bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Development of in situ Electrochemical Small-Angle Neutron Scattering (eSANS) for Simultaneous Structure and Redox Characterization of Nanoparticles
Authors: Prabhu Vivek M , Reipa Vytas , Rondinone Adam J , Formo Eric , Bonnesen Peter V
Published: February 2020

The demand for engineered nanomaterials in expanding research sectors, such as energy and healthcare, require materials with widely disparate physicochemical properties.  The oxidation and reduction (redox) properties of nanomaterials are crucial for catalysis, matching semiconductor band gaps for photovoltaics, as well as toxicology, since they may cause oxidative stress by generating reactive-oxygen species.  Optical spectroscopy analysis of molecular and nanomaterials undergoing redox reactions quantifies the electron transfer and energetics of the reaction via potential control and are the most common analytical techniques employed for this purpose.  However, with conjugation to organic ligands and smaller, well-defined particle sizes, engineered nanomaterial redox characterization would benefit by techniques that provide nanometer sensitivity to nanoparticle core and ligand structure. We developed an in situ electrochemical small-angle neutron scattering (eSANS) method to measure simultaneously the redox properties and size, shape, and interactions of solution-dispersed nanomaterials [1].  By combining multi-step potentials and chronocoulometry readout with SANS, the structure and redox properties of engineered nanomaterials are followed, simultaneously in one experiment.  Specifically, ZnO nanoparticles were examined as dilute dispersions in pH buffered deuterium oxide solutions under negative electrode potentials.  The ZnO disk-shaped nanoparticles undergo an irreversible size transformation upon reduction at the vitreous carbon electrode.  The decrease in average nanoparticle size near a current maximum shows the reduction reaction from ZnO to Zn occurs.  The eSANS method provides nanometer scale sensitivity to the nanoparticle size and shape changes due to an electrochemical reaction that is crucial to understand in energy, healthcare, and other applications.  These experiments utilized the EQ-SANS beamline at the Spallation Neutron Source, Oak Ridge National Laboratory that uniquely provides the ability to follow the redox kinetics under quasi-stationary potential step-scans. The methodology, contrast variation, and scattering properties of the micro and nanoporous carbon electrodes will also be described.

[1] V.M. Prabhu and V. Reipa, J. Phys. Chem. Lett. 3, 646 (2012)
(Invited) On the Modeling of the Charge Pumping Curves
Authors: Bauza Daniel
Published: February 2020

The Charge Pumping (CP) technique has been used to characterize insulator semiconductor interface traps in numerous device types and in a wealth of situations [1]. A few years ago and for the first time, the three basic CP curves types recorded from conventional silicon MOSFETs with thick SiO2insulating films have been simulated very accurately in a large range of experimental conditions [2, 3], demonstrating that the model derived satisfactorily accounts for the CP mechanisms and that the properties of the traps introduced, i.e. their distribution and electrical characteristics, were plausible. As far as we know no more recent results have been published in that field. Indeed, one may expect the electrical CP response of gate stacks with high-k dielectrics to be even more difficult to tackle [1].

A part of the above results has been used more recently to investigate the meaning of CP curve edges [4]. This study pointed out the role that surface potential plays in interface traps filling and in CP curves shape. It was also shown that the Si-SiO2interface trap density, Dit, usually extracted as proposed in [5], can be very simply obtained from the slope of the CP curve edges [4].

Besides, a few months ago, several Pbo centers, the amphoteric defect well-known to be the main trap type at the Si(100)-SiO2 interface after SiO2 growth have been identified in deep submicron area MOSFETs [6], pursuing the story of the Si-SiO2interface electrical characterization.

In this paper, starting from the results presented in [2, 3], the essential of the model, the major advances with regard to previous work and the main conclusion that can be drawn concerning the CP mechanisms will be recalled. The impact of the gate signal parameters on carrier capture and emission will be detailed. The contributions to the overall CP signal of the different traps introduced along with the impact on the CP curve shape of their characteristics will be presented. The limitations of this approach will also be pointed out.

 [1] Nanoscale CMOS – Innovative Materials, Modeling and Characterization, Ch. 15, Characterization of interface defects, by P. Hurley, O. Engström, D. Bauza, and G. Ghibaudo, Edited by F. Balestra, Ed. ISTE-Wiley 2010.

[2] D. Bauza, IEEE Trans. Electron Devices 56, 70, (2009).

[3] D. Bauza, IEEE Trans. Electron Devices 56, 78, (2009).

[4] D. Bauza, International Reliability Physics Symposium (IRPS) 2013, paper GD-2.

[5] G. Groeseneken, H.E. Maes, N. Beltran, and R. F. De Keersmaeker, IEEE Trans. Electron. Devices 31, 42 (1984). 

