Here, the local chemical environment of enzymatic HER and CO2RR systems were studied by bioelectrochemistry and computational methods using a finite element model (FEM). Firstly for the HER, and then for the CO2RR, the change in local pH on mesoporous electrodes were studied bioelectrochemically by the current density obtained in solutions with buffers of different pKa. For this purpose, DvH [NiFeSe] H2ase and DvH W-FDH were chosen as enzymes with high activity for their respective reduction reactions and low product inhibition (Figure ). The pH-activity solution assays for H2ase and FDH had previously been undertaken, showing an optimum pH of 6 and 7.1 respectively (Figure ). Independently, a FEM was developed from basic physical principles and enzyme-activity dependence studies for pH, buffer concentration and substrate concentration. The accuracy of the model was then confirmed by predicting the current density outcome of each experiment. The excellent match between the experimental and simulated results validated the FEM and hence the model could be used to simulate the changes in local pH, and other species concentrations. The model was then used to iterate the optimum conditions for each system and the resulting increase in current density was demonstrated experimentally. Finally, the conclusions were experimentally tested on a different electrode architecture, an inverse opal electrode, to demonstrate the wide-ranging applicability of this study.