bluuebunny/crossref_metadata_2025 huggingface dataset:
Operando XAS Studies: Electro-Reduction of CO2 on Nanoporous Cu Foams
Authors: Hecker Burkhard , Oezaslan Mehtap
Published: February 2020

New and improved strategies to secure our global energy economy and chemical industry in the future are needed due to the strong dependence on limited fossil resources and the socio-environmental problems associated with increasing anthropogenic emissions of CO2. To counteract this problem and simultaneously to reduce the concentration of the CO2 as well-known greenhouse gas, a very promising route is the electrochemical CO2 reduction reaction (CO2RR) into hydrocarbons and alcohols. Different reaction mechanisms and kinetics for the CO2RR are postulated.[1-4] In particular, the role of Cu oxide during the C2 formation like ethylene and ethanol is poorly understood to date. Further critical issues are addressed: (i) high overpotentials, (ii) broad product distribution, (iii) fast degradation by catalyst poisoning and (iv) competition reaction at high cathodic potentials, referred to as hydrogen evolution reaction.

Our work is focusing on the fundamental understanding about the mechanism and kinetics for the CO2RR on nano-porous copper (np-Cu) foams probed by XAS technique. The np-Cu foams prepared by dealloying of Cu-based alloys or by electrodeposition exhibit large surface area-to-volume ratios, improved catalytic performance and high C2 selectivity compared to a flat Cu surface. The catalytic properties (activity and selectivity) can be controlled by the pore size and curvature of the ligaments of the np-Cu. By using operando X-ray absorption spectroscopy (XAS), we studied the various structures and oxidation states of the Cu species in np-Cu foams as function of the applied potential, kind of electrolyte and pH value during the CO2RR. Linear combination fitting and multi-edge EXAFS fit analysis provide us information about the potential-controlled changes of oxidation state and local environment of Cu. In addition, we identified the potential range for the catalyst aging via coarsening and suggest strategies to stabilize the ligament structure and size of the Cu foams during the CO2RR.

Based on our operando XAS studies, we obtained a deeper insight to the mechanism and kinetics of the CO2RR on porous Cu foams and clarified the role of Cu oxides for the C2 production.

K. P. Kuhl , E. R. Cave, D. N. Abram, and T. F. Jaramillo, Energy Environ. Sci., 5 (2012) p. 7050.

A. Dutta, M. Rahaman, N. C. Luedi, M. Mohos, and P. Broekmann, ACS Catal., 6 (2016) p. 2804.

H. Mistry, A. S. Varela, C. S. Bonifacio, I. Zegkinoglou, I. Sinev, Y.-W. Choi, K. Kisslinger, E. A. Stach, J. C. Yang, P. Strasser, B. R. Cuenya, Nature Communications, 7 (2016) p. 12123.

R. Reske, M. Duca, M. Oezaslan, K. J. P. Schouten, M. T. M. Koper, and P. Strasser, J. Phys. Chem. Lett., 4 (2013) p. 2410.
Synthesis and Supercapacitance of Co3O4 Supported on Porous Carbon Derived from Biomass
Authors: Cui Zhenxing , Gao Xiaolei , Yu Jianhua , Dong Hongzhou , Zhang Qian , Dong Lifeng
Published: February 2020

With the increase of energy shortage and environmental pollution, it is critical to develop economic approaches to synthesize materials and fabricate devices for energy conversion and storage. In this study, we explored to synthesize Co3O4 supported porous carbon derived from biomass as electrode materials for supercapacitors. It is cost saving to obtain carbon materials with a porous structure and large surface area from biomass. The special structure of biomass carbon is beneficial for the deposition of functional nanoparticles and improvement in the supercapacitance. In this work, a simple method was applied to carbonize and activate alkali-treated wheat flour, and porous carbon with three-dimensional network structure was obtained. The porous carbon electrode exhibits a high specific capacitance of 185 F·g-1 at 0.5 A·g-1 in 2M KOH. Furthermore, Co3O4 supported porous carbon with excellent supercapacitance was synthesized. The results show that metal oxide supported biomass porous carbon has great potential application as electrode materials of supercapacitors.
(Invited) Advanced Electrochemical Hydrogen Compressor
Authors: Hamdan Monjid
Published: February 2020

U.S. automakers have invested significant resources in the research and development of hydrogen fuel cell vehicles (FCEVs). However, to enable the widespread use of FCEVs, an additional major investment will be required to achieve an infrastructure for hydrogen compression in fueling stations. In order to dispense hydrogen to FCEV tanks quickly the hydrogen must be compressed to a minimum of 875 bar at the fueling station.

Giner ELX has identified the use of mechanical hydrogen compressors as a key impediment to commercializing and implementation of high-pressure hydrogen refueling systems. Mechanical compressors have a high capital cost, high maintenance costs, poor reliability, and are noisy. The compressed hydrogen produced by a mechanical compressor often contains small amounts of pump oil; this oil will degrade performance of fuel cells receiving the hydrogen. Most importantly, the cost of a failure in a single hydrogen compressor oil filtering system will be very high, as considerable consequential damages will be incurred in on-board vehicle gas storage and fuel-cell systems. To eliminate the need for a mechanical compressor, and any chance of catastrophic oil contamination, Giner ELX has extended its extensive experience in high-pressure hydrogen-selective proton-exchange-membrane (PEM) to develop an electrochemical hydrogen compressor (EHC) system for refueling applications that can deliver hydrogen at pressures of greater than 875 bar.

