bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Influence of Salt Anion on the Electrochemical and Thermal Stability of Electrolyte
Authors: Xing Lidan , Li Weishan
Published: December 2020

Electrolytes for Lithium ion batteries mainly consist carbonate solvents and lithium salt. It has been well known that the species and component of solvents greatly affect the stability of electrolyte. While the role of salt anion in electrolyte stability has been neglected. In this presentation, we will reveal the influence of salt anion, mainly PF6
-, on the electrochemical stability and thermal stability of electrolyte. Specifically, on the anode surface, PF6
- shows great influence on the reduction stability and passivation capability of the induced solid electrolyte interphase (SEI) film; on the cathode surface, especially at high voltage, PF6
- affects the oxidation stability of solvent. Moreover, co-oxidation of PF6
- would generate HF. On the other hand, PF6
- reduces the thermal stability of the carbonate-based electrolyte, which would be significantly exacerbated when there are transition metal ions dissolved from cathode in the electrolyte. This overlooked effect is mainly due to the high catalytic effect of transition metal ions on the thermal decomposition of PF6
- to produce PF5. Understanding the mechanisms of the effect of salt anion on the stability of the electrolyte would provide a strong theoretical guidance for the design and development of the next generation lithium-ion battery electrolyte.

References:

[1]. Cun Wang, Lidan Xing, Jenel Vatamanu, Zhi Chen, Guangyuan Lan, Weishan Li, Kang Xu, Overlooked electrolyte destabilization by manganese (II) in lithium-ion batteries, Nat. Commun., 2019, 10,3423.

[2]. Kang Wang, Lidan Xing, Kang Xu, Hebing Zhou, Weishan Li, Understanding and Suppressing the Destructive Cobalt (Ⅱ) Species in Graphite Interphase, ACS Appl. Mater. Interfaces 2019,11,31490-31498.

[3]. Lidan Xing, Xiongwen Zheng, Marshall Schroeder, Judith Alvarado, Arthur von Wald Cresce, Kang Xu, Qianshu Li, and Weishan Li, Deciphering the Ethylene Carbonate–Propylene Carbonate Mystery in Li-Ion Batteries, Acc. Chem. Res., 2018,51, 282–289

[4]. Huozhen Zhi, Lidan Xing, Xiongwen Zheng, Kang Xu, Weishan Li, Understanding How Nitriles Stabilize Electrolyte/Electrode Interface at High Voltage, J. Phys. Chem. Lett. 2017, 8, 6048-6052.

[5]. Lidan Xing，Oleg Borodin, Grant Smith, Weishan, Li, A Density Function Theory Study of the Role of Anions on the Oxidative Decomposition Reaction of Propylene Carbonate, J. Phys. Chem. A. 2011,115, 13896-13905.
In Situ Growth Characterization of Electrodeposited Metal Contacts
Authors: Missault Nathan , Schwarzacher Walther
Published: December 2020

We have developed a new electrochemical method to study the morphology of electrodeposited metal in-situ at the nano-scale , without the need of any additional surface characterization techniques.

A metal-insulator-metal (MIM) pillar structure with exposed edges is fabricated and subsequently contacted in a customize 4-electrode electrochemical cell.

The current is measured during electrodeposition while a voltage bias is applied between the two working electrodes, separated by a 50 nm thin dielectric. For appropriate choices of the voltage bias and deposition potential, the current between the two working electrodes can easily be distinguished from the electrodeposition current. This current represents the tunnelling current and eventually the mesoscopic contact current. The change in conductance of the MIM structure during electrodeposition is highly indicative of the growth mode of the electrodeposited metal. A rough film growth leads to step-like, quantized current transients typical of mesoscopic point contacts. Some steps correspond to the conductance quantum but smaller steps in the tunnelling current are also observed [1]. In contrast, a uniformly growing film leads to smooth, exponential current transients due to the significant contribution of a tunnelling current before physical contact is made.

We use this method to investigate the growth of Au thin films from a thiosulfate-sulfite bath, and the growth of Cu from a sulfate bath. We also show the effect of common levelling additives for Cu electrodeposition, such as polyethylene glycol (PEG) and benzotriazole (BTA).

Additionally, we have observed a significant dependence of the film growth on the voltage bias applied between the top and bottom metals of the MIM that is independent of the deposition potential.

This technique provides a novel platform to study the effect of additives and other electrodeposition variables in a wide range of electrolytes. Furthermore, it provides an efficient platform to fabricate nanogap structures.

[1] Li, C. Z., H. X. He, and N. J. Tao. "Quantized tunneling current in the metallic nanogaps formed by electrodeposition and etching." Applied Physics Letters 77.24 (2000): 3995-3997.
Building Analogies between the Thermal and Electrochemical Reactivity of Hydrogen Using Proton-Intercalating Metal Oxides
Authors: McKone James , Miu Evan V , Patil Rituja
Published: December 2020

Motivated by the challenges of intermediate scaling relations, our research group is working to develop catalytic assemblies that integrate electrochemical and thermal activation to accelerate multi-step redox reactions. This presentation focuses on one approach that involves using transition metal hydrogen bronze compounds (HxMOy) as solid-state hydrogen sources where the hydrogen can be readily replenished via proton intercalation from water or acid equivalents. This approach enables the design of "thermo-electrochemical" reactor systems based on spatial or temporal coupling of thermal and electrochemical redox reactions. Initial modeling and experimental results will be discussed, which indicate that it is possible to execute hydrogenation reactions under conditions that would be impossible to achieve using traditional thermal hydrogenation reactors and catalysts.

