bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of Low-Cost Flexible Paper-Based Alcohol Sensor
Authors: Platero Justin , Soundappan Thiagarajan , Abdelazim Khaled , Platero Joshua , Wilson Katelyn , Begay Makeiyla , Billey Wayant , Plummer Dallen , Spencer Davina
Published: August 2024

The development of alcohol sensors has been an active research area for years. Alcohol detection can be applied to medicine, agriculture, and law enforcement. On the Navajo Nation, we have limited access to centralized analytical laboratory techniques, for on-spot testing. Regarding healthcare, the collected lab sample is sent to nearby bigger cities for analysis, and results for lab work may take weeks and even months to receive a detailed report; also, law enforcement relies on state support for analytical techniques. Through the NSF-PREM research collaboration with Harvard University at the NanoElectrochemical Analysis and Energy Storage Laboratory (NEST LAB) at Navajo Technical University (NTU), we have fabricated a versatile paper-based sensor to detect several analytes. Our sensor utilizes electrochemical analytical techniques such as cyclic voltammetry to monitor the concentrations of our target analytes (alcohol). Our sensors' versatility and low-cost appeal make them suitable for alcohol detection. We can optimize our sensor to detect alcohol samples for on-spot analysis. We can also apply our sensors to detect and determine alcohols derived from the biomass.

Contact Details:

Justin Platero, Student Researcher, Email:justin.platero@student.navajotech.edu

*

Corresponding Author:

Dr. Thiagarajan Soundappan, PI, NEST LAB, NTU.

Email: tsoundappan@navajotech.edu

Acknowledgment: NSF-PREM DMR-2122195 and USDA-NIFA-2021-38424-33455
Development of Nickel-Chromium Alloy Electroplating and Its Surface Morphology Studies for Automobile Industries
Authors: P Vignesh
Published: August 2024

In the electroplating industry, alloy plating is typically one of the most difficult processes. We are showcasing the Ni-Cr (Nickel Chromium) alloy electroplating in our work. Trivalent chromium bath is made in order to resist the hazardous hexavalent chromium, and co-deposition of chromium and nickel is accomplished. Our work is appropriate for industrial electroplating in the automotive industry because Ni-Cr alloy exhibits good corrosion resistance along with features including wear resistance, ductility, and thermal stability. Through the use of SEM (Scanning Electron Microscopy), EDAX (Energy Dispersive X-Ray Analysis), and XRD (X-Ray Diffraction) studies, we are able to clearly observe the surface morphology in this project. These research allow us to observe the Porous behavior surfaces.

Figure 1
Teaching Undergraduate Students Heterogeneous Electrocatalytic Water Oxidation Using Cyclic Voltammetry and Python Simulation
Authors: Qiu Jingjing , Moeller Anneke , Zhen Janet , Adelstein Nicole
Published: August 2024

Undergraduate students are motivated and engaged to persist in STEM by learning skills to combat climate change and reduce carbon dioxide (CO2) generation. Water electrolysis is not only an important process to produce the clean energy source hydrogen (H2), but also a classical reaction discussed in the undergraduate chemistry curriculum.

In this talk, we will discuss our efforts of developing an upper division laboratory to teach undergraduate students basic concepts in electrochemistry via the heterogeneous anodic electrocatalytic water oxidation in water electrolysis.1Both experimental work and simulation practices with Python were implemented in this laboratory. Key concepts including chemical reversibility, electrochemical reversibility and kinetics of heterogeneous charge transfer were introduced to students in the learning outcomes. The integrated experience of mini lectures, hands-on experience of materials preparation and electrochemical characterizations along with the simulations helped enhance students’ learning. Additionally, the experience of using Python simulations motivates students to learn programming, which will help prepare them for the workforce and other STEM careers.

Chem. Educ. 2023, 100, 8, 3036–3043
Materials Design for Critical Element Separation
Authors: Liu Chong
Published: August 2024

The development of renewable energy technologies and next-generation optoelectronic devices relies on the secured supply of critical elements (such as lithium and rare earth element). Traditional mining and separation methods are disruptive to the environment, consume large quantities of harsh chemicals, and are unable to access dilute resources due to low elemental selectivity. Therefore, the invention of new separation methods and the fundamental understanding of the separation processes are crucial to realizing sustainable mining while broadening minable resources. In this talk, I will introduce a platform method, electrochemical intercalation, for selective ion separation using lithium extraction as an example. I will explain the different roles of major ions in competition with lithium ion and discuss strategies to promote lithium intercalation during co-intercalation by materials design.
Ammonia Recovery from Manure Wastewater Using Membrane Electrochemical Systems
Authors: Burns McKenzie , Yang Kai , Qin Mohan
Published: August 2024

