Computational and Experimental Design of Quinones for Electrochemical CO₂ Capture and Concentration

Abstract

Current state-of-the-art thermal technologies for CO 2 capture and concentration (CCC) from industrial emissions and air are energetically inefficient. In contrast, electrochemical CCC (eCCC) using redox carriers can theoretically approach 100% efficiency. However, there are currently few oxygen-stable redox carriers suitable for eCCC. Quinone derivatives have previously been studied as redox carriers as they have no affinity for CO 2 in the fully oxidized state and an enhanced affinity for CO 2 in their reduced states. Unfortunately, the quinones used in prior studies displayed an unfavorable tradeoff between their second reduction potential (E 1/2 ) and CO 2 binding constant (K COd 2 ). As a result, reduced quinones that exhibit a sufficient K COd 2 for flue gas or atmospheric CO 2 capture have E 1/2 values negative of the O 2 /O 2 •− reduction potential. To improve our understanding of the structural and electronic relationships that correlate K COd 2 and E 1/2 , we report the largest set of quinones that have been experimentally evaluated for their K COd 2 and E 1/2 properties. The trends in the E 1/2 and K COd 2 properties were further investigated through extensive quantum chemical calculations to inform experimental carrier design. Notably, we identified structural handles to manipulate E 1/2 and K COd 2 properties of quinones; however, the altered steric and electronic effects did not disrupt their linear dependence.

Molecular design of redox carriers for electrochemical CO2 capture and concentration

“…O 2 stability of reduced quinones generally requires reduction potentials positive of the O 2 /O 2 ˙ − couple. 27,42 Very reducing redox carriers (with reduction potentials negative of this couple) can be oxidized by O 2 , to produce superoxide (O 2 ˙ − ) and regenerate the resting-state carrier (Scheme 1, eqn (I)). A cleavage of the C–C bond between the carbonyl groups was observed in the reaction of alpha-diketones (including 1,2-quinones) in air-saturated solution under electrochemical conditions.…”

“…À couple. 27,42 Very reducing redox carriers (with reduction potentials negative of this couple) can be oxidized by O 2 , to produce superoxide (O 2 À ) and regenerate the resting-state carrier (Scheme 1, eqn (I)).…”

Electrochemical Carbon Dioxide Capture and Concentration

“…investigated the validity of the proposed linear relationship between the second reduction potential and CO2 binding constant of quinones. 139 In their work, they synthesized and tested the ability of seven new quinones to capture CO2 in their dianion states. The measured 𝐾 CO 2 (DA) were in the range of ca.…”

“…20,124,128,[137][138][139][140][141] which is summarized in Table1. Numerous quinones also bind CO2 in their radical anion state (QRA).…”

Imidazolium-Functionalized Anthraquinone for High-Capacity Electrochemical CO2 Capture

“…9 Since then, several studies have focused on the application of quinone chemistry for CO 2 separation, revealing that the introduction of substituents (electron-withdrawing/donating groups) to the quinone skeleton can affect the affinity of the reduced quinones for CO 2 . 11, 16,17 Moreover, the formation of CO 2 adducts with reduced quinones has been elucidated using various spectroscopic methods such as UV−vis and Fourier transform infrared (FT-IR) spectroscopies. 18−20 Despite this progress, the poor solubility of quinones (e.g., <5 mM for anthraquinone in acetonitrile 21 and ∼200 mM for 2,6-di-tertbutyl-1,4-benzoquinone in dimethyl sulfoxide (DMSO) 10 ) remains a challenge for practical applications because it directly limits the total CO methylimidazolium tricyanomethanide ([emim][tcm]), by forming hydrogen bonds between NQ and the [emim] cation.…”