bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Standing Waves in a Thin Layer Sonoelectrochemical System
Authors: Landgren Jeffrey K , Strohmer Gerhard , Leddy Johna
Published: February 2020

Recent experiments in thin layer sonoelectrochemistry demonstrate that sonication increases the rates of electrocatalysis. Heterogeneous electron transfer rates increase substantially upon ultrasound irradiation. A model is developed using Partial Differential Equations and the Finite Element Method to understand catalytic effects observed when sound waves are applied in a thin layer electrochemical cell.

The cell consists of a hollow Teflon cylinder with a transducer as the base, seen in Figure 1. A three electrode system is used with the electrodes spaced equally apart and parallel to the cylinder base. The cylinder is filled with a redox probe and electrolyte solution such that a meniscus forms at the top. The transducer propagates sound waves through the solution (i.e., sonication). A comparison of cyclic voltammograms before, during, and after sonication reveals enhancement effects from the sound waves. For redox probes with slow kinetics, sonication simultaneously increases currents and appears to shift the reaction to more reversible. Data indicate that a combination of the height and shape of the meniscus play a vital role in this enhancement effect.

Partial differential equations is used in conjunction with numerical analysis to develop and solve the model, respectively. The model takes into account the shape and height of the meniscus as well as the pressure, density, elasticity, mass, and surface tension of the fluid near the meniscus. Then the Finite Element Method reveals the standing waves of the system. Standing waves occur in a stationary medium when waves are traveling in opposite directions and cause interference with one another. In general, if this scenario occurs with waves of approximately the same amplitude there is no net change in energy, another indication that the height of the meniscus is relevant.

To help quantify this phenomenon, four equations are used, seen in Figure 2. Following this basis functions in the finite element space are used to convert our continuous problem to a discrete one via the weak formulation. A reduction of the wave equation to an eigenvalue problem gives way to our standing waves in the form of an eigenfunction expansion. The wave interference taking place in the cell can be seen in Figure 1.

This model is important for prediction of behavior of the sound waves before and after they contact the top boundary and the role of the meniscus convexity. This will lead to advances in understanding the experimental system for applications in electrocatalysis.

Figure 1
(Invited) Application of Density Functional Theory in the Design of Materials for Fuel Cell Applications
Authors: Matanovic Ivana , Atanassov Plamen
Published: February 2020

Rational design of novel materials for energy applications demands a deeper understanding at the atomic level of the origin of relevant properties of materials and associated processes. The use of Density Functional Theory (DFT) has resulted in major breakthroughs in those efforts and has had an enormous impact both on fundamental and applied materials research. This paper will describe some of the efficient computational tools, which can be used in concert with experimental approaches to explore various aspects in the design of both platinum group metal and non-platinum group matal based materials for fuel cell applications.

The first part will be a discussion of the capabilities of DFT to model the structure of, and catalytic processes on different catalytic materials. Examples include an explanation of the observed catalytic activity of CuCo2O4  ORR/OER bi-functional catalysts by DFT methods, and the structure-property relationships in novel 3D graphene hybrid materials synthetized at UNM [1]. This will be followed by a description of theoretical modeling of the catalyst-ionomer interface, which can identify some key ionomer features of crucial importance for their efficient implementation with the specific electro-catalyst in the anion and proton exchange membrane fuel cells. Examples in this part include the interaction of organic cations with an extended platinum surface and nafion with M-N-C type catalysts. DFT based approaches as a support for spectroscopic measurements of surface phenomena will be discussed in the last part of this talk, including the advantages and disadvantages of DFT in reproducing accurate vibrational spectra of surface bound species [2]. Finally, the use of core level shifts obtained from DFT calculations can facilitate the interpretation of X-ray Photoelectron Spectroscopy (XPS) experiments, and thereby support the effort to determine structure to reactivity relationships that are essential for reaching an understanding of M-N-C catalysts on the molecular level.

[1] A. Serov, N. I. Andersen, A. J. Roy, I. Matanovic, K. Artyushkova, P. Atanassov, CuCo2O4 ORR/OER Bi-Functional Catalyst: Influence of Synthetic Approach on Performance. J.Electrochem. Soc.162 (4) F449-F454 (2015).

[2]I. Matanović, P. Atanassov, B. Kiefer, F. H. Garzon and N. Henson, Applicability of Density Functional Theory in Reproducing Accurate Vibrational Spectra of Surface Bound Species. J. Comput. Chem., 35, 1921-1929 (2014).

Figure 1
Design of Nanoporous Carbons As Anode Materials for Sodium (Na) Ion Batteries
Authors: Cai Qiong , Karatrantos Argyrios
Published: February 2020

Sodium (Na) ion battery (NIB) has recently attracted increasing interest worldwide as a promising next-generation energy storage technology, because of the natural abundance, wide availability and low cost of Na resources. Operating at ambient temperature, NIBs provide a safer and sustainable energy storage solution [1,2]. These batteries could potentially approach the performance of Li-ion batteries if optimal electrode and electrolyte materials are identified.  

In this project, we focus on the design of the negative electrode materials  for Na ion batteries [2]. Nanoporous carbons are one of the materials that have been used as negative electrode materials, providing the necessary low cost, low voltage and good capacity. However, the intercalation mechanism of Na ions into the complicated 3D porous structure is still unknown; these carbons need to be designed  and optimized for best performance in NIBs.