[6] T. Tsuchyia and Y. Ono, Jap. J. Appl. Phys. 54, 04DC01 (2015).
Effects of Precursor Flow Rates on Characteristics of Low-K SiOC(H) Film Deposited by Plasma-Enhanced Chemical Vapor Deposition
Authors: Cheng Yi-Lung , Huang Chiao-Wei , Sun Chung-Ren , Lee Wen-Hsi
Published: February 2020

In this study, low-dielectric constant (low-k) SiOC(H) films deposited using conventional plasma-enhanced chemical vapor deposition (PECVD) by varying flow rates of the deposition precursors were investigated through various characterization techniques. The deposition precursors were DEMS and ATRP, which acted as a network matrix and sacrificial porogen, respectively. Experimental results indicated that both DEMS and ATRT precursors influence the properties of resulting porous low-k SiOCH films. But matrix DEMS precursor causes greater impact. With an increase of DEMS flow rate, an enhanced cross-linking was formed, leading to a higher hardness, smaller pore size, better electric performance, and stronger dielectric breakdown strength. However, a higher dielectric constant (k) is the cost.  The k values of the porous low-k SiOCH films with various ATRP flow rates (1700~2500 sccm) remained unchanged, although, the optimized electrical characteristics and reliability were obtained as ATRP flow rate was 2100 sccm.
Characterization of SiOx/HfOx Bilayer Resistive-Switching Memory Devices
Authors: Chen Ying-Chen , Chang Yao-Feng , Wu Xiaohan , Guo Meiqi , Fowler Burt , Zhou Fei , Pan Chih-Hung , Chang Ting-Chang , Lee Jack C.
Published: February 2020

Oxide based resistive switching memory are the promising candidates for future non-volatile memory according to fast programing, low power operation, scalability and compatibility to the current CMOS process. Among, SiOx single layer resistive switching devices have been widely studied and characterized. The SiOx single layer resistive memory has good compatibility to CMOS fabrication process. However, it can only be programmed under the vacuum or non-oxidized ambient. Also, the previous results reported on SiOx-based memristors indicate that the electroforming and programming voltage is relatively higher than the other dielectric materials and obstructed for low-power applications. In this work, by using SiOx/HfOx stacking engineering, we have developed a low-voltage operation (< 2V) for SiOx-based ReRAM. The results show that with HfOx
(3nm) on bottom, the metal-insulator-semiconductor (MIS) structures exhibit resistive switching at low voltage (<2V) and operation in air atmosphere. The added hafnium layer apparently provides the source of proton exchange reaction with conduction bandgap offset reduction for low-voltage (< 2V) RS (Figure 2). Also, we have studied single HfOx-based MIS devices which exhibit bipolar-type resistive switching behaviors with small memory window.Clearly, SiOx/HfOx stacking optimization not only maintains the RS behaviors even in air environment without any programming window degradation, but also further reduces the switching voltage below 2V.

Figure 1 shows the results of three different structures, including SiOx single layer memristor, SiOx/HfOx bilayer memristor and HfOx single layer memristor. In terms of operation environment condition, inserting the HfOx layer would help the SiOx memristor to be able to programmed either under a pressure  of 1E-4 torr or in the atmosphere. The HfOx single layer memristor has the lowest electroforming voltage of 2.3 V, and which in SiOx/HfOx stacks has been reduced significantly to 5 V comparing which of 14 V for SiOx single layer. For the SiOx/HfOx bilayer, a memory window of 4 decades is achieved and comparable to that of SiOx single layer, and larger than that of single layer HfOx by 2 decades. In terms of operation voltage, the set voltage is reduced from 4V to 2 V and the reset voltage is also suppressed significantly from 10 V to 0.3 V by inserting the 3 nm HfOx layer.

Figure 2 shows the TEM images of both SiOx single layer memristor and SiOx/HfOx bilayer memristor. The 3 nm HfOx was deposited on N+ Si wafer at 250 oC by atomic layer deposition followed by 30 nm SiO2 deposition using e-beam evaporator and 160 nm TaN depositing by sputtering.

Figure 3. The single layer HfOx-based MIS devices resistive switching behaviors. (a) The electroforming process, resistive switching behaviors in 20 times cycling. (b) The switching voltage (SET/RESET) and states (HRS/LRS) distribution.

Figure 1
(Invited) Quantification and Characterization of Adsorbed BTA on Copper Surfaces Under Conditions Relevant to Barrier CMP
Authors: Wu Bing , Raghavan Srini
Published: February 2020

In the formation of copper interconnects by CMP, barrier polishing is typically carried out using alkaline slurries containing copper corrosion inhibitors. Benzotriazole (BTA) has been the inhibitor of choice in such slurries. The effect of BTA on copper corrosion has been extensively studied in the past few decades, and there is general agreement that the adsorbed film formed in acidic solutions is a multilayer film with a chemisorbed first layer. However, simultaneous real time measurement of the amount of BTA adsorbed and characterization of nature of the adsorbed film (rigid/viscoelastic) has received very little attention. 

The objective of this work was to measure the extent of BTA adsorption onto PVD Cu films and characterize the nature of the adsorbed film in real time using a quartz crystal microbalance with dissipation monitoring (QCMD) capability.  Quartz crystals (fundamental frequency of 5 MHz) coated with ~300 nm PVD copper layer were used in the experiments. To mimic the conditions during barrier polishing, BTA dissolved in alkaline solutions was pumped through the flow cell containing the crystal, and the change in crystal oscillation frequency and dissipation data were collected at a time resolution of fraction of a second for several minutes. This was followed by rinsing with DI or solutions containing selected surfactants to determine extent of desorption of BTA.

