO2 to C2H4 [1, 2].

Nanostructured supports that were selected for CO2 electroreduction studies include reduced graphene oxide (RGO), single walled carbon nanotubes (SWNT) and onion-like carbon (OLC) [3]. These three supports share some common features, such as good chemical and thermal stabilities and high specific surface areas. Cu nanoparticles were deposited on the three supports using traditional wet chemistry methods.

For synthesis of highly porous unsupported Cu structures, a scalable surficial support method was developed [4, 5] that led to production of Cu nanoparticles with the optimal cubic morphology [6].

References

[1] O.A. Baturina, Q. Lu, M.A. Padilla, L. Xin, W. Li, A. Serov, K. Artyushkova, P. Atanassov, F. Xu, A. Epshteyn, T. Brintlinger, M. Schuette, G. Collins, ACS Catalysis 4 (2014) 3682

[2] O. A. Baturina, Q. Lu, F. Xu, A. Purdy, B. Dyatkin, X. Sang, R. Unocic, T. Brintlinger, Y. Gogotsi, Catalysis Today (2016, DOI:10.1016/j.cattod.2016.11.001)

[3] J. K. McDonough, Y. Gogotsi, Interface, 22 (2013) 61.

[4] U. Martinez, A. Serov, M. Padilla, P. Atanassov, ChemSusChem 7 (2014) 2351

[5] A. Serov, N. I. Andersen, A. J. Roy, I. Matanovic, K. Artyushkova, P. Atanassov, J. Electrochem. Soc. 162 (2015) F449

[6] M. Padilla, O. Baturina, J. P. Gordon, K. Artyushkova, P. Atanassov, A. Serov, J. of CO2 Utilisation 19 (2017) 137
(Keynote) In Situ and Operando Insight into CO2 electroreduction over Size- and Shape-Controlled Nanoparticles and Nanostructured Films
Authors: Roldan Beatriz
Published: February 2020

Tailoring the chemical reactivity of nanomaterials at the atomic level is one of the most important challenges in electro-catalysis research. In order to achieve this elusive goal, we must first obtain a fundamental understanding of the structural and chemical properties of these complex systems. In addition, the dynamic nature of the nanostructured films and nanoparticle (NP) catalysts and their response to the electrochemical environment must be taken into consideration, since their working state might not be the state in which the catalyst was prepared, but rather a structural and/or chemical isomer that adapted to the particular reaction conditions. To address the complexity of real-world electrocatalysts, a synergistic approach taking advantage of a variety of cutting-edge experimental methods (EC-AFM, AP-XPS, XAFS) has been undertaken here.

This talk will focus on model electrocatalysts (Ag, Cu, Cu-M with M = Zn, Ga, Sn, Co, Ni, Au, Ag) for the electrocatalytic reduction of CO2. We will show how rationally design electrocatalytically active model NPs with narrow size, shape, interparticle distance distributions and tunable oxidation state. Furthermore, we will provide insight into structure/chemical state-reactivity correlations during the electrochemical reduction of CO2 through an in situ and operando approach under reaction conditions. The results are expected to open up new routes for the reutilization of CO2 through its direct selective conversion into valuable chemicals and fuels such as carbon monoxide, methane, ethylene, ethanol, and propanol.
(Invited) Electrochemical Reduction of CO2 on Ligand-Protected Metal Nanoclusters
Authors: Alfonso Dominic R , Kauffman Douglas R. , Tafen DeNyago , Matranga Christopher
Published: February 2020

In this presentation, we report on the utilization of first-principles based computational technique to study electrochemical CO2 reduction mechanism on ligand protected metal nanoparticles. These materials are being pursued by the National Energy Technology Laboratory’s CO2 Utilization Technologies program in the quest to develop more active and selective catalyst for CO2 conversion into higher value products. We previously discovered an excellent CO2 conversion catalyst based on negatively charged, ligand-protected Au25(SC2H4Ph)18
- nanoclusters. A significant finding from our modeling is that ligand-protected nanocatalysts must be activated through the creation of surface defects. The exposed metals site is then free to function as critical reaction center for the conversion of CO2 into more valuable products. We have used this concept in our ongoing effort to understand the reduction process on ligand protected bimetallic Au-Cu nanoparticles. The reduction properties of such materials were experimentally found to be sensitive to the variation in the Cu content. Lastly, we present our ongoing investigation to predict trends in the activity of Ag, Au, Cu, Ir, Ni, Pd, Pt and Rh nanoparticles for CO2 reduction. We specifically looked at different particle sizes to investigate its influence on the activity.
(Invited) Molecular Electrochemical Catalysis of CO2 Reduction with Fe and Co Complexes. from Mechanistic Studies to Highly Selective CO Production and to More Reduced Products
Authors: Robert Marc
Published: February 2020