Figure 1
Challenges in Moving to Multiscale Battery Models - Where Electrochemistry Meets and Demands More from Math
Authors: Shah Krishna , Subramaniam Akshay , Mishra Lubhani , Jang Taejin , Bazant Martin , Braatz Richard , Subramanian Venkat R.
Published: December 2020

There has been significant recent interest in studying multiscale characteristics of current and next-generation batteries, including lithium-metal and lithium-sulfur batteries. Multiple studies have conveyed the importance of microscale effects, pressure effects, and morphology changes. Advances in computing power make researchers believe that the detailed multiscale models can be efficiently simulated to arrive at the insights for the degradation and performance loss; however, this is not true and special attention needs to be paid to local singularities, boundary layers, moving boundaries, etc. This work presents 2D examples that illustrate the importance of grid convergence studies, provides well-defined detailed models to test the efficiency of numerical schemes, and discusses the associated simulation challenges. Perspective on important numerical aspects for robustness and efficiency, and recommendations on the possible best practices for studies involving multiscale modeling are also provided.
Solution-Processable All-Solid-State Batteries: Insights for Uniform Coatings
Authors: Emley Benjamin , Zhang Jibo , Liang Yanliang , Wu Chaoshan , Chen Zhaoyang , Fan Zheng , Yao Yan
Published: December 2020

The intense development of all-solid-state batteries utilizing thiophosphate electrolytes highlights the expectation for them to surpass conventional lithium-ion battery capabilities. Low Coulombic efficiency along with potential issues related to Li dendrite growth currently impedes their practical application. Thiophosphate materials are sensitive to unwanted chemical reactions and therefore require strict processing controls and are known to be compatible with a limited selection of processing materials for forming defect-free, uniform coatings during fabrication of the all-solid-state battery. Here we report progress made towards fabrication and electrochemical evaluation of all-solid-state batteries using a thiophosphate electrolyte and polymer binder in coated layers. We conducted a series of screening methods aimed at optimizing the mixing methods, processing solvent ratio, binder ratio, and post processing controls to identify which has the most impact considering the uniformity, porosity, and binder distribution in the coatings. Key markers during the evaluation included the area specific resistance and interfacial impedance of the solid electrolyte. In our full-cell demonstrations, a high-Ni layered cathode with high specific capacity (~200 mAhg-1) showed relatively high Coulombic efficiency after the initial cycles.
The Effect of Atomic Layer Deposition of ZrO2 on the Cathode on the Performance of Molten Carbonate Fuel Cell
Authors: Kim Dohyeong , Lee Min Hwan , Kim Kiyoung , Lim Sung Nam , Woo Ju Young , Han Haksoo , Song Shin Ae
Published: December 2020

Molten carbonate fuel cell (MCFC) is a high-temperature fuel cell for power plants. Since MCFC is operated at approximately 650 °C, the lifetime of the MCFC is limited by the thermal degradation of MCFC components. To reduce thermal degradation, the lower temperature for long-term operation is suggested. However, the electrochemical reaction on the cathode becomes slower at the lower operational temperature. To improve the performance for the long-term operation of MCFC, a ZrO2 coated cathode was fabricated by atomic layer deposition. The cell using the ZrO2 coated cathode showed a high voltage of 0.867 V at a temperature of 600 °C and a current density of 150 mA/cm2. The charge transfer resistance is also reduced dramatically at that same time. It can be confirmed that the high cell performance is presented when the electron-rich environment of NiO by ZrO2 coating improved the performance of the cell. Also, the cell using the ZrO2 coated cathode kept a stable performance over 2,000 h due to the prevention of NiO sintering by the uniform ZrO2 coating layer.
PEMFC Model Parameterization By Means of Differential Cell Polarization and Electrochemical Impedance Spectroscopy
Authors: Gerling Christophe , Hanauer Matthias , Berner Ulrich , Friedrich K. Andreas K
Published: December 2020

Understanding the contributions of the loss mechanisms in PEM fuel cells remains a key issue for the optimization of the membrane electrode assembly (MEA) with respect to performance and ageing.

A full parameterization of all the physics via adapted experiments is considered as too challenging and/or too expensive, thus the parameters of performance models are often only estimated or fitted to insufficient experimental data from single cell steady-state measurements. In this study, we aim to remedy this issue by combining polarization and impedance measurements over a wide range of operating conditions on a differential cell setup with 12 cm2 and a straight channels flowfield. For this purpose, a fuel cell test station is entirely automated and allows therefore to design a full factorial experiment with relative humidity, temperature, oxygen partial pressure and current density as parameters, leading to more than 1000 operating points. Self-developed Matlab-tools enable the analysis of the impedance spectra by fitting them to equivalent circuit models (ECM) and thus to understand the impact of the operating conditions on the cell parameters, cf. Fig. 1. This step is supported by the evaluation of the distribution of relaxation times (DRT) for well-chosen conditions.

Since it is commonly known that the main contribution to the overall performance loss at low and medium current densities originates from the sluggish oxygen reduction reaction (ORR) on the platinum catalyst of the cathode and that there is still no consensus in literature concerning its proper modeling and parameterization for a full cell, this study focuses on this very mechanism. In order to get a proper parameterization, the measurements are corrected by the anode contribution, the impact of hydrogen crossover through the membrane and by the ohmic resistance as well as the protonic resistance.