By means of atomistic molecular dynamics simulations [3], the diffusion of sodium (Na) ions is investigated for different carbon electrode geometries, such as slit nanopore and rough nanopore, and nanopore sizes.  Slit and rough nanopores predict a different Na ion dynamics. Also, for sub-nanometer pore sizes the electrostatic surface charge decreases the Na ions diffusivity inside the nanopore. Our goal is to understand the fundamentals of adsorption and diffusion of Na ions in nanoporous carbons and develop an improved carbon model for the design of these materials. 

Acknowledgement

The authors are grateful for funding support from EPSRC.

 References 

[1] H. Kang, Y. Liu, K. Cao, Y. Zhao, L. Jiao, Y. Wang, H. Yuan, J. Mater. Chem. A 3,  17899 (2015).

[2] V. L. Chevrier and G. Ceder, Journal of The Electrochemical Society, 158, A1011-A1014 (2011).

[3] G. Kamath, R. W. Cutler, S. A. Deshmukh, M. S. Fard, R. Parrish, J. Huether, D. P. Butt, H. Xiong, S. K. R. S. Sankaranarayanan, J. Phys. Chem. C, 118, 13406, (2014).
Simulation of a Multi-Hole Cathode Bipolar Plate Design for Polymer Electrolyte Membrane Fuel Cells
Authors: Baik Kyung Don , Ji Hyunjin , Kim Kiyeol , Kim Jiyeon , Cho Sung Baek
Published: February 2020

The utilization of fuel cells for powering various applications such as automotive and military equipment requires a reduction in size as well as an increase in power, as current fuel cell systems are not profitable and still too large. Solving these issues for fuel cells requires a novel fuel cells structure that enables high power density operation. In this study, the two-dimensinal steady state model considering the bipolar plate with multi-hole was developed to investigate how the multi-hole design affects the cell performance. We found out that the hole formation on the land area for the cathode bipolar plate has significantly influenced on the cell performance. Results show that the average current density for the multi-hole bipolar plate is increased up to 28.64% because of the uniform distribution of oxygen mole fraction.
(Science for Solving Society’s Problems Challenge Grant Winner) eLatrines: Development of a Fully Cardboard based Microbial Fuel Cell for Pit Latrines
Authors: Kretzschmar Jörg , Riedl Sebastian , Brown Robert K. , Schröder Uwe , Harnisch Falk
Published: February 2020

The aim of the project was to provide full experimental proof-of-concept that stand-alone power generation based on microbial fuel cells (MFCs) operated on human feces from pit latrines as substrate can be achieved. Thereby, the establishment of these eLatrines was based on MFC-technology and the components were to be gained from low-cost materials and through low-tech approaches. For the latter the system was to be developed so as to utilize as many components as possible that can be produced by non-trained persons in decentralized areas for example in developing countries, e.g. the cardboard based electrodes. This presentation summarizes achievements and the lessons learned for i) electrodes gained from corrugated cardboard to be used as anodes and cathodes; ii) anodes being operated using real human feces as substrate; iii) cathodes – with nitrogen functionalities derived from (artificial) urine and based on corrugated cardboard - for oxygen reduction reaction activity; iv) pre-tests on using vent-air from ovens/ fireplaces for allowing low-tech carbonization of corrugated cardboard, v) the operation of the described components in a combined approach under potentiostatic control as well as in fuel cell mode.

In summary, we will show that the overall concept of a stand-alone power generation from human feces in urine can become technically feasible as well as economically and societal relevant. However, the achieved current densities of less than 100 µA/ cm2 (geometric surface area) as well as challenges due to the operation with real, highly inhomogeneous substrates like clogging of electrodes’ pores, formation of insulating fat layers at cathodes, etc. highlight the need for a thorough process engineering.
TiO2@MnO2 Core-shell Nanofibers as Positive Electrodes for Asymmetric Supercapacitors
Authors: Kolathodi Muhamed Shareef , Voigt Victoria , Singh Gurpreet
Published: February 2020

Manganese dioxide coated titanium dioxide (MnO2-TiO2) nanofibers, prepared by electrospinning and post-hydrothermal process exhibited high electrochemical properties in aqueous Na2SO4 electrolyte. The thin MnO2 shell with average thickness of 10 nm contributed to the high electrochemical performance for charge storage by redox reaction and intercalation mechanisms, while the anatase phase TiO2 core provided an easy pathway for electronic transport with additional electrochemical stability over thousands of charge-discharge cycles. An asymmetric supercapacitor designed from the MnO2-TiO2 nanofibers and single walled carbon nanotubes showed high voltage window (2.2 V) with maximum gravimetric capacitance of 111.5 Fg-1.
(Invited) Carbon Nanotube Network As Stable and Efficient Electron Blocking Layer and Transparent Conductive Electrodes for Solar Cells
Authors: Maruyama Shigeo , Cui Kehang , Jeon Il , Chiba Takaaki , Xiang Rong , Chiashi Shohei , Kauppinen Esko , Matsuo Yutaka
Published: February 2020

Films of single-walled carbon nanotubes (SWNTs) network are promising flexible transparent-conductive electrode for various types of solar cells. Furthermore, adequately p-doped SWNTs network can also act as a stable conductive electron blocking layer (EBL). We have demonstrated these characteristics in honeycomb-structured SWNTs-Si solar cells [1], dry-deposited SWNTs-Si solar cells [2], graphene-Si solar cells, organic solar cells (OSC) [3,4], and perovskite-type solar cells [5]. Millimeter-scale single crystal graphene [6] also exhibits similar properties as SWNTs networks. Air-stable power conversion efficiency (PCE) of about 11 % are demonstrated for SWNT-Si or graphene-Si solar cells without the intentional doping. PCE about 5 % can be obtained for inverted and normal organic solar cells. The EBL and electrode functions of SWNT network were also demonstrated in normal and inverted type perovskite solar cells with over 9% PCE.