Recent attention aroused by the reduction of carbon dioxide has as main objective the production of useful products - the “solar fuels” - in which solar energy would be stored. One route to this goal consists in first converting sunlight energy into electricity, then used to reduce CO2 electrochemically. Conversion of carbon dioxide into carbon monoxide is thus a key-step through the classical dihydrogen-reductive Fischer-Tropsch chemistry. We will describe our work in this field using variously substituted iron tetraphenylporphyrin derivatives, that prove to be the most efficient molecular catalysts of the reduction of CO2 to CO when generated electrochemical at the Fe(0) oxidation state, both in terms of selectivity, durability, overpotential and turnover frequency. These catalysts are remarkably active not only in organic solvent (e.g. DMF) but also in pure water at pH 7. Benchmarking of the catalytic performances, through catalytic Tafel plots, leads to a fair comparison between various reported catalysts and detailed mechanisms were obtained from electrochemical studies. Going further, a complete CO2 conversion electrochemical cell functioning in pure water was also designed. Finally, our recent work and strategy to reduce CO2 beyond CO (for generating hydrocarbons) will be briefly presented.

References

[1] A. Tatin, J. Bonin, M. Robert, ACS Energy Lett.
2016, 1, 1062

[2] S. Drouet, C. Costentin, M. Robert, J-M. Savéant, Science, 2012, 338, 90-94.

[3] C. Costentin, M. Robert, J-M. Savéant, Chem. Soc. Rev., 2013, 42, 2423-2436.

[4] C. Costentin, G. Passard, M. Robert, J-M. Savéant, J. Am. Chem. Soc., 2013, 135, 9023-9031.

[5] C. Costentin, G. Passard, M. Robert, J-M. Savéant, J. Am. Chem. Soc., 2014, 136, 11821-11829.

[6] C. Costentin, M. Robert, J-M. Savéant, A. Tatin, PNAS
2015, 112, 6882-6886.

[7] A. Tatin, C. Cominges, B. Kokoh, C. Costentin, M. Robert, J-M. Savéant, PNAS
2016, 113, 5526-5529.

[8] A. Maurin, M. Robert, J. Am. Chem. Soc.
2016, 138, 2492-2495.

[9] I. Azcarate, C. Costentin, M. Robert, J-M. Savéant, J. Am. Chem. Soc.
2016, 138, 16639-16644.

[10] H. Rao, L. Schmidt, J. Bonin, M. Robert, 2017, in press.
Linear and Non-Linear Impedance Spectroscopy of Composite Gadolinia-Doped Ceria and LSCM Perovskite: Deconvolution of CO2 and H2o Co-Electrolysis
Authors: Witt Jonathan Michael , Stuve Eric M. , Adler Stuart B.
Published: February 2020

Recent advances in carbon capture create new opportunities for recycling CO2 into liquid fuels to store intermittent electrical energy1. One option is to co-electrolyze CO2 and H2O at high temperature using solid oxide electrolysis cells (SOECs). Although promising, the factors controlling rates of CO2 and H2O reduction in SOECs are not well understood, hampering development2,3. Traditional electrochemical techniques have difficulty resolving the various factors and mechanisms governing CO2 and H2O reduction. This limitation can potentially be overcome through the use of linear and non-linear electrochemical impedance spectroscopy (EIS and NLEIS) in conjunction with dynamic measurement of gas-phase species using mass spectrometry.

In regards to co-electrolysis, mixed ionic electronic conductors (MIEC) have gained interest as alternatives to nickel-yttria stabilized zirconia (Ni-YSZ) because the active region is not limited to the triple phase boundary and they are more stable in reducing environments3. Gadolinia-doped ceria coupled with perovskite La1-xSrxCr1-yMnyO3-δ (GDC-LSCM) has been a particularly well studied MIEC3.

