To design new materials for efficient and energy-dense electrochemical energy storage, it is critical to understand the interactions between metal oxides and alkali ions. Here, we discuss the solution-phase interactions of lithium, sodium, potassium, and alkylammonium cations with the Lindqvist-type polyoxovanadate alkoxide (POV alkoxide) cluster, [V6O7(OCH3)12]. In all cases, the presence of alkali cations positively shifts the half-wave potentials of the reduction events of the POV alkoxide cluster relative to alkylammonium. In contrast, the two cluster oxidation events are not affected by the presence of alkali ions, indicating that the observed changes in reduction potentials are the result of unique interactions with charge-compensating cations. Further analysis of the shift in reduction potential shows that the energetics of cation binding to the reduced cluster depend both on the charge state of the complex and the charge density of the compensating ion. Single-crystal X-ray diffraction studies indicate that two {Li}+ ions undergo site-selective coordination to opposite faces of the octahedron upon complete reduction, manifesting in sluggish reoxidation of this tightly associated, ion-paired species. Thus, this single molecular complex demonstrates redox behavior that spans the range from nonspecific to highly specific cation binding, which is directly analogous to the transition from double-layer capacitance to pseudocapacitance in bulk energy storage electrodes.

Electrochemical carbon dioxide capture recently emerged as a promising alternative approach to conventional energy-intensive carbon-capture methods. A common electrochemical capture approach is to employ redox-active molecules such as quinones. Upon electrochemical reduction, quinones become activated for the capture of CO 2 through a chemical reaction. A key disadvantage of this method is the possibility of side-reactions with oxygen, which is present in almost all gas mixtures of interest for carbon capture. This issue can potentially be mitigated by fine-tuning redox potentials through the introduction of electron-withdrawing groups on the quinone ring. In this article, we investigate the thermodynamics of the electron transfer and chemical steps of CO 2 capture in different quinone derivatives with a range of substituents. By combining density functional theory calculations and cyclic voltammetry experiments, we support a previously described trade-off between the redox potential and the strength of CO 2 capture. We show that redox potentials can readily be tuned to more positive values to impart stability to oxygen, but significant decreases in CO 2 binding free energies are observed as a consequence. Our calculations support this effect for a large series of anthraquinones and benzoquinones. Different trade-off relationships were observed for the two classes of molecules. These trade-offs must be taken into consideration in the design of improved redox-active molecules for electrochemical CO 2 capture.

The need for cost-effective carbon dioxide capture technology is rapidly increasing. To limit the global temperature increase to 1.5 °C within the next century, the level of CO2 mitigation needs...

Electrochemical carbon dioxide capture has recently emerged as a promising alternative approach to conventional energy-intensive carbon capture methods. The most common electrochemical capture approach is to employ redox-active molecules such as quinones. Upon electrochemical reduction, quinones become activated for the chemical capture of CO2. The main disadvantage of this method is the possibility of side-reactions with oxygen, which is present in almost all gas mixtures of interest for carbon capture. This issue can potentially be mitigated by fine-tuning redox potentials through the introduction of electron-withdrawing groups on the quinone ring. In this article, we investigate the thermodynamics of the electron transfer and chemical steps of CO2 capture in different anthraquinone derivatives with a range of substituents. By combining density functional theory calculations and cyclic voltammetry experiments, we discover a trade-off between redox potentials and the strength of CO2 capture. We show that redox potentials can readily be tuned to more positive values to impart stability to oxygen, but as a consequence, significant decreases in CO2 binding free energies are observed. This trade-off must be taken into consideration for the design of improved redox active molecules for electrochemical CO2 capture.

The need for cost-effective carbon capture technology is rapidly increasing. To limit the global temperature increase to 1.5 degrees within the next century, the level of CO2 mitigation needs to be increased drastically [1]. Current technology, i.e., amine scrubbing, provides several challenges which limit their deployment: high regeneration energy, high operational costs and degradation at high temperatures [2]. An electrochemical approach avoids large energy losses and can selectively uptake CO2 by utilizing redox-active organic molecules. To compete with conventional chemical scrubbing, the electrochemical cell needs high power density, high CO2 uptake and long cycle stability. Redox-active molecules such as quinone-based molecules have been utilized in this area however suffer from low cycling stability due to organic molecules leaking into the electrolyte [3,4]. Quinone-polymer electrodes have shown a high efficiency for CO2 capture however are prone to quinone degradation and low active-material mass [5]. Here we present our work on a new class of quinone-based electrodes for electrochemical CO2 capture, and explore their electrochemistry in the presence and absence of CO2 and quantify their CO2 uptake capacities. This work paves the way for the design and discovery of improved electrode materials for electrochemical CO2 capture. The Intergovernmental Panel on Climate Change (2018), Global Warming of 1.5 degrees. Available at: https://www.ipcc.ch/sr15/ (Accessed: 10 December 2021) Rahimi, M., Zucchelli, F., Puccini, M. and Alan Hatton, T., 2020. Improved CO2 Capture Performance of Electrochemically Mediated Amine Regeneration Processes with Ionic Surfactant Additives. ACS Applied Energy Materials, 3(11), pp.10823-10830. Apaydin, D., Głowacki, E., Portenkirchner, E. and Sariciftci, N., 2014. Direct Electrochemical Capture and Release of Carbon Dioxide Using an Industrial Organic Pigment: Quinacridone. Angewandte Chemie International Edition, 53(26), pp.6819-6822. Ranjan, R., Olson, J., Singh, P., Lorance, E., Buttry, D. and Gould, I., 2015. Reversible Electrochemical Trapping of Carbon Dioxide Using 4,4′-Bipyridine That Does Not Require Thermal Activation. The Journal of Physical Chemistry Letters, 6(24), pp.4943-4946. Voskian, S and Hatton, T., 2019. Faradaic Electro-swing Reactive Adsorption for CO2 Capture. Energy and Environmental Science, 12(12), pp.3530-3547