 

References:

[1] K. Cui, T. Chiba, S. Omiya, T. Thurakitseree, P. Zhao, S. Fujii, H. Kataura, E. Einarsson, S. Chiashi, S. Maruyama, J. Phys. Chem. Lett., 4 (2013), 2571.

[2] K. Cui, A. S. Anisimov, T. Chiba, S. Fujii, H. Kataura, A. G. Nasibulin, S. Chiashi, E. I. Kauppinen, S. Maruyama, J. Mater. Chem. A, 2 (2014) 11311.

[3] I. Jeon, K. Cui, T. Chiba, A. S. Anisimov, A. G. Nasibulin, E. I. Kauppinen, S. Maruyama, Y. Matsuo, J. Am. Chem. Soc., 137 (2015) 7982.

[4] I. Jeon, C. Delacou, A. Kaskela, E. I. Kauppinen, S. Maruyama, Y. Matsuo, submitted (2015).

[5] I. Jeon, T. Chiba, C. Delacou, Y. Guo, A. Kaskela, O. Reynaud, E. I. Kauppinen, S. Maruyama, Y. Matsuo, Nano Lett., 15 (2015) 6665.

[6] X. Chen, P. Zhao, R. Xiang, S. Kim, J. Cha, S. Chiashi, S. Maruyama, Carbon, 94 (2015) 810.
(Invited) Influence of Purity and Processing on Freestanding SWCNT Nanosheets and Nanotube-Silicon Heterojunctions
Authors: Hobbie Erik K.
Published: February 2020

Single-wall carbon nanotubes (SWCNTs) of varied polydispersity (length, electronic type and chirality) are used to study the impact of SWCNT purity and processing on both the durability of freestanding SWCNT nanosheets and the performance of SWCNT-silicon heterojunctions. Solution-processed SWCNT films are deposited on n-doped silicon substrates and p-doped to yield photovoltaic devices with competitive photo-conversion efficiency, fill factor and open-circuit voltage. The temperature dependence of the dark-current density and its transient recovery after an abrupt change in bias are used to clarify the nature of the junctions over a broad range of SWCNT polydispersity and processing schemes, where the latter varies from the vacuum filtration of aqueous colloidal SWCNTs to the flow-deposition of aligned nanotube super-acid suspensions. As an intermediate step in all of these processes, the durability of freestanding SWCNT nanosheets in a variety of solvents is considered in the context of large-deformation elasticity and plasticity.
Platinum-Tin Alloy/Reduced Graphene Oxide Nanohybrid for a Highly Efficient Counter Electrode in Dye-Sensitized Solar Cell
Authors: Jin Ik-Kyu , Dao Van-Duong , Larina Liudmila L. , Choi Ho-Suk
Published: February 2020

We report the synthesis of PtSn alloy/reduce graphene oxide (RGO) nanohybrid materials and their application as efficient counter electrodes (CEs) in dye-sensitized solar cells (DSCs). Well-dispersed Pt1-xSnx (1 ≥ x ≥ 0) alloy nanoparticles (NPs) were stabilized with RGO after a co-reduction of metal precursor ions and graphene oxide via a dry plasma reduction under an atmospheric pressure and close to room temperature. The nanohybrids exhibit a 3D network structure of RGO with high NP loading on the RGO surface. The NP size is in a range of 1 – 4 nm, with a mean size of 2 nm. The structure of the PtSn alloy/RGO nanohybrid was confirmed by X-ray diffraction spectroscopy and HAADF-STEM measurements. The chemical composition of a binary alloy can be adjusted by varying the volume ratio of the Pt to Sn precursors, as confirmed by an XPS analysis. We optimized the nanohybrid structure for high catalytic activity toward a reduction of triiodide ions. The highest electrocatalytic performance, which corresponds to the lowest charge transfer resistance of 1.12 Ω, is achieved with the Pt0.9Sn0.1 NPs/RGO nanohybrid. The application of the optimized Pt0.9Sn0.1 NPs/RGO nanohybrid as an alternative CE for DSCs results in an increase of the efficiency by 15% over that of a Pt/RGO-based DSC and an increase of 46% over the efficiency of a Pt-free device. These results suggest that tailoring the electronic structure of the alloy can serve to enhance the catalytic activity of a nanohybrid CE and, in turn, be utilized to formulate high-efficiency DSCs.
Engineering Graphene for Neural Sensing and Stimulation Applications
Authors: Lyu Hongming , Lu Yichen , Kuzum Duygu
Published: February 2020

