Biomaterials attract a lot of attention as next-generation materials. Especially in the energy field, fuel cells based on biomaterials can further develop clean next-generation energy and are focused on with great interest. In this study, solid-state hydrogen fuel (PSII–chitin composite) composed of the photosystem II (PSII) and hydrated chitin composite was successfully created. Moreover, a biofuel cell consisting of the electrolyte of chitin and the hydrogen fuel using the PSII–chitin composite was fabricated, and its characteristic feature was investigated. We found that proton conductivity in the PSII–chitin composite increases by light irradiation. This result indicates that protons generate in the PSII–chitin composite by light irradiation. It was also found that the biofuel cell using the PSII–chitin composite hydrogen fuel and the chitin electrolyte exhibits the maximum power density of 0.19 mW/cm². In addition, this biofuel cell can drive an LED lamp. These results indicate that the solid-state biofuel cell based on the bioelectrolyte “chitin” and biofuel “the PSII–chitin composite” can be realized. This novel solid-state fuel cell will be helpful to the fabrication of next-generation energy.

Energies based on biomaterials attract a lot of interest as next-generation energy because biomaterials are environmentally friendly materials and abundant in nature. Fuel cells are also known as the clean and important next-generation source of energy. In the present study, to develop the fuel cell based on biomaterials, a novel biofuel cell, which consists of collagen electrolyte and the hydrogen fuel generated from photochemical system II (PSII) in photosynthesis, has been fabricated, and its property has been investigated. It was found that the PSII solution, in which PSII was extracted from the thylakoid membrane using a surfactant, generates hydrogen by the irradiation of light. The typical hydrogen-generating rate is approximately 7.41 × 10¹⁴ molecules/s for the light intensity of 0.5 mW/cm² for the PSII solution of 5 mL. The biofuel cell using the PSII solution as the fuel exhibited approximately 0.12 mW/cm². This result indicates that the fuel cell using the collagen electrolyte and the hydrogen fuel generated from PSII solution becomes the new type of biofuel cell and will lead to the development of the next-generation energy.

As is well known, the realization of a zero-waste society is strongly desired in a sustainable society. In particular, architectural elements that provide an energy-neutral living environment are attractive. This article presents the novel environmentally friendly architectural elements that generate hydrogen energy by the photosystem II (PSII) solution extracted from waste vegetables. In the present work, as an architectural element, the window (PSII window panel) and roof (PSII roof panel) were fabricated by injecting a PSII solution into a transparent double-layer panel, and the aging properties of the power generation and the appearance of these PSII panels are investigated. It was found that the PSII roof can generate energy for 18 days under the sun shining and can actually drive the electronic device. In addition, the PSII window, for which light intensity is weaker than that for the PSII roof, can maintain power generation for 40 days. These results indicate that the PSII roof and PSII window become the architectural elements generating energy, although the lifespan depends on the total light intensity. Furthermore, as an additional advantage, the roof and window panels composed of the semitransparent PSII panel yield an interior space with the natural color of the leaf, which gradually changes over time from green to yellow. Further, it was also found that the thermal fluctuation of the PSII window is smaller than that of the typical glass window. These results indicate that the roof and window panels composed of the PSII solution extracted from waste vegetables can be used as the actual architectural elements to produce not only the electrical energy but also the beautiful, transparent natural green/yellow spaces.