As an example, adsorption of BTA from a solution of pH 10 is shown in figure 1. The measured frequency shift (Δf) and dissipation shift (ΔD) at different overtones (multiples) of crystal fundamental frequency are plotted as a function of time. At the time marked with t1, a sharp decrease of frequency may be seen, which indicates rapid adsorption of BTA. The data points for all frequencies fall on one curve indicating that the adsorbed BTA film on copper is quite rigid in nature. This is confirmed by very little measured change in the ΔD values. At the end of adsorption marked with t2, deionized water was introduced into the system, and the positive shift of frequency is indicative of BTA removal and/or etching of copper in DI water.

In the presentation, results of adsorption and desorption experiments carried out under different experimental conditions will be presented. The disruption of adsorbed BTA layer by selected chemicals will be addressed.

Figure 1
The Mechanism of the Bridge Defect Caused By the Reaction with the Dispersant Polymer in Slurry and the Double Patterning Photo Layer
Authors: Kim Hyun-Soo , Jang Dong-Hyuk , Hwang Ha-Sub
Published: February 2020

At the present time, semiconductor process technology node is going under 10nm from 20~30nm base. The 1X nm design rule will be general trend in the next few years. In this situation, the Chemical Mechanical Planarization (CMP) is focusing on the fine defect which is under 20nm.   At this conference, I would present the mechanism of defect which caused by dispersant polymer, additive polymer and slurry inhibitor in ultimate fine design technology era. We found the medium weighted polymer chains were still remained after polishing even if in situ cleaning and ex-situ cleaning was performed. And the remained polymer reacted with the Photo Resistance (PR) material while processing double patterning (DPT). Since the defect size was so small, the defect was not detected in the processing. It is supposed that the compounds composed of slurry polymer and PR material block the etching reaction and make a bridge between line and line spacer. To prevent these polymer enhanced defects, well designed slurry should be used and the perfect cleaning solution is especially needed. The failure mechanism is that a lot of minus charged polymers attached on plus charged layer react with PR and DPT layer and finally going hardening on annealing around 200°C. So, the cleaning solution have to have higher polymer solubility to remove the additive polymer chains on minus or plus charged layer.
Molecular Characterization and Design of CMP Pads
Authors: Arnó Jose
Published: February 2020

Together with slurries, pads play an important role in the mechanical and chemical processes used to polish and planarize wafers.  Pads are typically characterized based on their bulk physical, mechanical, and microstructural properties as they correlate to polishing performance.  Surface interactions at the pad-slurry interface can be characterized using contact angle and zeta potentiometry to measure surface energy and electrokinetic properties.  The molecular structure of the polyurethane material is a critical factor that defines many of the aforementioned pad characteristics.  For example, the stiffness of a chain and the degree of cross-linking are important factors in targeting hardness, elasticity, temperature resistance, and chemical affinity.  The ability to measure and understand the polymer structure and bond composition of a pad is a critical tool to rationalize performance and to design new materials that address future polishing needs.  In this paper, a fundamental molecular study on the polymer structure and network formation will be described.  The work was performed using Fourier Transform infrared spectroscopy coupled with a thermally controlled attenuated total reflection (ATR) accessory.  After an overview of the main polyurethane infrared absorption bands, the investigation will provide important molecular formation insights related to the polymerization reaction (gelation),  curing, and final structure of the polymer.
Mechanical Properties of Functionally Graded Boron Carbide/Aluminum Cermets Utilizing Electrophoretic Deposition (EPD)
Authors: Morales Jason Rolando , Landingham Richard , Pascall Andrew J. , Worsley Marcus A. , Kuntz Joshua D.
Published: February 2020

Gradient and laminate materials are an emerging area with the potential to impact a wide range of technologies including structural materials, energy storage, and defense applications.  However, fine control of gradients is a challenge for many material types.  This work aims to demonstrate the capability to tune the properties of ceramic-metal composites (cermets) by using electrophoretic deposition (EPD) to create compositional/microstructural gradients within the cermet part.  Controlling the outcome of microstructural features and phase composition enables the tailoring of the final product for desired applications.  B4C green body compacts comprised of tailored microstructures through EPD are then infused with Al during pressureless sintering.
Novel Liquid and Polymer Electrolytes for Lithium-Sulfur Batteries
Authors: Panero Stefania , Navarra Maria Assunta , Lombardo Lucia , Savi Fabiana , Aguilera Luis , Elamin Khalid , Matic Aleksandar
Published: February 2020

A major hurdle still hindering the practical development of the highly desirable lithium-sulfur batteries is the solubility in organic, carbonate-based electrolytes of polysulfide compounds formed as intermediates during charge and discharge processes. This high solubility results in a loss of active mass, which is reflected in a low utilization of the sulfur cathode and in severe capacity decay upon cycling. The dissolved polysulfide anions, by migration through the electrolyte, may react with the lithium metal anode to form insoluble products on its surface; this process also negatively impacts the battery operation. Various strategies to address the solubility issue have been explored, including the design of modified organic liquid electrolytes, the use of ionic liquid solutions and of polymer electrolytes [1, 2].

In this work we present a combined strategy, where optimized liquid electrolytes, composed by ether-based solvents and an ionic liquid additive, were used to swell a selected polymer matrix. This allows the formation of composite, highly conductive, gelled polymer electrolytes able to control the dissolution of the sulfide anions. In our approach, a dry poly(ethylene oxide) (PEO) membrane was first prepared, through a solvent-free route [3, 4], and then activated by the liquid electrolyte, according to a well addressed swelling procedure.

