Polyaniline-Facilitated Direct Electron Transfer from Photosystem II on Inverse-Opal CeO₂

Integrating natural photosystem II (PSII), the only enzyme that oxidizes water, with artificial electrodes enables semiartificial photosynthesis for solar energy conversion. A key challenge is to achieve a uniform PSII distribution with efficient charge transfer. Here, we grow an inverse-opal CeO₂ (IO-CeO₂) scaffold directly on the electrode and utilize polyaniline (PANI) electrodeposition to facilitate PSII attachment. The PANI interlayer improves PSII loading and alignment on IO-CeO₂, broadens visible-light absorption, and establishes a Z-scheme/type-II tandem heterojunction, enhancing photogenerated electron transfer and resulting in a photocurrent of 5.9 ± 0.1 μA cm^-2 in a direct electron transfer system. A 9 cm² PSII-PANI2-IO-CeO₂ photoanode produces 12.3 ± 0.1 μmol of O₂ after 1000 min, which is a 76% increase compared to PANI2-IO-CeO₂. This approach offers simple design rules for efficient biointerface engineering that can be applied to other biohybrid systems.