The concept demonstrates a cost-effective method for compressing hydrogen while eliminating the need for mechanical compressors. In addition, Giner ELX has demonstrated high efficiency through the use of an EHC stack that operates at high current density and utilizes a hydrogen selective PEM and integral water management membrane. The program leverages current work being conducted by Giner ELX to improve EHC efficiency and reduce EHC costs while simultaneously raising the pressure in PEM-based stacks to greater than 350 bar.
Study of the Transport of Ions through an Anion-Exchange Membrane By Electrochemical Methods
Authors: Rodríguez Francisca Alicia , Rivero Eligio Pastor , Cruz-Díaz Martin Rogelio , Ortega Arturo , González I
Published: February 2020

Studies of the ionic transport through ion exchange membranes and in their adjacent electrolyte films have become a topic of great importance, due to their different applications in environmental problems [1]. A better understanding of the phenomena and processes involved in the mass transport in devices with ion exchange membranes allows designing cells with higher performance and lower energy consumption. There are few studies about of transport of ions in membranes, Wang et al. (1990) studied the mass transport of monovalent cations across a polypyrrole membrane [2], Oulmi, (2012) [3] analyzed the transport of Na+ in cation-exchange membrane (CEM), in both previous work CEM are used, studies on anion-exchange membrane (AEM) are scarce, and the transport mechanism may be different from the one observed in a CEM. Therefore, in the present work, the transport of HSO4
- through AEM is studied. The system used consists of a cell of four electrodes, where anode and cathode are separated by an anionic-exchange membrane (Selemion) with an exposed area of 0.28 cm2 on each side. Two platinized titanium plates with an area exposed to the 10.8 cm2 are used as anode and cathode; two saturated calomel with Luggin capillaries were used as reference electrodes. The electrochemical studies were: open circuit potential, chronoamperometry of sampled current and cyclic voltammetry at different scan rate, H2SO4 concentration and different potential range.

The cyclic voltammograms at different H2SO4 concentrations are shown in the Figure 1. It exhibits that HSO4
- can transfer across the Selemion membrane due to a peak current. The peak current increases as the HSO4
- concentration increases, but when the species HSO4
- is depleted at the interface of the membrane, the intensity of current decreases until a limiting current is reached, similar to the phenomenon that occurs when a species depletes at the interface of an electrode/electrolyte [2]. By continuing to increase the potential, the current intensity begins to increase. The water splitting supplying new current carriers and giving rise to the so-called exaltation effect [4]. This phenomenon appears at all the HSO4
- concentration. On the other hand, electrochemical studies show that the transfer of the anions in the anion-exchange membrane (Selemion) is through a migration process and the adjacent films by migration and diffusion.

Figure 1
Optimum Design of Pore-Filled Ion-Exchange Membranes for Efficient Energy Conversion Applications
Authors: Kim Do-Hyeong , Song Hyeon-Bee , Park Jin-Soo , Kang Moon-Sung
Published: February 2020

Ion exchange membranes (IEMs) have been widely employed in various water treatment processes such as electrodialysis for a desalination of sea or brackish water. Recently, they have also gained increased industrial importance in the applications to electrochemical energy conversion and storage processes such as reverse electrodialysis, fuel cells, and redox flow batteries. Their intrinsic properties such as electrical resistance and permselectivity are the key parameters dominating the electrochemical energy conversion efficiencies. The cost-effectiveness of ion-exchange membranes should also be considered for successful commercialization of the IEM process. In recent years, pore-filled IEMs (PFIEMs) in which an inert porous substrate provides excellent mechanical and chemical stabilities while a filling ionomer selectively transports ions through the membrane have been receiving great interests in the application to various separation and energy processes. In this work, we have investigated the optimum design parameters of the cost-effective PFIEMs for successful application to various IEM processes. In more detail, novel PFIEMs were successfully fabricated by combining a highly porous polymer (i.e. PTFE and PE) films and cationic polyelectrolytes with structurally stable anion-exchange sites for the applications to alkaline direct liquid fuel cells, all vanadium redox flow battery, and reverse electrodialysis. The prepared PFIEMs exhibited excellent electrochemical characteristics and stabilities and also remarkable energy conversion efficiencies have been achieved by employing them.

Acknowledgments:

This work was supported in part by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (20153030031720) and the Technology Innovation Program funded by the Korea government (MOTIE) (No. 10047796).
Capacitative Deionization: A Promising Electrochemical Water Treatment Technology Employing Novel New Electrodes, Exciting and Clever Reactor Designs and a Potential Plethora of Applications Far Beyond Desalination. Will It Succeed?
Authors: Anderson Marc Arlen , Lado Julio , Garcia - Quismondo Enrique , Palma Jesús
Published: February 2020

Nearly a decade ago, one of us (MAA) co-authored a review article on the status of capacitive deionization (CDI) for the desalination of saline waters. Since this time, there has been an exponential explosion of research in CDI over this last decade. At the time of writing our first manuscript, the intention was to focus upon the ability of CDI to compete with well accepted and proven desalination technologies and in particular with reverse osmosis (RO). While this still remains one of the forces driving interest in CDI, it is not the only one! Indeed, other applications perhaps more lucrative exist for this technology This presentation examines a bit o history of CDI but focuses on newer reactor designs and as well the future of CDI with respect to alternative applications other than RO.
Electrochemical Combustion of the Antibiotic Levofloxacin By Electro-Peroxone Process
Authors: Cornejo Oscar Miguel , Nava José Luis
Published: February 2020

