bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsed Laser Deposition of Ti-Based MAX Compounds for Next-Generation Wiring Technology
Authors: Wakamatsu Kazunobu , Saito Takeyasu , Okamoto Naoki
Published: July 2021

Semiconductor wiring technology with a width of 10 nm or less is going in order to realize high performance and high integration of large-scale integrated circuits. Copper is currently used as the main wiring material, however, a barrier layer of TiN is necessary due to high diffusivity of Cu into Si or SiO2. In addition, the resistivity of TiN is ten times higher than that of Cu, which results in a drastic increase with decreasing line width less than 10 nm. Therefore, the development of a barrier layer free wiring material to replace copper should be necessary.

The MAX compounds (M: transition metal element, A: A-group element, X: either carbon or nitrogen) is one of the promising candidates for next generation wiring technology. The stoichiometry of MAX compounds is Mn+1AXn (n = 1~3), and exhibits the properties of both ceramics and metals, and some of the compounds have a low volume resistivity as 10 μΩcm. In this study, pulsed laser deposition of TiSiN and TiGeN were carried out and physical and electrical properties were evaluated.

Targets (TiN : Ti : Ge or Si = 3 : 1 : 1) was bought from TOSHIMA Manufacturing. Al2O3 (001) and 1-μm thickness thermal oxide on Si(001) was used as substrate. Substrate temperature was either room temperature or 600℃. N2 was introduced during deposition. Repetition frequency was fixed at 8 Hz, and laser energy was changed from 25 mJ to 75 mJ. Table 1 and 2 show deposition condition for TiGeN and TiSiN, respectively. X-Ray Diffraction and X-Ray Photoelectron Spectroscopy were used to evaluate the crystallographic structure and composition ratio, respectively. Film thickness was measured by using surface profiler. Electronic properties were measured by four point probe method.

Figure 1 shows XRD pattern of TiGeN film deposited on Al2O3 substrate. When TiGeN was deposited at 600℃ and B.P., peaks ascribed to Ge(111), TiN(111) and TiN(200) were observed. TiN(111) peak position 36.85° from TiGeN is 0.04° higher than that from TiN (111) (36.81°, Card No. 00-006-0642), which suggests that lattice parameter decreased from 2.440 Å to 2.437Å. On the other hand, the peak intensity of TiN(200) from TiGeN deposited at 600℃ becomes clear by introducing N2 to 2.0 Pa. TiN(200) peak positions from TiGeN at 600℃ with 0.02 Pa and 2.0 Pa were 39.30° and 39.35°, respectively, the difference from TiN(200) (42.61°, Card No. 00-006-0642) were 3.31° and 3.26°. This suggests that lattice parameter becomes larger from 2.120 Å, to 2.291 (0.02 Pa) or 2.288 Å (2.0 Pa), respectively. One possible reason could be the incorporation fo Ge into TiN lattice.

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Superhydrophobic Coatings by Electrophoretic Deposition
Authors: Saji Viswanathan S.
Published: July 2021

Electrophoretic deposition is an excellent surface coating approach to fabricate superhydrophobic coatings. The method relies on the colloidal process, where suspended and charged particles undergo electrophoresis and eventual deposition on an oppositely charged electrode. Electrophoretic deposition is a facile technique to fabricate functional coatings in several industrial applications, including energy conversion and storage, anti-corrosion, catalysis and biomedical materials. The presentation provides the most recent advancements in this area of research. The fundamental principles behind superhydrophobicity and electrophoretic deposition are covered. Detailed descriptions of the deposition processes with reference to micro/nanoparticles are included. Various application prospects and challenges will also be debated.

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(Industrial Electrochemistry and Electrochemical Engineering Division Student Achievement Award) Mass Spectrometry Titration for Quantitative Probing of Lithium Plating and Solid-Electrolyte Interphase Formation
Authors: McShane Eric J. , Colclasure Andrew M. , McCloskey Bryan D.
Published: July 2021

Rapid charging of lithium-ion batteries is crucial to encourage widespread adoption of electric vehicles, yet the precipitous capacity fade which typically accompanies fast charge limits its utility. Li plating on the graphite anode, which occurs due to the high overpotentials enacted during fast charge, is known to instigate this capacity fade, making precisely identifying the onset and amount of Li plating imperative. Methods have been proposed to detect plating, but these methods typically detect Li indirectly and non-quantitatively. In this presentation, I will outline a novel mass spectrometry titration (MST) technique, which I use to quantify inactive Li (defined as electrically isolated Li metal and LixC6 that remains on the electrode after cycling) via the amount of H2 evolved upon exposure to a sulfuric acid titrant. I extend the technique to additionally quantify carbonate-containing species (via CO2 evolution upon titration) and lithium acetylide (Li2C2, via the C2H2 evolution upon titration) in the solid-electrolyte interphase (SEI), and I demonstrate the utility of MST in characterizing the SEI formed under novel electrolyte formulations. Finally, I will show how MST can be strategically used to determine the onset of Li plating and to distinguish between the multiple capacity fade mechanisms that arise during fast charge.
Mathematical Modeling of Cyclic Voltammogram Curves of Copper Deposition Involving Multiple Additives
Authors: De Shuvodeep , Huang Qiang
Published: July 2021

The manufacturing of interconnects and the packaging of integrated circuits are achieved with electrodeposition of copper or other metals. In order to increase the rate of deposition, especially for the large features in packaging, forced convection is provided with certain agitation mechanisms. Although this reduces deposition time, it leads to non-uniform mass transport within each feature and between different features. Special organic additives are used in the solution during the process in order to tune the nucleation and growth of metal, as well as to modify the deposition rate and improve the uniformity. A mathematical model to describe the behavior of organic additives in conjugation with fluid flow and features of various geometry and dimensions is very much desired to facilitate chemistry and process development. In order to achieve this, the physiochemical kinetics of additive and their influence on the Cu deposition rate need to be described precisely.

