While the experimental currents and charge densities were lower than simulated (Table ), the trends were closely matched, demonstrating that while the model is approaching its useful limits for predicting the local environment and current densities it can still be highly beneficial for system design and optimization. Formate production after 48 h with CA was determined by IC quantification to be 0.22 ± 0.008 µmol cm -2 with a FE of 29 ± 7 at pH 7 and 0.69 ± 0.04 µmol cm -2 with a FE of 37 ± 4 at pH 7.75 at -0.6 V vs SHE. Product quantification was not possible without CA as the HCOO -was below the quantification limit (13 μM, corresponding to for-mate production of 0.20 µmol cm -2 in a minimized solution volume of 3 mL, Figure ), however was detectable in pH 7 with a concentration above the detection limit of 4.2 µM (64 nmol cm -2 ) but below the quantification limit. This fits the expected trend from the model and highlights the benefit of this carboxysome inspired approach to manage the local environment. While the achieved current densities are low, these experiments demonstrate that CO2R at atmospheric concentrations is greatly enhanced with higher dissolved HCO3 -concentrations. This can be used to increase local CO2 levels and current density when coupled to fast CO2 hydration kinetics to remove the kinetic limitation that prevents HCO3 -being utilized for enzymatic CO2R at low CO2 concentrations. This offers insights to the development of future catalyst systems as they approach the properties of enzymes, making the composition and availability of inorganic carbon in solution vital to their effective performance when integrated into real world systems.