Creation of novel solid-state PSII fuel cells without platinum anodes and determination of optimal anode composition

Solid-state PSII fuel cells fueled by photosynthetic reactions have the potential to be next-generation energy devices, but currently, they cannot generate sufficient power without a platinum catalyst, and the mediators for smooth proton transport in solid-state PSII fuels are not yet clear. In this study, a novel solid-state PSII fuel cell without a platinum catalyst was fabricated by combining PSII fuel and chitin electrolyte. As a result, high power was successfully obtained even without platinum. The solid-state PSII fuel cell was found to achieve the highest power density when using solid fuel with 8.5 $\times$ 10^–1 mg of chlorophyll a (Chl-a) per 1 g of chitin. This result suggests that photosynthetic proton generation reactions are important for the power generation properties of solid-state PSII fuel cells. Furthermore, it was also found that phosphate buffer acts as a mediator of proton transport in PSII fuels and that the optimal molar ratio of phosphate buffer, chitin, and Chl-a for power generation in solid-state PSII fuel cells is 1 mol: 2 mol: 0.5 mmol.