Figure 1
Facile Glycine-Assisted Synthesis of Non-Noble Metal Fe-N/C Electrocatalyst for Oxygen Reduction Reaction
Authors: Yulianti Riyani Tri , Irmawati Yuyun , Destyorini Fredina , Hardiansyah Andri , Yudianti Rike , Oktaviano Haryo Satriya
Published: December 2020

Transition metal-nitrogen-carbon (M–N/C) demonstrates a high oxygen reduction reaction (ORR) activity, and stability thus makes it a promising candidate to replace the use of commercial Pt-based electrocatalyst. Herein, Fe-N/C electrocatalysts were synthesized using a simple method by mixing Fe precursor with acetylene black and eco-friendly nontoxic amino-acid glycine as a carbon and nitrogen doping source, respectively. The Fe-N/C structure was obtained through pyrolysis at 900 °C (3h) under N2 atmosphere. Three different weight ratios of acetylene black to glycine were set at 1:1, 1:2, and 2:1. Structure and textural analysis of the catalysts were characterized using X-ray diffraction (XRD), Raman spectroscopy, and N2 physisorption. ORR activity was measured by cyclic voltammetry in both alkaline and acidic conditions. The results show that glycine not only acts as a nitrogen source, but it also improves the catalyst surface area up to 450 m2/g that could promote more electrochemical reactions. The ratio intensity of D-band to G-band (ID/IG) was used to identify the structural defects of carbon. The Fe-N/C catalysts have higher ID/IG (1.3-1.5) than that of acetylene black (0.9), suggesting the formation of defective structure on the catalysts. The catalyst with acetylene black to glycine ratio of 1:1 shows the highest ORR activity with an onset potential of 1.06 and 0.85 V vs. RHE in 0.1 M KOH and 0.5 M H2SO4, respectively. This study suggests that Fe-N/C electrocatalysts from glycine-assisted synthesis have prospective applications in both acidic and alkaline fuel cells. To study the catalyst performance, additional analysis in the polarization (J-V) curve will also be conducted in a single cell of PEMFC.

Figure 1
A Comparative Analysis of PEM and Alkaline Water Electrolyzers
Authors: Millet Pierre , Abdelmotagali Ali , Assaud Loïc , El Rouby Waleed
Published: December 2020

There are two main industrial techniques of water electrolysis operating under near-ambient temperature and pressure conditions: alkaline water electrolysis which uses a liquid electrolyte based on an aqueous solution of potassium hydroxide [1] and PEM water electrolysis [2] which uses a solid electrolyte made of a proton-conducting polymer. Both technologies present a set of strengths and weaknesses in view of practical application in the industry sector. The objective of this communication is to highlight the differences and similarities in terms of design (cell and stack) and balance-of-plant, and to present in a critical way what are these advantages and disadvantages, from a scientific viewpoint (that of materials science, especially for the selection of electrocatalysts), from a technological viewpoint (stack design and balance-of-plant) and from an economic viewpoint (comparative analysis of capex and opex). The discussion will take into account the situation which prevails on machines at the MW-scale. Particular attention will be paid to the ability of these machines to operate under transient conditions, in particular with a view to providing services to the electricity network. Several performance indicators such as the flexibility and reactivity of machines to the demands of network operators will be used to carry out this comparison. A detailed analysis of the existing limitations will make it possible to define a set of development perspectives highlighting possible complementarities.

[1] N. Guillet and P. Millet, in : Hydrogen Production: by Water Electrolysis’, chapter 4, Alkaline
Water electrolysis, A. Godula-Jopek, D. Stolten Editors, Wiley-VCH (2015).

[2] D. Bessarabov and P. Millet in: PEM water electrolysis, “Hydrogen and Fuel Cells Primers”, B.G. Pollet Editor, 1st Edition, Elsevier (2018).
Charge Transfer and Recombination Processes at p-CuBi2O4 Photoelectrodes
Authors: Oskam Gerko , Rodriguez Gutierrez Ingrid , Vega Alberto , Rodríguez Pérez Manuel , Coria Quiñones Sayda Dinorah , Jiménez Sandoval Omar , Rodriguez Gattorno Geonel
Published: December 2020

Photoelectrochemical water splitting is an attractive method to convert solar energy to storable chemical energy in the form of hydrogen, however, the materials requirements to achieve this efficiently are challenging: the semiconducting material needs to absorb sunlight efficiently, must to be capable of reducing and/or oxidizing water, and has to be stable under illumination under current flow in an aqueous electrolyte solution. In particular, for small bandgap semiconductors, stability is often an issue, and it is difficult to fully avoid degradation of the material. In addition, the water reduction and oxidation processes need to occur fast, in order to favorably compete with recombination or surface degradation processes; hence, the kinetic rate constants for charge transfer and surface recombination are very important parameters. Intensity-modulated photocurrent spectroscopy (IMPS) is a powerful technique to study the carrier dynamics in a photoelectrochemical cell. The photocurrent admittance corresponds to the frequency-dependent external quantum efficiency, and time constants for charge transfer and surface recombination can be determined, provided a simple model can be applied.1

In this presentation, we focus on the dynamic properties of p-CuBi2O4 in order to elucidate the rate determining steps that determine the efficiency of photocathodic reactions. In inert aqueous solutions at pH 5, an unfavorable balance exists between the rate constants for charge transfer and surface recombination, which limits the conversion efficiency.2 On the other hand, upon adding H2O2 as an electron acceptor, the photoelectron transfer efficiency is improved related to faster electron transfer to the solution or slower surface recombination due to passivation effects. Strategies to improve the applicability of CuBi2O4 in solar water splitting systems are discussed.