Livestock systems face a challenging future with increasing conflict between food production and the environment. Many of the environmental issues stem from livestock manure as it can lose manure constituents, including nutrients, pathogens, and organic matter, to the environment, degrading both surface and ground water quality, contributing to climate change, causing nuisance odors, and creating human health issues. Processing manure to recover embedded nutrients such as ammonium nitrogen and phosphorus can mitigate these impacts by increasing nutrient density, making a more manageable fertilizer that has a greater economically feasible transport distance. Membrane electrochemical system (MES), which uses electrochemical reactions to transport ions through ion exchange membranes, has been considered as an effective technology for separating ammonium ions from ammonia-rich wastewater towards recovery. This study investigates the system performance of MES for ammonia recovery from various streams of livestock manure. We elucidate the pathways of organic nitrogen mineralization and how they can be improved to enhance ammonia recovery in MES. Additionally, we develop a mathematical model to systematically investigate the ion transport behaviors in MES. Our analysis shows that current density, membrane properties, and initial competing ion concentrations can intensively affect the selectivity of ammonium ion transport over other ions. The findings of this study advance our understanding of the key metrics affecting ammonia recovery from livestock manure using MES and can guide the development of more efficient and effective systems.
Selective Recovery of Rare Earth Elements from Waste Magnets by Molten Salt Electrochemical Process
Authors: Nohira Toshiyuki , Kawaguchi Kenji
Published: August 2024

Neodymium magnets are the strongest permanent magnets with Nd2Fe14B as the main phase. In applications where high temperature operation is expected, such as motors for electric vehicles (EVs) and hybrid electric vehicles (HEVs), Dy is added to prevent degradation of magnetic properties. Currently, the demand for EVs and HEVs is growing rapidly, and Dy-doped NdFeB magnets are used in these vehicles. Thus, a large amount of waste magnets will be generated in the future. Moreover, for heavy rare earths such as Dy, high-quality resources are extremely unevenly distributed in the world, and there are already concerns about their stable supply. Given the above background, there is a need to develop an efficient recycling process that can replace the conventional wet recycling process, which has a large environmental impact and energy consumption.

Our research group has proposed a process for the separation and recovery of rare earth elements (REEs) from the waste of neodymium magnet using molten salt electrolysis and alloy diaphragms [1,2]. The principle of this process is shown in Fig. 1. First, the Nd and Dy ions in the waste magnet used as the anode are dissolved into the molten salt by anodic dissolution. Next, the dissolved Nd or Dy ions are reduced on the surface of the diaphragm, which functions as a bipolar electrode, and only one of the ions is reduced to form an alloy. Furthermore, Nd or Dy diffuses through the alloy diaphragm and is dissolved into the molten salt by anodic dissolution on the cathode chamber side surface of the diaphragm. Finally, Nd and Dy are separated and recovered on the cathode.

So far, we have reported that selective permeation of Dy [2] and Nd [3] is possible using LiCl-KCl as the molten salt and a solid Ni-RE alloy as the diaphragm. In the present study, we selected LiF-CaF2 as a more practical fluoride-based molten salt and Hastelloy as a more durable diaphragm, and investigated the electrochemical permeation of RE. We also considered that liquid Fe-RE alloy is expected to be a more desirable diaphragm with higher durability and faster permeation. As a fundamental study, the formation behavior of liquid Fe-Nd and Fe-Dy alloys was investigated, and the results will also be reported.

[1] T. Oishi, H. Konishi, T. Nohira, M. Tanaka, and T. Usui, Kagaku Kogaku Ronbunshu, 36, 299 (2010). [in Japanese]

[2] T. Oishi, M. Yaguchi, Y. Katasho, H. Konishi, and T. Nohira, J. Electrochem. Soc., 167, 163505 (2020).

[3] T. Oishi, M. Yaguchi, Y. Katasho, and T. Nohira, J. Electrochem. Soc., 168, 103504 (2021).

Figure 1
A Sustainable Process for Rare Earth Electrowinning in Chloride Based Molten Salts
Authors: Holcombe Benjamin P , Sinclair Nicholas Scott , Baker Alex , Kim Eunjeong , Mccall Scott , Akolkar Rohan
Published: August 2024

Neodymium production has become increasingly important due to use of neodymium–iron–boron (NdFeB) magnets in green energy, consumer technology and defense applications. The state-of-the-art practice features a neodymium fluoride and lithium fluoride molten salt with a consumable carbon anode converting dissolved neodymium oxide and carbon to neodymium metal and CO2.1-2 The anode effect results in PFCs and CO emissions, which make the current neodymium electrowinning process unsustainable.3-4 Some attempts have been made to electrolyze the chloride salt of neodymium to produce chlorine at the anode. Chlorine is a value-added product which neither consumes the anode nor produces other deleterious GHGs. Additionally, the chloride of neodymium can be non-carbothermically produced through a spontaneous reaction with hydrochloric acid, producing only water as a side product. However, a common problem in chloride rare earth electrowinning is the low Coulombic efficiency (10-50%) obtained in lab-scale and pilot-scale efforts.5 The neodymium chloride electrolysis process notoriously encounters a two-step reduction producing an intermediate divalent (Nd2+) oxidation state which is stable in the chloride media.6-7 The intermediate neodymium species diffuses away from the cathode leading to Coulombic efficiency loss. Additionally, the kinetics of the chlorine evolution reaction (CER) in chloride molten salts are known to be relatively sluggish, causing significant anodic overpotentials which elevate the specific energy consumption during electrowinning. Furthermore, electrowinning from molten salts often produces spongy or dendritic deposits of metal requiring energy-intensive purification. In this talk, we will address all aforementioned technical hurdles and report on our efforts achieving high Coulombic efficiency (~85%), and compact deposits with superior as-electrowon neodymium metal purity (>99 wt.%). Furthermore, we will report the development of a new anode which catalyzes chlorine evolution, lowering the anodic overpotential considerably during electrolysis at high current densities of practical interest for electrowinning. Specific energy consumption is calculated for some example cases and found to be between 2.1 and 3.5 kWh/kg representing a significant improvement over the conventional oxyfluoride process.