We are currently conducting NLEIS and EIS measurements of CO2 reduction, water reduction, and co-electrolysis reduction experiments on button cells composed of GDC and LSCM as the working electrode with electrolyte YSZ under various temperatures and gas compositions. Gas atmospheres surrounding the cells contain various mixtures of water, CO2, CO, H2, and carrier gas such as Ar or N2. Currently hypothesized mechanisms/models on H2O and CO2 reduction are considered and scrutinized against NLEIS data in order to further reveal the nature of water and CO2 reduction.

References

Graves, C., Ebbesen, S. D., Mogensen, M., & Lackner, K. S. (2011). Sustainable hydrocarbon fuels by recycling CO2 and H2O with renewable or nuclear energy. Renewable and Sustainable Energy Reviews, 15(1), 1–23. https://doi.org/10.1016/j.rser.2010.07.014

Graves, C., Chatzichristodoulou, C., & Mogensen, M. B. (2015). Kinetics of CO/CO2 and H2/H2O reactions at Ni-based and ceria-based solid-oxide-cell electrodes. Faraday Discussions, 182(0), 75–95. https://doi.org/10.1039/C5FD00048C

Valdes-Espinosa, H., Stuve, E. M., & Adler, S. B. (2015). Modeling Water Reduction on 10 Mole% Gadolinia-Doped Ceria (GDC10) Porous Electrodes. ECS Transactions, 66(2), 229–251. https://doi.org/10.1149/06602.0229ecst
Selectivity and Efficiency of Heat Treated Sputter Deposited Thin Films of Copper towards the Carbon Dioxide Electro-reduction
Authors: Permyakova Anastasia A. , Patru Alexandra , Herranz Juan , Schmidt Thomas J.
Published: February 2020

The CO2 electro-reduction has the potential to store energy from intermittent renewable sources and to produce valuable carbon-neutral fuels or chemical feedstocks. However, current CO2 reduction technologies are challenged by high overpotentials, poor overall faradaic efficiencies (FE) and low selectivity, producing a mixture of carbon monoxide, methane, ethylene, formate, methanol, ethanol, and others. Catalyst performance is a significant contributor to these factors due to multiple proton-coupled electron transfer steps of CO2 electro-reduction reaction [1-3].

Recent experimental studies on Cu electrocatalysts have shown that higher CO2 and CO reduction efficiencies and selectivities towards certain valuable products could be achieved by modifying these metallic electrodes [4, 5]. For example, Cu thin films prepared by electrochemically reduced thermally grown Cu oxide (Cu2O) layers exhibit dramatically improved selectivity towards ethanol at significantly lower potentials (up to 50% FE at -0.35 V vs. RHE) in comparison to non-treated Cu catalysts (»3% FE at -0.35 V vs. RHE) [5].

Herein, inspired by these studies, we will present detailed examination of modified Cu thin film electrodes for CO2 reduction. Cu thin films are fabricated by reactive sputter deposition and subsequently modified by heat treatment varying the temperature and time of exposure. A combination of SEM/EDX, XRD and XPS were used for physico-chemical characterization. Whereas, CO2 electro-reduction products were monitored using in line GC for gas products and capillary GC, IC, NMR for liquid products. The results show that these modified Cu surfaces can improve the selectivity and efficiency of the catalyst.

Acknowledgements

Financial support of this work by the Swiss Competence Center for Energy Research Heat and Electricity Storage, the Competence Center Energy and Mobility, and Swiss Electric Researach and the Swiss Federal Office of Energy are greatly acknowledged.

References

[1] J. Herranz, J. Durst, E. Fabbri, A. Patru, X. Cheng, A.A. Permyakova, T.J. Schmidt, Nano Energy
2016, 29, 4.

[2] J. Durst, A. Rudnev, A. Dutta, Y. Fu, J. Herranz, V. Kaliginedi, A. Kuzume, A.A. Permyakova, Y. Paratcha, P. Broekmann, T.J. Schmidt, Chimia
2015, 12, 69.