The authors gratefully acknowledge CONACYT, SENER and CICY for funding through the Renewable Energy Laboratory of South East Mexico (LENERSE; Project 254667; SP-4), and CONACYT under the Basic Sciences (CB) project A1-S-28734.

References

“Photoelectrochemical Water Splitting at Semiconductor Electrodes: Fundamental Problems and New Perspectives”. L. M. Peter and K. G. Upul Wijayantha, ChemPhysChem, 15, 1983–1995 (2014).

“Charge Transfer and Recombination Dynamics at Inkjet-Printed CuBi2O4 Electrodes for Photoelectrochemical Water Splitting”. Ingrid Rodríguez-Gutiérrez, Rodrigo García-Rodríguez, Manuel Rodríguez-Pérez, Alberto Vega-Poot, Geonel Rodríguez Gattorno, Bruce A. Parkinson, and Gerko Oskam. J. Phys. Chem. C, 122, 27169−27179 (2018).
Above Unity External Quantum Efficiency Photoelectrochemical Solar to Hydrogen Conversion
Authors: Ahsan Ragib , Chae Hyun Uk , Kapadia Rehan
Published: December 2020

Here we show that a p-silicon-insulator-graphene photocathode (i) increases the photon-to-hydrogen external quantum efficiency (EQE) above 1, and (ii) reduces the onset potential for the hydrogen evolution reaction via an applied voltage across the graphene-silicon junction. These devices were measured in an acidic solution of 0.5 M H2SO4 using a dual potentiostat setup, allowing independent control over solution potential, graphene potential, and silicon potential. An AM1.5G solar simulator was used to carry out solar illumination measurements. In comparison to a p-Si-insulator control sample, the addition of an insulator/graphene layer increases the saturation photocurrent from ~35 mA/cm2 to ~80 mA/cm2, respectively, indicating that a carrier multiplication process occurs due to the addition of graphene. In this way, the graphene/oxide behaves similarly to an electrocatalyst, where at a given overpotential, the current density is increased. However, in this case, the current density is driven by the incident photon flux and enhanced via a carrier multiplication process. To further understand this effect, a laser excitation source was used to measure power dependent quantum efficiency. The external quantum efficiencies of the SIG devices exhibit a strong dependence on power density, increasing to from EQE~1.5 to EQE~7 for low power densities of ~0.1 mW/cm2. Current component resolved measurements enabled us to separately measure the currents flowing in the graphene, silicon, and solution. During measurements, we show that the measured photoelectrochemical coccurs due to carriers in the silicon directly driving the hydrogen generation, not graphene. This unique result highlights that the graphene/silicon tunnel junction causes carrier multiplication at the silicon surface, which then drives hydrogen generation. This can occur due to electrons tunneling from silicon directly through the graphene and driving the hydrogen evolution reaction. When comparing the control and graphene photocathodes, it is shown that the turn-on voltages are nearly identical, highlighting that the carrier multiplication process does not require additional voltage input and instead is driven by the intrinsic electric field. Finally, we show that applying a bias across the silicon-graphene junction reduces the turn-on voltage for hydrogen evolution reaction by nearly 400 mV for current densities of 40 mA/cm2. It is expected that this applied bias increases the field across the oxide, increasing the total carrier multiplication rate at a given solution bias. Thus p-silicon-insulator-graphene photocathodes are shown to demonstrate: (i) EQE greater than 1, and (ii) a reduction in the voltage needed to drive the electrochemical reaction when a bias is applied across the graphene-silicon junction.
Electrochemical Oxidation of Phenolic Analogues Towards Formation of New C-C Bonds
Authors: Fabrizzi Samantha , Martic Sanela
Published: December 2020

The electrochemical oxidation of selected phenols 2,6-di-tertbutylphenol (1), 2,6-diphenylphenol (2), and 2,2'-dyhydroxybiphenyl (3) was studied using cyclic voltammetry, chronoamperometry, UV-vis spectroscopy and fluorescence spectroscopy. All compounds exhibited oxidation of the corresponding phenol using cyclic voltammetry and chronoamperometry. Electrochemical oxidation of phenols resulted in the electrochromic reaction and formation of yellow-coloured and fluorescent products. The photophysical properties of products were characterized by spectroscopy. Data indicates that electrochemical oxidation of phenols, via phenoxyl radical formation, lead to new carbon-carbon bond formation and synthesis of products with extended conjugation, absorbance in the visible range and enhanced fluorescence.
In Situ Measurement of Local pH at Working Electrodes in Neutral pH Solutions By the Rotating Ring‐Disk Electrode Technique
Authors: Yokoyama Yuko , Miyazaki Kohei , Kondo Yasuyuki , Miyahara Yuto , Fukutsuka Tomokazu , Abe Takeshi
Published: December 2020