Figure 1
Molecularly Selective Electrochemical Recovery with Redox Polymers for Platinum Group Metals
Authors: Chung Ching-Hsiu , Cotty Stephen Richard , Jeon Jemin , Elbert Johannes , Su Xiao
Published: August 2024

The platinum group metals (PGMs) are precious metals with scarcity and have widespread use in jewelry, automotive converter, catalysts, pharmaceutical drugs, and fuel cells.1 Because PGMs are keys for the energy transition towards renewables, creating a circular economy for PGMs can greatly contribute to the enduring sustainability of the energy industry. Electrosorption with redox materials has great application in low concentration desalination and ions recovery because of its low waste generation and nearly no chemical input during the operation.2, 3 Furthermore, it has been proved that ferrocene-based redox polymer can recycle platinum-based catalysts with 99.5% recovery.2 Nevertheless, the competitive electrosorption behavior between PGMs complexes with redox polymers is still unknown, which is critical to unlock more efficient pathways to purify PGMs particularly in the mining sector that separation of PGMs requires high energy and chemical input because of their similar physical and chemical properties. Here, we demonstrated for the first time an electrochemically reversible selective PGMs recovery system. Furthermore, because functional groups of redox polymers can affect the selectivity and the uptake of metal ions,3 redox polymers with different functional groups and redox potential were designed, synthesized, and applied for selective electrosorption of PGMs ions. Results showed that our redox polymer has regeneration efficiency of 92% for iridium and 83% for ruthenium. Separation tests showed that the separation factor of platinum over rhodium in the Pt/Rh binary mixture can be up to 40 at open circuit potential and enhanced to higher than 100 by applying potential. For the real-world application, the electrosorption platform was applied for recycling catalytic converter and showed 38% recovery of iridium. Overall, our approach expands the scope of selective electrochemical recovery of PGMs, providing a platform with high energy-efficiency for the multicomponent recovery of PGMs from waste feedstocks.

References

Yakoumis, I.; Panou, M.; Moschovi, A. M.; Panias, D., Recovery of platinum group metals from spent automotive catalysts: A review. Cleaner Engineering and Technology
2021,
3, 100112.

Cotty, S.; Jeon, J.; Elbert, J.; Jeyaraj, V. S.; Mironenko, A. V.; Su, X., Electrochemical recycling of homogeneous catalysts. Sci. Adv.
2022,
8 (42), 12.

Chen, R. L.; Feng, J. Y.; Jeon, J.; Sheehan, T.; Ruttiger, C.; Gallei, M.; Shukla, D.; Su, X., Structure and Potential-Dependent Selectivity in Redox-Metallopolymers: Electrochemically Mediated Multicomponent Metal Separations. Adv. Funct. Mater.
2021,
31 (15), 11.
Transforming Mining Tailings into Green Steel and Rare Earth Elements
Authors: Zhang Duhan
Published: August 2024

As critical components for energy and defense technologies, the U.S. rare earth element (REE) ore reserves are estimated at ~13 million tons, but domestic production is currently limited to one operational mine residing on high-grade ore deposits in Mountain Pass, CA. While low-grade REE deposits are abundant, high-grade American REE deposits are sparse. Meanwhile, hazardous REE-containing tailings pile up at the economic and environmental cost, and it is estimated that REE value locked within e.g., red mud, is $796 per ton. However, such low-grade deposits or mining tailings are challenging to access because REEs are usually locked within a mineral matrix, typically iron oxide, that renders the ore intractable to mechanical or chemical separation. Here, we propose a process for recovering REEs from low-grade deposits and tailings by electro-metallurgically removing iron oxide, hydro-metallurgically removing aluminum salt, and subsequent separating insoluble rare earth oxides. Our strategy produces not only refinable REEs concentrates but also emissions-free iron metal and supplementary cementitious materials as co-products for decarbonizing steel and cement industries, respectively. By addressing the economic and environmental challenges associated with low-grade REE deposits and mining tailings, our electrochemical approach offers a sustainable pathway for unlocking the potential of domestic rare earth resources.
Electrochemical Bioremediation of Uranium (VI) Using Geobacter Sulfurreducens on a Boron Doped Diamond Electrode Surface
Authors: Acevedo Alexis J , Rosario-Cruz Elliott G. , Toranzos Gary A. , Cabrera Carlos R.
Published: August 2024

