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1. Comparative Analysis of Chemical Redox between Redox Shuttles and a Lithium-Ion Cathode Material via Electrochemical Analysis of Redox Shuttle Conversion

   https://doi.org/10.1149/1945-7111/ac0068  

   Gupta, Devanshi ; Cai, Chen ; Koenig, Gary M. ( May 2021 , Journal of The Electrochemical Society)

   Chemical redox reactions between redox shuttles and lithium-ion battery particles have applications in electrochemical systems including redox-mediated flow batteries, photo-assisted lithium-ion batteries, and lithium-ion battery overcharge protection. These previous studies, combined with interest in chemical redox of battery materials in general, has resulted in previous reports of the chemical oxidation and/or reduction of solid lithium-ion materials. However, in many of these reports, a single redox shuttle is the focus and/or the experimental conditions are relatively limited. Herein, a study of chemical redox for a series of redox shuttles reacted with a lithium-ion battery cathode material will be reported. Both oxidation and reduction of the solid material with redox shuttles as a function of time will be probed using ferrocene derivatives with different half-wave potentials. The progression of the chemical redox was tracked by using electrochemical analysis of the redox shuttles in a custom electrochemical cell, and rate constants for chemical redox were extracted from using two different models. This study provides evidence that redox shuttle-particle interactions play a role in the overall reaction rate, and more broadly support that this experimental method dependent on electrochemical analysis can be applied for comparison of redox shuttles reacting with solid electroactive materials.

    

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2. One- and Two-Electron Redox Catalysis with Lutetium Enabled by a Tris(Amido) Redox-Active Ligand

   https://doi.org/10.1021/acs.organomet.2c00673  

   Belli, Roman G. ; Tafuri, Victoria C. ; Garcia, Nicholas A. ; Roberts, Courtney C. ( June 2023 , Organometallics)
3. Carbon-free Solid Dispersion LiCoO2 Redox Couple Characterization and Electrochemical Evaluation for All Solid Dispersion Redox Flow Batteries

   https://doi.org/10.1016/j.electacta.2017.01.061  

   Qi, Zhaoxiang ; Liu, Aaron L. ; Koenig, Gary M. ( February 2017 , Electrochimica Acta)
4. Ru-promoted perovskites as effective redox catalysts for CO 2 splitting and methane partial oxidation in a cyclic redox scheme

   https://doi.org/10.1039/D2NR04437D  

   Iftikhar, Sherafghan ; Martin, William ; Wang, Xijun ; Liu, Junchen ; Gao, Yunfei ; Li, Fanxing ( July 2022 , Nanoscale)

   The current study reports AxA’1-xByB’1-yO3-𝛿 perovskite redox catalysts (RCs) for CO2-splitting and methane partial oxidation (POx) in a cyclic redox scheme. Strontium (Sr) and iron (Fe) were chosen as A and B site elements with A’ being lanthanum (La), samarium (Sm) or yttrium (Y), and B’ being manganese (Mn), or titanium (Ti) to tailor their equilibrium oxygen partial pressures (P_(O_2 ) s) for CO2-splitting and methane partial oxidation. DFT calculations were performed for predictive optimization of the oxide materials whereas experimental investigation confirmed the DFT predicted redox performance. The redox kinetics of the RCs improved significantly by 1 wt.% ruthenium (Ru) impregnation without affecting their redox thermodynamics. Ru impregnated LaFe0.375Mn0.625O3 (A=0, A’=La, B=Fe, and B’=Mn) was the most promising RC in terms of its superior redox performance (CH4/CO2 conversion >90% and CO selectivity~ 95%) at 800oC. Long-term redox testing over Ru impregnated LaFe0.375Mn0.625O3 indicated stable performance during the first 30 cycles following with a ~25% decrease in the activity during the last 70 cycles. Air treatment was effective to reactivate the redox catalyst. Detailed characterizations revealed the underlying mechanism for redox catalyst deactivation and reactivation. This study not only validated a DFT guided mixed oxide design strategy for CO2 utilization but also provides potentially effective approaches to enhance redox kinetics as well as long-term redox catalyst performance. 

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5. All-PEGylated redox-active metal-free organic molecules in non-aqueous redox flow battery

   https://doi.org/10.1039/d0ta02303e  

   Chai, Jingchao ; Lashgari, Amir ; Wang, Xiao ; Williams, Caroline K. ; Jiang, Jianbing “Jimmy” ( August 2020 , Journal of Materials Chemistry A)

   null (Ed.)

   Non-aqueous organic material-based redox flow batteries (NAORFBs) possess the advantage of using organic solvents to achieve high electrochemical potential. However, regardless of the great progress made in this regard in the past decade, further development has been restricted by the lack of stable electroactive organic materials and highly selective separators. Here, we present a NAORFB with all-PEGylated, metal-free, organic compounds as electroactive materials. PEGylated phenothiazine and PEGylated viologen are utilized as the catholyte and anolyte, respectively. Combined with a composite nanoporous aramid nanofiber separator, the all-PEGylated NAORFB presents outstanding cyclability, with a capacity retention of 99.90% per cycle and average coulombic efficiency of 99.7%. By contrast, NAORFBs using half-PEGylated and non-PEGylated electrolytes display inferior cyclability owing to the crossover of non-PEGylated materials. An extended investigation was also performed on the batteries using non-PEGylated or half-PEGylated materials for mechanistic elucidation. This work validates the PEGylation strategy in NAORFBs for enhanced overall performance with respect to solubility, cyclability, and alleviated crossover. 

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