This presentation focuses on a method to extract the kinetic parameters describing the combined effect of multiple additives during copper deposition using rotating disk electrode (RDE). The one-dimensional steady state convection-diffusion equation for each of the chemical species including copper is solved by a semi-analytical method for a range of potentials. The boundary conditions of these differential equations are coupled on the surface of the RDE through the surface coverage of the absorbed species. The steady state of surface coverage of the species represents a dynamic equilibrium of three key processes i.e., adsorption, desorption, and consumption (incorporation). When equilibrium is achieved, the net rate of adsorption and desorption becomes equal to the rate of consumption. At each value of potential, the surface coverage of the additives is solved. At first, the solution is obtained with only one species known as suppressor and it was found that in a specific range of voltage and kinetic parameter multiple solutions of the surface coverage exist at same applied potential. This mathematically explains the S-shaped negative differential resistance (NDR) feature in experimental Cyclic Voltammogram (CV) curves. Figure 1 shows three such experimental S-shaped curves for different concentration of suppressors. The NDR region obtained in the theoretical CV curve is sensitive to the kinetic parameters of the additives. It is possible to match the theoretical and the experimental CV curves by optimizing the kinetic parameters. Determination of the kinetic parameters by particle swarm optimization using experimental data for multiple additive concentration will be discussed in detail in this talk.

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Understanding 3D/2D Interfaces for Ion Battery Technologies
Authors: Sharma Vidushi , Datta Dibakar
Published: July 2021

Composites and heterostructures composed of 3D bulk layered with two dimensional (2D) materials are actively being utilized in energy technologies for enhanced performance, mechanical stability and flexibility. 2D materials such as graphene and transition metal carbides (MXenes) provide a mechanically stable skeleton to high volumetric capacity electrodes such as silicon(Si), selenium(Se) and tin(Sn) to name a few. The physical and chemical attributes of the formed 3D/2D interfaces directly propels the electrochemical performance of the composite electrode. We utilize Density functional theory (DFT) to quantify the strength of 3D/2D interfaces formed and further corelated the interface strength to the crystal structure, surface chemistry and electrochemistry of the electrodes. We investigate the interface strength variations between amorphous Si and Ti3C2Tx MXene as the MXene surface functional groups (Tx) are varied from -OH to -OH/O mixed, and -F. The Si/MXene interface is further compared with Si/Graphene interface for Lithium ion battery applications. In additional, ability of Deep Learning(DP) potential to accurately describe structural and dynamic properties of such interfaces has been explored. A DP based potential is generated from vast 3D/2D interface dataset from quantum mechanical calculations and its accuracy has been compared with DFT output of interface dynamics. Issues related to the development of DP for such systems will also be discussed.
(Invited) Materials and Process Technologies for Scaling BEOL Interconnects
Authors: Lee Rinus , Yu Kai-Hung , Pattanaik Gyana , Bourque Ronald , Wajda Cory S , Leusink Gert J
Published: July 2021

Historically, complementary metal-oxide-semiconductor (CMOS) technology was driven by geometrical scaling of the front-end-of-line (FEOL) transistor but it has slowed down significantly in recent years. On the other hand, back-end-of-line (BEOL) interconnects are projected to continue scaling aggressively to meet power, performance and area targets in advanced nodes. In this paper, we will introduce and review BEOL interconnect options targeting sub-7nm metal pitch with an emphasis on materials and process technologies.
Fully Three-Dimensional Silicon-Integrated Dielectric Capacitor at 1 µFmm-2 for on-Chip Energy Storage
Authors: Paghi Alessandro , Strambini Lucanos , Mariani Stefano , Sood Anjali , Kalliomaki Jesse , Jarvinen Paivi , Toia Fabrizio , Scurati Mario , Morelli Marco , Lamperti Alessio , Barillaro Giuseppe
Published: July 2021

The increasing request of on-chip energy storage devices is driven by the augmented connectivity between people and things for IoT, portable, and wearable electronic applications. These systems require high performance components with low power consumption, compact size, and high energy storage capability. Supercapacitors (SCs) achieve capacitance density in the order of 0.1–1 mF/mm2. Nonetheless, their poor performance in terms of operation frequency (from Hz to tens of Hz, rarely beyond 1 kHz) and voltage (rarely exceeding 2 V), together with their low compatibility with standard integrated circuit (IC) technologies, have inhibited their integration to date.

Dielectric capacitors (DCs) make use of solid-state dielectrics sandwiched between two conductive electrodes. These capacitors operate at high frequency (up to a several MHz) and voltages (exceeding tens of Volt). However, the areal capacitance of DCs is order of magnitude smaller than that of SCs. The use of high dielectric constant materials (k>10) and the exploitation of the third dimension (3D capacitor) to increase the effective surface area of the capacitor per unit volume have been proposed.