[3] Y. Hori, «Electrochemical CO2 reduction on metal electrodes. Modern aspects of electrochemistry», eds C. Vayenas, R. White, M. Gamboa-Aldeco (Springer, New York), 2008, Vol 42, pp 89–189.

[4] Y. Chen, C. W. Li and M. W. Kanan, J. Am.
Chem. Soc. 2012, 134, 19969 – 19972.

[5] C. W. Li, J. Ciston and M. W. Kanan, Nature
2014, 508, 504 – 507.
Implicit Solvation for Electrochemical Interfaces
Authors: Schwarz Kathleen , Letchworth-Weaver Kendra , Sundararaman Ravishankar
Published: February 2020

Solvation plays a key role in determining the capacitance behavior of the electrochemical interface, yet it presents significant challenges for computational modeling due to its complexity. We have recently demonstrated (doi: 10.1063/1.4976971) that the solvation models currently implemented in density functional theory (DFT) codes such as VASP perform poorly for the capacitance of aqueous metallic interfaces. In this talk, I identify solvation model characteristics that are necessary for capturing the nonlinear capacitance behavior of aqueous metallic interfaces.
Structure and Transport of “Water-in-Salt” Electrolytes from Molecular Dynamics Simulations
Authors: Borodin Oleg , Suo Liumin , Olguin Marco , Cresce Arthur v. , Vatamanu Jenel , Wang Fei , Ren Xiaoming , Dura Joseph A. , Faraone Antonio , Gobet Mallory , Munoz Stephen , Greenbaum Steven , Wang Chunsheng , Xu Kang
Published: February 2020

Currently used lithium ion batteries for portable electronics utilize flammable and often toxic non-aqueous electrolytes in order to achieve high energy densities. They also require a low humidity manufacturing environment resulting in an increased cost. Aqueous electrolytes have recently emerged as potential intrinsically nonflammable alternatives after their electrochemical stability window was expanded beyond 3.0 V by employing a new class of “Water-in-Salt” electrolytes. In such super-concentrated electrolyte, the decomposition of salt anion occurs preferentially on the anode before hydrogen evolution takes place, creating a kinetic protection against electrochemical decomposition via a dense solid electrolyte interphase (SEI).

In this presentation, results from classical molecular dynamics (MD) simulations using a polarizable APPLE&P force field are analyzed in order to examine in detail the ion transport mechanism in bis(trifluoromethane sulfonyl)imide (LiTFSI-water) “Water-in-Salt” electrolytes (WiSE) for safe, green and low cost aqueous lithium ion batteries. They are complemented by Born Oppenheimer MD simulations of smaller systems that yield similar structural features. Simulations revealed an unusually low activation energy and fast ion transport for highly concentrated solutions even at low temperatures that is quite different from the dramatic increase of the activation energy for conductivity found in traditional battery electrolytes. A high conductivity and lithium transference number in WiSE is attributed to the formation of fast ion transporting pathways that are connected to the unexpected structure of WiSE electrolytes, which was confirmed by small angle neutron scattering experiments (SANS). The ability of MD simulations to describe dynamics of ion and solvent in WiSE electrolytes was further validated via pfg-NMR and conductivity measurements, while IR spectroscopy measurements provide a comprehensive picture of the salt electrolyte aggregation that is coupled with ion transport.

The connection between the double layer structure of WiSE electrolytes and its electrochemical stability will be briefly discussed.
Computational Study of the Effect of Surface-Bound Disulfide on the Oxygen Reduction Reaction
Authors: Allison Thomas C , Tong YuYe
Published: February 2020

The ability of certain surface-bound species to significantly reduce or prevent activity on catalyst surfaces is well established. However, it was recently discovered that disulfide (S2–) bound to a Pt (111) surface could promote the oxygen reduction reaction (ORR). Despite this important observation, the mechanism by which it takes place remains unclear. As the ORR plays a critical role in areas such energy conversion, understanding some or all of the mechanistic steps in this process should be of great value in producing improved OOR catalysts and in understanding promotion effects of surface-bound species.

