Enzymatic electrochemistry has rapidly expanded into research fields that encompass applications across disciplines from fundamental understanding of enzymology to biosensors, biofuel cells and semi-artificial photosynthesis. Hydrogenases (H2ases) combine protons and electrons to reversibly produce H2 at the thermodynamic potential using Fe or NiFe active sites and have therefore been extensively studied as a model system for reversible electrocatalysis. Formate dehydrogenases (FDH) have similarly garnered attention due to their ability to reversibly reduce CO2 to formate, with high selectivity when immobilised on an electrode. Bioelectrochemistry on thin-film electrodes has long provided mechanistic and analytical insight into enzyme function, as well as establishing bioelectrolysis as a potential method of product synthesis. Porous electrodes enable higher enzyme loading, and hence higher current densities, improving the overall performance by increasing the consumption or production of desired chemicals. Solution assays provide insight into the influence of bulk pH and ionic strength on enzyme activity and the conclusions have informed the choice of electrolyte in electrochemical studies. However, the high current densities achievable using the latest generation of high surface area electrode scaffolds, usually used as stationary electrodes, presents a significantly different local chemical environment during turnover to that of bulk solution assays. With enzymes operating at a high rate of catalysis, for example D. vulgaris Hildenborough (DvH) [NiFeSe]-H2ase has a turnover frequency (TOF) of ~8300 s -1 for H2 evolution, the local proton concentration is likely to change significantly if the enzyme is placed in a porous environment. Therefore, consideration of local concentration gradients, as opposed to the bulk electrolyte solution, appears to be critical to understand and optimise enzymatic activity in such porous electrodes.