Over the last years pharmaceuticals have been receiving a lot of attention as emergent pollutants worldwide. These compounds can reach the environment through many vias, i.e. excretion in urine and faeces of humans and livestock, household disposal or hospital wastes and their concentration in water can vary between ng L-1 to mg L-1 [1]. Despite their low concentration these persistent organics can have adverse effects on the environment, for this reason its elimination is a big concern. Different processes have been tried to remove these compounds from water among which are the electrochemical advanced oxidation processes (EAOP´s) like electroFenton (EF), photo electroFenton (PEF), solar photo electroFenton (SPEF) and electro-peroxone (E-peroxone) [1]. E-peroxone is a relatively new process that employs two reactants, the electrogenerated hydrogen peroxide (via O2 reduction in acidic media) and ozone to produce homogeneous hydroxyl radicals [2]. The E-peroxone process has been studied for the removal of several pharmaceuticals showing great potential in their elimination from water [3]. This work deals with the removal of the antibiotic Levofloxacin (LVN) from synthetic wastewater using the E-peroxone process. The electrolyzes were performed in a laboratory flow plant containing 1.5 dm3 of solution having 50 mg dm-3 of LVN and 0.05 M NaSO4 as background electrolyte at pH 3; a Ti-Ir-Sn-Sb oxides was used as anode and a graphite felt on top of carbon cloth was used as gas diffusion cathode [4], where compressed air was fed at 0.36 psi of pressure. The trials were conducted at a constant cathodic potential (Ecat
) of -0.3 V vs SHE at a volumetric rate (Q) of 1.5 dm3 min-1. The results showed a chemical oxygen demand (COD) decay of 70 % at 6 hours of electrolysis. The influence of current density, O3 feed and initial concentration of LVN on the rate of degradation of LVN and mineralization current efficiency was also analyzed. Finally, the by-products of LVN were followed by chromatographic techniques to propose a reaction pathway.

[1] Sirés I., Brillas., E. Remediation of water pollution caused by pharmaceutical residues sed on electrochemical separation and degradation technologies: A review. Environmental International, 40 (2018) 212-229.

[2] Li X., Wang Y., Yuan S., Li Z., Wang B., Huang J., Deng S., Yu G. Degradation of the anti-inflammatory drug ibuprofen by electro-peroxone process. Water Research, 63 (2014) 81-93.

[3] Wang H., Zhan J., Yao W., Wang B., Deng S., Huang J., Yu G., Wang Y. Comparison of pharmaceutical abatement in various water matrices by conventional ozonation, peroxone (O3/H2O2), and an electro-peroxone process. Water Research, 130 (2018) 127-138.

[4] Pérez T., Coria G., Sirés I., Nava J.L., Uribe A.R. Electrosynthesis of hydrogen peroxide in a filter-press flow cell using graphite felt as air diffusion cathode. Journal of Electroanalytical Chemistry, 812 (2018) 54-58.
Redox Conversion of Organic and Inorganic Pollutants in Ice
Authors: Kim Kitae
Published: February 2020

According to Arrhenius Equation, chemical reaction take place slowly when temperature decreases. However, several chemical processes extremely accelerated in ice phase. It is also reported that redox chemical reaction can be enhanced by freezing. For example, Takenaka et. al. reported that the NO2
- oxidation to NO3
- in the presence of O2 which is very slow reaction in aqueous solution was markedly accelerated (appx. 105 times) by freezing Redox transformation of compounds may control the bioavailability, mobility, toxicity, and environmental fate. In this presentation, we will introduce accelerated redox transformation of organic and inorganic pollutants in ice such as Cr(VI)/organic reductants, Cr(VI)/Ar(III), Cr(VI)/H2O2, Cr(VI)/NO2
- and Cr(VI)/phenolic pollutants systems. The detailed experimental conditions and mechanism will be discussed in the presentation. We also discuss about the environmental implication and application of these intrinsic redox transformation in ice on icy environments.
Simulations of H2-H2o Flow during the Electrolysis of Water in a Continuous Reactor Equipped with a Six-Cell Stack
Authors: Castañeda Ulloa Locksley Fabiàn , Nava José Luis
Published: February 2020

Nowadays the electrochemical reactors in specific the filter-press type in parallel plates configuration are commonly used in industrial and laboratory applications and as multipurpose flow cells utilized in a widely range of electrochemical processes [1]. The characterization of the reaction environment inside of any filter-press reactor must be considered in the design to obtain effective flow dispersion, plus a uniform current and potential distribution. The hydrodynamics is so important inside the reaction environment, because the uniformity and magnitude of mass transport and therefore the current distribution depend on the flow pattern inside the cell, specifically near the electrodes. In many electrochemical processes such as chlorine production, water electrolysis, alumina reduction, electrocoagulation, and many other electrochemical processes appears gas release on the electrodes, H2 or O2 [2]. The hydrodynamic properties and the gas-flow motion in electrochemical cells is of great interest in practice, because the dispersed phase (gas) modifies the electrical properties of the electrolyte (as well as mass and heat transfers), and therefore the macroscopic cell performance. Therefore, this works deals with the H2O-H2 flow simulations inside of a pre-pilot-scale continuous reactor with a stack of six cells in a serpentine array by solving the Reynolds-averaged Navier-Stokes (RANS) equations with κ-ε turbulence model (Euler-Euler approach). The hydrogen evolution reaction comes from the electrolysis of water. The electrodes were plates of aluminum, typically used in electrocoagulation processes. In order to perform a more complete flow pattern characterization, residence time distribution (RTD) studies were carried out to validate the CFD simulations. The RTD simulations were calculated solving the averaged diffusion-convection equation. Close agreement between experimental and theoretical RTD simulations were attained. Finally, comparisons between H2O-H2 and single-phase flow (H2O) simulations were also performed, highlighting that the dispersed phase improves the dispersion of the continuous phase.

