bluuebunny/crossref_metadata_2025 huggingface dataset:
Tunable Heterostructured Nanomaterials for Efficient Hydrogenation Reactions at Intermediate Temperatures
Authors: Li Meng , Hua Bin , Wang Lucun , Wu Wei , Ding Dong
Published: July 2021

To address rising environmental concerns and energy challenges, it is highly desirable to develop green technologies for a sustainable future. Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds. Electrochemical CO2 and N2 hydrogenation using renewable electricity is considered one of the most promising pathways to reach the environmental economics. Among various electrochemical devices, a solid state electrolyzer working at intermediate temperatures has the advantages of high reaction rates and low overpotentials. As CO2 and N2 molecules are quite stable, it is critical to develop electrocatalysts with high activity to reduce electricity engagement. Also, CO2 hydrogenation has multiple pathways which normally results in low selectivity for a target product. A tunable electrocatalyst with high selectivity to different products is desirable for CO2 hydrogenations. Heterostructured nanomaterials attracts great attentions in electrochemical systems. With careful design, they can show very high activity and selectivity towards an electrochemical reaction. In this work, we combine theoretical simulations, including density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations, with experimental methods (characterizations and electrochemical measurements) for rational design of highly efficient heterostructured nanomaterials for CO2 and N2 hydrogenations.

We studied the strong metal-support interaction (SMSI) in a doped CeO2 supported noble metal nanoparticles (NPs) system using theoretical calculations. The results indicate that SMSI largely depends on chemical conditions of the support and particle size of dispersed metal NPs. By tuning the SMSI, we can successfully change the catalytic activity and selectivity towards CO2 and N2 hydrogenation reactions. Based on these findings, we designed tunable heterostructured nanomaterials for efficient hydrogenation reactions at intermediate temperatures. These predictions were further confirmed by experimental method. By using a combination of high-throughput theoretical calculations and electrochemical measurements, we developed highly active catalysts for electrochemical CO2 and N2 hydrogenation reactions. This framework is also applicable to other electrochemical systems using heterostructured materials.
(Invited) A Stable Integrated Photoelectrochemical Reactor for Hydrogen Production from Water
Authors: Idriss Hicham , Khan Mohd Adnan , Ziani Ahmed , Alshankiti Ibraheam
Published: July 2021

Among the major challenges in solar water, splitting to molecular hydrogen and oxygen is making a stable and affordable system for largescale applications. In this work we present results of the design, fabrication, and testing a photoelectrochemical reactor composed of the following. 1) An integrated device to reduce the balance of the system cost. 2) A concentrated sunlight to reduce the photoabsorber cost. 3) An alkaline electrolyte to reduce catalyst cost and eliminate external thermal management needs. The system consists of an III-V-based photovoltaic cell integrated with Ni foil as catalyst for oxygen production that also protects the cell from corrosion. At low light concentration and without the use of optical lenses, the solar-to-hydrogen (STH) efficiency was found to be 18.3%, while at high light concentration (up to 207 suns) with the use of optical lenses, the STH efficiency was 13%. Catalytic tests conducted for over 100 hours at 100–200 suns showed no sign of degradation nor deviation from product stoichiometry (H2/O2=2). Further tests projected a system stability of over nine years.

Figure 1
(Invited) Conjugated Semiconductors for Photoelectrochemical and Photocatalytic Hydrogen Production Via Water Splitting
Authors: Sivula Kevin
Published: July 2021

The application of pi-conjugated polymeric semiconductors toward direct solar-to-fuel energy conversion by photoelectrochemical (PEC) or heterogeneous photocatalytic (PC) approaches is an emerging trend.[1] While these materials offer impressive tunability of energy levels and light absorption, their long-term robustness under the harsh conditions of PEC or PC water splitting is a major concern.[2] In this presentation critical factors that influence the operational stability of donor:acceptor bulk heterojunction photoelectrodes[3] for solar hydrogen production are discussed and routes to significantly advance their performance under long term operation are presented. An outlook on employing organic based semiconductor systems in comparison to their inorganic counterparts will be presented with respect to the possible economic viability of this technology.

[1] Adv. Energy Mater.
2018, 8, 1802585.

[2] ACS Energy Lett. 2020, 5, 1970.

[3] J. Am. Chem. Soc. 2020
, 142, 7795.
Interface Engineering of Hematite By Dual for Sunlight Driven Water Oxidation Activity
Authors: de Souza Flavio Leandro
Published: July 2021

The efficiency of nanostructures for solar-to-hydrogen production via carbon-free technology such as photoelectrochemical water-splitting cell is fundamentally governed by the capability of the surface to sustain the reaction without electron trapping or recombination by photogenerated charge. This work addresses the role of different modifiers on the overall photocurrent response, which allowed a dual material insertion, increasing the charge separation without compromise the surface catalysis. Sn-addition onto hematite electrodes clearly increased flat band potential, promoting a good charge separation and shifting the onset to a higher potential, attributed to the surface trapping state created by this modification. Notoriously, Sn-hematite electrode loaded with NiFeOx exhibited the highest photocurrent density, suggesting a partially recovered surface trapping states created during the electrode designing. The well-known co-catalyst acted in the overall photoelectrocatalytic response with no significant effect on the turn-on voltage, in other words, with minor effect related to catalytic efficiency. The dual modification contributes to understand the role of different modifiers allowing to satisfactorily improve charge separation while maintaining the conductivity attributed to intermetallic ions.
Integrating Materials Design and Operando Spectroscopy for the Development of Next Generation CO2 Reduction and Biomass Valorization Catalytic Systems
Authors: Kornienko Nikolay
Published: July 2021