Graphene has recently emerged as an attractive material for neural sensing and stimulation, owing to its flexibility, transparency, excellent electrical conductivity and low noise characteristics. Monolayer graphene and multi-layer porous graphene can be engineered for neural interface applications showing advantages in different aspects. The transparent monolayer graphene electrodes enable simultaneous optical imaging and electrophysiological recordings. We have demonstrated that neural tissue can be imaged through transparent graphene electrodes using multi-photon microscopy without causing any light-induced artifacts in the electrical recordings. Combining optical imaging with electrophysiological recordings enables studies of neural activity with high spatial and temporal resolution simultaneously. Furthermore, graphene electrodes exhibit five to six times less noise compared with Au electrodes of the same size in in vivo recordings. In order to increase the surface area and charge injection capability, porous graphene have been utilized to fabricate neural stimulation electrodes. The 3D structure benefits from graphene’s good conductivity and generates greatly increased capacitance compared to the planar graphene and traditionally used bulk metals. Electrochemical tests were performed on electrodes with various areas. Impedance of the porous electrodes show two orders of magnitude decrease compared to Au electrodes of comparable size. Cyclic voltammetry and pulsed voltammetry results show enhanced charge storage and charge injection capacity for the porous electrodes. 16-electrode and 64-electrode arrays fabricated using standard micro fabrication processes have been used in in vivo neural recording and stimulation experiments. We have demonstrated recordings of evoked potentials from rat somatosensory cortex with high SNR using porous graphene electrodes. Moreover, we have used same arrays for cortical stimulation from the motor cortex of rat to evoke transient ankle and knee flexion in the contralateral leg. In summary, two forms of graphene, namely the monolayer graphene and porous graphene, were engineered for different neural applications. The monolayer graphene electrode shows the capability to record brain activity while simultaneously resolving individual cells and their connections through optical imaging. The porous graphene electrode greatly increases the charge-injection capacity for neural stimulation applications.
Non-Destructive Detection of Metabolites Using Single Walled Carbon Nanotubes
Authors: Galassi Thomas Vito , Shah Janki , Jena Prakrit Vaibhav , Roxbury Daniel , Horoszko Christopher Peter , Heller Daniel A
Published: February 2020

The transport, storage and degradation of macromolecules in cells represent tightly regulated processes that are vital to cellular function. Cells and organisms that are unable to regulate these processes will exhibit deleterious phenotypes such as impaired nervous system or liver function. Developing treatments for such disorders is challenging, due in part to a lack of methods for quantifying specific metabolites within live cells and animals. As such, this work aims to develop a tool with the ability to non-invasively detect cellular metabolites in live cells and animals. To achieve this goal, an optical reporter was engineered using single walled carbon nanotubes (SWCNTs). Semiconducting SWCNTs exhibit properties that make them ideal materials for the engineering of optical probes. These include fluorescence in the near infrared region of the spectrum which is modulated by the local environment, a lack of photobleaching, and a large Stokes shift. In this work, we developed an optical reporter capable of detecting cellular metabolites and demonstrated its use in live cells. Future work will focus on applying this reporter to study the pathologies of various diseases in vitro and in vivo.
Determination of Redox Potentials of Oxygen-Doped Single-Walled Carbon Nanotubes Based on in Situ Photoluminescence Electrochemistry
Authors: Nakashima Naotoshi , Shiraishi Tomonari , Juhász Gergely , Shiraki Tomohiro , Miyauchi Yuhei , Matsuda Kazunari
Published: February 2020

Single-walled carbon nanotubes (SWNTs) doped with a limited amount of oxygen (O-doped SWNTs) are novel materials due to the appearance of red-shifted new emission and dramatic enhancement of the PL quantum yields compared to those of pristine SWNTs, which are of importance for the development of high performance biosensors, imaging materials, and optical devices. The appearance of the new optical properties is due to the change in the electronic states induced by the O-doping of the SWNTs, thus quantitative analysis of the electronic states of the O-doped SWNTs is crucial. In this study, we have successfully determined the precise electronic states of the O-doped SWNTs based on the in situ PL electrochemical method. The measurements revealed the presence of at least two distinct O-doping sites with unique optical and electrochemical properties for all the four studied chiralities. The electrochemical measurements also showed that shifts in the valence and conduction band resulting from the O-doping is on the order of 0.02-0.03 eV, which is much lower than the red shift of the photoluminescence peak. This behavior agrees with the theoretical simulations using the Density Functional based Tight Binding (DFTB) method. This study suggests that the doped sites on the SWNTs act as a neutral quantum dot trapping exciton generated on the tubes.
(Invited) Regioselective Thiolation of Perchlorinated Graphene
Authors: Tan Yuanzhi
Published: February 2020

Chemical and physical properties of graphenes are naturally determined by its edge structures. Chemical functionalization is one of promising strategy to modulate the peripheral structure of graphenes. As a molecular-level model system, large polycyclic aromatic hydrocarbons (PAHs), i.e. so-called nanographenes, can be chemically modified through edge functionalization. Although the synthetic protocols for edge substitution of nanographenes are well developed, the regioselective chemical functionalization of nanographenes remains an enormous challenge, most likely due to the lack of suitable synthetic protocols. Here we show a regioselective peripheral thiolation of nanographenes by selective thiolation of perchlorinated nanographene. Based on two model perchlorinated nanographenes C42Cl18 and C60Cl24, we found the chlorines at the vertex of nanographenes are regioselectively substituted by the thiophene-2-thiol, which shows the first case of selective functionalization of nanographenes. The rest chlorines at the bay positions provide the platform for further functionalization. It enables us to design and produce a series of edge functionalized nanographenes.

Figure 1. Regioselective thiolation of perchorinated graphene

Figure 1
(Invited) Water-Dimer Encapsulations into C84
Authors: Slanina Zdenek , Nagase Shigeru , Akasaka Takeshi , Lu Xing
Published: February 2020

The water-dimer formation and its encapsulation into D2(22)-C84 and D2d(23)-C84 fullerenes is computed, following similar evaluations [1] with C60. The water-dimer equilibrium populations are calculated using the potential-energy change from the ab initio G3 theory and anharmonic partition functions from the MP2/AUG-cc-pVQZ approach. The encapsulation energetics is treated at the M06-2X/6-31++G** level and it is found that the water-dimer storage in C84 is attractive, yielding an energy gain of more than 10kcal/mol. This substantial encapsulation energy together with the computed temperature increase of the water-dimer population in the saturated steam suggest that the (H2O)2@C84 endohedrals could be produced in a high-temperature/high-pressure approach similarly to encapsulation of rare gases in fullerenes.