References

[1] F.F. Rivera, C. Ponce de Le_on, F.C. Walsh, J.L. Nava, The reaction environment in a filter-press laboratory reactor: the FM01-LC flow cell, Electrochim. Acta 161 (2015) 436e452.

[2] Lokmane Abdelouahed, Rainier Hreiz, Souhila Poncin, Gérard Valentin, Francois Lapicque, Hydrodynamics of gas bubbles in the gap of lantern blade electrodes without forced flow of electrolyte: Experiments and CFD modelling, Chem. Eng. Sci. 111 (2014) 255–265.
Nanomechanical Properties of Germanium-on-Insulator (GeOI) Films
Authors: Mohammed Yousuf , Zhang Kai , Baumgart Helmut , Elmustafa A A
Published: February 2020

Silicon-on-insulator (SOI) is envisaged as a better alternative to bulk silicon due to its superb performance and less power consumption. The fabrication of the silicon-on-insulator (SOI) and strained silicon-on-insulator (SSOI) is accomplished using wafer bonding and the SMART CUT layer splitting technology for film exfoliation. Strained SOI (SSOI) substrates are specifically developed with SiGe straining layers for high mobility channel devices [1-3]. The fabrication of Germanium-on-Insulator (GeOI) proved to be the best choice material for Si-based photodetection. Ge possesses a strong linear absorption of up to 1.55 µm, a strong compatibility with Si CMOS process, and direct energy bandgap of 0.8 eV [4]. Also, Ge retains higher carrier mobility as compared to Si, which promises faster operation. Although the lattice mismatch parameter between Ge and Si is large i.e., 4.2%, epitaxial growth of high quality Ge thick films on Si can be accomplished.

GeOI films of 100, 220, 250, and 290 nm thick were fabricated using wafer bonding and Smart Cut technology.

The structural and surface properties were explored using field emission scanning electron (FE-SEM) and atomic force microscopy (AFM). The crystal structure and orientation of the films were examined using X-ray diffraction. The GeOI film thickness was verified using field emission scanning electron microscopy (FESEM) in cross-section as shown in Figure 1. The nanomechanical properties were measured using nanoindentation to determine the modulus and hardness of the GeOI films. Constant displacement indentations in CSM mode of 10% of the film thickness, to circumvent the substrate effects were performed on each film to study the film properties.

References

Mazure and A.J. Auberton-Herve, Proc. of 35th
European Solid-State Device Research Conf. ESSDERC, p. 29 (2005)

A. Langdo, M. T. Currie, Z.-Y. Cheng, J.G. Fiorenza, M. Erdtmann, G. Braithwaite, C.W. Leitz, C.J. Vineis, J. A. Carlin, A. Lochtefeld, M. T. Bulsara, I. Lauer, D.A. Antoniadis, M. Somerville, Solid-State Electronics,
48 , 1357 (2004).

I. Cayrefourcq, A. Boussagol and G. Celler, in SiGe and Ge: Materials, Processing, and Devices, ECS Trans. 3, (7), 399 (2006)

Figure 1
(Keynote) Contemporary and Future Logic Devices
Authors: Maszara Witek P.
Published: February 2020

Headwinds faced by scaling efforts of high performance logic technology have forced engineering teams to go beyond dumb shrinking of device dimensions and into clever employment of new materials and structures, over last few technology nodes. We departed technology staple, planar transistors, and entered into 3D structures, half a dozen years ago. Such paradigm shifts will continue to happen more often in the years to come. We will look at today's state-of-the-art devices - FinFETs - and explore capability and suitability of new architectures for years to come. Those include variants of gate-all-around (GAA) transistors, horizontal and vertical, negative-capacitance FET (NCFET), tunnel FET (TFET), and spin-based devices. We'll assess feasibility of material contenders for better channel transport - III-V, SiGe/Ge, carbon nanotubes (CNT) and 2D transition metal di-chalcogenides (TMD). Finally, we discuss 3D monolithic device stacking and standard cell level design-technology co-optimization role in scaling.
(Invited) Ion Trap Quantum Computing - a New Computing Regime
Authors: Mukherjee Manas , Dutta Tarun , Horne Noah Von , Lie Yisheng , Liu Peiliang , Phua Jasper , Yum Dahyun
Published: February 2020

Quantum computing is an emerging technology that is going to be disruptive in almost all sectors. Quantum computing is not just about the speed of computing but its ability to solve certain class of problems which are considered to be unsolvable by any computer of today or near future. The reason behind the phenomenal power of a quantum computer lies in the underlying physics of its operation which is quantum mechanics. Quantum mechanics is based on the natural laws which are found to be agnostic. At present there are different platforms to implement a quantum computer but the fore-runners are superconductor and ion trap based quantum processors. The basic abilities and techniques of implementing basic quantum gates will be discussed along with challenges to scale up the devices. The implementation of gates in case of ion traps requires more than one technological stalk. As the technology is rapidly progressing, the complexity of the implementation is getting more limited by engineering than by fundamental physics. These issues will be discussed in details as concluding remark.
Pulse Electrodeposition of Cu through-Silicon-Via (TSV) with Surface Suppressor
Authors: Lee Jinhyun , Park Kimoon , Kim Youjung , Yoo Bongyoung
Published: February 2020

In recent years, many researches have been focused on the miniaturization of the integrated circuit (IC) feature size to improve the performance of semiconductor devices. However, we are facing the problems such as physical limit of the miniaturization and then increasing processing cost. To overcome these problems the Through-Si-Via (TSV) interconnection, a kind of the 3D interconnection, is a promising technology that could achieve high density, lower energy consumption and high performance in the IC.