Developing nuclear science and technology has increased nuclear waste containing uranium. The contamination associated with nuclear activity is a significant concern for human and environmental health. Due to the high toxicity, radioactivity, and extensive half-life of uranium, it is necessary to find means to remediate contaminated environments, bioremediation being an alternative. Microorganisms can reduce, eliminate, contain, or transform hazardous waste such as radionuclides. This work proposes using Geobacter sulfurreducens to reduce uranium (VI) to uranium (IV). The research consists of electrochemical processes for the G. sulfurreducens' immobilization using boron-doped diamond electrodes (BDD) as electron donors. Taking advantage of the microbial metabolic processes and using U (VI) as an electron acceptor, we can reduce the ion to U(IV) - the electrochemical methods involve using a BDD electrode coupled with Geobacter sulfurreducens. First, using the chronoamperometry technique, a potential of -600mV (vs. Ag/AgCl) was applied. In this way, G. sulfurreducens was immobilized on the BDD electrode surface. After the bacteria immobilization process, a 2mM solution of uranyl acetate was added, an applying the reduction potential oof -600mV, the uranyl ion was reduced and removed from the solution. the bacteria electrochemical immobilization was suggested first due to the changes in current with respect time. This process with G. sulfurreducens was demonstrated with scanning electrode microscopy (SEM), where the bacterium was observed modifying the BDD electrode surface. In the same way, the uranium electrochemical reduction process using the immobilized bacteria on the electrode was suggested and corroborated. Moreover, using SEM and energy dispersive X-ray spectroscopy (EDS), the uranium electrochemical remotion using G. sulfurreducens and the presence of this element on the BDD electrode surface were identified. Finally, Raman spectroscopy analysis was used to determine the uranium species present on the electrode surface. The results obtained help in the advancement of the electrochemical bioremediation processes for the treatment of hazardous waste in the environment.

Figure 1
Electrochemical Recovery of Cd and Te from CdTe Solar Panels
Authors: Repukaiti Reyixiati , Shi Meng , Diaz Aldana Luis
Published: August 2024

CdTe photovoltaic (PV) solar panel occupies approximately 5% of the PV solar panel market worldwide, as the second deployed PV technology following crystalline silicon. To ensure a circular economy of critical materials, it is important to recover Cd and Te from end-of-life CdTe solar cells. Current industrial recycling processes of CdTe solar panels involve multiple stages of chemical oxidation, separation, and precipitation, which require high energy and chemical consumption. Different electrochemical processes are compared and evaluated to recover Cd and Te from shredded CdTe solar cells as possible alternatives. Cd and Te are selectively leached and precipitated with mediated electrochemical oxidation processes. In this ongoing work, electrochemical systems show potential to decarbonize the CdTe recycling industry.
Solid-State Lithium-Ion Conductor via Reversible Self-Assembly of Aramid Amphiphiles
Authors: Cho Yukio , Fincher Cole D. , Ortony Julia , Chiang Yet-Ming
Published: August 2024

Lithium-ion batteries are critical in advancing carbon neutrality and sustainable development. However, their end-of-life management and the recyclability remain significant challenges. We investigated an alternative approach to improve the recyclability of lithium-ion batteries by incorporating a layer of reversible materials, acting as an 'upon-disposal switch.' This switch facilitates the smooth delamination of battery components upon recycle process, enabling a more efficient and clean separation of battery components to facilitate direct recycling. Inspired by the principles of biodegradability, we explore the use of organic small molecule self-assembled nanoribbons as the reversible layer integrated in the battery cell. These supramolecular nanoribbons are tailored to overcome the typical stability issues of self-assembled nanostructure and conduct lithium-ion as a solid-state electrolyte. This study delves into the performance and transport mechanisms of these supramolecular nanomaterials and presents a proof-of-concept demonstration of direct recyclability.

Figure 1
A Sustainable Recycling Approach to Regenerate Graphite from Industrially Sourced Failed Anodes
Authors: Rica Brunilda , Briqueleur Elsa , Mankovsky Denis , Royer Ilona , Dolle Mickael , Waldron Karen
Published: August 2024

Recycling graphite from Li-ion battery (LIB) waste plays an important role in increasing the accessibility of graphite resources and sustainable recovery. This presentation describes our work to purify graphite from failed (i.e., out-of-specification) anodes in LIB manufacturing by focusing on the most common contaminant: copper, used as the current collector in LIB anodes.

A new, three-step scalable and environmentally friendly approach was used to provide a cost-effective and sustainable method in industrial settings to recycle failed anodes during the early stages of battery manufacturing.

The study aimed to understand the differences between new, battery-grade graphite and recycled graphite from anode production waste. In particular, focus was placed on the effect of metallic Cu residues on electrochemical performance. The efficiency of Cu removal from graphite was quantified by Microwave Plasma – Atomic Emission Spectroscopy (MP-AES) analysis of leachates. The following experimental parameters were studied to maximize Cu leaching efficiency: solid-to-liquid ratio, temperature, acid concentration, time and stirring speed.

The surface morphology and elemental composition of leached and thermally treated purified graphite were analysed by Scanning Electron Microscopy – Energy Dispersive Spectroscopy (SEM-EDS) and Laser Induced Breakdown Spectroscopy (LIBS). The specific surface area and crystallographic parameters were measured by Braunauer–Emmett–Teller Analysis (BET) and X-Ray Diffraction (XRD), respectively. The electrochemical performance was evaluated by galvanostatic cycling with potential limitation versus Li+/Li. These five techniques were carried out on the solid residues after each stage of the regeneration procedure. The results were compared with battery-grade graphite to assess the effectiveness of our sustainable recycling approach to reuse graphite from failed anodes in LIBs.
CO2 Reduction in a Bio Mass-Paired Systems for the Production of e-Chemicals
Authors: Brueckner Sven , Hauke Philipp , Ju Wen , Strasser Peter
Published: August 2024

The electrification of chemical manufacturing is an important pathway toward reduced CO2 emissions. Direct electrochemical CO2 reduction can thereby become a key technology. CO2 electrolyzers produce cathodically platform chemicals as CO, format, ethanol or ethylene. The state-of-the-art anode process is the oxygen electro evolution which suffers from high over potentials and moderate valorization. An alternative is the anodic oxidation of biomass to valorized carbonaceous products, such as the oxidation of hydroxymethylfurfural (HMF) to the biopolymer precursor 2.5-furandicarboxylic acid (FDCA).