Electrochemical conversion of abundant feedstocks to fuels and value-added chemicals is rapidly gaining significance as a promising method to harness renewable electricity. Specific reactions within this context that my research group is focused on are the reduction of CO2 and oxidation of biomass platforms to fuels and value-added chemicals. Because the design of new catalytic systems is inherently linked to a precise understanding of how these reactions proceed on heterogeneous surfaces, we put considerable efforts in developing methodology for operando probing with vibrational spectroscopy. In all, I show how using these experiments provide the key mechanistic information on surface reaction mechanisms that enhance our understanding of functional hybrid interfaces and how the research provide avenues for future materials design within the context of electrosynthesis of fuels and chemicals.
(Invited) Interfacial Chemistry As an Enabling Tool in the Development of Transition Metal Phosphide Electrocatalysts
Authors: Cossairt Brandi , Ung David , Murphy Ian , Rivera-Maldonado Ricardo
Published: July 2021

We are interested in achieving control of heterogeneous interfaces to promote inner-sphere electron-proton-transfer reactions using insights from molecular chemistry. Toward this end, we are developing solution-phase methods for the synthesis and post-synthetic modification of colloidal nanostructures with low overpotentials and high activity for multi-electron, multi-proton electrocatalytic reactions. Ligand exchange, surface etching, and covalent modification will be presented as complementary methods for altering the catalytic activity of colloidal transition metal phosphide electrocatalysts. A combination of electrochemical characterization, structural analysis, and electronic structure characterization will be presented. Together with stoichiometric probes of inner-sphere reactivity, these data will serve to reveal mechanistic details and design principles for catalysis in these systems.
(Invited) Critical Effect of Particle Size in Ru-Catalyzed Electrosynthesis of Ammonia
Authors: Feng Xiaofeng
Published: July 2021

Electrochemical reduction of N2 to NH3 has recently received considerable attention, because it may enable sustainable, distributed production of NH3 when powered by solar- or wind-generated electricity. However, typical catalysts show a low activity and selectivity for N2 reduction reaction (NRR) due to the barrier for N2 activation and the competing hydrogen evolution reaction (HER). A rational design of NRR catalysts relies on our understandings of structure-activity relationships and active sites for the NRR, and such study requires model catalysts with well-defined structures. Here we present a study of size-dependent activity for the NRR on Ru nanoparticle catalysts. We first tried colloidal synthesis method with polyvinylpyrrolidine (PVP) as a surfactant to control the size of Ru nanoparticles, while the derived Ru catalysts showed negligible activity for NRR, which was attributed to residual surfactant molecules that blocked catalyst surfaces. Therefore, we used atomic layer deposition (ALD) method to prepare Ru nanoparticles with controlled sizes and clean surfaces. We also quantified the electrochemical active surface areas of Ru samples and measured surface-area-normalized activity for the NRR. Consequently, the effect of Ru nanoparticle size on the NRR activity and Faradaic efficiency was revealed, which can provide insights into the active sites for the NRR and guidance on the design of NRR catalysts via surface site engineering.
Rapid in Situ Detection of Ammonia with Surface Enhanced Raman Spectroscopy
Authors: Liu Yuanchao , Murphy Eamonn , Matanovic Ivana , Potma Eric , Fishman Dmitry , Atanassov Plamen
Published: July 2021

Rapid and reliable ammonia detection is of great significance to environmental monitoring and heterogeneous electrocatalysis, wherein ammonia serves as a product or reaction intermediate. Non-perturbative and sensitive or even in operando ammonia detection is of particular interest to the rapidly booming field of the electrochemical nitrogen reduction reaction for ambient and distributed ammonia synthesis.1 Various ex-situ analytical methods have been applied or recently developed, including colorimetric methods, nuclear magnetic resonance (NMR) and liquid chromatography − mass spectrometry (LC-MS).2–5 In this talk, we will present a novel approach to ammonia detection, with the aid of surface enhanced Raman scattering (SERS).6 This is a simple, fast and sensitive method that provides chemical selectivity to ammonia. In addition, there is no need for a complex sensor design, specific beam path geometry, or chemical modifications of the solution. The method features a detection of sub-1 ppm ammonia concentrations in less than 1 second, which paves the way to ultrasensitive in operando electrochemical experiments in the conventional H-cell or other assemblies. Considering the short spatial reach of plasmonic enhancement, the observed signals correspond to approximately 104–105 molecules detected locally at the region of interest. Moreover, the concept of SERS detection does not enforce any limitations on the identity or morphology of the electrode so long as it can be placed close enough to the SERS substrate. Then, the SERS substrate can be easily engineered according to specific experimental constraints to probe the ammonia near the electrode surface. This enables the possible detection of local ammonia in closest proximity to the reaction site.

Acknowledgement

We gratefully acknowledge the support from DOE-EERE Advanced Manufacturing Office award via Sandia National Laboratories (AOP 34920). We would also like to acknowledge the NSF grant CHE-0960179 and the UNM Center for Advanced Research Computing for computational resources.