[1] F. Uhlik, Z. Slanina, S.-L. Lee, B.-C. Wang, L. Adamowicz, S. Nagase, J. Comput. Theor. Nanosci. 12, 959 (2015); 12, 2622 (2015).
Effect of Antifreeze Additives on Low Temperature Performance of Lithium-Ion Aqueous Battery
Authors: Belgibayeva Ayaulym , Mentbayeva Almagul , Umirov Nurzhan , Molkenova Anara , Adi Akylbek , Kurmanbayeva Indira , Bakenov Zhumabay
Published: February 2020

Poor low temperature performance of Li-ion batteries is considered as one of the major technical issues restricting their wide application in stationary energy storage systems and energy sources for transportation systems, including electric vehicles. The low temperature deactivates all main reaction steps, such as ionic diffusion/conduction in the electrolyte, Li+ transport through a solid electrolyte interface layer, interfacial charge transfer, and solid state lithium ion diffusion, leading to a remarkably lower kinetics [1]. These losses are even more manifested in case of aqueous rechargeable lithium-ion batteries (ARLBs) due to the higher freezing point of water, although, at room temperature the fast lithium diffusion in aqueous electrolyte media allows for the operations under high electric current conditions.

In this work, we report on investigation of low temperature performance of an aqueous rechargeable battery based on Zn/LiFePO4 system developed in our group [2]. At room temperature, this battery exhibits a superior rate capability with 72 mAh g-1 and 45 mAh g-1 at 30 and 60 C cycling rates, respectively. However, such excellent kinetics could be remarkably reduced at temperatures close and below the solvent (water) freezing temperature, as it can be seen from Fig. 1. Therefore, the effect of addition of antifreezes, such as ethylene glycol or propylene glycol, on the low temperature performance of Zn/LiFePO4 aqueous battery was investigated using galvanostatic charge discharge, ac impedance spectroscopy and other methods.

The further details of this work will be reported at the Meeting.

References

D.P. Abraham, J.R. Heaton, S.-H. Kang, D.W. Dees, A.N. Jansen, J. Electrochem. Soc. 155, A41, (2008).

N. Yesbolati, N. Umirov, A. Koishybay, M. Omarova, I. Kurmanbayeva, Y. Zhang, Y. Zhao, Z. Bakenov, Electrochimica Acta,
152 (2015) 505.

Acknowledgements

This research was supported by a Research Grant from Nazarbayev University.

Figure 1
Layered and Tunneled Manganese Oxides As Battery Cathode Materials - the Role of Electrochemically Active and Inert Metal Cations
Authors: Marschilok Amy C , Takeuchi Esther S , Takeuchi Kenneth J
Published: February 2020

Fundamental studies involving the impact of physical and chemical properties of materials on their electrochemical properties are critical to the rational development of battery materials which may address the present and future requirements for stationary and portable power. For large scale batteries, the use of environmentally benign and low cost energy storage materials is desired. Manganese-based materials are desirable in this regard as they are environmentally friendly, inexpensive, and can be prepared using scalable, aqueous based synthesis methods. Preparation, characterization, and battery electrochemistry of two promising structural motifs of manganese oxides will be described, specifically tunneled (hollandite) and layered (birnessite) crystallographic structures. The use of complimentary bulk (synchrotron based diffraction, thermogravimetric analysis, optical emission spectroscopy) and local (transmission electron microscopy based atomic imaging, nanodiffraction and electron energy loss spectroscopy) to elucidate structures of as-prepared, electrochemically reduced and oxidized materials will be highlighted. The impact of crystallite size will also be discussed.

Hollandites (Mx’Mn8O16) are one-dimensionally (1D) structured materials consisting of octahedral units of edge-sharing manganese oxide octahedra which interlink to form tunnels of 2 x 2 dimensions. Bimetallic hollandite type materials have been prepared where cations with 1+ or 2+ charge partially occupy locations within the manganese oxide tunnels, and the Mn cations possess mixed 3+ and 4+ oxidation states. Typically, the ion located within the tunnel (M’) is electrochemically inert (i.e. K+); however, silver hollandite is an interesting case as the Ag+ cationic center is potentially electrochemically active. The electrochemistry of potassium and silver based hollandites in lithium-ion and beyond lithium-ion battery systems will be described. The impact of the structural M’ cation and the role of oxygen vacancies on ion transport will be discussed. A novel recyclable battery electrode will also be described, which provides full restoration of initial capacity after a facile regeneration process.