Since the TSV filling process is costly in the entire TSV process, the TSV filling process which the Cu electrodeposition for TSV is one of key processes. The TSV bottom-up filling which the filling of Cu from the bottom to the top of via with suppressed lateral growth is the solution to ensure a void free filling in high aspect ratio TSV. The bottom-up filling could be achieved by using additives like a suppressor and an accelerator in the electrolyte.

In a theoretical model, the suppression breakdown at the bottom of TSV cause the bottom-up filling of TSV. Simultaneous desorption of suppressor by high potential due to ion depletion in the via bottom leads focus of current at the via bottom. Due to adsorption/desorption behavior of the suppressor, the bottom-up TSV filling could be achieved by only using the suppressor.1-3 Furthermore, it was reported that the suppressor at the sidewall is replaced by the accelerator and then the bottom-up filling performance was degraded.3

Lu et al. introduced the nanotwin Cu thin film, which had been attained with pulse electrodeposition.4 Mechanical properties of the Cu thin film is significantly enhanced by highly dense coherent twin boundaries without the degradation of electrical conductivity. Because it could effectively block the dislocation motion without interrupting the migration of electrons.4 The mechanical property of TSV interconnection such as thermal behavior is important as well as the electrical property including electrical conductivity for improvement TSV performance. Therefore, the nanotwin Cu is proper for the TSV interconnection.

In this study, nanotwin Cu was applied to fill into high aspect ratio of via (diameter = 5 µm, depth = 60 µm) with pulse current conditions. The deposition condition between direct current and pulse current was compared to observe the filling characteristics. The mechanical properties as the thermal expansion behavior, which is critical to adopting integrated devices, of nanotwin Cu were investigated. As a result, the results with pulse current condition showed obvious improved the TSV filling property than direct current condition.

1. T. P. Moffat and D. Josell, J. Electrochem. Soc., 159, D208 (2012).

2. T. Moffat and D. Josell, Journal of The Electrochemical Society, 159, D208 (2012).

3. L. Yang, A. Radisic, J. Deconinck, and P. M. Vereeckena, J. Electrochem. soc., 160, D3051 (2013).

4. L. Lu, Science, 304, 422-426 (2004).
(Invited) Next Generation CMOS Devices: Transistor Module Challenges and Opportunities
Authors: Colombeau Benjamin P
Published: February 2020

In this presentation, we first review the overall trends for advanced CMOS devices in terms of scalability and performance. To carry on Moore’s law, devices need to be scaled from node to node. To enable this scaling, taller, more rectangular FinFETs with narrower body width at scaled pitches has been demonstrated. However this leads to several key process and integration challenges such as Fin integrity, capacitance increase, channel mobility, sub-fin isolation, and sidewall doping as well as contact resistance reduction. Next, we review the challenges of increasing FinFET device performance (e.g., mobility boost, Rexternal reduction) such as fin smoothing, epi Source Drain proximity or contact resistance reduction. Regarding alternate channel material, SiGe p-channel FinFET has gained quite a lot of attention in the past several years. Several SiGe integration approaches have been reported in the literature and will be briefly discussed. Consideration of the entire process flow is critical to ensure maximum strain is achieved in the channel with very low defectivity – two critical requirements for High Volume Manufacturing of high performance, low power devices. These topics will be explored for several of the integration approaches mentioned above. Finally, we will discuss the potentially disruptive transition to new device architecture – the Gate-All-Around (GAA) transistor - and discuss process requirements and challenges for this novel device type.
(Invited) 2D MoS2 Memristors with Variable Switching Characteristics
Authors: Liang Xiaogan , Li Da
Published: February 2020

Memristors has been extensively studied as an important candidate device structure for realizing non-Von Neumann computers, neuromorphic and analog computing systems. The conventional memristors are made from transition metal oxides such as TiOx, TaOx, WOx, and HfOx.1 The conductance states of such memristors can be adjusted through modulating the distribution of oxygen vacancies in the oxide channels. Recently, memristor-like transport behaviors have been also observed in the electronic devices made from emerging 2D-layered transition metal dichalcogenides (TMDCs, such as MoS2 and WSe2).2 Such emerging 2D-material-based memristors could be used for constructing novel neural networks with a significantly improved level of connectivity and enabling bio-realistic emulation of brain neuron functions. Therefore, it is highly desirable to further perform nanofabrication and nanoelectronics research to fully explore the applicability and advantage of 2D-TMDC-based memristors for practical neuromorphic applications.

Here, we present a study on the nanofabrication and characterization of memristive devices based on mechanically printed few-layer MoS2 structures. This work shows that mechanically printed MoS2 memristors with critical thicknesses exhibit a very low threshold electric field for initiating memristive-switching processes, which is essential for the successful construction and operation of energy-efficient memristor-based neural networks. More importantly, such MoS2 memristors exhibit both analogue (i.e., gradient) and discrete switching characteristics, which could be further exploited for making reconfigurable memristors for both analog and digital computing applications.