Reference

J. G. Chen et al., Science, 360, eaar6611 (2018)

S. Z. Andersen et al., Nature, 570, 504–508 (2019)

R. Y. Hodgetts et al., ACS Energy Lett., 736–741 (2020)

A. C. Nielander et al., ACS Catal., 9, 5797–5802 (2019)

W. Yu, N. S. Lewis, H. B. Gray, and N. F. Dalleska, ACS Energy Lett., 1532–1536 (2020)

Y. Liu et al., iScience, 23, 101757 (2020) https://doi.org/10.1016/j.isci.2020.101757.

Figure 1
Ruthenium-Iridium Nanocrystals Anchored Homogeneously on MOF-Derived Support for Efficient and Stable Oxygen Evolution in Acidic and Neutral Media
Authors: Liu Lifeng
Published: July 2021

Achieving efficient and stable oxygen evolution reaction (OER) in acidic or neutral medium is of paramount importance for hydrogen production via proton exchange membrane water electrolysis (PEM-WE). Supported iridium based nanoparticles (NPs) are the state-of-the-art OER catalysts for PEM-WE, but the non-homogeneous dispersion of these NPs on the support together with their non-uniform sizes usually lead to catalyst migration and agglomeration under strongly corrosive and oxidative OER conditions, eventually causing the loss of active surface area and/or catalytic species and thereby the degradation of OER performance. Here, we design a catalyst comprising surface atomic-step enriched ruthenium-iridium (RuIr) nanocrystals homogeneously dispersed on a metal organic framework (MOF) derived carbon support (RuIr@CoNC), which shows outstanding catalytic performance for OER with high mass activities of 2041, 970 and 205 A gRuIr
-1 at an overpotential of 300 mV and can sustain continuous OER electrolysis up to 40, 45 and 90 hours at 10 mA cm-2 with minimal degradation, in 0.5 M H2SO4 (pH = 0.3), 0.05 M H2SO4 (pH = 1) and PBS (pH = 7.2) electrolytes, respectively. Comprehensive experimental studies and density functional theory (DFT) calculations reveal that the good performance of RuIr@CoNC can be attributed, on one hand, to the presence of abundant atomic steps which maximize the exposure of catalytically active sites and lower the limiting potential of the rate-determining step of OER; on the other hand, to the strong interaction between RuIr nanocrystals and the CoNC support which endows homogeneous dispersion and firm immobilization RuIr catalysts on CoNC. The RuIr@CoNC catalysts also show outstanding performance in a single cell PEM electrolyzer, and their large-quantity synthesis is demonstrated.
Redox-Responsive H-Bonding: Amplifying the Effect of Electron Transfer with Proton Transfer
Authors: Smith Diane , Baek Kiyeol , Choi Hyejeong
Published: July 2021

Recently we have reported a new strategy to create highly redox-responsive H-bond dimers based on proton-coupled electron transfer.1 The strategy capitalizes on the importance of secondary H-bonds in determining overall binding strength in H-bond dimers. Specifically, this study shows that electron-transfer induced proton transfer across a H-bond can be used to significantly strengthen the overall binding by both creating strong ionic H-bonds and by changing the secondary H-bonds from unfavorable to favorable. The power of this approach is demonstrated with the electroactive DAD (A = H-acceptor, D = H-donor) array 1 paired with the electroinactive ADA array 2. NMR titration in 0.1 M NBu4PF6/CD2Cl2 gives a Kassoc of 500 M−
1 in the starting oxidized state, a value typical of DAD-ADA dimers. However, upon two electron reduction in 0.1 M NBu4PF6/CH2Cl2, CV studies indicate a 1.8×105 increase in binding strength, corresponding to a very large Kassoc of 9×107 M−
1. The latter value is typical of DDD-AAA H-bond dimers, consistent with proton transfer across the central H-bond upon reduction. In this presentation, the results of a full investigation of this system will be reported, including UV-vis spectroelectrochemical studies that support proton transfer and NMR studies of possible 1-1 and 2-2 homodimerization. Furthermore, theoretical CV’s that include, if needed, homodimerization will be fit to the experimental CV’s to provide a more exact measure of the binding enhancement in this system.

1H. Choi, K. Baek, S. Toenjes, J. L. Gustafson, and D. K. Smith, J. Am. Chem. Soc.
2020, 142, 17271-17276. DOI: 10.1021/jacs.0c07841

Figure 1
Understanding and Controlling the Efficiency of Au24
m(SR)18 Nanoclusters As Singlet-Oxygen Photosensitizers
Authors: Agrachev Mikhail , Fei Wenwen , Antonello Sabrina , Bonacchi Sara , Dainese Tiziano , Zoleo Alfonso , Ruzzi Marco , Maran Flavio
Published: July 2021

Singlet oxygen, 1O2, is an excited oxygen species [1] that can be efficiently generated by photosensitizers. These are molecules that upon photoexcitation eventually generate a triplet excited state that can be quenched by the ground state oxygen triplet, 3O2, to form 1O2 [1]. The latter finds uses in many applications, especially organic synthesis, photocatalysis, and photodynamic therapy [2-4]. On the other hand, its possible use depends on its effective lifetime, as 1O2 is a very reactive species that decays via quenching by the solvent and/or interactions with other molecules in solution [1]. This is the case of the photosensitizers themselves, and this may result in a serious drawback for efficient applications of 1O2. In this area, the use of monolayer-protected metal nanoclusters as photosensitizers is limited. We carried out a systematic study on the photosensitizer behavior of a series of molecular Au24M(SR)18 clusters [5,6], where the R group and the doping metal M were varied. Electrochemical characterization allowed us to select the best R/M combinations to test a sufficiently large oxidation-potential range. 1O2 detection was carried out by time-resolved electron paramagnetic resonance [7], which allowed us to determine 1O2 lifetimes spanning more than one order of magnitude (on the microsecond time scale), depending on the specific cluster employed. Among the main results, we found that: (i) a more positive potential for the oxidation of the cluster is matched by a (beneficial) longer 1O2 lifetime; (ii) proper design of the electrochemical properties of the cluster yields the same results as those of reference photosensitizers, despite the unprecedented low oxidation potentials exhibited by these clusters; (iii) kinetic analysis based on the Marcus theory provides important insights into the mechanism of the quenching of 1O2 by gold nanoclusters, how to control it, and why properly doped gold nanoclusters may perform very well in 1O2 photosensitization [8]. Further effects, detected by electrochemistry, are under investigation.

