Qualitative carbon energetics of CO2 capture and conversion
to CO via the sequential integration pathway (i.e., integrated air
contactor, CO2 regeneration, and CO2 conversion:
1, red) and via the direct integration pathway (i.e., integrated air
contactor with bicarbonate and carbonate conversions: 2 and 3, green
and blue). Note that we do not show the detailed mechanism of these
molecular transformations but indicate the presence of transition
states in each. We do not include the in situ CO2 regeneration
in the direct integration pathway to highlight the promise of combining
the regeneration and conversion steps into a single step. Also note
the qualitative energy requirement scale at the right-hand side of
the figure, which qualitatively emphasizes the thermodynamic favorability
of directly converting captured CO2 (i.e., (bi)carbonates)
into desired products.