In this work, we successfully address the challenge of achieving a 3D silicon-based dielectric capacitor with high capacitance density and large operation voltage and frequency range, using a fabrication process that is compatible with silicon ICs technology.

Specifically, we report on 3D DCs fully integrated in a silicon chip with areal capacitance up to 1 μF/mm2 by atomic layer deposition of conductive (TiN) and high-k dielectric (Al2O3 and HfAlOX) nanocoatings (20 and 40 nm) into trenches electrochemically etched in silicon with aspect ratio up to 100 [1]. The 3D DCs operate up to 70kHz with an excellent stability with voltage (up to 16V) and temperature (up to 100°C), over 100 h of continuous operation (>108charge/discharge cycles). The 3D DCs exhibit power and energy densities of 566 W/cm2 and 1.7 μWh/cm2, respectively, greater that those of most state-of-the-art dielectric capacitors and supercapacitors.

[1] L. M Strambini, A. Paghi, S. Mariani, A. Sood, J. Kalliomäki, P. Järvinen, F. Toia, M. Scurati, M. Morelli, A. Lamperti, G. Barillaro, Three-dimensional silicon-integrated capacitor with unprecedented areal capacitance for on-chip energy storage, Nano Energy, 68, 104281 (2020)
pH Sensitivity Improvement of Vertical Silicon-Nanowire Extended-Gate Ion-Sensitive Field Effect Transistor
Authors: WANG Rui_Xing , Teng Nan-Yuan , Lin Chih-Ting
Published: July 2021

The extended-gate ion-sensitive field-effect transistor (EGISFET) is essential to the field of bio-chemical sensing. It has been reported that the nano-textured gate ISFET is suitable for high pH sensitivity. The small distance between each nano-structure results in the high sensitivity. However, due to the difficulties of manufacturing process, the distance between each nano-structure will no longer be shrunk, which means that it will be a challenge to keep improving sensitivity. To address this issue, we turn to make good use of the space above these nano-structures. Thus, a series of vertical silicon nanowire (SiNW) sensing membranes with different heights was developed in EGISFET pH sensors. The vertical SiNW sensing membranes were fabricated using the electroless etching technique called metal-assisted chemical etching (MACE). The ultra-thin Au nanomesh served as a catalyst in MACE process was replicated from a reusable porous anodic aluminium oxide (AAO) membrane. By photo-lithography the sensing area on the SiNW sensing membrane was defined. The transfer characteristics of such vertical SiNW EGISFET pH sensors exhibited a higher sensitivity (75.86 mV/pH) than that of the conventional planar EGISFET pH sensors (38.53 mV/pH) for the different pH solutions (pH 4, pH 7 and pH 10). The scanning electron microscopy images of SiNW with different heights are also presented.
(Invited) Transition Metal Oxide Catalysts for the Oxygen Evolution Reaction
Authors: Browne Michelle P , Jaśkaniec Sonia , Tyndall Daire , Gannon Lee , McGuinness Cormac , McEvoy Niall , Nicolosi Valeria
Published: July 2021

Currently, approximately 96% of global H2 production is carried out by fossil fuel based routes such as steam reforming of natural gas or coal gasification;1 while only 4% of H2 is generated by renewable energy routes such as water splitting. To increase the percentage of H2 produced by water splitting, it is necessary to lower the overall cost and, at the same time, to improve the efficiency associated with water splitting technologies, which is, closely related to cost, durability and kinetic issues arising from the catalysts used.

Water splitting, also known as water electrolysis, is the separation of the H2 and O2 from water using an external power source, denoted as the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER), respectively.2 Even though the main goal of water splitting is to produce H2, the opposite reaction, the OER, hinders the overall performance of this process. Hence, to make the overall process of water splitting more efficient, new active and more conductive OER catalysts need to be developed.

In general, layered/2D materials exhibit higher surface area and are more conductive than their bulk counterparts therefore hold great promise as next generation materials for the OER.3 Hence, as Transition Metal Oxide (TMO) based materials are currently the best performing catalysts for the OER, it is logical that few layer and 2D TMO materials are likely candidates to emerge as alternative low cost and active catalysts for this electrochemical energy conversion application.2 In this talk, layered/2D TMO based materials as potential catalysts for the OER will be discussed.4

S. Shiva Kumar and V. Himabindu, Materials Science for Energy Technologies, 2019, 2, 442-454.

M. P. Browne, Z. Sofer and M. Pumera, Energy & Environmental Science, 2019, 12, 41-58.

J. N. Coleman, M. Lotya, A. O’Neill, S. D. Bergin, P. J. King, U. Khan, K. Young, A. Gaucher, S. De, R. J. Smith, I. V. Shvets, S. K. Arora, G. Stanton, H.-Y. Kim, K. Lee, G. T. Kim, G. S. Duesberg, T. Hallam, J. J. Boland, J. J. Wang, J. F. Donegan, J. C. Grunlan, G. Moriarty, A. Shmeliov, R. J. Nicholls, J. M. Perkins, E. M. Grieveson, K. Theuwissen, D. W. McComb, P. D. Nellist and V. Nicolosi, Science, 2011, 331, 568-571.