References

[1] Bregnhoj, M.; Westberg, M.; Minaev, B. F.; Ogilby, P. R. Acc. Chem. Res.
2017, 50, 1920.

[2] Turro, N. J.; Ramamurthy, V.; Scaiano, J. C. Molecular Oxygen and Organic Photochemistry. In Modern Molecular Photochemistry of Organic Molecules; University Science Books: Sausalito, CA, 2010; Ch. 14.

[3] Ghogare, A. A.; Greer, A. Chem. Rev.
2016, 116, 9994.

[4] Nosaka, Y.; Nosaka, A. Y. Chem. Rev.
2017, 117, 11302.

[5] Antonello, S.; Maran, F. Curr. Opin. Electrochem.
2017, 2, 18.

[6] Fei, W.; Antonello, S.; Dainese, T.; Dolmella, A.; Lahtinen, M.; Rissanen, K.; Venzo, A.; Maran, F. J. Am. Chem. Soc.
2019, 141, 16033.

[7] Agrachev, M.; Ruzzi, M.; Venzo, A.; Maran, F. Acc. Chem. Res. 2019, 52, 44.

[8] Agrachev, M.; Fei, W.; Antonello, S.; Bonacchi, S.; Dainese, T.; Zoleo, A.; Ruzzi, M.; Maran, F. Chem. Sci.
2020, 11, 3427.
Quantification of Effects of Hydrophobicity and Mass Loading on the Effective Coverage of Surface-Immobilized Elastin-like Peptides for Electrochemical Applications
Authors: Su Zihang , Kim ChulOong (Christoph) , Renner Julie N.
Published: July 2021

Polypeptide engineering allows for a high degree of control at the molecular level, and thus has emerged as a promising tool for surface modification. Immobilized elastin-like peptides (ELPs), known for their stimuli-responsive behavior, have recently gained attention due to their potential applications in electrochemical sensing as well as bioenabled electrode assembly. Key to the success of these applications is understanding how ELPs impact the access and electron transfer of reacting species to the solid surface. In this study, short ELPs with varying guest residues and sequence length were designed for gold electrode attachment, and the influence on the ability of a redox probe to access a gold surface was characterized by cyclic voltammetry. Based on the results, a quantitative model describing the relationship between ELP effective surface coverage as a function of the mean hydrophobicity and mass loading was elucidated, illustrating the ability to precisely control surface properties by tuning the ELP sequence. This model can be used to design surface-bound ELP sequences design that exhibit desired effective surface coverage for electrochemical applications.
(Invited) Controlled DNA Bioconjugations to Electroactive Surfaces
Authors: Furst Ariel L
Published: July 2021

DNA is unique in its abilities to both self-assemble and recognize biomolecules, enabling its application in a variety of fundamental scientific and medical devices. Many DNA-based platforms depend on thiol groups to tether DNA to gold surfaces, but this method suffers from the lack of control over DNA assembly. We have developed multiple, complementary, one-pot bioconjugation reactions to attach oligonucleotides to electroactive surfaces. With these methods, we can control the final DNA surface coverage by varying the reaction time and concentration of reactive species. We have shown the broad applicability of these methods by developing electrochemical biosensors using them and by specifically capturing living nonadherent cells through DNA hybridization. These methods have shifted the paradigm of DNA attachment to metal surfaces and represents a new direction for selective biomolecule attachment to surfaces.
Detection of Biomolecules by HPLC-EC
Authors: Sanchez Fonseca Fabiola N. , Cunci Lisandro , Lopez Luis F.
Published: July 2021

Peptides which are biologically active are attracting remarkable interest due to its influence in different areas such as pathophysiological and psychiatric disorders. Neuropeptide Y (NPY) is a 36 amino acid amidated neuropeptide that occurs in both the central nervous system and peripheral tissues. This neuropeptide is known because its different levels have been reported affect different processes such as stress-related disorders, major depressive disorders and ingestive behavior. NPY is a neurotransmitter produced by chromaffin cells of adrenal medulla, it acts through different G protein-coupled receptors ( Y1 Y2 Y 3 Y 4 Y5) and its important because it stimulated catecholamines release.Catecholamines are nerve-endogenous substances with amine and catechol groups such as epinephrine, norepinephrine and dopamine. These molecules also play an important role in the regulation of the central and peripheral nervous system and they are mostly used to diagnose and treat several diseases. The importance of this project lies on the use of High-Performance Liquid Chromatography couple with Electrochemical Impedance Spectroscopy for catecholamines detection. This techniques allow researchers to detect these biomolecules more accurately in time and space. For a better understanding of the catecholamines release we use HPLC-EC. This is a method with high sensitivity which has been used during years for the characterization of different biomolecules. Our HPLC have a electrochemical detector (HPLC-EC) which improves the sensitivity and the resolution of our analysis. We decided to make our analysis by Size Exclusion using 1X PBS.
A New Approach to Selectivity in a Preparative Electrochemical Reaction
Authors: Jing Qiwei , Feng Enqi , Moeller Kevin D
Published: July 2021

We have been trying to introduce new selectivity into electrochemical reactions by modifying the surface of an electrode and then confining chemical reactions to the region of the reaction close to that surface. The goal is to translate the extremely high levels of site-selectivity seen in chemical reactions on a microelectrode array into a tool for preparative synthetic reactions. As a proof-of-principle experiment, we have coated a Pt-anode with a diblock copolymer that is known to have an affinity for pyrene groups. The electrode is then used in the oxidation of two alcohol substrates; one having the pyrene group and one not having a pyrene group (Scheme 1). The oxidation reactions are mediated by a TEMPO-derived oxidant. The oxidant can be confined to the region immediately surrounding the electrode with the use of methyl-α-D-glucopyranoside which is known to undergo fast oxidations with the TEMPO derived oxidant.