This work leveraged the unique transport properties of 2D layered MoS2 for memristor-related applications and advanced the scientific/technical knowledge for controlling memristive switching behaviors.
Wireless Si-Based Back Buried Junction Photoelectrochemical (BBJ-PEC) Cells for Solar Fuels
Authors: Fu Hui-Chun , Varadhan Purushothaman , Lin Chun-Ho , He Jr-Hau
Published: February 2020

Spontaneous splitting of water into hydrogen and oxygen is of great attention for a clean and storable form of chemical fuels. Silicon, the most investigated material has a great potential to be employed as both the single photoelectrode and as a bottom absorber in a tandem photoelectrochemical (PEC) system. However, a major inadequacy in the simultaneous achievement of the optical, electrical management, and bandgap engineering limits the efficiency. Herein, to achieve concurrent enhancement of light-harvesting, surface protection and catalytic reactions, we implement a novel photon decoupling scheme to fabricate back buried junction photoelectrochemical (BBJ-PEC) cells by n-type crystalline Si (c-Si). The light decoupling scheme enables the maximum light-harvesting from the top surface without any metal contacts that avoids the shading effect, while the electrochemical reaction happens at the bottom side of the PEC cell. The resultant single-junction Si-based BBJ-PEC cell archives the current density of 41.76 mA/cm2 for hydrogen evolution the best reported so far, with the open-circuit potential of 0.62 V and the half-cell solar-to-hydrogen conversion efficiency (SHCE) of 11.44 %. The outstanding results achieved here sets a record SHCE efficiency for single-junction Si-based PEC cells. By connecting the three BBJ-PEC cells in series, we have also realized an unassisted photoelectrochemical water-splitting with the solar-to-hydrogen conversion efficiency (STH) of 15.62 %, with 240 μg.cm-2h-1 of hydrogen. Finally, we have developed a model to understand the loss mechanisms involved in the PEC cell, with the comprehensive analysis on the absorptance, quantum efficiencies and absorbed photon-to-current efficiencies (APCE).
(Invited) in-Vacuo Studies of MBE Grown Transition Metal Dichalcogenides
Authors: Litwin Peter M , McDonnell Stephen John
Published: February 2020

Here we present recent work on the synthesis and characterization of two-dimensional transition metal dichalcogenides (TMDs) grown by molecular beam epitaxy (MBE). Bulk TMD crystals consist of two-dimensional layers bonded together by van der Waal interactions; the lack of primary bonds at the TMD interface allow for the growth of TMD heterostructures on a variety of substrates without the need to consider lattice constant mismatch or crystal structure of the substrate which we aim to demonstrate. TMDs are grown and characterized in an all in-vacuo ultra-high vacuum system which enables the simultaneous co-deposition of multiple transition metals and chalcogens allowing for the study of TMD ternary alloys and layered heterostructures followed by their compositional and intrinsic electronic characterization prior to atmospheric exposure. Presented will be a review of our work studying the interface chemistry between TMD and conventional semiconducting substrates, as well as our investigations of 2D-2D heterostructure grown by MBE.

Figure 1 shows an example of in-vacuo x-ray photoelectron spectroscopy (XPS) carried out on GaAs(001) before an after the growth of monolayer MoSe2. The sample was initial passivated by a sulfur based treatment, and the presence of sulfur bonded to the surface can be observed in the As 2p and Ga 2p spectra. The asymmetry observed in the As 2p and Ga 2p core-levels suggest that some reactions with Se take place during the growth. The thermal stability of this interface will be investigated using in-situ UHV heating and XPS.

In separate work we evaluated the valence band offsets using in-vacuo XPS and UPS (ultraviolet photoelectron spectroscopy). This is achieved by measuring core-level to valence band maximum separation for control samples as well as the core-level shifts in heterostructure. In-vacuo XPS analysis can also be used to reveal any interface reactors that may occur between the TMDs. It is found that for chalcogen deficient growths, metallic signatures can be detected.

Of particular interest is the process structure relationships. Presented will be parametric studies showing impact of growth temperature and relative metal-chalcogen flux ratios on the electronic structure and interface chemistry in both the 2D-2D and 2D-3D systems. The all in-vacuo synthesis and analysis cluster tool allows these investigations to be carried out without air exposure which can induce substantial changes in the chemistry of these materials.

Figure 1
Multiscale Simulation of the Fabrication Process of Lithium Ion Battery Electrodes
Authors: Franco Alejandro A. , Ngandjong Alain , Rucci Alexis , Primo Emiliano
Published: February 2020

I present here our ongoing efforts at developing and demonstrating a multiscale computational framework devoted to rationalize the formulation of lithium ion battery composite electrodes containing next-generation material chemistries. The framework is being established through the combination of discrete particle (Coarse Grained Molecular Dynamics) and continuum mathematical models within a multiparadigm and multiscale approach mimicking the different steps along the electrode fabrication process, i.e. slurry preparation, drying and calendering. In strong complement to dedicated experimental characterizations, the theoretical framework provides fundamental insights on self-organization mechanisms of material mixtures in slurries and on the relationship between the materials properties, the electrode composition (formulation), the fabrication process layout and the arising electrode microstructure.

Practical application of the framework to lithium ion battery electrodes based on NMC materials is presented. Finally, I discuss its potential to provide insights leading to proposals of new and highly efficient industrial techniques for the fabrication of cheaper and reliable next-generation lithium ion battery electrodes for a wide spectrum of applications, including Electric Transportation.