Thermal, spectroscopical and electrochemical characterizations were performed on both liquid and gelled polymer electrolytes and will be discussed. The successful practical application in Li-S cells was demonstrated by prolonged galvanostatic cycles where very high and stable capacity values (i.e., 900 mAh/g) were achieved.

Acknowledgments:

The results of this work have been obtained by the financial support of the European Community within the Seventh Framework Program LISSEN (Lithium Sulfur Superbattery Exploiting Nanotechnology) Project (project number 314282).

[1] Junghoon Kim , Dong-Ju Lee , Hun-Gi Jung , Yang-Kook Sun , Jusef Hassoun , Bruno Scrosati, Adv. Funct. Mater. 2013, 23, 1076–1080

[2] Rezan Demir-Cakan, Mathieu Morcrette, Gangulibabu, Aur´elie Gu´eguen, R´emi Dedryv`ere, Jean-Marie Tarascon, Energy Environ. Sci., 2013, 6, 176–182

[3] P.P Prosini, S Passerini, R Vellone, W.H Smyrl - J. Power Sources, 75 (1998), p. 73

[4] G.B Appetecchi, S Scaccia, S Passerini - J. Electrochem. Soc., 147 (2000), p. 4448
(Invited) Nature of MIEC Cathode/Electrolyte Interfaces
Authors: Ivers-Tiffée Ellen , Szász Julian , Wankmüller Florian , Wilde Virginia , Störmer Heike , Gerthsen Dagmar , Weber André
Published: February 2020

Modern solid oxide fuel cells (SOFC) use a high-performance mixed ionic-electronic conducting (MIEC) La1-xSrxCo1-yFeyO3-δ (LSCF) cathode. This perovskite, when directly applied to Y2O3 stabilized ZrO2 (YSZ), forms a blocking layer of Strontiumzirconate (SrZrO3 - SZO). This secondary phase reaction is prevented by inserting a dense Gd-doped Ceria (GDC) between LSCF and YSZ [1]. Mostly, the GDC interlayer is screen printed and the correct density is assured by subsequent sintering. This high temperature treatment however causes a low-ionic conductivity GDC-YSZ interdiffusion phase [2]. The correct balance between GDC density and GDC-YSZ interdiffusion is crucial for achieving highly functional GDC interlayers. Microstructure evolution after GDC sintering (Fig.1a) and after LSCF sintering (Fig.1b) reveals the dramatic influence of LSCF as sintering aid for porous, fine grained GDC layers. On the other hand, GDC sintered at 1400°C shows effective inhibition of SZO formation, but enhanced GDC-YSZ interdiffusion. The changing nature of the gas/cathode/electrolyte interface goes hand in hand with a drastic decrease in ASRcat by over two orders of magnitude. The interface changes from a layer sequence LSCF/GDC/SZO/GDC-YSZ/YSZ at 1100°C gradually to LSCF/GDC/GDC-YSZ/YSZ at 1400°C. We will discuss the origin of this solid/gas interface in detail, and link the effects to electrochemical performance, i.e., contributions of the electrolyte phases (GDC, GDC-YSZ interdiffusion, YSZ) to the ohmic resistance, and contributions of LSCF, SZO and GDC to the cathodic polarization resistance (ASRcat).

These findings confirm a complex heterogeneous solid/gas interface at a mixed conducting cathode/electrolyte side of a SOFC cell. Its drastic influence on electrochemical performance points to the necessity of understanding the nature of MIEC cathode/electrolyte interfaces for individual cell concepts.

References

[1]         H. Yokokawa, N. Sakai, T. Horita, K. Yamaji, M.E. Brito, H. Kishimoto, J. Alloys Compd. 452 (2008) 41.

[2]         A. Tsoga, A. Naoumidis, A. Gupta, D. Stöver, Mater. Sci. Forum 308-311 (1999) 794.

Figure 1
Addition of Protonic Conductors to Enhance SOFC Anode Performance
Authors: Irvine John , Jiang Cairong , Ma Jianjun , Connor Paul , Cassidy Mark
Published: February 2020

A BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BCZYYb) infiltrated Ni-YSZ anode was investigated for biogas conversion. The infiltration of BCZYYb significantly promoted the electrochemical reactions and the cells exhibited high power output at the operational temperatures over 750 °C. At 800 °C, supplied with 20 ml min-1 biogas, the cell with a BCZYYb-Ni-YSZ anode, generated 1.69 A cm-2 at 0.8 V with an optimal amount of 0.6 wt% BCZYYb, whereas only 0.65 A cm-2 was produced with a non-infiltrated Ni-YSZ in the same conditions. At 750 °C, a maximum power density of 1.43 W cm-2 was achieved on a cell with a BCZYYb-Ni-YSZ anode, a 3 µm dense YSZ film electrolyte, a Gd0.1Ce0.9O2 (GDC) buffer layer and a La0.8Sr0.2Co0.8Fe0.2O3-Gd0.1Ce0.9O2 (LSCF-GDC) composite cathode. The cell remained stable, while operating at 0.8 V for 50 hours with a current density of 1.25 A cm-2. A well-designed cell structure and selected components made it possible to obtain excellent performance at good fuel utilisation. The analysis of gases in open-circuit conditions or under various current loads suggested that the prevalent reaction was reforming of methane without coking. This study demonstrated that BCZYYb-Ni-YSZ is a promising electrode for carbon-containing fuels.
A New Cathode for Sodium Ion Batteries: Alluaudite Na1.702Fe3(PO4)3
Authors: Palmore G. Tayhas R. , Liu Dan
Published: February 2020