In this talk, periodic planewave calculations of the ORR on a Pt(111) catalyst surface with varying coverages of disulfide will be discussed. Comparison of computed and experimental IR spectra of intermediate species will be used to validate the computational methodology. The results of the calculations will be used in a mean-field microkinetic model to better understand the origin of the promotion effect due to the presence of the disulfide.
Density Functional Theory Studies of CO-Tolerant Stabilized Platinum Skin/Platinum Alloy Catalysts for the Hydrogen Oxidation Reaction
Authors: Tryk Donald A. , Yano Hiroshi , Shi Guoyu , Ogihara Yoshiyuki , Iiyama Akihiro , Uchida Hiroyuki
Published: February 2020

Carbon monoxide is a common contaminant in hydrogen produced by the reformation of natural gas and acts as a poison for platinum-based catalysts in hydrogen anodes in polymer electrolyte fuel cells (PEFCs). CO poisoning can be alleviated through the use of Pt skin-covered Pt alloys including first row transition metals, e.g., Pt-Fe, Pt-Co and Pt-Ni, as well as second row transition metals, e.g., Pt-Ru, on which CO is known to adsorb more weakly than on pure Pt.1 Thus, hydrogen would be able to compete more successfully for adsorption sites. The weakened CO adsorption has usually been explained on the basis of the d-band center being lowered and antibonding orbitals becoming populated. However, our recent density functional theory (DFT) results, together with a range of experimental results, as reported by our group (H. Yano, et al.) separately at this Meeting, suggest that the situation is somewhat more complicated.2-5 In addition, little attention has been paid to the hydrogen oxidation reaction (HOR) itself, which we have found to be enhanced on these surfaces in parallel with experimental work.2,3 Our calculations indicate that the adsorption of H atoms is also weakened, so that the latter can become more mobile on the surface. The largest degree of weakening was found for the Pt-Fe alloy.3 Making use of realistic models for the surfaces, with (110) steps and (111) terraces, we found evidence for a new type of hydrogen spillover mechanism, in which H2 adsorbs at steps, dissociates, and the dissociated H atoms diffuse to (111) terraces.3,4 Finally, the calculations indicate that the Pt skin/Pt alloy structure is more rigid than that of pure Pt, which might be a factor in the enhanced durability of the catalyst under fuel cell operating conditions.5

This work was supported by funds for the “Superlative, Stable, and Scalable Performance Fuel Cells (SPer-FC)” project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

References

H. Igarashi, T. Fujino, Y. Zhu, H. Uchida, and M. Watanabe, P
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G. Y. Shi, H. Yano, D. A. Tryk, M. Watanabe, A. Iiyama, and H. Uchida, Nanoscale
8, 13893 (2016).

G. Y. Shi, H. Yano, D. A. Tryk, A. Iiyama, and H. Uchida, ACS Catal.
7, 267 (2017).

Y. Ogihara, H. Yano, T. Matsumoto, D. A. Tryk, A. Iiyama, and H. Uchida, Catalysts
7, 8 (2017).

G. Y. Shi, et al., to be submitted.

Fig. 1. Adsorption energies for (A) H2 or 2H, (B) CO, and (C) H2O at step edges (triangles) and terraces (squares). In (A), the solid symbols denote dissociated 2H, while the open symbols denote undissociated H2. In all cases except for PtRu, undissociated H2 does not adsorb on the surface, either at step edges or terraces. On pure Pt(221), H2 dissociates spontaneously when close to the surface, while on Pt1AL–PtFe, Pt1AL–PtCo and Pt1AL–PtNi, it “floats” away from the surface.3

Figure 1
Doping Amorphous Ti Oxides to Decrease Oxygen Reduction Rates
Authors: Groenenboom Mitchell C. , Keith John A.
Published: February 2020

Galvanic corrosion is powerful enough to degrade materials that are individually corrosion resistant. Metal oxidation at an anodic reaction site on the less noble metal is coupled to reduction reactions at a cathodic reaction site on the more noble metal. The oxygen reduction reaction (ORR) is a major controlling reaction for galvanic corrosion in atmospheric conditions.1-2 Thus, inhibiting ORR rates is a chance to inhibit galvanic corrosion. We use Kohn-Sham density functional theory to predict dopants that best inhibit ORR rates on natively formed Ti oxides.

