While the relative increase in local CO2 concentration is similar when CA is introduced at 10 and 1% CO2, the improvement in CO2R current density is greater at 1% CO2 since the rate of fuel production becomes more dependent on available substrate concentrations as purged CO2 levels decrease below the KM of FDh towards atmospheric concentrations. Much like the colocalization of CA and RuBisCO within carboxysomes, fast CO2 hydration kinetics improve enzymatic CO2R within the nanoconfined mesoporous electrode by increasing available CO2 concentrations through the utilization of HCO3 -as an indirect carbon source in well buffered solutions that remove the requirement of the carbon pool to act as a buffer system.