Quinone-functionalised carbons as new materials for electrochemical carbon dioxide capture

Abstract

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 to increase drastically. Current capture technology, i.e., amine scrubbing, provides several challenges that limit widespread deployment: high regeneration energy, high operational costs and degradation issues. An emerging energy-efficient technology that can address some of the limitations of amines is electrochemically driven carbon dioxide capture. For example, redox-active quinone molecules are capable of capturing carbon dioxide following electrochemical reduction, and can then be regenerated upon electrochemical oxidation. Despite great advances in the chemistry of quinones for electrochemical CO₂ capture, however, the integration of quinones in carbon capture devices remains an ongoing challenge. Here we present a new class of quinone-functionalized electrodes for electrochemical CO₂ capture, using the diazonium radical reaction to graft quinone molecules to a porous carbon surface. By grafting redox-active molecules to this conductive surface, not only is carbon dioxide capture significantly enhanced when the bound quinone species are electrochemically reduced, but the functionalization process also improves the energy storage of the carbon material. Through constant current experiments in the presence of CO₂, reversible carbon capture was observed with initial uptake capacities at 0.4 mmol g⁻¹ which stabilizes to 0.2 mmol g⁻¹ over 100 cycles with an energy consumption of 254 kJ mol⁻¹ per cycle. Our facile low-cost synthesis of quinone-functionalised carbons is highly tunable since both the carbon and redox-active molecule can be modified, and our work therefore paves the way for the design and discovery of improved electrode materials for electrochemical CO₂ capture.