Photobio-electrocatalytic production of H₂ using fluorine-doped tin oxide (FTO) electrodes covered with a NiO-In₂S₃ p-n junction and NiFeSe hydrogenase

Clean energy vectors are needed towards a fossil fuel-free society, diminishing both greenhouse effect and pollution. Electrochemical water splitting is a clean route to obtain green hydrogen, the cleanest fuel; although efficient electrocatalysts are required to avoid high overpotentials in this process. The combination of inorganic semiconductors with biocatalysts for photoelectrochemical H₂ production is an alternative approach to overcome this challenge. N-type semiconductors can be coupled to a co-catalyst for H₂ production in the presence of a sacrificial electron donor in solution, but the replacement of the latter with an electrode is a challenge. In this work we attach a NiFeSe-hydrogenase with high activity for H₂ production with the n-type semiconductor indium sulfide, which upon visible irradiation is able to transfer its excited electrons to the enzyme. In order to enhance the transfer of the generated holes towards the electrode for their replenishment, we have explored the inclusion of a p-type material, NiO, to induce a p-n junction for H₂ production in a photoelectrochemical biocatalytic system in absence of sacrificial reagents.