Sodium-ion batteries hold promise as an enabling technology for large-scale energy storage that is safer, less expensive, and lower in terms of environmental impact than their equivalent lithium-ion batteries. In this presentation the synthesis, crystal structure, and electrochemical properties of a new sodium-ion battery cathode material, an alluaudite phase of Na1.702Fe3(PO4)3 will be described. After ball milling and carbon coating, this material exhibits a reversible capacity of 140.7 mAh/g with good cycling performance and excellent rate capability. In addition, we report a new compound in the alluaudite class, Na0.872Fe3(PO4)3, which was obtained upon desodiation of Na1.702Fe3(PO4)3. Both compounds exhibit high thermal stability. Together, these compounds represent a new cathode material for large-scale battery applications that are earth-abundant and sustainable.
An Effective Way of Suppressing Main Degradation Mechanisms of Carbon Supported High Surface Area Catalysts at Elevated Temperatures
Authors: Polymeros George , Baldizzone Claudio , Geiger Simon , Grote Jan-Philip , Knossalla Johannes , Mezzavilla Stefano , Cherevko Serhiy , Zeradjanin Aleksandar R. , Schüth Ferdi , Mayrhofer Karl J.J.
Published: February 2020

On the pathway to the broader implementation of low temperature polymer electrolyte fuel cells (PEMCs) their performance, which is defined by the equally important factors of the activity and stability of the electrocatalyst, has to be further improved for meeting the demanding benchmarks. Various studies have been lately conducted directly on PEMFCs as well as ex-situ in order to firstly understand and then improve the stability issues, especially concerning the catalyst on the cathode. This work intends to further enlighten and rationally disentangle the complex interplay between the different aging mechanisms of this electrode and at the same time proposes a new strategy for circumventing considerable active surface area losses by tuning the morphology of the electrocatalytic layer.  For this reason two Pt to carbon supported nanocatalysts are put to the test which are different only in respect to the geometry and nature of the carbon support. Thanks to the combination of several advanced experimental techniques the dominating degradation mechanism of each stage of a demanding/long degradation protocol will be demonstrated. The techniques applied are  namely the rotating disk electrode (RDE) setup for the standard electrochemical characterization, the identical-location transmission electron microscopy (IL-TEM) to demonstrate the consecutive stages of the degradation of identical locations of the electrocatalyst on the nanometer scale, the coupled scanning flow cell (SFC) to an inductively coupled plasma mass spectrometer (ICP-MS) to investigate the dissolution of the Pt catalyst during the degradation process in-situ and the SFC coupled to an online electrochemical mass spectrometer (OLEMS) to study the corrosion process of the carbon support in-situ. For the sake of the application relevant conclusions of this study all the aforementioned techniques were operated in application oriented temperature (60 oC). Although dealing with a specific nano-engineered class of materials, the reported results are of high interest for the whole catalysis/energy conversion community, as they offer an alternative pathway for increasing the performance of the electrode by refining the catalytic support.
Hydrogen Peroxide Reduction in Aqueous Electrolytes: Influence of a Heterogeneous Decomposition Step
Authors: Georgescu Nicholas Stefan , Scherson Daniel
Published: February 2020

It has been traditionally assumed that the reduction of hydrogen peroxide proceeds by a simple, first-order, 2-electron reduction, to yield water as the product.  Under this model, a plot of the reciprocal of the current vs the reciprocal square root of the rotation rate, known as a Koutecky-Levich plot, should be linear, from which kinetic information can be obtained based on the magnitude of the intercepts as a function of  the overpotential. However, close inspection of many such plots reported in the literature do exhibit some curvature especially at high rotation rates and low overpotential, a behavior that has been largely ignored but which may affect the interpretation of such plots1. One reaction seldom considered in this context is the well-documented heterogeneous disproportionation of hydrogen peroxide, a process known to occur on many surfaces that yields dioxygen2, a species that could subsequently reduce and thus contribute to the overall current observed (see Scheme 1). According to this Scheme, the current derived from the mass balances associated with peroxide and dioxygen is expressed in Equation 1.

Shown in Panel A, Figure 1, are a series of Koutecky-Levich plots based upon this formalism for three reasonable values of the heterogeneous electron transfer rates for the processes involved for disproportionation rates spanning the entire domain.  As clearly indicated, and for certain values of these parameters, the plots display the same type of curvature as those reported in the literature. Shown in Panel B of the Figure are curves for a fictitious set of parameters which were deliberately chosen to obtain a curvature equal in magnitude but opposite in direction. Several methods are currently being considered in order to measure independently the rates of peroxide disproportionation for the same type of rotating disk electrodes used for collecting data of the type discussed herein3. 

