Direct Electrochemical CO₂ Capture Using Substituted Anthraquinones in Homogeneous Solutions: A Joint Experimental and Theoretical Study

Abstract

Electrochemical capture of carbon dioxide (CO 2 ) using organic quinones is a promising and intensively studied alternative to the industrially established scrubbing processes. While recent studies focused only on the influence of substituents having a simple mesomeric or nucleophilicity effect, we have systematically selected six anthraquinone (AQ) derivatives (X-AQ) with amino and hydroxy substituents in order to thoroughly study the influence thereof on the properties of electrochemical CO 2 capture. Experimental data from cyclic voltammetry (CV) and UV–Vis spectroelectrochemistry of solutions in acetonitrile were analyzed and compared with innovative density functional tight binding computational results. Our experimental and theoretical results provide a coherent explanation of the influence of CO 2 on the CV data in terms of weak and strong binding nomenclature of the dianions. In addition to this terminology, we have identified the dihydroxy substituted AQ as a new class of molecules forming rather unstable [X-AQ-(CO 2 ) n ] 2– adducts. In contrast to the commonly used dianion consideration, the results presented herein reveal opposite trends in stability for the X-AQ-CO 2 •– radical species for the first time. To the best of our knowledge, this study presents theoretically calculated UV–Vis spectra for the various CO 2 -AQ reduction products for the first time, enabling a detailed decomposition of the spectroelectrochemical data. Thus, this work provides an extension of the existing classification with proof of the existence of X-AQ-CO 2 species, which will be the basis of future studies focusing on improved materials for electrochemical CO 2 capture.

Anthraquinone and its derivatives as sustainable materials for electrochemical applications – a joint experimental and theoretical investigation of the redox potential in solution

“…35,36 In addition, AQ and its derivatives have shown great promise as an electrode material in the electrochemical capture and release of CO 2 . 37,38…”

“…35,36 In addition, AQ and its derivatives have shown great promise as an electrode material in the electrochemical capture and release of CO 2 . 37,38 Virtual screening approaches based on quantum mechanical (QM) calculation methods provide an alternative and highly promising route to pre-assess potential candidate structures. Considering the numerous possible substitutions of the AQ lead structure (see Fig.…”

How to use a rotating ring-disc electrode (RRDE) subtraction method to investigate the electrocatalytic oxygen reduction reaction?

“…This effect is caused by intramolecular hydrogen bondings and is absent in the case of alkoxy-substituents, 55 and is already well-described for aprotic solvents in previous experimental and computational studies. 56–58 In contrast to the AQ derivatives, RF did not show remarkable redox features in organic, aprotic solvents, mainly attributed to the low solubility of the highly polar RF structure. As the electrocatalytic O 2 to H 2 O 2 reduction reaction is known to be most efficient for certain material classes in alkaline solutions, 40 homogeneous solutions of the compounds shown in Fig.…”

Imidazolium-Functionalized Anthraquinone for High-Capacity Electrochemical CO2 Capture

“…Previous studies also reported a similar red shift for pristine AQ upon electrochemical reduction. 18,41,42 Duan et al reported that the radical anion exhibits two distinct absorption bands in a shorter range (350−450 nm) and a higher range (550−770 nm), which were assigned to the second and first transitions of the π → π* excited state, respectively. 42 The spectrum showed a reversible behavior of the transition from [BAQMIM] •− to [BAQMIM] after switching the electrode potential to an oxidative potential (0 V vs Ag/Ag + ), and simultaneously the vicinity of the Pt electrode returned to being colorless.…”