Thioether Quinone Redox Mediators for Acid-Stable Flow Batteries
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Solution Overview
Problem
Existing quinones used in electrochemical cell technologies, such as organic mediator flow batteries and mediated fuel cells, are inadequate due to instability in aqueous acid solutions and low reduction potentials, limiting their effectiveness in oxygen reduction processes.
Innovation Solution
Development of highly substituted hydroquinones/quinones with thioether and sulfonate moieties that maintain high reduction potentials and stability in acid solutions, along with a method for synthesizing these compounds using mercaptoalkylsulfonates and electrolysis to install thioether sulfonate groups on the hydroquinone/quinone ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If sulfonate groups are added to hydroquinone to improve water solubility, then water solubility increases, but stability in acid solution decreases
Solution Approach 1:
The patent combines multiple substituent types (sulfonate groups for solubility, thioether groups for stability, and electron-withdrawing groups for potential enhancement) on the hydroquinone core to create a composite molecular structure that simultaneously achieves high water solubility, acid stability, and high reduction potential
Solution Approach 2:
Different regions of the hydroquinone molecule are assigned different functional groups with specific local functions: sulfonate groups at certain positions provide solubility, thioether groups at other positions provide stability, and electron-withdrawing groups contribute to high reduction potential, with each local region optimized for its specific function
2Stability of the object's composition
If substitution on hydroquinone is increased to improve stability in acid solution, then stability improves, but reduction potential decreases
Solution Approach 1:
The patent uses a composite substitution strategy combining thioether groups (providing stability), sulfonate groups (providing solubility), and electron-withdrawing groups (providing high reduction potential), where the synergistic interaction of different functional groups overcomes the typical trade-off between substitution and reduction potential
Solution Approach 2:
The patent systematically varies substitution parameters including the type of substituents (thioether, sulfonate, electron-withdrawing), their positions on the ring, and their combinations to optimize the balance between stability and reduction potential, achieving compounds with both high stability and high reduction potential
3Quantity of substance
If vigorous sulfonation conditions are used to achieve high water solubility, then water solubility increases, but compound stability decreases due to decomposition
Solution Approach 1:
The patent performs substitution reactions on the hydroquinone core in a controlled sequence, installing stabilizing thioether groups and electron-withdrawing groups before or alongside sulfonate groups, thereby pre-establishing molecular stability that prevents decomposition during subsequent sulfonation or storage
Solution Approach 2:
The patent uses controlled substitution reactions as intermediary steps to build the final stable compound, where intermediate structures with partial substitution serve as stable precursors that can be further modified without decomposition, allowing gradual assembly of the multi-functional final product
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting compounds are water-soluble, stable in acid, and have reduction potentials comparable to or exceeding those of unsubstituted benzoquinone, making them suitable as improved redox mediators for oxygen reduction in electrochemical cells.
Implementation Method 1
The quinone/hydroquinone redox couple is used in many different technologies and has been extensively studied
Implementation Method 2
a method for synthesizing these compounds using mercaptoalkylsulfonates and electrolysis to install thioether sulfonate groups on the hydroquinone/quinone ring
Data Source
AI summary
Substituted hydroquinones and quinones and methods of synthesizing such compounds are disclosed herein. The substituted hydroquinones have the formula:while the substituted quinones have the corresponding oxidized structure (1,4-benzoquinones). One, two, three, or all four of R1, R2, R3 and R4 comprise a thioether moiety and a sulfonate moiety, and wherein each R1, R2, R3 and R4 that does not comprise a thioether and a sulfonate moiety sulfonate moiety is independently a hydrogen, an alkyl or an electron withdrawing group.The substituted hydroquinones and quinones are soluble in water, stable in aqueous acid solutions, and have a high reduction potential in the oxidized form. Accordingly, they can be used as redox mediators in emerging technologies, such as in mediated fuel cells or organic-mediator flow batteries.