S. Jaśkaniec, C. Hobbs, A. Seral-Ascaso, J. Coelho, M. P. Browne, D. Tyndall, T. Sasaki and V. Nicolosi, Scientific Reports, 2018, 8, 4179.
(Keynote) Electrochemical Behavior and Applications of Electrically Conducting MOFs
Authors: Dinca Mircea , Banda Harish , Mariano Ruperto , Dou Jin-Hu , Miner Elise
Published: July 2021

Owing to their high surface areas, metal-organic frameworks offer intriguing opportunities in various electrochemical applications, where geometric current density can be increased by the high density of (electrochemically) competent sites. Indeed, many MOFs have been employed already in applications such as electrochemical double-layer capacitors, electrocatalysis, and batteries. However, in most cases, various binders are necessary because the vast majority of MOFs are not electrically conductive. One subset of MOFs that stands out in this respect are two-dimensional materials that are connected via fully conjugated organic ligands and single metal ions that typically feature square-planar coordination environment. These graphene/graphite-like MOFs exhibit electrical conductivities in excess of 10-100 S/cm, which obviates the need for additional conductive binders when used in devices. We will discuss the fundamental electronic and structural features that make these materials attractive for electrochemistry, and show initial results from their use in supercapacitors and electrocatalytic devices.
(Invited) Sustainable and Energy-Efficient (nano)Structured Oxidation Electrocatalysts in Acidic Media from Earth Abundant Metals
Authors: Galan-Mascaros Jose Ramon , Garcés Pineda Felipe , Yu Jiahao , Gelmetti Ilario
Published: July 2021

The establishment of a sustainable renewable fuels technology will depend on the electrocatalytic reduction of substrates into fuels, but also on the electrocatalytic oxidation of water or other feedstock to extract the needed electrons and protons. The requirements for the oxidation electrocatalysts are typically more demanding regarding long term stability, since these catalysts must be fast, selective and efficient, but also robust to high oxidation potentials, water, oxygen, electrolytes, acids or bases, etc. Several earth abundant metal oxides are excellent electrocatalysts in neutral and basic conditions, with multiple examples from different labs.1 However, most active transition metal oxides are unstable in acidic media, where they just dissolve even in open circuit conditions. Only noble metal oxides, such as IrO2, are able to exhibit competitive electrooxidation activity in aqueous acidic conditions (pH < 3), where reduction electrochemistry is easier and faster, and proton exchange membrane (PEM) technology may facilitate high current density performance in compact electrolyzer architectures.

In this communication we will report our latest results in the search for efficient, low cost oxidation electrocatalysts from earth abundant, non-critical raw materials able to work in aqueous acidic media. We showed how Co-containing polyoxometalates (POMs), are active electrocatalysts for the oxygen evolution reaction (OER) in acidic conditions when stabilized by a partially hydrophobic support.2 Although with some limitations, a hybrid composite of an insoluble salt of the polyoxoanion [Co9(H2O)6(OH)3(PW9O34)3]16– blended with a carbon paste electrode exhibited superior performance and higher current densities than the corresponding IrO2-based electrodes in the low overpotential range. We are extending this same strategy to bulk and nanostructured transition metal oxides to provide fast and robust OER at pH < 1. Furthermore we will show how some of these metal oxides can also catalyze alternative electrochemical oxidation processes of high interest for the chemical industry, such as the selective oxidation of alcohols to aldehydes or carboxylic acids.

[1] J. R. Galan-Mascaros, ChemElectroChem, 2015, 2, 37. [2] M. Blasco-Ahicart, J. Soriano-Lopez, J. J. Carbó, J. M. Poblet, J. R. Galan-Mascaros, Nat. Chem.
2018, 10, 24.
(Invited) Porphyrin Aerogel Catalysts for Oxygen Reduction Reaction in Anion-Exchange Membrane Fuel Cells
Authors: Elbaz Lior , Zion Noam
Published: July 2021

Platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) have shown high oxygen reduction reaction activity in alkaline media. In order to reduce the overpotential losses in anion-exchange membrane fuel cells (AEMFCs), PGM-free catalysts need to have a high site density to compensate for their which will enable reaching high cell current and power densities. Herein, we will present our work on the synthesis, characterization, and utilization of heat-treated iron porphyrin aerogels as cathode catalysts in AEMFCs. The heat treatment effect was thoroughly studied using several techniques, and the best performing aerogel was showing an excellent performance in AEMFCs, reaching a peak power density of 580 mW cm-2 and a limiting current density of as high as 2.0 A cm-2, which can be considered as the state-of-the-art for PGM-free based AEMFCs.
A Mechanistic Understanding of Electrochemical Bistability Induced By the Presence of 1,10-Phenanthroline in the Cathodic Deposition of Copper
Authors: Rospendowiski Julia , Pinto Maria Rodrigues , Hessel Cristian , Sitta Elton , Nagao Raphael
Published: July 2021

We report herein a precise control of the electrochemical bistability induced by surface area changes during the cathodic deposition of copper. Small additions of 1,10-phenanthroline (Phen) in the reaction media present an inhibiting effect on the global rate mainly due to the adsorption of protonated Phen. The increase of its concentration favors a shrinkage of the bifurcation diagram and shifts it to less negative potentials. The dynamic instability is verified by impedance measurements, and a negative impedance is clearly found. We calculated the apparent molar mass of the adsorbents using in situ gravimetric monitoring in the electrochemical experiments, and the results indicate that mass changes occur mainly due to the reduction of copper from bivalent ions dissolved in the reaction media. Importantly, the adsorption of protonated Phen molecules does not show a considerable contribution in mass variations but prevents the formation of a copper course grained morphology over the surface. Imaging analysis indicates finer nodulations at the lower branch compared to the upper branch in the bistability domain. On the basis of these observations, a kinetic mechanism is proposed and a good agreement is obtained between the apparent molar mass extracted from experiments and the theoretical values. Altogether, our results contribute to a detailed physicochemical description of the nonlinear behavior, bringing new insights about this reaction and pointing out the possibility to design switchable surface electrodes by taking advantage of the bistable behavior.

