The FEM was then used to iterate the optimum electrolyte for enzymatic CO2RR to provide the greatest predicted currents. The resultant conditions consisted of MOPS (86 mM) and NaHCO3 (50 mM) at a bulk pH of 6.39. Experimentally, this optimum electrolyte (BC-MOPSopt) gave 20% higher current densities (Figure ). Thus showing again that a high buffer capacity and matching the pKa of the additional buffer to the local pH, as opposed to the bulk pH, is critical to stabilising the local pH and hence maximising product formation.