Correlating the Structure of Quinone-Functionalized Carbons with Electrochemical CO2 Capture Performance

Electrochemical carbon dioxide capture is emerging as an energy-efficient alternative to traditional carbon capture technology. In particular, redox-active molecules that can capture carbon dioxide when electrochemically reduced and release carbon dioxide when electrochemically re-oxidized are under active development. To prepare a carbon capture device these molecules can be incorporated in a solid electrode in a battery-like cell. In this work we explore the scope of a recently developed method where anthraquinones are covalently attached to porous carbon supports to obtain electrodes for electrochemical carbon dioxide capture. We functionalize four different porous carbon materials with varying porosities and surface chemistries, and use gas sorption analysis and solid-state NMR spectroscopy to probe the location of the grafted anthraquinones. All four functionalized materials show electrochemically mediated capture and release of carbon dioxide and we explore the factors that determine their performance. While the anthraquinone-functionalized mesoporous carbon, f-CMK-3, showed the highest quinone loading, it showed poor quinone utilization for CO2 capture, and poor long-term cycling stability. In contrast, the predominantly microporous functionalized carbon, f-YP-80F, showed a higher quinone utilization and improved cycling stability. Finally, thermal annealing experiments were conducted to remove pre-existing functional groups on a third carbon, but this did not improve the cycling stability of the resulting anthraquinone-functionalized material. Overall our measurements suggest that the pore environments in which anthraquinones are grafted play a crucial role in determining the electrochemical CO2 capture performance. This work can guide the design of functionalized carbon electrodes for electrochemical carbon dioxide capture.