In the experiment, we found that a competition study between the two substrate led to a 1:1 mixture of the two aldehydes when a bare Pt-electrode was used, a 2:1 mixture (4:3) of the two aldehydes when the Pt electrode was modified with the diblock copolymer, and a 20:1 ratio (4:3) of the two aldehydes when the modified electrode was used in conjunction with the confining agent. From this experiment it was clear that a molecular recognition event on the surface of the electrode could be used to control the selectivity of the reaction in the reaction was confined to the surface of the electrode.

The origin of the selectivity in this reaction and its implications for future synthetic transformations will be discussed.

Figure 1
(Invited) Hole-Mediated Photoredox Catalysis: Tris(p-substituted)Biarylaminium Radical Cations As Tunable, Precomplexing and Potent Photooxidants
Authors: Barham Joshua Philip
Published: July 2021

As a combination of visible light PhotoRedox Catalysis and Synthetic Organic Electrochemistry, electrochemically-mediated PhotoRedox Catalysis (e-PRC) emerged as a powerful synthetic technique in recent years, overcoming fundamental limitations of electrochemistry and photoredox catalysis in the single electron transfer activation of small organic molecules. Herein we report a tunable class of electroactivated photoredox catalyst, tri(para-substituted)biarylamines, that become superoxidants in their photoexcited states even able to oxidize molecules beyond the solvent window limits of cyclic voltammetry(such as polyfluorobenzene and trifluorotoluene). Furthermore, we demonstrate that precomplexation not only permits the excited state photochemistry of otherwise picosecond-lifetime tris(para-substituted)biarylaminium cations, but enables and rationalizes the surprising photochemistry of their higher-order doublet (Dn) excited states, unlocking extremely high oxidative potentials (up to a record-breaking ~+4.4 V vs. SCE).

Figure 1
Electrochemical Oxidation of Phenol-Based Analogues Towards C-C Bond Formation
Authors: Gao Stephanie , Lewis Tyra , Dobson Breenna , Martic Sanela
Published: July 2021

The use of phenolic compounds range from the industrial sector and agriculture to pharmaceuticals. These compounds may serve as a phenolic precursor to produce raw materials in a wide range of applications. The selective electrochemical oxidation of bulky phenols was recently achieved [1]. Herein, the 2,2-dihydroxybiphenyl (DHBP) was characterized in an aprotic environment using cyclic voltammetry, square-wave voltammetry, and UV-vis spectroscopy. The DHBP was characterized with an irreversible oxidation. The electrooxidation of DHBP by CV and chronoamperometry resulted in the solution colour change and the formation of new products. The product formation was monitored by UV-vis and fluorescence spectroscopy and characterized by mass spectrometry.

[1] Zabik, N. L.; Virca, C. N.; McCormick, T. M.; Martic-Milne, S. Selective Electrochemical versus Chemical Oxidation of Bulky Phenol. J. Phys. Chem. B
2016, 120 (34), 8914–8924. https://doi.org/10.1021/acs.jpcb.6b06135.
(Invited) Battery-Inspired Strategies in Synthetic Electrochemistry
Authors: Sevov Christo
Published: July 2021

This seminar will highlight our group's efforts to integrate insights from the energy storage community into electrosynthetic applications. Many of the strategies developed by battery chemists to address critical issues in energy storage devices can be translated to synthetic chemistry for the remediation and upcycling of wastes. In memory of Prof. Peters and his inspiring contributions to this area, this seminar will discuss our work on electrochemical recycling of phosphine oxides and electrochemical funcitionalization of polychlorinated wastes.
(Invited) Electrochemical Hydrodefluorination of Trifluoromethyl Groups
Authors: Lennox Alastair J. J.
Published: July 2021

The difluoromethyl group (CF2H) has attracted significant recent attention in medicinal chemistry. This complements the well-documented importance of fluorine in small-molecule pharmaceuticals that impact bioavailability, potency and pharmacokinetics. This is exemplified by 28% of FDA-approved drugs containing one or more fluorine atom. The CF2H group is an H-bond donor that is also lipophilic, which is a unique combination, and is thus becoming an increasingly valuable tool within drug discovery. Current methods to prepare them are limited either by a limited scope or by the prohibitively expensive reagents that are required.