The pH is one of the most important factors for electrochemical reactions. The solution pH is often measured prior to the electrochemical measurements, but it is not sufficient to consider only bulk pH, especially for the measurements in neutral pH solutions. When electrochemical reactions occur that produce/consume protons or hydroxide ions, the local pH in the vicinity of an electrode becomes considerably different from the bulk pH. This local pH is important in considering electrodeposition and corrosion. Furthermore, it also has an critical effect on the operating voltage of aqueous batteries and capacitors, as local pH affects the electrochemical stability of water.1 However it is difficult to measure the local pH, because the measurements have to be made in a small region adjacent to the electrode. Herein, rotating ring-disk electrode (RRDE) is a promising tool for the local pH measurements, though it has not been applicable to neutral pH solutions.2 In this study, the theory of local pH measurements using RRDE was extended to apply to solutions over a wide pH range.3 This extended theory was corroborated by measurements of the local pH change during hydrogen oxidation/evolution reactions on platinum disk electrode in solutions with near-neutral pH. This reversible reaction makes it possible to control the local pH on the disk electrode by the applied potential. The platinum ring electrode successfully detected the local pH changes by potentiometry, and the measured local pH was in good agreement with the theoretical predictions (Fig. 1a). In addition, using the RRDE modified with iridium oxide (IrOx) ring, we were able to evaluate the dynamic changes in the local pH of the working electrodes during oxygen evolution reaction in Ar-saturated neutral-pH solution (Fig. 1b).4 Thus, RRDE with IrOx ring has the potential to be a widely applicable tool for measuring the local pH of the electrode during any electrochemical reactions.

Reference

Y. Yokoyama, T. Fukutsuka, K. Miyazaki, and T. Abe, J. Electrochem. Soc., 165, A3299–A3303 (2018).

W. J. Albery and A. R. Mount, J. Chem. Soc. Faraday Trans. 1, 85, 1181–1188 (1989).

Y. Yokoyama, K. Miyazaki, Y. Miyahara, T. Fukutsuka, and T. Abe, ChemElectroChem, 6, 4750–4756 (2019).

Y. Yokoyama, K. Miyazaki, Y. Kondo, Y. Miyahara, T. Fukutsuka, and T. Abe, Chem. Lett., 49, 195–198 (2020).

Figure 1
Development of Reliable Methods and Protocols for Electrocatalytic N2 Reduction
Authors: Blair Sarah J. , Nielander Adam C. , Jaramillo Thomas F
Published: December 2020

The electrocatalytic reduction of nitrogen gas to ammonia (N2RR) is touted as a sustainable, low-emissions alternative to the energy-intensive Haber-Bosch process, which occurs at high temperature and pressure and accounts for 1% of global CO2 emissions. However, creating device architectures that produce both high Faradaic efficiencies and high currents is challenging due to low demonstrated selectivity toward ammonia, which results in low product yields commensurate with the quantities of ammonia that can be introduced by contamination. Thus, the ability to accurately distinguish and quantify ammonia formed electrocatalytically and contaminant NH3 is of the utmost importance. Herein, we discuss work by our group and others to establish a protocol for rigorous N2RR testing to enable the progression of the field while minimizing reports of false positives. Using purified, isotope-labeled 15N2 was found to be critical for the reliable quantification of synthesized ammonia, and we review our development of ammonia-detection strategies including colorimetric methods, quantitative NMR, and LC-MS. We recently reported our construction of a custom-built glass piston pump with carefully controlled pressure and headspace to be used in a variety of electrochemical conditions, and we discuss the advantages and disadvantages of closed electrochemical systems for the N2RR. Using these methods, we continue to investigate catalyst and electrolyte conditions to promote the N2RR, and we present our latest efforts in developing an improved theoretical and mechanistic understanding of this reaction.
Theoretical Insights into Volcano Correlations of the Oxygen Reduction Reaction with MN4 Catalysts
Authors: Matute Ricardo A. , Zagal Jose H
Published: December 2020

The design of metal complex catalysts for the oxygen reduction reaction (ORR) [1] can be assisted with the use of computational chemistry and Quantum Mechanics (QM) methods. In this work, we have implemented theoretical models and have used the computational chemistry for the rational design of MN4 catalysts with optimal catalytic efficiency for ORR. The application of ab initio and DFT-based methodologies were employed to assess binding energies on the interaction of O2 and the metal center of MN4 systems. [2] The energetic assessment on reactive paths has proved to be affected, in organic systems, by dynamical effects and strongly influenced by the electronic structure of substituents [3,4]. Hence, the electrocatalytic performance of porphyrins and phthalocyanines were assessed by the analysis of volcano correlations against computed binding energies. In these plots, substitution patterns on the catalysts include both in-plane and axial ligands. Besides the binding energies, other descriptors were assessed as well (e.g., the DFT-based hardness). The systematic study of volcano plots provided a deeply understanding on the the pivotal role of the ligands and the nature of electronic effects underlying the Sabatier principle for the electrocatalysis of the ORR by MN4 molecular systems.

Acknowledgements

The authors want to acknowledge the funding of Anillo Project ACT 192175

References

[1] A. Kulkarni, S. Siahrostami, A. Patel, J. K. Nørskov, Chem. Rev.
2018, 118, 2302.

[2] J.H. Zagal, M.T.M. Koper, Angew. Chem. Int. Ed.
201
6, 5
5, 14510.

[3] R.A. Matute and K.N. Houk, Angew. Chem. Int. Ed., 2012, 51, 13097.