We created an amorphous TiO2 surface model that both agrees with experimental XRD data and predicts an ORR overpotential in good agreement with experimental measurements (exp = 0.45 V, PBE = 0.5 V and HSE06+VASPsol = 0.43 V). By modeling the ORR intermediates adsorbed to metal dopants embedded into our model surface at their most favorable oxidation states, we successfully predicted dopants that have been experimentally verified to reduce ORR currents by up to 77%. PBE predicted overpotentials agree with those predicted by hybrid DFT (HSE06) with VASPsol continuum solvation. Further work studying the potential impact of oxygen vacancies will be discussed.

References

1. Mansfeld, F.; Parry, E. P., Galvanic Corrosion of Bare and Coated Al Alloys Coupled to Stainless Steel 304 or Ti-6Al-4V. Corros. Sci.
1973,
13, 605-621.

2. Zhou, X.; Luo, C.; Hashimoto, T.; Hughes, A. E.; Thompson, G. E., Study of Localized Corrosion in AA2024 Aluminium Alloy Using Electron Tomography. Corros. Sci.
2012,
58, 299-306.
Understanding and Tailoring the Performance of Transition Metal Oxides for the Oxygen Evolution Reaction
Authors: Tripkovic Vladimir , Hansen Heine A. , Garcia Lastra Juan Maria , Vegge Tejs
Published: February 2020

The oxygen evolution reaction (OER) is a bottleneck in direct solar and electrocatalytic water splitting cells, and rechargeable aqueous metal-air batteries. Improving the cost-efficiency of these devices requires development of efficient and cheap oxygen evolving catalysts. A good catalyst material should fulfil several important criteria: the composition and structure should be stable at conditions of interest, it should be able to conduct electrons from the active site, and it should be sufficiently active to catalyze water oxidation to oxygen. Furthermore, the catalyst should be cheap and non-toxic.

We explore two different oxide classes: pristine and doped perovskite oxides (ABO3, where A is the alkaline earth or lanthanide metal and B the 1st row transition metal) and several MnO2polymorphs. Stability and the electronic conductivity of doped materials are assessed and compared to pristine catalysts by computing formation energies and analyzing the electronic structure of bulk crystals, respectively. After selecting stable dopants, we calculate the relevant surface termination and deduce the reaction overpotential from the energetically most favorable reaction mechanism.

For the perovskite oxides, we identify Fe4+, Co3+(IS), Ni3+ and Mn3+/Mn4+ pairs as electronically conductive species and distinguish among three different electron conduction types: intrinsic conductance (Fe4+ and Ni3+), electron polaron hoping along the Metal-Oxygen-Metal chains (Mn3+/Mn4+) and conduction via oxygen holes in the valence band. Although, the intrinsic stabilities of La perovskites are rather low, they are likely to be the most stable catalysts in open systems because they do not form carbonates. From a combinatorial analysis on La perovskites, we identify the most promising oxygen evolving catalysts.

We find that the OER activity of MnO2 polymorphs reduces in the αMnO2 > βMnO2 > γMnO2 sequence. We pinpoint αMnO2 as the most active catalyst and subsequently investigate whether its performance can be furthered by doping. The electronic conductance is greatly improved by creating Mn3+ sites, i.e. Mn3+/Mn4+ pairs, which is accomplished by intercalating electrolyte ions (e.g. Na+ or K+) inside αMnO2 voids. From catalytic analysis, we identify Pd and Co doped αMnO2 as the most active catalyst for oxygen evolution.

This work was supported by the Horizon 2020 framework, grant number 646186

Figure 1
(Invited) Electrochemical Energy Storage of Magnesium in Hydrated and Anhydrous Tungsten Oxides
Authors: Wang Ruocun , Augustyn Veronica
Published: February 2020