Acknowledgments

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

References

1. S. J. Amirfakhri, J.-L. Meunier and D. Berk, Electrochimica Acta, 114, 551 (2013).

2. E. R. Vago and E. J. Calvo, Journal of Electroanalytical Chemistry, 339, 41 (1992).

3. A. Muthukrishnan, Y. Nabae, T. Okajima and T. Ohsaka, ACS Catalysis, 5, 5194 (2015).

Figure 1
The CO Induced the Deposition of Hightly Ordered Pt Monolayer on Au(111) Electrode and Its Electrocatalytic Properities
Authors: Liao Weicheng , Yau Shuehlin
Published: February 2020

In situ scanning tunneling microscopy (STM) was used to examine the ordered microstructures of platinum (Pt) deposited on Au(111) substrate in aqueous Na2PtCl6 solution saturated with carbon monoxide (CO) without potential control at room temperature. PtCl6
2- complexes were reduced by CO molecules and deposited on Au(111) in a hexagonal array without potential control. At the same time, we introduced electron spectroscopy for chemical analysis (ESCA) to prove the Pt adatoms were reduced to metallic state after the CO was oxidized in air. According to the results of CV and STM, the coverage of Pt on Au(111) substrate increased sharply with the time passed initially and finally had the value of 0.87monolayer (ML) after 200min dosing. After 5min dosing, the adsorption of CO molecules first mobilized and rearranged Pt adatoms on Au(111) from disordered Pt aggregates to 0.9 nm wide tortuous stripes, and finally to patches of ordered Pt adatoms at 0.1 V (versus reversible hydrogen electrode) in 0.1M H2SO4 saturated with CO. However, the Pt adlayer seem to be too stable to be observed any change with time after 10min dosing. Deposition of Pt in the presence of CO ceased with a monatomic Pt film capped with CO molecules arranged in a (2 × 2) array in both with and without potential control. The CO monolayer adsorbed on Pt/Au(111) was stripped off at 0.96 V in 0.1 M H2SO4, as compared with 0.83 V observed with Pt(111). The E1/2 potential for oxygen reduction reaction (ORR) observed with the Pt-modified Au(111) electrode was 0.81 V in 0.1M sulfuric acid, which is 0.16 V more positive than that of Pt(111). The microstructures of the as-prepared Pt monolayer on Au(111) changed with potential cycling between 0.05 and 1.0 V.

Figure 1
Elucidating Molecular Underpinnings of Extracellular Electron Transfer in Bioelectrochemical Systems Using Evolutionary Genomics Approaches
Authors: Phadke Sujal , Carpenter Kayla , Bretschger Orianna
Published: February 2020

Microbes can be promising catalysts for the conversion of chemical energy to electrical energy in important technologies such as bioelectrochemical systems (BESs) that can support biosensing and wastewater treatment applications. The reliability of BESs depends on the ability of microbes to move electrons from various donor substrates to solid phase electron acceptors through a process known as extracellular electron transfer (EET). Although some of the genes responsible for EET have been identified in a few model prokaryotes, we lack system-wide knowledge about how key genetic interactions evolve under BES conditions and how evolution may affect the long-term operation of these systems. Because mutation and evolution together represent an inevitable aspect of any technology that uses engineered or natural strains as biocatalysts, we need to understand how the genome-wide mutational landscape changes over time under various environmental conditions in BESs. We combined the power of experimental evolution and next generation sequencing to identify the rates as well as patterns of single nucleotide polymorphisms in pure cultures of electrogenic bacteria grown under controlled laboratory conditions with or without BES stimuli. Our analysis reveals how genetic makeup of the biofilm vs. planktonic populations of electrogenic microbes diverges away from each other during evolution. Our approach also allows us to reveal previously hidden players in the genetic networks underlying the EET activity during BES operation. Lastly, our results emphasize the need to characterize evolutionary trajectories of potential biocatalysts in pure cultures as well as multi-species communities to advance the development and efficacy of bioelectrochemical systems.
(Invited) Polymerized Ionic Liquid Block Copolymers As Solid-State Electrolytes in Alkaline Fuel Cells
Authors: Elabd Yossef A
Published: February 2020

Alkaline fuel cells (AFCs) that employ solid-state anion exchange membranes (AEMs) as the electrolyte separator are of great interest as they produce high power densities at low operating temperatures (< 200 °C) and enable the use of non-platinum electrodes (e.g., nickel), significantly reducing cost relative to proton exchange membrane fuel cells. Several challenges limiting the wide scale use of membrane-based AFCs is the alkaline chemical stability and ion transport of polymers used as AEMs. Recently, polymerized ionic liquid (PIL) block copolymers with a range of chemically stable heterocyclic cations have become candidates to investigate for AFCs. PIL block copolymers constitute an emerging class of polymers and a distinct set of block copolymers that synergistically combine the advantageous properties of both PILs and block copolymers and are synthetically highly versatile with numerous cation and anion chemistries available. Specifically, the unique physiochemical properties of PILs, such as high solid-state ionic conductivity, high chemical, thermal and electrochemical stability, and widely tunable physical properties (e.g., via anion exchange), are incorporated in the block copolymer architecture, which allows for self-assembly into a range of nanostructures, where morphology type and domain size are tunable. In this talk, the synthesis, alkaline chemical stability, and ion transport of numerous PIL block copolymers developed in our research group will be discussed. More specifically, both the cation and backbone chemistry have a significant effect on alkaline chemical stability and various chemistries and chain architectures have a significant impact on ion conductivity. The AFC performance of PIL block copolymers as both the electrolyte and ionomer in the catalyst layer will also be discussed.
Construction of Non-Enzymatic Hydrogen Peroxide Sensors By Exploiting the High Electrocatalytic Activity of Pd-Ag/Rgo Nanocomposites
Authors: Uzunoglu Aytekin , Song Siyi , Stanciu Lia
Published: February 2020