[4] D.E. Ortega, R.A. Matute, J. Phys. Chem. A
2020, 124, 3573.
Spectroelectrochemistry of Non-Aromatic Explosives in Acetonitrile and the Influence of Superoxide
Authors: Holubowitch Nicolas , Budimir Zachary
Published: December 2020

The spectroelectrochemistry of non-aromatic explosive compounds, namely two nitramines (RDX and HMX), a nitrate ester (PETN), and a plastic explosive composite (Semtex 1A) in acetonitrile (AN) is reported. The redox behavior of these compounds is studied using cyclic voltammetry while monitoring changes in UV absorbance to identify transient intermediates and product species. In search of a low-cost solution-phase detection technique for explosives, we compare the spectroelectrochemistry of these compounds in the presence and absence of naturally dissolved oxygen (2 mM in AN), where the superoxide radical is co-electrogenerated during analyte reduction. Free superoxide yields a prominent UV signal in this medium (λmax = 250 nm) that the explosives’ nitro or methylene groups attenuate stoichiometrically. Overlapping UV spectra of multiple species are deconvoluted using a new strategy, spectral regional baselining, for time- and potential-resolved spectroelectrochemical (SEC) analysis. SEC data for nitrite (NO2
-), nitrate (NO3
-), and nitromethane (CH3NO2) were also collected to support proposed reaction mechanisms for the transformation of explosives that include superoxide adducts and dimerized azoxy reduced intermediates. The findings expand the understanding of high-explosive solution-phase chemistry and offer a route to novel signal transduction for (electro-)chemical sensors for energetic materials.

Figure 1. Spectroelectrochemistry of PETN in aerated acetonitrile with regions denoted for differential baseline analysis. (a) 3-D projected cyclic voltammogram (black) with UV absorbance from relevant wavelength (red, unscaled) as a function of time and potential; (b) full spectra (time domain) during cyclic voltammogram.

Figure 1
A Sensitive Urea Sensor Based NiO Nanoparticles Supported on the 3D Porous Carbonized Eggshell Membrane
Authors: Lu Shun , Gu Zhengrong
Published: December 2020

Urea (CO(NH2)2) is the main nitrogen-containing substance from the urine of human/animal, which is also an effective and critical indicator in evaluating various metabolic disorders. Urea can decompose naturally to toxic ammonia and nitrates permeating into groundwater, then cause environmental problems and even health issues. Therefore, the detection of urea concentration and decomposition of urea-rich sewage is vitally important in the human health and environmental industries. Urea oxidation reaction (UOR, CO(NH2) 2 + 6OH- → N2 + CO2 + 5H2O + 6e-) has been known as a viable method for renal/liver disease diagnostic detection. Here, we reported nickel oxide (NiO) nanoparticles dressed on the carbonized eggshell membrane (3D NiO/c-ESM) as a modified electrode toward urea detection. The unique network structure of ESM composed of biomacromolecular fibers provides a novel template for the functional groups, also with superior porosity and specific surface area, which can offer multiple transport pathways for both electrons and ions.

Consequently, an integrated 3D network composed of NiO nanoparticles anchoring on the carbonized ESM using a mixed method of hydrothermal and pyrolysis. The NiO nanoparticles anchored 3D carbonized network of the catalyst provides more catalytic active sites and enables easy access of reactants to the catalyst surfaces. NiO/c-ESM modified electrode exhibits an outstanding performance for urea determination with a linear range from 0.05 to 2.5 mM, and limit detection of ∼20 µM (3σ). This work offered a green approach for introducing 3D nanostructure through employing biowaste ESMs as templates, providing a typical example for producing new value-added nanomaterials with urea detection.
Enhanced Li-Ion Transport in Nanosized Li10GeP2S12
Authors: Dawson James Alexander
Published: December 2020

The discovery of the lithium superionic conductor Li10GeP2S12 (LGPS) has led to significant research activity on solid electrolytes for high-performance and safe solid-state batteries. LGPS exhibits a remarkably high room-temperature Li-ion conductivity of 12 mS/cm, comparable to that of the liquid electrolytes used in current Li-ion batteries. Here, we predict that nanosizing of LGPS can be used to further enhance its already outstanding Li-ion conductivity. By utilizing state-of-the-art nanoscale molecular dynamics techniques, we are able to simulate the Li-ion conductivities of nanocrystalline LGPS systems with average grain sizes from 10 to 2 nm. Our results reveal that the Li-ion conductivity of LGPS increases with decreasing grain volume. For the smallest nanometric grain size, the Li-ion conductivity at room temperature is three times higher that of the bulk system. These findings reveal that nanosizing LGPS and related solid electrolytes could be an effective approach for enhancing their Li-ion conductivity.
(Invited) Polymer Electrolytes and Metal Anodes: Ion Transport and Interfacial Impedance
Authors: Park Bumjun , Liu Jiacheng , Ford Hunter O. , Schaefer Jennifer L.
Published: December 2020

Advances in energy storage devices are required for the widespread implementation of intermittent renewable electricity generation technologies such as photovoltaics and wind power. In addition, electrification of transportation will allow for the substitution of liquid fossil fuel energy with renewably sourced energy. Energy storage platforms based on more abundant resources are essential for sustainable solutions. High energy density storage devices with enhanced safety are also needed. In this talk, I will discuss our research on polymers for next generation batteries based on lithium metal and magnesium metal anodes. Flowable polymer electrolytes that can be married with porous current collectors are compared with crosslinked polymer electrolytes and conventional flat electrodes. Metal deposit morphology is found to be strongly influenced by polymer electrolyte bulk properties as well as interfacial properties.
(Invited) Multi-Modal Operando Analysis of Lithium-Solid Electrolyte Interfaces
Authors: Dasgupta Neil P.
Published: December 2020

Solid-state batteries (SSBs) have the potential to revolutionize energy storage by increasing energy density and improving safety compared to state-of-the-art Li-ion batteries with liquid electrolytes. However, the formation of solid-solid interfaces poses unique challenges compared to solid-liquid interfaces. This requires new methods to study the fundamental behavior of solid-solid interfaces, and understand their dynamic evolution during cycling1.