In this work we report the design of electrolyzers flow cells with paired valorization of biomass and CO2. NiNC cathode GDEs are used for CO2 reduction to CO and NiFe-LDH anodes for the HMF oxidation in a zero-gap membrane electrolyzer flow cells. We used a bipolar membrane to separate and optimize either half-cell reactions. Inside the membrane, water is dissociated and the protons will neutralize carbonates on the cathode which is beneficial for a higher CO2 utilization and single pass. So, we can report close to 95% FE and 100% utilization efficiency towards CO.

On the other hand, the hydroxide will stabilize the anode pH and enable PGM-free anodes compared to AEM CO2 electrolyzer. State-of-the-art HMF oxidation is a semi-batch setup, in which the HMF containing anolyte is recycled to complete HMF depletion and utilization. This design suffered from severe mass limitations. Therefore, we modified the semi-batch process into a continuous process and made tradeoffs between faradaic efficiency and utilization. As HMF is not stable in alkaline solutions we decided that a high utilization is beneficial because the intermediates are stable and could be recycled. We can report a single pass conversion of around 70 % towards FDCA at 200 mA cm-2 at a total utilization of 90%.

Figure caption: Paired continuous HMF/CO2 electrolyzer with performance parameter.

Figure 1
Improving the Selectivity and Efficiency of Synthetic Organic Electrosynthesis
Authors: Minteer Shelley D.
Published: August 2024

Although electrochemistry is a current focus area in improving the sustainability and safety of chemical manufacturing, electrochemical techniques for synthesis rarely have sufficient selectivity and frequently have low faradaic, product, and energy efficiencies. This paper will discuss the use of biocatalytic systems to improve the selectivity of electrosynthesis followed by a discussion of materials, reactor, and technique strategies to improve the faradaic, product, and energy efficiencies in these systems. Examples will be shown that range from commodity chemical synthesis to fine chemical synthesis to pharmaceutical synthesis with a comparison of the concerns and advantages of electrosynthesis for each chemical industry.
Durability Assessment of Roll-to-Roll Coated PEM Water Electrolysis Anodes
Authors: Parrish Chance , Engtrakul Chaiwat , Iyer Radhika , Ware Sam , Blair Sarah J. , Padgett Elliot , Kominowski Andrew , Wrubel Jacob A , Schaffer Corey , Bender Guido , Mauger Scott A
Published: August 2024

Widespread adoption of green hydrogen relies on the high-throughput production of key electrolyzer components in a manner yielding acceptable stack manufacturing costs. Roll-to-roll liquid coating methods, such as slot die and gravure coating, are particularly relevant means to produce key components (e.g., membranes and electrodes) at high throughput. In the case of proton exchange membrane water electrolysis (PEMWE), thrifting of expensive iridium-based catalysts poses additional challenges to the implementation of such high-throughput coating methods for iridium-based anode manufacture.

Herein, we investigate key challenges around roll-to-roll manufacture of low-loaded (<0.2 mgIr/cm2) iridium-based electrodes for PEMWE. In particular, we highlight fundamental limitations in coating the thin layers required to manufacture low-loaded electrodes, for which the improper choice of coating conditions may lead to macro- and micro-scale heterogeneity. By addressing causes of this heterogeneity, homogeneous slot-die coated iridium oxide anodes of varying iridium loading are produced on decal substrates. Catalyst coated membranes (CCMs) are subsequently produced from these anodes via hot-pressed decal transfer, and 1,000 hour constant current tests are conducted with intermediate diagnostics (polarization curves and impedance spectroscopy). Key effects of loading and homogeneity on electrode durability are highlighted, and future directions are discussed.

This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office and Advanced Manufacturing Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.
(Invited) Ferroelectric Nonvolatile Capacitive Synapse for Charge Domain Compute-in-Memory
Authors: Phadke Omkar , Kim Tae-Hyeon , Luo Yuan-Chun , Yu Shimeng
Published: August 2024

The rise of Artificial Intelligence has led to an increased demand for computing hardware which can handle data intensive tasks in an energy efficient manner. Compute-in-memory architecture which combines information processing and data storage at the same location and specializes in Multiply-and-Accumulate (MAC) operation has emerged as an attractive candidate to meet this demand. Non-volatile capacitive (nvCAP) devices are investigated to realize the synaptic devices to enable CIM in charge-domain-computing. Charge-domain-CIM works as follows: The synaptic weights of a neural network are stored as the capacitance state of the nvCAP device in a crossbar array. The input of the neural network is applied as voltages to the crossbar array, and the resulting charges are summed up as the MAC operation. The nvCAP synaptic devices also provides benefits over traditional resistive synapses such as: only static power consumption, negligible sneaky current, suppressed read-disturb due to small-signal-read out. Recently, the Ferroelectric Field Effect Transistor (FeFET) has been demonstrated to operate in nvCAP mode, with S-D terminal of the FET shorted and Body-Floating. Here, the Field Effect Transistor part exhibits a gate voltage-dependent capacitance behavior, where the high capacitance originates from the transistor gate area, while the low capacitance originates from the overlap region between the gate oxide and source-drain region of FET. The ferroelectric layer part introduces a lateral shift in the C-V curve of FET, leading to either a high (CON) or low capacitance (COFF) state at 0V that can be tuned by an applied electric field. The CON/COFF ratio of the device can be designed as-per the application by increasing the channel area and reducing the overlap length. For a robust and consistent performance in CIM, reliability aspects of ferroelectric nvCAP are investigated. The FeFET in nvCAP mode demonstrates an initial endurance of 106 Program-Erase cycles while maintaining the ON/OFF >5. It is found that a CV sweep performed on the device help recover the performance. By performing repeated endurance-recovery operation, a recovered endurance of 108 cycles is achieved. The nvCAP device demonstrates memory retention of at least 1 day @85C for all fresh, fatigued and recovered states of the device. The nvCAP device also shows multi-level-cell capabilities for atleast 4 levels by changing the Program voltages.