References

ERC Project "ARTISTIC" (Advanced and Reusable Theory for the In Silico- optimization of composite electrode fabrication processes for rechargeable battery Technologies with Innovative Chemistries) (European Research Council funded project, grant agreement No. 772873).

A. Ngandjong, A. Rucci, M. Maiza, G. Shukla, J. Vazquez-Arenas, A.A. Franco, "Towards A Multiscale Simulation Platform Linking Lithium Ion Battery Electrode Fabrication Process With Performance At The Cell Level", J. Phys. Chem. Letters, 8 (23) (2017) 5966.

A.A. Franco, M.L. Doublet, W. Bessler, Eds., book title: "Multiscale Modeling and Numerical Simulation of Electrochemical Devices for Energy Conversion and Storage", Springer, UK (2015).
Polybenzimidazole Supported Monolayer Graphene Membrane for Inexpensive PEM Fuel Cells
Authors: Sahoo Madhumita , Kalangi Vasu , Perez-page Maria , Nair Rahul Raveendran , Holmes Stuart
Published: February 2020

One atom thick structure of the two dimensional single layer graphene has distinguished itself as a very promising material due to its unique properties. Excellent in-plane electron conductivity and permeability to proton but barrier to other kinds makes it a very tempting and cost effective membrane material for environment friendly alternative energy devices-proton exchange membrane (PEM) fuel cells. Expensive Nafion and Pt are the commonly used membrane and catalyst for fuel cells, covering 50 % of the total amount of the fuel cell cost [1]. To make them commercially viable, the overall cost needs to be reduced or the performance has to be enhanced at the expense of the same cost.

Our work showed that incorporation of monolayer graphene into the membrane electrode assembly with the Nafion enhances the direct methanol fuel cell power density by 45 %, owing to the graphene’s methanol barrier properties [2]. In this work we report inexpensive polybenzimidazole (PBI) membrane as mechanical support for the monolayer graphene substituting Nafion. The composites are tailored with different degrees of graphene coverage. The influence of these ‘defects’ are studied with respect to the fuel cell operation in different conditions. Further functionalization of the composition demonstrated to be a cost effective solution, showing a good prospect as an alternative to Nafion.

References:

1. US Department of Energy Hydrogen and Fuel cells programs record, 2017

2. Stuart M. Holmes, Prabhuraj Balakrishnan, Vasu. S. Kalangi, Xiang Zhang, Marcelo Lozada-Hidalgo, Pulickel M Ajayan, Rahul R. Nair., 2D Crystals Significantly Enhance the Performance of a Working Fuel Cell. Advanced Energy Materials 7 (2017) 1601216.
Exploring Interfacial Stability of Inorganic Solid-State Electrolytes at the Lithium-Metal Anode for Lithium-Sulfur Batteries
Authors: Camacho-Forero Luis E , Balbuena Perla B
Published: February 2020

The increasing demand for energy requires development of high-performance energy storage devices that provide superior properties than the traditional Li-ion batteries. In the screening of alternative chemistries, Lithium-Sulfur (Li–S) batteries are one of the most promising candidates among rechargeable battery systems due to its low cost, high energy density, and high theoretical capacity. However, there are still some limitations that need to be overcome before Li-S batteries are viable for commercialization. One of the main drawbacks of this technology is the “shuttle” effect - migration of soluble polysulfide species from the cathode to the anode, which leads to parasitic reactions at the Li anode that yields a passivation layer that will lower the performance of the battery. In addition, the use of liquid organic electrolytes rises safety concerns due to their flammability. Unlike organic electrolytes, solid-state electrolytes (SSEs) are nonflammable and have the potential to suppress dendrite formation, improve battery lifetime, and enable the use of Li-metal anodes, which would increase considerably the energy density. However, before practical applications of SSEs with metal anodes, it is crucial to gain insights of the stability of the SSE/Li-metal interface. In this work, we use density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations in order to study the SSE/Li-metal interface. To learn more about the interfacial chemistry, we selected Li2P2S6, Li3PS4, Li7P3S11, and Li10GeP2S12 as representative of the sulfide SSEs, which can exhibit high conductivity, good mechanical strength, and mechanical flexibility. Here, two low-index facets, (001) and (100), of the SSEs in contact with a Li electrode surface are studied. Reaction mechanisms, structure of fragments, and charge transfer evolution are examined and characterized in detail. Finally, some insights on the effect of a thin film of Li2S (<1 nm) on the electrode/electrolyte interfacial stability are provided.
Synergistic bifunctional catalytic effect at metal oxide-based catalyst for oxygen electrodes: influence of support and investigation in DMSO
Authors: Amin Hatem M.A. , Soltani Mohammad , Bondue Christoph , Zan Lingxing , Baltruschat Helmut
Published: February 2020

Li-air batteries are one of the most promising candidates for rechargeable systems.[1] Within the context of elucidating the possibilities of aqueous Li-air batteries, developing a cost-effective bifunctional catalyst for oxygen reactions is a key issue. Metal oxides including spinels and perovskites have been shown as efficient catalysts for OER,[2] while Ag is known as a good catalyst for ORR. We have recently shown that a mixture of Ag particles with Co3O4 nanoparticles has superior bifunctional activity than its own components.[3] Here, we will demonstrate that such effect can also be observed when other support materials than Ag are used. Therefore, this effect could partially be due to a conductivity effect. However, experiments using smooth electrodes suggest that there is a synergistic effect. We will further demonstrate that this effect is also observed for various perovskites loaded on Ag. XPS analysis has shown that the presence of Ag+ in contact with Co3O4 facilitates the redox switching of Co3O4, which might be the reason for the enhanced catalytic activity of the mixture.[4]

