Photosystem II‐Carbon Nitride Photoanodes for Scalable Biophotoelectrochemistry

Abstract Photosystem II (PSII) is a vital photosynthetic enzyme with the potential for sustainable bioelectricity and fuel generation. However, interfacing PSII with intricate, small‐scale electrodes for practical applications has been challenging. This study addresses this by creating protonated macroporous carbon nitride (MCN) as support and developing a scalable spray‐freeze method to wire PSII with MCN. This facilitates the production of large‐area MCN‐PSII photoanodes up to 33 cm 2 for biophotoelectrochemical water oxidation to O 2 , achieving efficient interfacial charge transfer and initial photocurrents in the mA range with Faradaic yield of 93.5 ± 8.5% over 5 h. A bias‐free biophotoelectrochemical (BPEC) device is designed by connecting the MCN‐PSII photoanode to a carbon nanotube cathode loaded with bilirubin oxidase. An array of eight tandem BPEC cells with a photoactive area of 72 cm 2 successfully powers low‐power electronics, such as LEDs. This work paves an efficient way for bioelectrode fabrication, showcasing the potential of PSII‐based semi‐artificial systems for BPEC and biophotovoltaic applications.