Rospendowiski, J.; Pinto, M. R.; Hessel, C.; Sitta, E.; Nagao, R. ACS Omega
2018,
3, 13636.
A Numerical Investigation of the Effect of External Resistance and Applied Potential on the Distribution of Periodicity and Chaos in the Anodic Dissolution of Nickel
Authors: Rodrigues Caio Silva , Pereira dos Santos Caio Guilherme , Miranda Renan Carneiro Cavalcante de , Parma Eduardo , Varela Hamilton , Nagao Raphael
Published: July 2021

In the latest years, the world has witnessed intense research on the synthesis of nanostructured materials. One of the most interesting methodologies recently proposed to this end is the use self-organized electrochemical reactions, on which the structuring emerges spontaneously from the reaction, permanently engraved on the electrodes. To achieve a robust process for a rational synthesis utilizing this technique, however, one must have a detailed description of the reaction’s dynamical properties, as they are closely related to the nanometric patterns formed [ChemElectroChem, 2020, 7, 2979].

One of such self-organized electrochemical reactions is the anodic dissolution of nickel. This reaction has the added benefit of being successfully modelled computationally in the literature, contributing to the dynamical studies on the system [J. Phys. Chem., 1992, 96, 2676]. This work presents a numerical exploration of the system’s dynamics, and its relation to the applied voltage and external resistance, two parameters that can be readily accessed on the experimental counterpart. Dynamical phase diagrams were built by varying these parameters (used in their dimensionless form), using the morphological period and Lyapunov exponents of the time-series to characterize its dynamical behavior.

Magnifications of the diagrams’ chaotic regions revealed the presence of self-similar periodic islands (often referred as shrimps) on them, a feature commonly found on chaotic electrochemical dynamics. Period-doubling, a frequent route to chaos, was found on these shrimps, and a period-adding sequence was successfully identified on a shrimp dispersion, even though the shrimp density on the diagrams were low, when compared to other chaotic electrochemical systems.

The shrimps were deformed as both control parameters were increased, being stretched diagonally when the system moved from potentiostatic to galvanostatic condition. For large values of external resistance and potential applied, this stretching was so extreme that the shrimps gave place to parallel linear diagonal domains of periodicity intertwined by chaotic regions. Period-doubling cascades were also found in these domains, suggesting that some dynamical properties from the shrimps were preserved after the stretching. The hypothesis that the stretching is closely related to the exponential terms on the Butler-Volmer equations that makes up the kinetic model was raised.

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Atomically Dispersed Ruthenium-Based Multifunctional Electrocatalysts for Efficient Overall Water Electrolysis Assisted By a Bipolar Membrane
Authors: Yu Zhipeng , Escobar-Bedia Francisco Javier , Sabater Maria J. , Amorim Isilda , Araújo Ana , Concepcion Patricia , Liu Lifeng
Published: July 2021

Electrocatalysts play a crucial role in hydrogen production via water electrolysis. In this presentation, we report the synthesis of atomically dispersed ruthenium (Ru) supported on nitrogen-doped carbon (Ru-NC) with ultra-low Ru loading (0.2 wt%) through a two-step deposition-pyrolysis method. Briefly, controlled amounts of ammonium alginate (AG), 20% wt., were dispersed on a carbonaceous support (Norit CN-1) followed by subsequent introduction of the ruthenium precursor (RuCl3·3H2O) under alcoholic solution (1-butanol). Finally, the Ru-containing solids were pyrolized at 800 ºC for 2 h under N2 flow to yield the Ru-NC catalyst. Extensive transmission electron microscopy investigations reveal that Ru is dispersed on the NC support in the form of both single atoms and small clusters (Figure 1a). The as-prepared Ru-NC exhibits superior electrocatalytic activity and good stability for both HER and OER, showing bifunctionality. It only requires a low overpotential of 47.1 and 72.8 mV to deliver a current density of 10 mA cm-2 for HER in 0.5 M H2SO4 and 1.0 M KOH, respectively, and 300 mV for OER in 1.0 M KOH. The overall water electrolysis performance has been investigated in alkaline solution using Ru-NC as both HER and OER catalysts in the presence of an anion exchange membrane water electrolysis (AEM-WE), where a cell voltage of 1.67 V is needed to achieve 10 mA cm-2. Furthermore, with a bipolar membrane (BPM), we demonstrate water electrolysis in acid-alkaline dual electrolytes (BPM-WE), where HER is accomplished in a kinetically favorable acidic solution and OER in a kinetically favorable basic solution. Such asymmetric acid-alkaline BPM-WE operates under a low cell voltage of only 0.89 V to deliver a current density of 10 mA cm-2 and can sustain over 100 hours without significant performance decay due to the assistance of electrochemical neutralization resulting from the crossover of the electrolytes, which shows a great potential for energy-saving hydrogen production.