Figure 1
(Invited) Enabling Bio-Realistic Artificial Intelligence Hardware with Neuromorphic Nanoelectronics
Authors: Hersam Mark C
Published: August 2024

The exponentially improving performance of digital computers has recently slowed due to the speed and power consumption issues resulting from the von Neumann bottleneck. In contrast, neuromorphic computing aims to circumvent these limitations by spatially co-locating logic and memory in a manner analogous to biological neuronal networks [1]. Beyond reducing power consumption, neuromorphic devices provide efficient architectures for image recognition, machine learning, and artificial intelligence [2]. This talk will explore how low-dimensional nanoelectronic materials enable gate-tunable neuromorphic devices [3]. For example, by utilizing self-aligned, atomically thin heterojunctions, dual-gated Gaussian transistors have been realized, which show tunable anti-ambipolarity for artificial neurons, competitive learning, spiking circuits, and mixed-kernel support vector machines [4,5]. In addition, field-driven defect motion in polycrystalline monolayer MoS2 enables gate-tunable memristive phenomena that serve as the basis of hybrid memristor/transistor devices (i.e., ‘memtransistors’) that concurrently provide logic and data storage functions [6]. The planar geometry of memtransistors further allows multiple contacts and dual gating that mimic the behavior of biological systems such as heterosynaptic responses [7]. Moreover, control over polycrystalline grain structure enhances the tunability of potentiation and depression, which enables unsupervised continuous learning in spiking neural networks [8]. Finally, the moiré potential in asymmetric twisted bilayer graphene/hexagonal boron nitride heterostructures gives rise to robust electronic ratchet states. The resulting hysteretic, non-volatile injection of charge carriers enables room-temperature operation of moiré synaptic transistors with diverse bio-realistic neuromorphic functionalities and efficient compute-in-memory designs for low-power artificial intelligence and machine learning hardware [9].

[1] V. K. Sangwan, et al., Matter, 5, 4133 (2022).

[2] V. K. Sangwan, et al., Nature Nanotechnology,
15, 517 (2020).

[3] M. E. Beck, et al., ACS Nano, 14, 6498 (2020).

[4] M. E. Beck, et al., Nature Communications, 11, 1565 (2020).

[5] X. Yan, et al., Nature Electronics, DOI: 10.1038/s41928-023-01042-7 (2023).

[6] X. Yan, et al., Advanced Materials, 34, 2108025 (2022).

[7] H.-S. Lee, et al., Advanced Functional Materials, 30, 2003683 (2020).

[8] J. Yuan, et al., Nano Letters, 21, 6432 (2021).

[9] X. Yan, et al., Nature, DOI: 10.1038/s41586-023-06791-1 (2023).
Understanding Atomic-Scale Dynamics of Defects in Complex Oxides for Memristive Devices
Authors: Narayanan Badri , Pidathala Ranga Teja
Published: August 2024

The exceptional resistive switching characteristics of complex oxides make them promising for use in memristors to mimic biological synapses in neuromorphic computing architectures in an energy-efficient manner. Specifically, the electrical conductance of complex oxides can be controllable switched across multiple orders of magnitude by either (a) electroforming a conduction channel (e.g., in tungsten oxide), or (b) inducing Mott-Hubbard transition (e.g., in rare-earth nickelates)– both via controlled migration of defects (such as oxygen vacancies) under applied bias. However, development of accurate neuromorphic computers (i.e., low variability) remains extremely challenging due to a lack of fundamental understanding of the atomic-scale processes that underlie migration and spatiotemporal evolution of oxygen vacancies (and other extended defects) over nano-to-mesoscopic length/timescales under applied electric field. Here, we demonstrate that a synergistic integration of density functional theory (DFT) calculation, ab initio/classical molecular dynamics (AIMD/CMD) simulations, precision synthesis, and multi-modal X-ray imaging experiments provides an effective route to address this knowledge gap. First, we use a combination of multi-modal X-ray imaging (with chemical/structural sensitivity) and CMD simulations to show that the intrinsic randomness of electroforming process in tungsten-oxide memristors can be minimized by careful introduction of sharp protrusions in the electrode gap. We find that sharp protrusions confine the electric field, which yields a reproducible distribution of oxygen vacancies over several switching cycles; and reliably form conduction channel in a specific location in the memristor. Next, we employed a large dataset of data from DFT calculations and short AIMD trajectories to develop deep neural network (DNN) models to accurately capture energetics, atomic forces, atomic charges, and maximally localized Wannier centers in rare-earth nickelates (RNO). CMD simulations based on these newly developed DNNs show that metal-insulator transition (MIT) in RNO occurs via a local structural distortion in the extended nickel structure, which facilitates the electronic instability and causes a sharp concomitant Ni-O bond and Ni-charge disproportion with decreasing temperature; this MIT is also strongly influenced by applied pressure and rare-earth ion. Furthermore, DFT calculations reveal the correlations the oxygen stoichiometry, OV distribution (including different NiOx motifs), OV transport, and electron-lattice coupling in perovskite nickelates. These results will be discussed in the context of controlling defect-induced transitions to design accurate and reliable memristive devices for neuromorphic computing platforms that are vital for artificial intelligence technologies.
Polyacrylamide/Cellulose Nanofibers Composite As Quasi Solid Electrolyte for Rechargeable Zinc-Ion-Battery
Authors: Ahmed Adnan , Pattananuwat Prasit
Published: August 2024