Birnessite (Mx’MnO2), a layered manganese oxide, exists as a monoclinic crystal comprised of layers of edge-sharing manganese-oxygen octahedra (MnO6) with cations positioned between the layers. Although birnessite can be formed without any interlayer cations, monovalent (i.e. Na+, K+, Li+, Cs+) or divalent (Mg2+ or Cu2+) cations can also be incorporated between the layers. The impact of an electrochemically active interlayer cation, copper (Cu2+), on capacity and structural integrity of the birnessite structure upon discharge-charge cycling will be described, including a detailed view of the Mn and Cu oxidation state changes along with variations of the local neighboring atom environments around the Mn and Cu centers.
Performance and Cost Characteristics of Multi-Electron Transfer, Common Ion Exchange Non-Aqueous Redox Flow Batteries
Authors: Laramie Sydney M , Milshtein Jarrod David , Breault Tanya Marie , Brushett Fikile R. , Thompson Levi T
Published: February 2020

Non-aqueous redox flow batteries (NAqRFBs) have recently received considerable attention as promising high voltage, low cost grid-level energy storage technologies. Despite these attractive features, NAqRFBs are still at an early stage of development, and innovative design techniques are necessary to improve performance and decrease costs. In this work, we investigate multi-electron transfer, common ion exchange NAqRFBs. Common ion systems decrease the supporting electrolyte required for RFB operation, which subsequently improves active material solubility and decreases electrolyte cost. Voltammetric and electrolytic techniques are used to study the electrochemical performance and chemical compatibility of model redox active materials, Fe(bpy)3(BF4)2 and Fc1N112-BF4. These results help to disentangle complex cycling behavior observed in flow cell experiments. Further, a simple techno-economic model demonstrates the cost benefits of employing a common ion exchange NAqRFB, afforded by decreasing the salt and solvent contributions to the total chemical cost. This study offers the first analysis of the benefits of common ion exchange NAqRFBs and the demonstration of a 2e- flow cell. In addition, the compatibility analysis developed for asymmetric chemistries can apply to other promising active species, including organics, metal coordination complexes (MCCs) and mixed MCC/organic systems, enabling the design of low cost NAqRFBs.
Turning Lead into Gold: Systematic Electrocatalytic Water Oxidation Current Enhancement at Nanostructured Fe2O3 Electrode Surface
Authors: Bachmann Julien , Haschke Sandra , Manshina Alina
Published: February 2020

We coat the pore walls of an anodic nanoporous template with atomic layer deposition (ALD) to obtain structured electrode surfaces that provide the experimentalist with a well-defined, tunable geometry. Indeed, the platform consists of a hexagonally ordered array of metallic or oxidic nanotubes of cylindrical shape, embedded in an inert matrix. The diameter of the tubes can be defined between 20 and 300 nm and their length between 0.5 and 100 μm, approximately. We utilize them as a model system in which the electrode's specific surface area can be increased and its effect on the electrocatalytic current characterized systematically.

Diffusion-limited electrochemical transformations remain unaffected by changes in the length of the electrode's pores, whereas the steady-state galvanic current density observed for slow multielectron transformations increases linearly with the pore length. In particular, this approach enables us to increase the electrochemical water oxidation turnover at iron oxide surfaces by two to three orders of magnitude at the optimal point. An additional roughening effect occurring upon annealing and steady-state electrolysis is further evidenced by a combination of spectroscopic, microscopic, and electrochemical methods.

These results highlight a strategy for optimizing electrochemical energy transformation devices which could be generalized: the geometric tuning of catalytically mediocre but abundant and cost-effective material systems.

We acknowledge the Center for Optical and Laser Materials Research and the Interdisciplinary Resource Center for Nanotechnology at Saint Petersburg State University for their participation.

Figure 1
(Invited) Tribute to Prof. Zempachi Ogumi : In Operando Studies and in Situ Techniques for Li-Ion and Lithium Metal Polymer Batteries
Authors: Zaghib Karim , Marceau H , Hovington P , Wen Z , Kim C , Trudeau M , Veillette R , Laul D , Paolella A , Lagace M , Chaker M , Vijh A , Guerfi A , Mauger A , Julien C.M , Armand M
Published: February 2020

Prof. Ogumi is one the leading pioneers of lithium-ion technology in Japan and worldwide. His research studies on battery materials include LiCoO2, graphite, and highly oriented pyrolytic graphite (HOPG), Much of his research involved in situ techniques that utilized X-ray, Raman spectroscopy and atomic force spectroscopy (AFM) to investigate the SEI (passivation layer) and lithium intercalation in graphite and HOPG in propylene carbonate (PC)- and ethylene carbonate (EC)-based electrolytes.

In this presentation, we will show data and video movies that were obtained during studies of lithium-ion and solid-state batteries using various In operando studies and in situ techniques involving scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction and ultraviolet-visible absorption spectroscopy (UV-vis). These in situ studies are helpful to understand the mechanisms for volume expansion of anodes consisting of lithium metal (20 %), graphite (10 %) and LTO (0 %). Another example that will be discussed is the dimensional changes of the anode, cathode and electrolyte that occur during charge/discharge. The mechanism of lithium dendrite formation was also studied, and details will be discussed in this presentation.

 [Don’t know what is meant by Bleand and deleted because I‘m not sure it is needed.] Lithium/solid polymer electrolyte (SPE)/sulfur cells were studied by two in situ techniques:  SEM and UV-vis. During the operation of the cell, extensive polysulfide dissolution in the solid polymer electrolyte (cross-linked polyethylene oxide) leads to the formation of a catholyte.

