In photosynthesis, solar energy is chemically stored in the carboxylate anions in concert with CO2 capture. Nature combines the separate elements of capture and conversion into a single process where the capture environment "activates" CO2 into sp2-hybridized anions which are then converted. We can apply the same chemical principles for H2storage, by using the capture solvent as the storage medium, providing a kinetically and thermodynamically more accessible CO2 in solution, which may enable more facile or rapid CO2hydrogenation into energy carriers such as formate, or ultimately methanol. Hydrogenations on this "activated" and highly condensed CO2 benefit from lower activation energies through ionic solvent stabilization of key intermediates and transition states, faster kinetics via substantially higher concentrations of "CO2" in solution, and a facilitated coordination of anionic CO2 to homogeneous or heterogeneous catalysts. We present here, a conceptual approach to H2 storage using anhydrous tertiary alkanolamines as liquid H2 carriers. In this process, tertiary alkanolamines capture CO2, forming zwitterionic alkylcarbonate liquids, which are then be hydrogenated to form alkanolammonium formate salts. These liquids can then be catalytically dehydrogenated, where the alkanolamines then re-capture the CO2, enabling delivery of H2 at elevated pressure. The process is reversible, either storing or delivering H2 when needed and the process is catalytic with respect to CO2 and alkanolamine. The chemistry of capturing and subsequently hydrogenating CO2 is presented, followed by discussions on the viability of this conceptual process to deliver H2 for fuel cells under elevated pressures.

Integrated CO2 capture and conversion, a synergistic approach for liquid-based H2 carriers

255th National Meeting (2018)

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