Transition metal oxides are of interest as cathodes for rechargeable, non-aqueous Mg2+ batteries due to the possibility for high voltage and capacity when paired with a magnesium metal anode. In general, it has been found that Mg2+ storage in oxides is much more sluggish than monovalent cation storage such as Li+ or H+. Several strategies have been proposed to overcome the kinetic activation barrier of Mg2+ storage in oxides, including the use of interlayer structural water and nanostructuring. While hydrated metal oxides such as MnO2 and V2O5 have been investigated, relatively little is known about the exact role of the structural water in such materials during Mg2+ storage. In this study, we utilize a model system of crystalline tungsten oxides with different degrees of hydration (WO3·nH2O, where n = 0, 1, or 2). This materials system allows for an investigation of two different types of structural water: one that is covalently bound to tungsten, and one that is present only in the interlayer. The effect of covalently bound water has not yet been investigated for Mg2+ storage. Using cyclic voltammetry and ex situ Raman spectroscopy and scanning electron microscopy, we find that in these materials, the Mg2+ energy storage mechanism is due to intercalation. Moreover, we find that the interlayer water in WO3·2H2O is not stable in a non-aqueous electrolyte and that the material quickly transforms to WO3·H2O. However, the covalently bound water in WO3·H2O is stable and as a result, this material exhibits faster kinetics than WO3. The improved kinetics come at the expense of the capacity, which decreases by approximately half as compared to the anhydrous material. These results provide additional insights into the benefits and drawbacks to use of hydrated metal oxides for Mg2+ storage.
(Invited) Capabilities and Opportunities for Next-Generation Ag–3D Zn Batteries
Authors: Parker Joseph F. , Ko Jesse , Rolison Debra R. , Long Jeffrey W.
Published: February 2020

Silver–zinc batteries offer high specific energy (up to 190 Wh kg–1) and the highest specific power of any known commercial battery (up to 600 W kg–1 continuous power and 2,500 W kg–1 pulses). The Ag–Zn system operates using water-based electrolytes and nonhazardous active materials, providing an ideal battery alternative to Li-ion (flammable; explosive) and Pb-acid (toxic) in the diverse markets where these drawbacks must be avoided. Despite the many advantages of Ag–Zn batteries, adoption beyond specialized applications is hindered by a Zn anode that accesses only middling zinc specific capacity and has limited rechargeability. We have recently overcome these hurdles by developing a monolithic Zn sponge electrode that exhibits cycling durability in prototype Ni–Zn cells and a 50% greater specific capacity in Zn–air cells, both relative to the same systems that use conventional powder-bed Zn electrodes. The cathodes used in those chemistries are ill-equipped to counter-balance the specific power that the Zn sponge has to offer. Silver–zinc presents higher power and energy density than Ni–Zn batteries and a more market-ready cathode than Zn–air, making Ag–3D Zn an attractive battery chemistry with which to demonstrate the triumvirate of rechargeability, high specific energy, and high specific power. We present prototype Ag–3D Zn cells that discharge to record-breaking extreme depths-of-Zn-discharge, support rechargeability rarely seen in the Ag–Zn system, and can operate at 104–105 W kgZn
–1. Toward the goal of developing next-generation Ag–3D Zn batteries, we also describe our breakthroughs and existing challenges in: (i) the design of full cell Ag–3D Zn prototypes; (ii) the fabrication of beta 2.0 Zn sponges with tunable density; and (iii) the preparation of AgxO cathodes that support the high performance of Zn sponge anodes.
(Invited) Metal-Organic Framework-Derived Electrocatalysts for Li‒O2 Batteries
Authors: Lu Jun , Tan Guoqiang , Amine Khalil
Published: February 2020

Recently, metal-organic framework (MOF) materials have been studied as cathode materials for Li‒O2 batteries due to their high catalytic activity, uniform structure, and simple preparation process. However, further optimization of materials and structures should be undertaken to improve their electrochemical performance for the practical application.1-3 Here we report a uniform MOF-derived multiple-capsule heterostructure, nitrogen-doped cobalt@graphene, as the cathode catalysts for Li‒O2 cells. This N-Co@graphene multiple-nanocapsule structure improves the electrical properties and makes the high/uniform electroactive zones possible. In addition, the rational design of flexible foam-based electrodes possessing colander-like porous structures facilitates the oxygen diffusion, catalytic reaction, and deposition of discharge products. The electrode thus exhibits much improved electrochemical performance associated with unique morphologies of electrochemically grown lithium peroxides.