In this talk, I will present a suite of multi-modal in situ/operando characterization approaches that we have used to study Li metal-solid electrolyte interfaces during cycling. First, to gain an improved understanding of the electrochemical stability, I will discuss operando X-ray photoelectron spectroscopy (XPS) analysis of lithium metal-solid electrolyte interfaces2. This approach allows us to directly observe interphase formation and evolution as the electrochemical potential of the solid-electrolyte surface is biased to potentials below the thermodynamic potential for Li plating. A range of sulfide and oxide ceramic electrolytes were explored, since they exhibit a range of (in)stability levels during Li metal plating.

To compliment these spectroscopic measurements, a range of in situ/operando microscopy techniques will also be presented. First, operando optical microscopy results will be presented, which allow for direct observation of the nucleation and growth of Li filaments both into, and out of, solid electrolyte surfaces2-3. By time synchronizing the optical video analysis with the electrochemical signatures of plating and stripping, new insights into the dynamic evolution of morphology and associated electrochemical analysis can be obtained. This micro-scale imaging will also be complimented by in situ analysis at the nanoscale, through a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By integrating the observations across this multi-modal characterization approach, the implications for SSB performance and stability will be discussed, and critical needs for future research will be described.

1) K. B. Hatzell, X. C. Chen, C. L. Cobb, N. P. Dasgupta, M. B. Dixit, L. E. Marbella, M. T. McDowell, P. P. Mukherjee, A. Verma, V. Viswanathan, A. S. Westover, W. G. Zeier “Challenges in Lithium Metal Anodes for Solid State Batteries” ACS Energy Lett.
5, 922 (2020).

2) A. L. Davis, R. Garcia-Mendez, K. N. Wood, E. Kazyak, K.-H. Chen, G. Teeter, J. Sakamoto, N. P. Dasgupta “Electro-Chemo-Mechanical Evolution of Sulfide Solid Electrolyte/Li Metal Interfaces: Operando Analysis and ALD Interlayer Effects” J. Mater. Chem. A
8, 6291 (2020).

3) E. Kazyak, R. Garcia-Mendez, W. S LePage, A. Sharafi, A. L. Davis, A. J. Sanchez, K.-H. Chen, C. Haslam, J. Sakamoto, N. P. Dasgupta “Li Penetration in Ceramic Solid Electrolytes: Operando Microscopy Analysis of Morphology, Propagation, and Reversibility” Matter
2, 1 (2020).
Effect of Ta-Doping on LLZO Garnet Solid Electrolytes for Solid State Batteries Applications
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Du Jia-Hong
Published: December 2020

Compared with conventional lithium-ion batteries, all-solid-state lithium batteries based on inorganic solid electrolytes have shown advantages over conventional lithium-ion batteries, such as explosion resulted from flammable liquid electrolyte, low energy density. Therefore, solid state batteries are considered a promising candidate with better safety features. Among oxide electrolytes, garnet-type LLZO electrolyte exhibits high ionic conductivity and electrochemical potential window. However, it is reported that there are difficulties to prepare Li7La3Zr2O12(LLZO) pellets with high relative density. In this study, LLZO containing Ta ion as a dopant is expected to show more Li vacant sites to enhance its conductivity and density. The LLZO powder calcined at 1200 °C with a cubic phase was confirmed by X-ray diffraction (XRD). The sintered Ta-LLZO pellets exhibit relative density of 88.45% and ionic conductivity of 1.04*10-4 S/cm at room temperature and good electrochemical stability with Li metal. After assembling LiCoO2/Ta-LLZO/Li battery, the discharge capacity reached 105.2 mAh/g for the first cycle.
Free-Standing Garnet-Type Solid Electrolyte Separators Fabricated By Water-Based Tape-Casting
Authors: Ye Ruijie , Finsterbusch Martin , Figgemeier Egbert
Published: December 2020

The garnet-type Li-ion-conductor Li7La3Zr2O12 (LLZO) is regarded as a promising oxide-ceramic based solid electrolyte (SE) material for all-solid-state lithium ion battery (Li-ASB) owing to its wide electrochemical stability window, chemical stability versus Li metal and excellent conductivity. However, one of the challenges regarding the fabrication of such ASBs is the industrial scalability of manufacturing methods. Tape-casting of ceramic components is known e.g. from SOFC manufacturing to enable the large-scale production of free-standing ceramic components and cells with low thickness. Additionally, in conventional tape-casting, organic solvents are usually employed, which give rise to health and safety issues and lead to high cost for solvent recovery. Hence, development of a green, water-based processing route is favorable.

Herein, we report an aqueous tape-casting process of LLZO separators using a water-soluble biopolymer as binder. A lattice expansion of LLZO is observed by X-ray diffraction in aqueous green tape due to the partial replacement of Li+ by H+, whereas the lattice parameter of LLZO in sintered sheet decreases to the same value of pristine LLZO powder, indicating the Li-recovery in the LLZO structure after sintering. This observation confirms that the Li+/H+-exchange reaction is reversible during the aqueous processing. The obtained free-standing LLZO sheet after sintering shows high ionic conductivity observed by impedance spectrometry in Li/LLZO/Li symmetric cell at room temperature, which is comparable with reported thin garnet separators fabricated by conventional non-aqueous tape-casting.