We have developed methods to form these important difluoromethyl groups from readily installed trifluoromethyl groups using an electrochemical reductive approach. This reaction requires “deeply-reductive” potentials, which poses several problems, including functional group intolerance and low charge efficiencies. We have developed conditions that overcome these problems to produce a single-step process that can be applied to a wide scope of substrates, including those containing reductively sensitive functionality. Details of our studies into the electrochemical hydrodefluorination at highly reductive potentials will be presented.
Reductive Electrosynthesis
Authors: Lin Song
Published: July 2021

Owing to its many distinct characteristics, electrochemistry represents an attractive approach to discovering new reactions and meeting the prevailing trends in organic synthesis. Recently, we developed various new synthetic strategies that harness the power of electrochemistry for the functionalization of alkenes to access a diverse array of vicinally functionalized structures. Recently, we have also ventured into electroreductive chemistry and discovered various transformations that selectively couple multiple electrophiles to form C-C and C-Si bonds. This talk discusses our design principle underpinning our recent methodology developments.
(Invited) Chiral Lewis Acid-Catalyzed Asymmetric Electrochemical Reactions
Authors: Guo Chang
Published: July 2021

Although the field of electrochemical synthesis has been developed rapidly, it is still highly desirable to develop the asymmetric electrochemical transformation as a general strategy for controlling the reactivity and enantioselectivity.1 More importantly, the routine application of asymmetric electrosynthesis to pursue the total synthesis of bioactive molecules remains an unsolved challenge in organic chemistry. Our goal was to provide an attractive and sustainable alternative for the distinctive activation of bond connections in a highly asymmetric fashion. We apply a reliable chiral Lewis acid-catalytic strategy in the asymmetric electrochemical transformations.2

Reference:

(1) Chang, X.; Zhang, Q.; Guo, C.* Angew. Chem. Int. Ed.
2020, 132, 12612-12622.

(2) a) Zhang, Q.; Chang, X.; Peng, L.; Guo, C.* Angew. Chem. Int. Ed.
2019, 131, 7073-7077; b) Chang, X.; Zhang, J.; Zhang, Q.; Guo, C.* Angew. Chem. Int. Ed. 2020, 132, 18658-18662.

Figure 1
(Invited) Electrogenerated Radical Ions: A Platform for Extreme Reactivity with Unique Selectivity
Authors: Wickens Zachary Kimble
Published: July 2021

Metal-based catalysts and reagents possess unique reactivity profiles that are inaccessible using conventional organic molecules and, consequently, occupy a privileged role in organic synthesis. We are investigating how organic radical ions–typically thought of as fleeting intermediates–can be tamed and exploited to expand the reactivity of bench-stable organic molecules. Our central hypothesis is that these organic radical ions will not only mimic the unique reactivity of metallic species but will also engender selectivity profiles inaccessible using existing synthetic tactics. Herein, we will describe two new reaction platforms enabled by electrochemically-generated persistent organic radical ions. In the first system, we report a strategy to mediate single electron transfer to substrates with reduction potentials more negative than <–3.0 V vs. SCE. In the second, we will discuss a new approach to oxidatively couple of alkenes and electron-rich nucleophiles via a metastable electrophilic intermediate.
(Student Battery Slam Best Presentation Award Winner) Enhancing the Stability of the Electrode/Electrolyte Interface in Solid State Li-Ion Batteries
Authors: Gogia Ashish , Estevez Luis , Subramanyam Guru , Kumar Jitendra
Published: July 2021

All-solid-state Lithium-ion batteries (LIBs) based on solid ceramic electrolytes are a promising next-generation energy storage technology for high energy density and enhanced cycle life. A key requirement for such batteries is packing high energy in low form factor (i.e. in thin-film form) to increase both the gravimetric and volumetric energy densities. Lithium superionic conducting (LISICON) solid electrolytes are prominent candidates among liquid, gel, polymer and solid electrolytes that can enable safety and optimum performance in a high energy density battery with thin-film cell components. One particular LISICON material, lithium aluminum germanium phosphate (LAGP), is a promising solid-electrolyte due to its high ionic conductivity (~ 5 mS/cm at 23 °C), high electrochemical stability window (> 5V), and single Li+ ion conduction (high transference number, low porosity mitigating dendrite propagation), enabling a high energy battery and mitigating safety and packaging issues of conventional LIBs. However, most solid electrolytes, suffer from low chemical stability with the lithium (Li) anode. This is especially true for LAGP, with such chemical instability invariably leading to the formation of a highly resistive electrode/electrolyte interface which is detrimental for high power and cell longevity. Therefore, despite the promise of solid ceramic electrolytes for next-generation solid-state LIBs, if they are to be practical for use in solid-state LIBs with Li metal anodes, it is very important to design a chemically stable interface with kinetically efficient charge transport processes (i.e. Li+ transport).

In order to enhance the chemical stability of the electrode/electrolyte interface, we identified lithium compatible materials (such as thin film of lithium phosphorus oxynitride (LIPON), gold (Au), carbon nanotube (CNT) layer, aluminium oxide (Al2O3) and suitable methods to apply them at the Li metal/LAGP interface. The evolution of the interfacial resistance as a function of time was monitored using Electrochemical Impedance Spectroscopy (EIS). We will present data showing that the application of the lithium-compatible, thin film interfacial layer, results in enhanced stability and a significant reduction in resistance compared with the unmodified Li metal/LAGP interface, offering an interfacial engineering approach for improved performance of an all-solid-state LIB.
Long-Term Cycling Stability of 18650 Li-Ion Batteries Cells Using NMC811 Core@Shell Structure with Tetra-Materials
Authors: Khunrugsa Chirayu , Chiochan Poramane , Duriyasart Farkfun , Jangsan Chonticha , Kullawattanapokin Pattranit , Sawangphruk Montree
Published: July 2021