Figs. 1a-c display the microstructure and morphology of N-Co@graphene nanocomposite. The composite has a lotus shower-like shape, where the crystalline Co nanoparticles, sized of 10‒20 nm, display highly ordered lattice fringes, being wrapped by few-layer graphenes, thus forming core-shell nanostructures. Note that there are few layers of specific lattice fringes with 0.25 nm lattice spacing existing on the surface of Co particles, which are indexed to be cobalt nitride that are generated from the nitrogen dopant into surficial lattices of Co crystalline. Fig. 1d show its EELS profile, which confirms the presence of C, N, and Co elements in the composite. Figs. 1e, f show its electrochemical performance in Li‒O2 cells. The composite electrodes exhibit reduced charge-discharge overpotential and good cycling stability. This finding is mainly attributed to the improved electrical properties, electrocatalytic activity, and structural stability of N-Co@graphene nanostructures.

Fig. 1 Structural and electrochemical characterization of MOF-derived N-Co@graphene catalysts. (a-c) TEM images, and (d) EELS profile of N-Co@graphene nanocomposite. (e,f) Voltage profiles versus selected cycles of N-Co@graphene composite based on carbon fiber (e) and nickel foam (f) electrodes.

References

1. Li, Q.; Xu, P.; Gao, W.; Ma, S.; Zhang, G.; Cao, R.; Cho, J.; Wang, H. L.; Wu, G. Adv. Mater.
2014, 26, 1378-1386.

2. Wu, D.; Guo, Z.; Yin, X.; Pang, Q.; Tu, B.; Zhang, L.; Wang, Y. G.; Li, Q. Adv. Mater.
2014, 26, 3258-3262.

3. Tan, G.; Chong, L.; Amine, R.; Lu, J.; Liu, C.; Yuan, Y.; Wen, J.; He, K.; Bi, X.; Guo, Y.; Wang, H.-H.; Shahbazian-Yassar, R.; Hallaj, S. A.; Miller, D. J.; Liu, D; Amine, K. Nano Lett. 2017, DOI: 10.1021/acs.nanolett.7b00207.

Figure 1
(Invited) Decoding Multi-Gas Mixtures Using a Mixed-Potential Sensor Array for Vehicular Emission Monitoring
Authors: Ramaiyan Kannan Pasupathikovil , Javed Unab , Kreller Cortney R. , Brosha Eric L. , Morozov Alexandre , Mukundan Rangachary
Published: February 2020

Electrochemical gas sensors with the ability to detect the concentration of individual gases in a multi-gas environment are in huge demand in many areas of technology, such as threat detection, industrial quality control and, importantly, vehicular emission monitoring. While oxygen l sensors are used for on-board diagnostics in spark-ignition vehicle emission systems, a similar sensor is not available for NOx, NH3 and non-methane hydrocarbon (NMHC) gases found in diesel engine exhaust. LANL has developed patented pre-commercial prototype mixed-potential sensors with strong sensitivity and selectivity towards these target gases, but a single device with absolute selectivity is still elusive (1, 2).

To address this pressing problem, we have tested and successfully demonstrated the utility of employing a sensor array rather than individual sensors, in conjunction with a first-principles data analysis approach. Our computational framework was employed to predict the composition of gas mixtures containing two individual gases, both of which affect sensor readings, with less than 2% average error (3). Here we present the results of our model trained on three and four-gas mixtures involving NO, NO2, NH3 and C3H6. The three sensors used in the array comprise a dense La0.8Sr0.2CrO3 or AuPd sensing electrode and dense Pt electrode with porous YSZ electrolyte. A physically motivated model is used to analyze the data and find the composition of the gas mixture. This work aims to provide robust and accurate estimates of NOx, NH3 and unburnt non-methane hydrocarbon content in diesel vehicle exhaust, laying a foundation for on board, real-time sensing applications. Acknowledgments

The research was funded by the Los Alamos National Laboratory Directed Research Development Exploratory Research (LDRD-ER) program.

References

R. Mukundan, E. L. Brosha, F. H. Garzon, US 7,575,709 (2009).

R. Mukundan, E. L. Brosha, F. H. Garzon, Journal of The Electrochemical Society
150, H279 (2003).

K. P. Ramaiyan, C. R. Kreller, E. L. Brosha, R. Mukundan, U. Javed, A. V. Morozov, ECS Transactions (2016) 75, 107-111.

LA-UR-17-23016