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Integration of Photocharging Perovskite Solar Cells-Lithium Ion Battery (PSC-LIB) System
Authors: Kotta Ashique , Kim Eun-Bi , Seo Hyung Kee
Published: July 2021

Solar energy is an important part of the sustainable energy demand of future generations. The further improvements are needed in the present photovoltaic technology, which includes conversion efficiency, sustainability, durability, and cost. The rapid growth in the field of nanotechnology provides better research in photovoltaic technologies. Perovskite solar cells (PSCs) are referred to the future generation solar cells, and has promising future research scopes. In Comparison to other possible photovoltaic technologies, PSC have many advantages over conventional solar cells, such as low manufacturing cost, high stability, and flexibility. Constructing integrated devices from lithium ion batteries (LIBs) and perovskites solar cells (PSCs) is an approach that can achieve self-chargeable LIBs and suitable energy storage. In recent years, several reports about inverted perovskite solar cell based self-rechargeable batteries have emerged and related advances have attracted intense attention from researchers and industries; these works offer some unique strategies for charging the battery by the integration of PSC and LIB system.

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Structure and Stability of Small Metal Clusters on Stoichiometric and Defective 2D MoS2
Authors: Nies Cara-Lena , Nolan Michael
Published: July 2021

Layered materials, such as MoS2, are of great interest to the research community due to their wide range of potential applications. They are of particular interest as supports for low dimensional metal catalysts, as well as for use in the electronics industry as ultra-thin diffusion barriers in semi-conductor device interconnects.

Thus, understanding the interaction between a variety of metal structures and the MoS2 monolayer is of great importance. In previous studies the focus has been largely on the strength of the interaction between a single atom or a nanoparticle of a wide variety of metals, which creates a significant knowledge gap in thin film nucleation on 2D materials. To begin addressing this deficit, we present a density functional theory (DFT) study of the adsorption of small metal structures, with up to four atoms, on a monolayer of MoS2. The metals of interest are Cu, Co and Ru, chosen for their relevance in electronics applications. We show how the metal-substrate interaction changes depending on the particular metal, as well as the mode of adsorption and overall nanocluster structure. Further, we show the effect that the presence of a sulphur vacancy in the monolayer has on the metal-substrate interaction, as this is a commonly observed defect.

The strength of interaction between the metals and MoS2 is in the order Co > Ru > Cu. The effect of adsorption on MoS2 is localised to the metal cluster, however depending on the particular structure, some distortions of the MoS2 lattice can be observed upon adsorption of Ru.
Recycling Diesel Combustion Byproducts As Electrode Material for Lithium-Ion Batteries
Authors: Ketelsleger Cameron , Gregory Darrell , Ozdogru Bertan , Yang Sisi , Cronin Stephen B. , Capraz Omer Ozgur Özgür
Published: July 2021

Lithium-ion (Li-ion) batteries are the most widely commercialized mode of portable, rechargeable energy storage in the twenty-first century. These batteries were introduced in the early 1990s and since have been massively produced to power personal electronics, store renewable energy, and more recently power electric automobiles. As demand for lithium-based batteries increases, it is important to recycle materials pertinent to the battery set up as frequently as possible. In this study, we examine the electrochemical performance of diesel exhaust soot particles as a conductive carbon in cathode composite electrodes and as active anode particles in anode composite electrodes. Diesel soot is a toxic byproduct of diesel combustion which contributes to an estimated 3,500 premature respiratory-related deaths per year in California alone [1]. By removing contaminates in the soot via annealing or tunnel process, we can adjust the electrochemical performance such that it is suitable for batteries.

Electrochemically active diesel particulate matter is obtained from particulate scrubbers attached to diesel-powered engines. Diesel soot powders were annealed at 250 oC for one hour. The material was tested as conductive carbon in cathode electrodes and as an anode in Li-ion batteries. For testing conductive carbon for cathode electrodes, we used lithium iron phosphate (LFP) as the active material and prepared composite electrodes by mixing LFP, conductive carbon, and carboxymethyl cellulose in 8: 1: 1 weight ratio. We compare the performance of the soot as a conductive material with the commercially available Super P carbon (Figure 1A). In the second part of the study, we investigated the ability to store lithium ions as an anode material (Figure 1B). To do this, we prepared composite electrodes made with 80% soot, 10% binder, 10% Super P carbon. The electrochemical performance of these electrodes was tested with cyclic voltammetry, galvanostatic testing, and impedance spectroscopy at various rates.

We find that both diesel soot materials perform closely to Super P as a conductive carbon in LFP composite cathodes (Figure 1A). We find that the electrochemical performance of the recycled carbon waste as a conductive carbon is close to that of the standard, Super P, in composite cathode electrodes. Figure 1B shows that the capacity - voltage profiles of diesel soot anode electrode cycled at different C-rates. Considering performance in both electrodes, this is a novel development which shows hope for making an industrial waste and toxic byproduct useful in electrochemical energy storage.

Acknowledgement: Cameron Ketelsleger and this work were supported by the Lew Wentz Foundation.