LiNi0.8Mn0.1Co0.1O2 (NMC811) material has been considered as a next-generation cathode of lithium-ion batteries, which can be used for many applications such as long-distance electric vehicles. Although NMC811 has high theoretical specific capacity and energy, its major drawbacks such as microcracks, cation mixing, too reactive surface reaction, result in poor long-term cycling and stability. In this work, the tetra-materials of garnet (Li7La3Zr2O12), reduced graphene oxide (rGO), carbon black (CB), and titanium dioxide (TiO2) were coated on the surface of the NMC particle by a green and scalable mechano-fusion technique, forming the core@shell structure (namely NMC@4M) to protect the morphological instability and the electrolyte decomposition leading to long-term cycling stability. Also, the 4M shell elevates the Li-ion diffusion and ionic conductivity. Moreover, we have firstly reported the finely tuned step formation protocol of cylindrical cell type in lithium-ion battery (18650). As a result, the NMC@4T can deliver high-capacity retention over 85% after long cycling (400 cycles) at 1C.

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Surface Coating of NMC811 with Four Functional Materials for Next-Generation Li-Ion Batteries
Authors: Anansuksawat Nichakarn , Chiochan Poramane , Duangdangchote Salatan , Duriyasart Farkfun , Jangsan Chonticha , Kullawattanapokin Pattranit , Tejangkura Worapol , Sawangphruk Montree
Published: July 2021

Ni-rich lithium transition metal oxides with a layered structure is one of the promising cathode candidates for Lithium-ion batteries owing to their many advantages, e.g., high energy density, low cost, and eco-friendly. However, the Ni-rich cathodes such as NMC811 show poor cycle life, which obstructs their large-scale applications. Herein, we introduce a scalable mechanofusion process to produce a core-shell structure of NMC811 that can enhance its electrochemical capacity and cycling stability, exclusively at 18650 cell level. The multifunctional shell consists of four materials including conductive carbon black, reduced graphene oxide (rGO), lithium garnet (LLZO), and Al2O3. As a result, the coated NMC811 shows outstanding performance with high-capacity retention of 95% after 250 cycles. The improved electrochemical performance is due to the core-shell structure with enhanced electrical conductivity and better protection of highly active NMC811 materials.

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Enhanced Battery Cell Lifespan of Lithium Metal Battery Via Using Lithium Metal Alloy Protective Layer Anode and Aluminum Oxide Modified NMC Cathode
Authors: Srimanon Krisara , Vadivel Selvamani , Sawangphruk Montree
Published: July 2021

Lithium-metal batteries (LMBs) have much attention over the state-of-the-art lithium-ion batteries (LIMs) in term of the energy density. As compared with the conventional graphite anode of LIBs, lithium anode has a high theoretical specific capacity (3860 mA h g-1) and a low electrochemical potential (-3.04 V vs SHE). Nonetheless, no stable solid-electrolyte interphase (SEI) forms on the surface of lithium metal. The continuous electrolyte consumption along with the non-uniform lithium deposition leads to the limited cell lifespan and cell safety concern, both of which impede their LMBs practical applications. To address the problems, herein, we introduce an alloying protective layer on lithium metal anode integrating with thin Al2O3 layer modified on LiNi0
.8Co0
.1Mn0
.1O2 (NMC811) cathode to prolong lifespan of batteries. By using the lithium alloy protective layer, the LMB exhibits good stability performance better than the fresh Li metal approximately 20%. We hope that this perspective together can be a guiding principle for the next-generation practical batteries.

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Study Insight into the Single Crystal Structure of NMC811 As the Next-Generation Cathode in 18650 Lithium-Ion Batteries
Authors: Homalamai Kan , Chiochan Poramane , Duangdangchote Salatan , Duriyasart Farkfun , Jangsan Chonticha , Kullawattanapokin Pattranit , Tejangkura Worapol , Sawangphruk Montree
Published: July 2021

Among the various types of metal oxide cathode materials, the nickel-rich layered materials as Polycrystalline Lithium nickel-cobalt-manganese-cobalt oxide (denoted as poly-NMC ) reveal the promising potential to be the next-generation cathode of lithium-ion batteries due to its high specific capacity and energy. However, poly-NMC has not been achieved commercialization owing to the structural instability during the discharging-charging process, caused by active material dissolution and intergranular cracking. A single crystal NMC (denoted as SC-NMC) could replace the poly-NMC to alleviate the aforementioned issues since it can provide the same practical capacity but superior in cyclability. In this work, we investigate insight into the fundamental of SC-NMC, comparing to the poly-NMC with regard to unit cell parameter changes, transition metal dissolution, SEI/CEI formation at difference voltage windows, and phase transition of these materials. This work shed light on the use of SC-NMC in 18650 cylindrical cell configurations.

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Towards Better Stability and Reversibility of Mn2+/Mn4+ Double Redox Activity in Disordered Rocksalt Oxyfluoride Cathode Materials
Authors: Shirazimoghadam Yasaman , El kharbachi Abdel , Fichtner Maximilian
Published: July 2021