This research aims to optimize the cellulose nanofiber content in polyacrylamide (PAM) using as quasi-solid electrolyte composites for zinc-ion batteries (ZIBs). The cellulose nanofibers (CNFs) derived from hemp were prepared via alkaline treatment and bleaching process, followed by mechanical defibrillation. The chemical functional group analysis confirmed the successful extraction of lignin and cellulose from hemp fiber. The improved thermal stability of cellulose nanofibers indicated the success of the chemical treatment in removing non-cellulosic components. Furthermore, quasi-solid electrolyte composites of PAM / CNFs at 0.25, 0.5, 0.75, and 1 wt.% of cellulose nanofibers were prepared. At 1 wt.% CNFs addition, PAM / CNFs composites showed the highest values for electrolyte uptake, and electrochemical impedance spectroscopy with the highest ion conductivity of 59.6 mS cm-1. For the plating/stripping testing with symmetrical zinc cell, PAM / CNFs at 1.0 %wt CNF also demonstrated the lowest overpotential with the best zinc dendrite suppression feature. For zinc-ion battery performance test, the quasi-solid electrolyte composites of PAM / CNFs at 1.0 %wt CNF were fabricated and employed with electrochemical properties testing, including cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy, and cycle stability. This optimized quasi-solid electrolyte composites reached the highest specific capacity of 134.2 mA g-1 at a current density of 0.1 A g-1 and maintained capacity retention of 90.8% of initial capacity with 94.4% coulombic efficiency after 500 cycles.
Electronic Properties of [Ru(NH3)6][M(CN)6] Double-Complex Crystals and Their Thermal Decomposition to Prussian Blue Analogs
Authors: Robinson Donald "Donny" A , Talin Albert Alec , Shivanna Mohana , Sagar Srikrishna , Ferguson Andrew J , Smeaton Michelle A , Wheeler Lance M , Jungjohann Katherine L , Ghotbi Maryam , Babuena Perla B
Published: August 2024

The complex ions, [Ru(NH3)6]2+/3+ and [Fe(CN)6]3-/4-, are well known redox couples exhibiting fast interfacial and homogeneous electron transfer rates in aqueous solution. Here we show that when mixed together, they form insoluble double-complex Ax[Ru(NH3)6][Fe(CN)6] crystals with rhombohedral symmetry, where A is a cationic species and 0≤x≤2. The analogous interactions of [Ru(NH3)6]2+/3+ with [Ru(CN)6]3-/4- produces Ax[Ru(NH3)6][Fe(CN)6] crystals. Electrical measurements of these single crystals exhibit ohmic current-voltage responses, with corresponding conductivities on the order of 0.1 mS/m. We propose a solid-state charge transport mechanism based on Marcus theory for homogeneous outer-sphere electron transfer.

Thermal decomposition at mild temperatures removes ammine ligands and transforms these crystals into nanopolycrystalline Prussian blue analogs (PBAs) that retain the macroscopic geometry of the double-complex crystals but adopt the familiar highly defected porous crystal structure and intervalence charge transfer characteristics of PBAs.
Temperature Jump Methods for Measuring the Pme of RuO2
Authors: Smith Collin , Ness Carter , Harlow Gary S
Published: August 2024

The potential of maximum entropy (PME) is used to understand the structure and charging of the electrochemical double layer. Closely related to the potential of zero charge (PZC), the PME occurs when disorder of the solvent molecules at the surface reaches a maximum. Using a laser induced temperature jump (LITJ) to measure the PME has been shown to be a convenient method for metal electrodes. We present experiments using LITJ to investigate a metal oxide thin film and film thickness. The PME of these thin films appears to change with thickness, correlating with surface strain where a thinner film shifts the PME closer to OER potentials in turn reducing the overpotentials required. Our experiments are shown to be reproducible and independent of sweep rate or the vertex potentials selected. Interestingly we observe a hysteresis with scan direction, of 100-250 mV which we nominally attribute to surface adsorbates. Our results highlight the link between excess surface charge and catalytic activity and how this may be tuned via surface strain.

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Morphology Controled LiFePO4 Electrodes Via Polyol Refluxing for Enhanced Lithium-Ion Battery Performance
Authors: Seo Sehong , Jeong Wangchae , Kim Jaekook
Published: August 2024

In the synthesis of LiFePO4 cathodes with secondary nanorod structures and nano-plate morphologies, researchers utilized a polyol refluxing process. Notably, we achieved this without the use of characteristic structure directing agents. Through varying the reaction time, they were able to modulate the morphological characteristics of the synthesized samples.