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Different Redox Mediators Applied to Elastin-like Polymer Surfaces
Authors: Austin Katherine , Feeney Stanley , Balog Eva Rose M , Halpern Jeffrey M
Published: July 2021

Previous investigation of elastin-like polymer (ELP) modified surfaces showed successful modification followed by a reversible extension and collapse, as measured by electrochemical impedance spectroscopy (EIS). This work indicated successful modification of an electrode with ELP corresponds with a charge transfer resistance of 10-20 kOhms in 10 mM ferri/ferrocyanide (FFC).1 The EIS charge transfer resistance value can be seen to increase with a stimulus predicted to cause ELP collapse and then decrease again with a re-extension of the ELP. We investigated the effects of the FFC concentration and other solution conditions on the interpretation of EIS signals in monitoring ELP response.

For these experiments, ELP was attached to the surface of a gold electrode by binding a cysteine thiol from the ELP to the gold surface in the presence of the reducing agent TCEP. This was followed by EIS experiments to measure the electrochemical impedance of the same ELP-modified surface under three different electrochemical mediator conditions: (1) 5 mM FFC in water, (2) 10 mM FFC in water, and (3) 5 mM FFC in 0.5 M KCl aqueous solution. Before the exchange of electrochemical mediator, the electrode was washed. We observed an increased charge transfer resistance in the presence of 5 mM FFC and a decrease in charge transfer resistance in the presence of 5 mM FFC 0.5 M KCl relative to experiments performed in 10 mM FFC. We predict that the type of electrochemical mediator and supporting electrolyte used in conjunction with ELP modified surfaces will impact the interpretation of data. We will present our progress on the interpretation of ELP-modified surfaces using different electrochemical mediator concentrations, and what we learned from these results.

Acknowledgments: This work was supported by NIH P20 GM113131

References

M. A. Morales, W. A. Paiva, L. Marvin, E. R. M. Balog, and J. M. Halpern, Soft Matter, 15, 9640–9646 (2019).
Development of an Electrochemically-Reversible Hydride Transfer Mediator for Electroorganic Synthesis
Authors: Karr Dylan , Baek Kiyeol , Smith Diane
Published: July 2021

Hantzsch’s ester or amide is commonly used as a stoichiometric hydride transfer reagent in organic synthesis. The goal of this research is to see if Hantzsch’s ester or amide can be converted into an electrochemically-reversible hydride transfer mediator. The first step in achieving this is to realize the reversible 2 electron, 1 proton reduction of the corresponding pyridinium, 1, as shown below. Normally reduction of pyridiniums such as 1 are chemically irreversible due to the dimerization of the initially formed uncharged radical. We believe the key to avoid this pathway is to add a H-donor that can H-bond to the carbonyl O’s in such a way that an acidic H is properly positioned to H-bond to the radical, facilitating a second electron-transfer, proton-transfer step to generate the hydride donor. This presentation will describe the results of our initial efforts to achieve reversibility in this system.

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A Model for Sonochemistry in a Thin Layer Sonochemical Cell: What Constructive Interference Yields
Authors: Parr Daniel , Leddy Johna
Published: July 2021

Traditional sonochemistry (TS) in bulk solution is violent and expensive. Typically, a high power (> 60 W) ultrasonic horn is directed at a planar working electrode. Compression and rarefaction oscillations elicit cavitation bubble formation. Upon bubble collapse, high temperature (> 5000 K) and pressure (> 1000 atm) are produced locally, which enhances rates of chemical reactions. Bubble collapse near the electrode causes solvent jets directed at the surface to effect the surface cleaning and mass transport enhancements attributed to TS.

While productive, TS obscures quantitative measurement of electron transfer kinetics and mass transport and requires a large laboratory footprint. An alternative and efficient sonochemistry is needed. Thin Layer Sonochemistry (TLS) exploits natural acoustics in a thin layer electrochemical cell. Low power transducers (e.g., quartz crystal oscillators) are appropriate because TLS achieves resonance in the cell to amplify input sound to the limit set by the solvent. TLS is more efficient and allows finer control of experimental and acoustic parameters. The footprint of TLS is minimal, and so TLS is appropriate for energy production applications (e.g., fuel cells) in portable devices.

Experience suggests a subtle relationship between acoustic parameters and resonance. Here, a model is presented for calculation and explanation of resonance in a thin layer sonochemical cell. Background physics are explained and a step-by-step assembly guide is presented.

References:

Suslick, K. S.; Didenko, Y.; Fang, M. M.; Hyeon, T.; Kolbeck, K. J.; McNamara, W. B. III; Mdleleni, M. M.; Wong, M. "Acoustic Cavitation and Its Chemical Consequences" Phil. Trans. Roy. Soc. London A, 1999, 357, 335-353.

Johna Leddy, Chester G. Duda, Jacob Lyon, and William J. Leddy III, US Patent 10,300,453 B2, "Thin Layer Sonoelectrochemistry and Sonoelectrochemistry Devices and Methods," 28 May 2019.