Recently discovered cation disordered rocksalt (DRS) materials have shown high reversibility towards Li ions due to facile insertion and extraction in the structure. Nonetheless, issues with manganese containing compounds have been identified due to instabilities of the structure and/or solubility of manganese in the electrolyte. In our study, we combined the use of high-valent cations with partial substitution of fluorine for oxygen anions in DRS-structure phase to achieve optimal Mn2+/Mn4+ double-redox reaction in the composition system Li2MnxTi1-xO2F (1/3 ≤ x ≤ 1). Four different compositions (Li2MnIIIO2F, Li2MnII
1/3MnIII
1/3TiIV
1/3O2F, Li2MnII
1/2TiIV
1/2O2F and Li2MnII
1/3TiIII
1/3TiIV
1/3O2F) have been synthesized and optimized according to the starting precursors and their oxidation states. By studying the electrochemical behavior of different compounds, we found that Ti+4 keeps Mn at the second state of charge in the structure which lead to double redox reaction of Mn2+/Mn4+. Galvanostatic cycling and rate capability tests of the sample with the composition Li2Mn2/3Ti1/3O2F showed notable electrochemical kinetics and cycling performance, with initial high discharge capacity of 227 mAh g-1 in the voltage window of 1.5-4.3 V and 82% coulombic efficiency after 100 cycles.In a further study, synthesis related issues and limitations due to fluorination were examined. In fact, lithium diffusion can be impeded due to preferable strong Li-F bonds. Thus, two more samples based on the Li2Mn2/3Ti1/3O2F composition were synthesized and their properties were investigated (Li1.5MnII
1/3MnIII
1/3TiIV
1/3O2F0.5 and Li1.25MnII
1/3MnIII
1/3TiIV
1/3O2F0.25), in order to find the proper amount of fluorine which compromises the structural/chemical stability and electrochemical storage against Li-ions.We will present and discuss the structural characteristics of these selected DRS materials using XRD-Rietveld refinement analysis, energy-dispersive X-ray spectroscopy and scanning electron microscopy. The oxidation states and charge transfer mechanism using a combination of CV and XPS will be also addressed, in which the results approve the double redox mechanism of Mn2+/Mn4+ in agreement with Mn-Ti structural charge compensation. The findings pave the way for designing high capacity electrode materials with multi-electron redox reactions.

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(Student Battery Slam Best Presentation Award Winner) Sodiation Induced Chemo-Mechanics in Sn Electrodes
Authors: Sarkar Susmita , Nelson George J. , Mukherjee Partha P.
Published: July 2021

Binder free self-supporting tin (Sn) foil with the promise of high theoretical capacity and outstanding volumetric capacity is an outstanding anode candidate for sodium-ion batteries. However, it suffers from an undesirable initial coulombic efficiency (ICE), indicating higher irreversible losses associated with particle isolation and solid electrolyte interphase (SEI) formation. In the present work, we have studied the electrochemical behavior (Cycling performance, Electrochemical Impedance Spectroscopy) and damage mechanisms of Sn foil in the context of thickness and temperature. Bulk Sn foil showed mechanical failure caused by pulverization and microscopic images revealed different types of fracture modes at different temperatures and different thicknesses of the foil. The crystallographic changes during sodiation/de-sodiation and ex-situ XRD patterns were analyzed to understand the phase transformation. The pristine Sn foil has a polished surface and post-mortem observations show random cracks formed on the Sn surface after cycling. In lower temperature, the thinner Sn foil cracked into pieces, where the thicker foil showed deformed Sn structures. Different types of physical, electrical, and/or electrochemical degradation of the electrode led to continuous cell capacity loss with cycling. This study focuses on understanding different types of electrode damage behavior on thick and thin Sn foil during the sodiation/de-sodiation process, and thus open new avenues for dense Sn foil-based anode to be used in full cell batteries.
High Capacity and High Rate Nasicon Naxv(Mn/Mg/Al)(PO4)3cathodes for Na-Ion Batteries
Authors: Ghosh Subham , Barman Nabadyuti , Senguttuvan Premkumar
Published: July 2021

Electrochemical energy storage devices, particularly rechargeable batteries, are attractive solution to balance energy production of intermittent natural sources such as wind and solar. Despite its success in portable electronics market, Li-ion technology faces serious hurdle for grid storage application due to scarcity and geographical access of lithium sources. From the viewpoint of cost and abundance of raw materials, sodium ion batteries are appealing for grid storage application.1 Various classes of Na-ion electrode and electrolyte materials have been developed recently based on the know-how knowledge gained from Li-ion chemistry. However, the commercialization of NIBs has been impeded by the lack of high energy density cathodes. To this end, multi-electron based polyanionic cathodes are attractive, because of their high insertion voltages and storage capacities.2

Among the cathode materials, NASICON type cathodes with a general chemical formula NaxMM’(PO4)3(x= 2-4; M=V, Ti, Fe, Cr; Mʹ =Mn, Co, Mg, Fe) have garnered significant interest due to higher sodium ion conductivities as well as enhanced chemical and thermal stabilities.3 In this talk, we will present our recent studies on the impact of Mg2+ and Al3+ cationic substitution into the Na3V2(PO4)3 framework.4,5 The Mg- and Al-substituted NVMP cathodes exhibit smoother voltage profiles, facile sodium (de)intercalation, enhanced rate performances (80 mA h g-1 at 5C rate) and better capacity retention (~96% after 100 cycles) compared to the unsubstituted sample. Their improved performances are attributed to suppressed Jahn-Teller effect, enhanced covalent character and Na-ion vacancies created in the NASICON framework.

References:

N. Yabuuchi, K. Kubota, M. Dahbi, S. Komaba, Chem. Rev.
2014, 114, 11636.

C. Masquelier, L. Croguennec, Chem. Rev.
2013, 113, 6552.

R. Liu, Z. Liang, Z. Gong, Y. Yang, small methods
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S. Ghosh, N. Barman, M. Mazumder, S. K. Pati, G. Rousse, P. Senguttuvan, Adv. Energy Mater.
2020, 10, 1902918.

S. Ghosh, N. Barman, P. Senguttuvan, Small
2020, 16, 2003973.

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