These encapsulated organic photoelectrodes maintain their performance even under benign aqueous conditions , making them suitable for biocatalytic applications. Chopped PFVs of OPV|IO-TiO2|H2ase photocathodes displayed an onset potential of 1 V vs. RHE, consistent with opencircuit potential measurements (Fig. ). The addition of CA (100 pmol) enhanced photocurrent densities from -4 mA cm -2 to -8 mA cm -2 (Fig. ), which stands out compared to previous H2ase PEC reports , especially in the absence of external buffer components (Table ). Accordingly, OPV|IO-TiO2|H2ase+CA photoelectrodes produced 239±8 µmolH 2 cm -2 (FY = 101±1%) over 10 h at 0.6 V vs. RHE (Fig. , Fig. and Table ). As an OPV provides a Voc of 1.0 V, this effectively corresponds to an applied potential of -0.4 V vs. RHE on the IO-TiO2|H2ase+CA biohybrid, consistent with electrochemical data above (Fig. ). An exclusion control experiment in the absence of H2ase did not produce H2, validating the selective catalytic nature of H2ase, and that chopped photocurrents observed for bare OPV|IO-TiO2 electrodes correspond to the capacitive charging of TiO2 (Fig. and trumpet-shaped PFV in Fig. ).