D.L. Parr IV and J. Leddy, "Sonoelectrochemistry - A Sketch of Thin Layer Advantages," ECS Trans. (2019) 92(10), 65-73; Open Access, DOI:10.1149/09210.0065ecst
Batteries Made with Calcium Could be Better for Electric Cars or Storing Renewable Energy
Authors: Gerber Colton , Woodcox Michael , Smeu Manuel
Published: July 2021

In coming decades, energy storage demand is projected to increase greatly, in part due to accelerated transition to renewable energy and greater demand for electric cars. Should demand keep pace with projections, dependence on cobalt and lithium poses a humanitarian risk, as high demand for cobalt has incentivized mining with unethical labor practices. Multivalent-ion batteries (MVIBs) may offer an alternative to lithium-ion batteries (LIBs), as materials are orders of magnitude more plentiful and MVIB voltage and capacity may be able to match LIBs. MVIBs may be well-suited for applications like electric cars or utility-scale storage, which lack the constraints of small consumer devices like cell phones. Building off earlier work suggesting CaMn2O4 spinel cathodes should have favorable voltage and volumetric expansion characteristics, the present work focuses on building a voltage profile for CaMn2O4. DFT calculations with VASP were used to calculate stable structures through stepwise intercalation and deintercalation of a Ca8Mn16O32 supercell followed by convex hull analysis. Results showed a lower-than-expected voltage with the Ca- and Mg-intercalated cathode. This may be because of differences in how calculations were performed, as previous work used a selective dynamics (SD) approach and included exchange-correlation corrections with DFT+U. It is assumed that the structures obtained approach the lowest possible energy, but this cannot be verified using the approach taken in this work. Even after many intercalation cycles of the cathode, it is still not clear whether lowest-energy structures were found. Future work should focus on whether it can be safely assumed that the spinel “backbone” does not change with intercalation, at least as far as voltage calculations are concerned. Alternatively, techniques like ab initio molecular dynamics (AIMD), quantum Monte Carlo (QMC), or machine learning (ML) could prove useful in finding lowest-energy structures from which to calculate voltage.

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(Invited) Sars-Cov-2 Rapidplex: A Graphene-Based Multiplexed Telemedicine Platform for Rapid COVID-19 Diagnosis
Authors: Gao Wei
Published: July 2021

The COVID-19 pandemic is an ongoing global challenge for public health systems. Rapid and early identification of infection is critical in preventing widespread COVID-19 infection by presymptomatic and asymptomatic individuals, especially in the community and in-home settings. I will introduce an ultrasensitive and low-cost telemedicine platform, the SARS-CoV-2 RapidPlex, based on target-specific immunoassays built off laser-engraved graphene for rapid and remote assessment of COVID-19 biomarkers (i.e., nucleocapsid protein, anti-spike protein IgG and IgM, and C-reactive protein). Multiplex sensing of these targets provides information on three key aspects of COVID-19 disease: viral infection, immune response, and disease severity. We successfully evaluated the applicability of our SARS-CoV-2 RapidPlex platform with COVID-19-positive and COVID-19-negative blood and saliva samples. Based on this pilot study, our multiplexed immunosensor platform may allow for high-frequency at-home testing for COVID-19 telemedicine diagnosis and monitoring.

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Deep Learning Combined with Surface-Enhanced Raman Spectroscopy for Chemical Sensing and Recognition
Authors: Bertz Morten , Yanagisawa Masahiro , Homma Takayuki
Published: July 2021

Surface-enhanced Raman spectroscopy (SERS) combines the unique advantages of Raman spectroscopy – namely detection of specific molecular fingerprints without requiring prior labelling – with enhanced sensitivity. SERS takes advantage of the amplification of the incident electric field by localized surface plasmons on noble metal nanoparticle surfaces, which allows the rapid, non-destructive detection of a wide variety of analytes ranging from small molecules to entire microorganisms.

The data obtained from SERS experiments, however, can be difficult to interpret. Spectra are dominated by the chemical species in closest contact with the plasmonic field, and consequently spectra recorded at different points in time from the same sample can exhibit considerable differences. The rich chemical information contained in the spectral data therefore is often not utilized to its full potential or lost altogether.

Here, we combine deep convolutional neural networks (CNNs) with SERS to classify series of spectra obtained from mixtures of different sample species (1). We find that CNNs outperform standard chemometric methods, such as principal component analysis, but also support-vector machine classifiers, shallow artificial neural networks, or even trained human experts while requiring minimal data preprocessing, such as background subtraction or smoothing. We discuss optimizing the classifier with regards to network topology, learning strategy, and data augmentation.

In addition, we show that we can extract useful information from trained networks. In simple cases, activation maximization spectra, which represent the spectral features that are most relevant to discriminate between different sample classes, can provide a good approximation of the spectra in the original sample. We also train generative adversarial networks (GANs) (2) to generate / extract characteristic spectra from large, more heterogeneous datasets. These spectra can provide additional insight into the composition of the sample and might thus be relevant to guide further experiments.

Deep learning and SERS are two powerful techniques that complement each other. The high sensitivity of SERS quickly generates large, but often highly complex spectral datasets, which are in turn well-suited to the analysis by CNNs. Most importantly, deep learning not only excels at classification but can be used as a more general tool to facilitate the interpretation of heterogeneous, seemingly intractable datasets. Given the tremendous attention deep learning has attracted over the past decade, we anticipate that it will play an increasingly prominent role in spectral analysis as well.

Yang, J. et al., 2019. Deep learning for vibrational spectral analysis: Recent progress and a practical guide. Analytica chimica acta, 1081, pp.6–17.

Odena, A., Olah, C. & Shlens, J., 2016. Conditional Image Synthesis With Auxiliary Classifier GANs. arXiv:1610.09585 [stat.ML]

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