Moreover, the mechanism underlying OER on Co3O4 and mixed Ag+Co3O4 catalysts is further studied using differential electrochemical mass spectrometry together with 18O-isotope labelling experiments.[4-5] The results revealed that the lattice oxygen of the oxide takes part in OER and that the amount of oxygen exchange on the mixed catalyst is larger than that on Co3O4. The active surface area is also estimated from these measurements and is compared to that obtained from a simple ball model and BET data.[6]

Investigation of the catalytic activity of Co3O4 catalyst towards oxygen reactions in aprotic electrolytes, namely DMSO, is also presented.

Literature:

[1] K. M. Abraham, Z. Jiang, J. Electrochem. Soc.
1996, 143, 1-5.

[2] A. Bergmann, E. Martinez-Moreno, D. Teschner, P. Chernev, M. Gliech, J. F. de Araújo, T. Reier, H. Dau, P. Strasser, Nature Communications
2015, 6, 8625.

[3] H. M. A. Amin, H. Baltruschat, D. Wittmaier, K. A. Friedrich, Electrochim. Acta
2015, 151, 332-339.

[4] H. Amin, C. J. Bondue, S. Eswara, U. Kaiser, H. Baltruschat, Electrocatalysis
2017, 8, 540-553.

[5] S. Fierro, T. Nagel, H. Baltruschat, C. Comninellis, Electrochem. Commun.
2007, 9, 1969-1974.

[6] H. M. A. Amin, H. Baltruschat, Phys. Chem. Chem. Phys.
2017, 19, 25527-25536.
Advanced Anode Material with Porous Nanofibers Comprising 2-D Nanosheets and Carbon
Authors: Cho Jung Sang
Published: February 2020

A novel structured porous nanofiber comprising MoSe2 nanosheets and carbon was prepared through the application of a simple selenization treatment to electrospun nanofibers. Size-controlled polystyrene nanobeads in the form of an aqueous suspension are introduced for the first time as an electrospinning solution, which enables the precise control of void size and uniform distribution of nanovoids in the one-dimensional (1D) nanostructure. Few-layered MoSe2 and highly conductive carbon facilitate ion and electron diffusion during cycling. Uniformly distributed nanovoids in the structure can accommodate the volume expansion induced by electrochemical reaction of Na+ ions with the composites and allow efficient penetration of electrolyte into electrodes. The simple synthetic method introduced in this study can be applied to the preparation of porous transition-metal compounds nanofibers with various compositions for a wide variety of applications, including energy storage.
Electronic and Ionic Conductivity of Nanocrystalline Sodium Peroxide
Authors: Philipp Martin , Lunghammer Sarah , Hanzu Ilie , Wilkening Martin
Published: February 2020

The development of advanced electrochemical energy storage systems is considered as one of the most important steps to drive the shift from fossil to renewable energies forward. Among the few alternatives to Li-ion batteries that would exceed significantly their specific energy, Li-oxygen and Na-oxygen batteries have attracted significant interest. In order to fully understand their electrochemical properties and to identify potential failure mechanisms, electrochemical properties and charge carrier transport of their discharge products (e.g. Na2O2) need to be known in detail. Here, we investigated the overall and electronic conductivity of nanocrystalline Na2O2 that was prepared by mechanical treatment of coarse-grained Na2O2 in a high-energy ball mill. The powder obtained is expected to be rich in defects and structural disorder. Thus, we expect that the sample investigated would be at the upper limit of reachable conductivities. Impedance measurements and DC-polarization experiments show that the overall conductivity is rather poor; it is in the order of 10−13 S/cm yielding diffusion coefficients in the order of 1.8 × 10−23 m2/s at approximately 300 K [1]. At room temperature the partial electronic conductivity ranges between 7.6 and 9.5 × 10−14 S/cm. Thus, the total conductivity in Na2O2 is largely influenced by electronic contributions rather than ionic conduction [2]. Furthermore, we also anticipate a strong coupling between ionic and electronic charge carrier transport. We measured the electronic conductivity at different temperatures to calculate the underlying activation energy. It turned out that electronic conductivity is governed by an activation energy as high as 0.95 eV while for overall charge transport values range from 0.85 and 1.03 eV depending on the samples exact properties and measurement conditions.

Acknowledgement:

Financial support by the Deutsche Forschungsgemeinschaft (DFG Research Unit 1277, grant no. WI3600/2-2 and 4-1 and HA6996/1-2) as well as by the Austrian Federal Ministry of Science, Research and Economy, and the Austrian National Foundation for Research, Technology and Development (CD-Laboratory of Lithium Batteries: Ageing Effects, Technology and New Materials) is greatly appreciated.

References:

[1] Dunst, A.; Sternad, M.; Wilkening, M.: Overall conductivity and NCL-type relaxation behavior in nanocrystalline sodium peroxide Na2O2 – Consequences for Na-oxygen batteries. Mat. Sci. Engin. B 211 (2016) 85-93.

[2] Philipp, M.; Lunghammer, S.; Hanzu, I.; Wilkening, M.: Partial electronic conductivity of nanocrystalline Na2O2. Mater. Res. Express 4 (2017) 075508.