The precise conditions of the local chemical environment are decisive for enzyme activity and the local environment must therefore be tailored to the nature of the immobilised enzyme for optimal catalysis. Both the enzymatic H2 evolution reaction (HER) (eq. 1) and formate production by the enzymatic CO2 reduction reaction (CO2RR) (eq. 2) involves the net consumption of protons as part of their mechanism, leading to an increased local pH at the electrode surface. Due to their high activity and selectivity, H2ases can provide a simple, illustrative model system of how catalysis causes local pH changes within porous architectures, whilst FDHs can demonstrate the effect for the CO2RR.