A Finite Element Model (FEM) using a previously reported approach was used to model the local environment that was experimentally inaccessible (Figure ). This uses well understood physical and analytical equations, with enzyme properties determined from solution assays, solved over a mesh that represents the geometry of the system to model the response and was in good agreement with experimentally observed currents (lines, Figure ), allowing the concentrations of species within the porous electrode to be determined (Figure ). It is apparent that the comparable currents with and without accelerated CO2 hydration kinetics are due to very different local environments at both 10 (Figure ) and 1% CO2 (Figure ). In both cases the local pH and [CO2] are reduced, and the [HCO3 -] is increased when CA is co-immobilized. These changes can be attributed to the accelerated conversion of CO2 and H2O to HCO3 -and H + promoted to mitigate the local pH increase within the mesoporous electrode.