In summary, we successfully fabricate self-supporting LLZO sheet with high ionic conductivity by aqueous tape-casting process, which is enabled by reversible Li+/H+-exchange. This free-standing LLZO sheet can be later used as separator in the Li-ASBs having an electrolyte-supported configuration.
Ionic Liquid Stabilized TEMPO Catalysis for Alcohol Oxidation
Authors: Li Min , Minteer Shelley
Published: December 2020

N-oxyl compounds, in particular 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), have attracted considerable attention in alcohol oxidations due to their remarkably low-cost, high selectivity, and metal-free nature. TEMPO-mediated oxidations are often performed in high pH electrolytes as high OH - alleviates both kinetic and thermodynamic limitations. However, the degradation of TEMPO is also favorable in base, resulting in significant loss of catalytic activity and challenging long-term electrosynthesis. By contrast, ionic Liquids (ILs) possess high alkaline chemical stability. Herein, we designed electrode composites in which ILs are used as on part of a biphasic system (electrode phase and buffer phase) preserving TEMPO catalytic stability. Polycaprolactone (PCL), a binder that also possesses low melting point, was applied as a comparison. The results indicated that the IL-TEMPO composite showed no loss of current for glycerol oxidation at pH 10.0 after 2.0 h, while 67.1% current was lost using PCL-TEMPO. This stability enhancement was further evaluated in an 800 μL electrochemical cell using bulk chemical analysis and successive cycles of glycerol oxidation. The strategy demonstrated here not only offers an opportunity to prepare catalytic systems with enhanced stability, but also converts what are typically homogeneous catalysts to heterogenous systems. In subsequent studies, we aim to exploit poly(ionic liquids) (PILs) to further regulate TEMPO catalytic activity at various pH conditions.

Figure 1
Characterization of Electrode-Electrolyte Interfaces in Deep Eutectic Solvents
Authors: Dean William , Klein Jeffrey Michael , Gurkan Burcu
Published: December 2020

Deep eutectic solvents (DESs), compromised of hydrogen bond donors and acceptors, are concentrated electrolytes with extremely low volatility and tunable physical properties, and therefore they are promising for large scale energy storage. The electrode-electrolyte interfaces of concentrated and complex electrolytes such as DESs have not been rigorously studied. Owing to the similarity of DESs to ionic liquids (ILs) where a camel shape potential-dependent capacitances have been reported with significant deviations from dilute electrolytes, it will be critical to understanding the DES behavior near polarized surfaces to inform electrochemical kinetics. In this work, the excess charge accumulation of mixtures of choline chloride and ethylene glycol with 1:2 (Ethaline DES composition), 1:4 and 1:6 molar ratios are probed on silver and glassy carbon electrodes via electrochemical impedance spectroscopy. To study the surface species and changes with applied potential, in-situ surface-enhanced Raman spectroscopy was employed on an electrochemically roughened silver substrate as the electrode. Results from these studies suggest Ethaline DES is different than most ILs and present u-shaped differential capacitance and more in line with regular electrolytes. We will present the results from our ongoing studies of the electrode-DES interfaces outlining the impact of composition and electrode material.
Reaction Kinetics of Zn2+ with Radiolysis Products in Molten LiCl-KCl Eutectic
Authors: Iwamatsu Kazuhiro , Horne Gregory P. , Gakhar Ruchi , Phillips William C. , Halstenberg Philip , Layne Bobby H. , Pimblott Simon M. , Wishart James F.
Published: December 2020

A thorough understanding of radiation effects on molten salt media is necessary to support the design, development, and deployment of molten salt reactor, using either fuel salt or solid fuel with salt as the coolant. Fundamental issues include the determination of the initial yields and reactivity of the primary radiolytic species, i.e., the solvated electron (esolv
–), chlorine atom (Cl•), and dichloride radical anion (Cl2
•–) as their reactivity varies depending on the environment such as the salt cation and temperature. Here we report on the reaction kinetics for esolv
– and Cl2
•– in molten LiCl-KCl eutectic doped with Zn2+ ions. Electron pulse radiolysis absorption spectroscopy was used to observe the transient behavior of esolv
– and Cl2
•– on the nanosecond to microsecond time scale. Experiments were performed using the Brookhaven National Laboratory Laser-Electron Accelerator Facility (LEAF)1 and utilizing a recently developed high-temperature sample holder.2 Decay kinetics of of esolv
– and Cl2
•– in 9.41 mM ZnCl2 in LiCl-KCl are shown in the figure. esolv
– and Cl2
•– decays in different time scale due to different reaction kinetics and decay speed increase as temperature.

This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center, funded by the U.S. Department of Energy (US-DOE), Office of Science, Basic Energy Sciences, at BNL, INL and ORNL under contracts DE-SC0012704, DE-AC07-05ID14517 and DE-FC02-04ER15533, respectively. The Laser Electron Accelerator Facility of the BNL Accelerator Center for Energy Research is supported by the US-DOE Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract DE-SC0012704.

Wishart, J. F.; Cook, A. R.; Miller, J. R.; Rev. Sci. Instrum., 2004, 75 (11), 4359.

Phillips, W. C.; Layne, B.; Gakhar, R.; Horne, G. P.; Ramos-Ballesteros, A.; Iwamatsu, K.; LaVerne, J. A.; Pimblott, S. M.; Wishart, J. F.; Rev. Sci. Instrum., 2019, in peer review.

Figure 1