Photosynthesis Z-Scheme biomimicry: Photosystem I/BiVO₄ photo-bioelectrochemical cell for donor-free bias-free electrical power generation

Photo-bioelectrochemical cells that are based on photosynthetic proteins are drawing increased attention for both fundamental and applied research. While novel photosynthetic based systems have been introduced, further optimization in terms of stability and efficiency is required. Photosystem I has been utilized extensively in bioelectronic devices, often in conjugation with viologen moieties which act as electron acceptors. It has been shown previously that a partial reduction of oxygen to H₂O₂ can facilitate damage to proteins hence, limits their long-term activation. Here, we show a newly developed bias-free, donor-free photo-bioelectrochemical system that mimics the natural photosynthetic Z-scheme. Polymethylene blue and polybutyl-viologen were tailored to fit the photosystem I donor and acceptor sides, respectively. Furthermore, we show that by coupling the developed biocathode with a BiVO₄/CoP photoanode, a power output of 25 μW/cm² can be achieved. We further show that our configuration can minimize the damaging effect of H₂O₂ by two different pathways, oxidation at the photoanode or reduction by the polymethylene blue layer at the biocathode.