Under all conditions, the addition of the kinetically fast Good's buffer 3-(N-morpholino)propane sulfonic acid (MOPS) substantially improves the CO2R current density. This buffer system was chosen because the pKa of MOPS is close to the optimal pH for FDh (7.1), and the electrolyte does not affect the FDh activity. CA co-immobilization significantly increased the observed jformate 1.7× from -135 ± 26 to -235 ± 37 µA cm -2 in 10% CO2 purged pH 7 MOPS solutions at -0.6