A clear micrograph was obtained of the thick passivation layer on the sulfur-rich anode and the decreased SPE thickness during cycling confirmed the failure mechanism; the capacity decays by reducing the amount of active material, which contributes to a charge inhibiting mechanism called polysulfide shuttle. The formation of elemental sulfur is clearly visible in real time during the charge process beyond 2.3 V. The non-destructive UV-vis also shows the characteristic absorption peaks that evolve with cycling, demonstrating the accumulation of various polysulfide species, and the predominant formation of S4
2- and of S6
2- during discharge and charge, respectively. This finding implies that the charge and discharge reactions are not completely reversible and proceed along different pathways.
A Joint Experimental and Theoretical Approach to the Question of Anion Redox in Lithium-Rich Layered Oxides
Authors: Gent William , Liang Yufeng , Li Yiyang , Lim Jongwoo , Shapiro David , Vine David , Kilcoyne David , Tyliszczak Tolek , Yang Wanli , Prendergast David , Chueh William C
Published: February 2020

The concept of oxygen anions acting as redox couples in the high energy density lithium-rich layered oxide positive electrode materials has been the focus of intense debate in recent years. While it is known that transition metal oxidation does not account for the extended high voltage plateau capacity during the first charge, there is still little consensus on the exact mechanism of charge compensation in this regime. Early on it was proposed that oxygen evolution compensated the removal of lithium ions during the plateau, but more recently it has been suggested that an oxide/peroxide redox couple accounts for the bulk redox capacity. More recent still is the hypothesis that the formation of localized oxygen holes compensates lithium ion extraction in the bulk. In this work, we resolve the controversy by employing a variety of experimental and theoretical tools to develop a multi-length scale understanding of the anion redox phenomenon in lithium-rich layered oxide electrodes. Through Scanning Transmission X-ray Microscopy operating at the oxygen K and transition metal L edges, we observe a dichotomy in the behavior of the surface and the bulk of individual primary particles, confirming that multiple redox processes occur during the plateau. By coupling the spatially resolved X-ray absorption spectra with ab initio spectroscopy simulation and super-resolution Resonant Inelastic X-ray Scattering, we develop a nuanced understanding of both redox processes, involving a combination of anion redox and oxygen evolution. Crucially, we reveal that peroxide/superoxide species do not form during the plateau, and instead develop a model that clarifies the nature of the bonding between the activated oxygen species and its surrounding ions in the bulk.
Electrocatalytic Reduction of Selenate on Gold Electrodes Alongside Copper Deposition
Authors: Strobl Jonathan , Scherson Daniel
Published: February 2020

Reduction of aqueous selenate (SeO4
2-) to lower oxidation states of selenium is regarded as a very difficult reaction and thus far, only very few methods have yielded positive results [1-6]. One such previous study asserts that gold electrodes can catalyze reduction of commercial selenate at potentials below 0.6 V vs SHE [1], forming an elemental selenium deposit that can be anodically stripped above 0.9 V vs SHE, (see peaks A and B, black curve in Fig. 1 recorded in 1 mM Na2SeO4 in 0.1 M HClO4). However, commercially supplied selenate usually contains some selenite (SeO3
2-), a far more electroactive selenium oxyanion believed to yield elemental selenium and/or selenides as the product(s) of reduction. In fact, as shown by experiments performed in our laboratories, such voltammetric features vanished upon removal of selenite from the selenate solutions by adsorption on TiO2(see red curve in Fig. 1).

This contribution will present strong evidence that the reduction of selenate under the same conditions can proceed on a layer of underpotentially deposited copper on Au, yielding a corresponding layer of CuxSe. To be discussed are various aspects of the formation mechanism of this CuxSe using potentiostatic deposition and linear sweep stripping voltammetry (LSSV) experiments. During LSSV experiments, Cu can be anodically stripped, leaving behind a layer of adsorbed elemental Se (peak C, Fig. 2). At higher potentials, this layer is oxidized to selenite (peak B, Fig. 2) [7-9]. Repetitive formation and oxidation of the CuxSe product on gold electrodes via an AC deposition / stripping waveform may allow for continuous turnover of selenate into selenite.

References:

Ivandini, T. A.; Einaga, Y. Electrocatalysis. 2013, 4, 367-374.

Koshikumo, F.; Murata, W.; Ooya, A.; Imabayashi, S.-I. Electrochem. Soc. Japan.
2013, 81, 350-352.

Kozhakov, B. E.; Baeshov, A.; Buketov, E. A.; Zhurinov, M. Zh. Elektrokhimiia. 1985, 21, 550-551.

Kikuchi, E.; Tanaka, M.; Liang, R.; Sakamoto, H. Trans. Mat. Res. Soc. Japan. 2004, 29, 2337-2340.

Hayashi, H.; Kanie, K.; Shinoda, K.; Muramatsu, A.; Suzuki, S.; Sasaki, H. Chemosphere. 2009, 76, 638-643.

Ladriere, J. Bulletin des Societes Chimiques Belges. 1973, 82, 99-122.

Lister, T. E.; Stickney, J. L. J. Phys. Chem.
1996, 100, 19568-19576.

Huang, B. M.; Lister, T. E.; Stickney, J. L. Surface Science.
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Acknowledgements:

This work was supported by a grant from the NSF, # CHE-1412060.

Figure 1. Cyclic voltammograms recorded with a Au wire in a solution of 1 mM Na2SeO4 before (black curve) and after purification (red curve, see text) in 0.1 M HClO4at a scan rate ν = 0.2 V/s.

Figure 2. Linear scans recorded at ν = 0.1 V/s obtained for a Au RDE after holding the potential at Ehold = 0.375 with the electrode rotating at ω = 1500 rpm in 0.1 M HClO4, 1 mM Na2SeO4 (purified) and 1.2 mM Cu(ClO4)2 solutions for thold = 10 (red), 100 (blue) and 1000 s (green).

