Oxygen-Resistant Redox Species for CO2 Capture

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Solution Overview

Problem

Electrochemical CO2 capture systems require an oxygen-free environment to prevent oxidation of redox-active species, which is challenging due to the presence of molecular oxygen in air and flue gas, leading to incomplete cycles and device degradation.

Innovation Solution

The use of water-soluble, oxygen-resistant redox-active species in flow cells that incorporate aromatic redox cores with substituents that enhance resistance to oxidation, allowing for stable operation in the presence of oxygen.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional redox-active species are used in electrochemical CO2 capture systems, then CO2 capture function is achieved, but the system requires oxygen-free environment which increases device complexity and operational difficulty

Engineering Contradiction:

ImproveCO2 capture functionVSAvoidoxygen-free environment requirement

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent modifies the chemical parameters of redox-active species by introducing electron-withdrawing groups (such as fluorine, chlorine, nitro, or cyano groups) attached to aromatic cores. These structural modifications raise the redox potential of the reduced state, making it thermodynamically stable against oxidation by molecular oxygen, thereby eliminating the need for oxygen-free environments while maintaining CO2 capture functionality.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite redox-active species that combine aromatic cores (such as phenazine, viologen, or quinone structures) with electron-withdrawing substituents. This composite molecular structure achieves both CO2 capture capability through proton-coupled electron transfer and inherent resistance to oxygen oxidation, resolving the contradiction between functionality and environmental requirements.

Inventive Principle:

Principle #40Composite materials

2Productivity

If redox-active species are reduced to capture CO2, then CO2 capture efficiency is improved, but the reduced state becomes susceptible to oxidation by molecular oxygen

Engineering Contradiction:

ImproveCO2 capture efficiencyVSAvoidresistance to oxidation

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent systematically adjusts the redox potential parameter of the redox-active species by incorporating electron-withdrawing groups. These groups increase the redox potential of the reduced state, creating a thermodynamic barrier against oxidation by molecular oxygen. This parameter modification allows the reduced state to simultaneously maintain high CO2 capture efficiency and exhibit robust resistance to oxidation in ambient conditions.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If conventional electrochemical CO2 capture methods are used, then CO2 capture is achieved, but incomplete cycles occur due to oxidation of reduced species, leading to accumulation of hydroxide and carbon species

Engineering Contradiction:

ImproveCO2 capture cycle completionVSAvoidaccumulation of hydroxide and carbon species

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

The patent converts the potentially harmful interaction between reduced redox species and molecular oxygen into a beneficial feature by designing species whose reduced states are thermodynamically stable against oxidation. The electron-withdrawing groups transform what would normally be a degradation pathway into a stable, reversible electrochemical cycle, preventing accumulation of unwanted species and enabling complete capture cycles under ambient conditions.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

This approach enables safe, scalable, and potentially inexpensive CO2 capture and release, operating at ambient temperature and pressure, with high current densities and improved air stability of reduced redox states.

Implementation Method 1

Molecules that undergo proton-coupled electron transfers (PCET) change the solution pH from near neutral to highly basic during charging

Methodology Applied

Scientific EffectProton-coupled electron transfer (PCET):

Implementation Method 2

Since hydroxide binds with CO2 to form bicarbonate and then carbonate, the electrolyte captures CO2 upon charging

Methodology Applied

Scientific EffectCO2 binding with hydroxide:

Implementation Method 3

electrochemically reducing the redox-active species to a reduced state

Methodology Applied

Scientific EffectElectrochemical reduction:

Implementation Method 4

a redox potential of the redox-active species in its reduced state may be sufficiently high to be stable to oxidation by oxygen

Methodology Applied

Scientific EffectOxidation resistance: Oxidation

Data Source

PatentUS20250144562A1Electrochemical co2 capture with air stable redox species

Publication Date: 2025.05.08 PRESIDENT & FELLOWS OF HARVARD COLLEGE

AI summary

The invention features solutions of water-soluble, oxygen-resistant redox-active species circulated in flow cells to electrochemically capture CO2 from air or flue gas and release pure CO2. The method is safe, scalable, and potentially inexpensive, as it utilizes non-volatile and potentially low-cost redox organic and inexpensive inorganic species and can operate at ambient temperature and pressure and can operate at high current densities.