The detection of hydrogen peroxide (H2O2) plays a key role in various applications including food and environmental analysis, industrial manufacturing, pharmaceuticals, and biochemistry. Besides, the level of H2O2 in aerobic cells is used to diagnose some pathological conditions ranging from diabetes and Alzeimer’s disease to cancer. Therefore, the construction of H2O2 biosensors with high sensitivity and selectivity have attracted great deal of interest in the last couple of decades. Although there are various analytical methods to detect H2O2, such as photometry, chemiluminescence, chromatography, titrimetry, and colorimetry, electrochemical detection of H2O2 is considered one of the most promising techniques due to its high sensitivity, selectivity, and simplicity.  In this work, we designed novel electrochemical non-enzymatic H2O2 sensors by exploiting the high surface area and fast electron transfer rate of reduced graphene oxide (RGO), as well as the high electrocatalytic activity of palladium-silver nanoparticles which were used to decorate RGO. The Pd-Ag/RGO nanocomposites were synthesized using a one-step reduction technique. The prepared metal nanoparticle-decorated RGOs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) techniques. Electrochemical H2O2 sensors were constructed by casting a certain amount of nanocomposite/dimethylformamide solution on glassy carbon electrodes and subsequent drying at room temperature in air. The analytical performance of the sensors was evaluated by cyclic voltammetry and chronoamperometry methods. The preliminary results revealed that Pd-Ag/RGO sensors had higher electrocatalytic activity towards the reduction of H2O2 compared to Pd/RGO and Ag/RGO sensors. The sensitivity of Pd-Ag/RGO sensors to the reduction of H2O2 was found to be -243 µA mM-1 cm-2 at the working potential of -500 mV (vs. Ag/AgCI). In addition, the Pd-Ag/RGO-based sensors yielded a linear analytical response up to 30 mM.
(Vittorio de Nora Award) Mathematical Modeling of Electrochemical Systems
Authors: White Ralph E.
Published: February 2020

Mathematical modeling of electrochemical systems on the continuum scale will be reviewed in this presentation by way of several examples taken from my career. The purpose of such modeling is usually to develop a model that can be used to make predictions of the performance and perhaps the degradation of an electrochemical system of interest. Typically, we seek a model that is as simple as possible, but does not “throw the baby out with the bath water.” In addition, we seek a model that does not require significant computation time since it is necessary to validate the model based on experimental data. It has been and still is a challenge to develop a model of an electrochemical system of interest in a timely manner so that it will be useful in industry. Fortunately, software such as COMSOL Multiphysics is available now to assist in the development of models of electrochemical systems and includes a significant library of such models. Several examples of industrially useful mathematical models of electrochemical systems will be presented.
Additional Voltage Loss to Explain an Equilibration Process in Response to a Change in the Anode Gas Using Sm-Doped Ceria Electrolytes
Authors: Miyashita Tomofumi
Published: February 2020

The electronic conductivity of Sm-doped ceria is very low in air and increases substantially under hydrogen gas. We measured the equilibration process using a very thick (6.6 mm) samarium-doped ceria electrolyte in response to a change in the anode gas. The open circuit voltage gradually increased to an equilibrium voltage of 0.80 V within 5 minutes. The time constant was only 1 minute. However, according to Weppner’s approach, the equilibrium time should be much longer than 5 minutes. It is impossible to calculate the open current voltage during equilibration in response to a change in the oxygen activity of the anode gas. With the assumption of a current-independent constant anode voltage loss, the calculation results provided a significantly improved explanation of the experimental results, both quantitatively and qualitatively. Consequently, both Weppner’s approach and Wagner’s equation can coexist with this method. This proposed voltage loss does not contradict the model for very thin films but is necessary for improvement to explain the experimental results. Furthermore, a current-independent constant anode voltage loss is a general topic in electrochemistry and important to explain physical phenomena not only in the area of solid oxide fuel cells.
Unveiling the Dynamic Capacitive Storage Mechanism of Co3O4 @NiCo2O4 Hybrid Nanoelectrodes for Supercapacitor Applications
Authors: Li Yonghe , Zhang Yuefei , Li Yujie , Wang Zhenyu , Fu Haoyu , Chen Yanhui , Zhang Hongzhou , Li Xiaodong
Published: February 2020

For pseudocapacitors, the electrode material plays a vital role in the electrochemical properties. Among various electrode materials, spinel nickel cobaltite (NiCo2O4) has been widely investigated as an advanced electrode material owing to its better electronic conductivity (two orders of magnitude higher than conventional transition metal oxides), low cost, and high availability. With all the excitement about new electrode materials, less attention has been paid to their dynamic storage mechanism that commonly exhibit intriguing capacitive activation during charge/discharge cycling. Here, we report a simple and cost-effective approach to the synthesis of hierarchical mesporous Co3O4@NiCo2O4 nanoforests on Ni foam for supercapacitor (SC) electrode applications by a coupled one-step solution and annealing process. The synthesized electrode exhibits capacitive activation during charge-discharge cycling (from 0.73 F/cm2 of the pristine state to the peak value of 1.12 F/cm2 after 2000 cycles with only 1.8% loss compared to the peak capacitance after another 2000 cycles). Using ex situ TEM characterization and electrical test, We attribute such dynamic capacitive activation to (1) enlarged electroactive surface area through the formation of Co3O4@NiCo2O4 core-shell structure and (2) enhanced electrical conductivity by forming oxygen vacancies and hydroxyl groups during charge-discharge cycling. Our findings provide a scientific explanation for the capacitive activation in cobalt oxide-binary nickel cobaltite compounds, and a new design guideline for the development of capacitive activation enabled, high performance transitional oxide electrodes.