Figure 1
High Activity Oxygen Evolution Reaction Catalysts from Additive-Controlled Electrodeposited Ni and Nife Films
Authors: Gewirth Andrew A. , Hoang Thao Thi Huong , Schmitt Kevin Gary
Published: February 2020

We use electrodeposition for energy and microelectronics purposes. Electrodeposition of Ni or NiFe films exhibiting fractal-like behavior from plating baths containing an inhibitor, such as 3,5-Diamino-1,2,4-triazole (DAT), is found to yield oxygen evolution reaction (OER) catalysts for alkaline solutions exhibiting high current densities (100 mA/cm2), high mass activity (~ 1200 A/g of catalyst), high stability (> 72 hours) and low overpotentials (~ 300 mV). By changing electrodeposition time, the activity of the catalyst can be tuned, with longer times yielding higher activities. The electrodeposition method works with any conductive substrate yielding unprecedented performance and providing an easy route to high activity catalysts.

We also investigate the mechanism of 3-mercapto-1-propanesulfonate (MPS) acceleration of Cu electrodeposition in the presence of Cl- through comparison with the inactive but related model compounds 1-butanesulfonate and 1-butanethiol (BuSH). In situ Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) was used to evaluate these additives as a function of potential. MPS adsorbs to the Cu electrode in the presence of Cl- through the thiol functional group. DFT calculations reveal that the adsorption of thiol has a depolarizing effect on the strength of the interaction between adsorbed Cl- and the electrode surface, the consequences of which are observed spectroscopically. The sulfonate moiety does not interact directly with the electrode. However, cyclic voltammetry used to assess the permeability of adsorbed MPS and BuSH adlayers indicates that the sulfonate group has a more direct role in Cu deposition beyond simple disruption of the surface layer.
(Electrodeposition Division Early Career Investigator Award) Self-terminated Electrodeposition – A New Way for Growing Metal Thin Films
Authors: Liu Yihua
Published: February 2020

Electrodeposition is a more than century-old growth technique that has gained widespread usage in both academic research and industrial sectors, given its scalability, versatility, and cost-effectiveness. Through years of scientific inquiry and industrial employment, the basic understandings have been acquired for electrodeposition. Indeed, some of those knowledges have become guiding principles for practitioners in devising growth protocols. In this talk, an unorthodox approach, emerging from recent Pt electrodeposition studies, will be described. Rather than experiencing mass-diffusive control, Pt growth got quenched when overpotential was applied in excess of 1 V. Interestingly, a Pt monolayer film could be deposited before the quenching took place. This finding has led to the development of self-terminated electrodeposition, a method that has since found usage in synthesizing Pt core-shell catalysts for fuel cells and electrolyzer applications. Recent efforts to gain mechanistic insights on the quenching process itself will also be highlighted. Additionally, opportunities and challenges involving self-termination in materials design and engineering will be shown and discussed.
(Invited) Electrochemical Deposition of Thick and Adherent MnO2 Films for Thin-Film Batteries
Authors: Labyedh Nouha , Arman Meryem Ozge , Timmermans Marina , Deheryan Stella , Vereecken Philippe M.
Published: February 2020

Electrolytic manganese dioxide (EMD) is fabricated by anodic electrodeposition typically from acid manganese sulfate baths. After electrodeposition it is peeled from the electrode and ground into powder, hence poor adhesion is required. EMD powder is mainly used for primary alkaline-Zn and Li-ion batteries. EMD allows Li-ion intercalation in the open channels in the γ-MnO2 lattice. In our research group we are interested in adapting the EMD process for bulk batteries to be used for fabrication of thin-film Li-ion batteries.

EMD thin films deposition was developed on different substrates. Scanning electron microscopy (SEM) and Rutherford Backscattering Spectrometry (RBS) measurements were performed to extract the film porosity. It was found that all the deposited films have similar porosity values around 50 %.

Anodic electrodeposition of EMD films from conventional acid manganese sulfate baths is not possible on easy to oxidize substrates like TiN (passivation) or Ni (dissolution). For this reason a neutral and complexing acetate bath was used. Using this deposition bath thick and adhesive EMD film were deposited on Ni and even on TiN substrates. Up to 1 μm thick film on planar substrate and 600 nm on 50 μm high Si pillar array with 2 μm pillar diameter and 2 μm interpillar spacing. A study of the EMD film deposition in a temperatures range from 5 °C to 50 °C using the neutral acetate deposition bath was performed. The relationship between the morphology and the electrochemical performance of the EMD films deposited at different temperatures were investigated.
Enhanced Photoelectrochemical Behavior of Undoped and Doped BiVO4 inverse Opal Photoelectrode for Photoelectrochemical Water Splitting
Authors: Maheswari Balamurugan , Kang soon Hyung
Published: February 2020

Semiconductor metal oxides are one of the most interesting materials for photoelectrochemical (PEC) applications because of inexpensive, robust and strong photocorrosion as well as the possibility of easily morphological control. Among the most investigated metal oxides, BiVO4 metal oxides have attracted considerable interest due to their unique optical and electrical properties with a band gap of 2.4 eV. In this work, the introduction of new photoelectrode architectures to improve the light-harvesting and charge-collection properties was performed using the polystyrene opal template with a size of approximately 380 nm. Upon this template, undoped BiVO4 inverse opal (IO) film was developed via sandwich like infiltration method. Furthermore, to enhance the electric conductivity of undoped BiVO4 material regarded as one of weak points to retard the high efficient PEC performance, the doping process of undoped BiVO4IOs was done to facilitate the various candidates such as- Nb, Ag, Ce and so on.., Related results and discussion would be presented.

Keywords: BiVO4, polystyrene opal template, Photoelectrochemical water splitting, Doped BiVO4