X-ray diffraction studies conducted on the prepared samples indicated a highly crystalline nature. This suggests that the synthesized cathodes possessed a robust and ordered atomic structure, which is crucial for their electrochemical performance.

Electron microscopy investigations provided insights into the morphology of the samples obtained at different reaction times. Samples produced after 1 to 16 hours of polyol reaction exhibited secondary nanorod bundles. However, the sample recovered after 32 hours of polyol reaction displayed a distinct nano-plate morphology. These observations highlight the influence of reaction time on the final morphology of the synthesized cathodes.

The dimensions of the obtained samples ranged from a few tens to a few hundred nanometers. This nano-scale size is advantageous for enhancing the electrode's surface area, which can facilitate rapid ion diffusion and electron transport during battery cycling.

When employed in lithium test cells, the LiFePO4 cathodes synthesized for different durations delivered varying discharge capacities. Specifically, cathodes prepared under 1, 4, 8, 16, and 32 hours of reaction time exhibited discharge capacities of 161, 162, 171, 143, and 155 mAhg−1, respectively. Notably, all samples displayed a well-defined discharge plateau at 3.4 V, indicating stable electrochemical behavior during cycling.

Remarkably, among the prepared electrodes, the LiFePO4 nanorod bundle cathode synthesized under 1 hour reaction time demonstrated the highest average reversible capacities. It maintained capacities of 123 and 103 mAhg−1 at C-rates as high as 3.2 and 6.4 C, respectively. This highlights the importance of reaction time in controlling the electrochemical performance of the synthesized cathodes.

The crystal growth mechanism during the polyol refluxing method can be elucidated through several stages. These include precursor dissolution and nucleation, oriented crystal growth and alignment through self-assembly, aggregation, partial dissolution, and finally, complete re-crystallization. Understanding these mechanisms is essential for optimizing the synthesis process and tailoring the properties of LiFePO4 cathodes for various applications.

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Amatucci GG, Tarascon JM, Klein LC. CoO2, the end member of the LixCoO2 solid solution. J Electrochem Soc 1996;143:1114–23

Ravet N, Chouinard Y, Magnan JF, Besner S, Gauthier M, Armand M. Electroactivity of natural and synthetic triphylite. J Power Sources 2001;97–98:503–7

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Probing the Activity and Selectivity of Nickel Carboxylethylphosphonate 2D-MOF for the Electrochemical Conversion of CO2 to Syngas
Authors: Mahmud Musa Muhammad , Ogunbanjo Oriyomi Olalekan
Published: August 2024

The increasing concentration of CO2 in the atmosphere is alarming for modern society and the reduction of CO2 into valuable products would be a unique solution.1 Metal–organic frameworks (MOFs), constructed from organic linkers interconnected with metal (oxide) nodes, with high porosity and large surface area, have become an emerging class of electrocatalysts for reduction of CO2.2,3 Herein, we report the synthesis and characterization of a two-dimensional nickel metal-organic framework (2D Ni-MOF) with 3-phosphopropionic acid and 4,4-bypyridine as ligands and Ni2+ as the node (figure 1). The electrocatalytic activity of this material is explored for the electrochemical CO2 reduction reaction (CO2RR). An onset potential for the electrochemical reduction CO2 activity of -0.51 V vs RHE was observed which is 70 mV more positive than the HER in Ar-saturated electrolyte suggesting an efficient CO2 reduction. This catalyst showed a high current density of 33.5 mA cm-2 at 1.01 V vs RHE, exhibiting superior performance to most of the MOFs tested so far for CO2 reduction (figure 2a and b). Long term electrolysis at -0.8 V (vs RHE) yielded a current density of ∼10 mA cm-2 with high selectivity towards the formation of CO and H2 with an average production ratio of 30:70%, respectively (figure 2c and d). This new Ni-MOF catalyst retained its crystallinity and morphology after electrolysis as confirmed by powder XRD, HRTEM, FT-IR and Raman spectroscopy, indicating promising stability of the catalyst.

Density functional theory (DFT) was employed to calculate adsorption-free energy of the reaction intermediates to identify the active catalytic sites responsible for CO2 reduction in our 2D Ni-MOF structure. Findings show that the catalyst more readily reduces H* to H2 (with a limiting potential of 0.48 eV) than CO2 to COOH* (limiting potential of 0.78 eV). The reaction mechanism upon which this calculation was based begins with the removal of the H2O molecule bound to the Ni (II) site, followed by CO2 adsorption and the two proton-coupled electron transfer steps yielded COOH* and then CO & H2O. The H2O is more strongly adsorbed to the Ni (II) site than CO which closes the mechanistic cycle.

Reference

1. M. J. B. Kabeyi and O. A. Olanrewaju, Frontiers in Energy Research, 2022, 9.

2. B.-X. Dong, S.-L. Qian, F.-Y. Bu, Y.-C. Wu, L.-G. Feng, Y.-L. Teng, W.-L. Liu and Z.-W. Li, ACS Applied Energy Materials, 2018, 1, 4662-4669.

3. J.-X. Wu, S.-Z. Hou, X.-D. Zhang, M. Xu, H.-F. Yang, P.-S. Cao and Z.-Y. Gu, Chemical Science, 2019, 10, 2199-2205.

Figure 1