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Lithium Biphenyl-3,3',4,4'-Tetracarboxylate Based Anode Material for Li and Na-Ion Battery Application
Authors: Veerababu Medabalmi , Varadaraju U V , Ramanujam Kothandaraman
Published: February 2020

Li-ion batteries (LIBs) contribute prominently to the energy storage field due to their acceptable cyclibility and higher energy density [1]. However the traditional inorganic based electrode materials suffering due to the constraint imposed by their structural aspects and scarcity of resources. Hence the focus is on the alternative electrode materials which could be synthesized from renewable sources via eco-friendly processes [1,2]. Recently redox active conjugated carbonyl compounds have gained great attention due to their structural diversity, rate capability and ease of synthesis [1]. In this context we report, lithium biphenyl-3,3',4,4'-tetracarboxylate (Li4-BPTC)  as a potential anode for  both Li-ion and Na-ion batteries for the first time. Li4-BPTC electrode delivered a stable capacity and as well as good rate performance in both Li and Na half cells. Reversible capacities of 92 mAh g-1 after 100 cycles (vs. Li+/Li) and 107 mAh g-1 after 200 cycles (vs. Na+/Na) were observed at a current density of 160 mA g-1. The exchange of Li-ion in the Li4-BPTC by Na-ion during electrochemical cycling against Na+/Na was confirmed by ICP-OES and XPS analysis.

References:

Song Z, Zhou H. Towards sustainable and versatile energy storage devices: an overview of organic electrode materials. Energy Environ Sci., 2013 (6) 2280-301.

Renault S, Brandell D, Gustafsson T, Edström K. Improving the electrochemical performance of organic Li-ion battery electrodes. Chem Commun., 2013 (49) 1945-7.

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Functionalization of Carbon with Manganese Oxide for Enhanced Wettability and Capacitance in Neutral Aqueous Electrolyte
Authors: Grewal Simranjit , Read Brandon , Lee Min Hwan
Published: February 2020

Supercapacitor is one of the most promising energy storage devices to meet surging demands of high-power supply and long-cycle life. Aqueous electrolytes are advantageous over organic electrolytes due to its low cost, safety and ease of assembly but have a major drawback of low energy density due to their small potential windows (~1.2 V). While neutral water is preferred over its acidic or alkaline counterpart to mitigate the drawback (i.e. small potential window), its wettability on carbon, the usual supercapacitor electrode material, has significant room to improve. To address this issue, we considered the incorporation of a metal oxide, MnOx, to the carbon-based structure. MnOx is chosen due to its superior pseudocapacitive capability, wider electrochemical potential window, abundance, and low cost.

In this study, we functionalized active carbon-based structures with a metal oxide (MnOx) by electro-pulse deposition to improve both the electrode wettability and pseudocapacitance. Pulse deposition is chosen to afford a precise control over coating thickness and surface chemistry by controlling the pulse amplitude (0.5 – 3 V), duration (1 – 500 ms) and number of pulsing process. Results showed that there is an optimum in the resulting capacitance; electrodepositing of MnOx at 1 V for 50 ms showed the best performance by improving the overall specific capacitance by 30%. However, the higher pulsing amplitude/duration generally improved wettability. A series of observations indicates that the overall capacitance is co-limited by multiple factors including wettability, surface area and area-specific pseudocapacitance.
Modification of Hierarchical CNT Honeycomb Structures with Fe2O3 for Li-Ion Battery Anodes
Authors: Jessl Sarah , Copic Davor , De Volder Michael F. L.
Published: February 2020

Carbon nanotubes (CNTs) are attractive additives for battery electrodes because of their excellent electrical and thermal conductivity. However, these properties typically degrade by an order of magnitude in assemblies of CNTs compared to the properties measured in individual CNTs. This discrepancy can be bridged by aligning CNTs into yarns, sheets, or vertically aligned forests. In our work, we study aligned CNTs organized in micro-scale honeycomb structures which are desirable due to their mechanical robustness, conductivity, and high surface area. Because of their mechanical robustness, their surface chemistry can be modified to design battery electrodes.

 Here we focus on developing Li-ion battery anodes with a well-defined honeycomb morphology. These honeycombs are fabricated using chemical vapour deposition of CNTs from lithographically patterned catalyst particles. The grown CNTs are subsequently compacted using an elasto-capillary self-aggregation process and thus shaped into honeycomb patterns with varying cell diameters. These electrodes are tested and compared against unaligned CNT powders decorated with the same active nanoparticles, i.e. Iron(III)-Oxide (Fe2O3). The influence of the cell sizes and aspect ratios on the electrode performance is measured after the decoration with Fe2O3 as an active material.

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