Diatom microalgae-based living biophotovoltaics for high-performance photocurrent and hydrogen generation: indirect...

The conversion of solar energy into storable chemical fuels using biological systems offers a sustainable route toward carbon neutral energy technologies, yet the range of microorganisms that can operate efficiently within bio hybrid photoelectrochemical platforms remains limited. Here, microalgae (Nitzschia navis-varingica) isolated from marine mucilage, subsequently purified and cultivated under controlled conditions, are integrated into a graphene-cellulose acetate nanofibrous photoanode to construct a stable biophotovoltaic system capable of generating significant photocurrent and measurable hydrogen under visible light. In this configuration, microalgae function as photoactive electron donors at the biohybrid photoanode, while hydrogen evolution is electrochemically catalyzed at an abiotic Pt-based cathode. Despite the intrinsic biological constraints of diatoms, including their rigid silica frustule and sensitivity to osmotic stress, the mucilage derived BPV device produced unexpectedly high and stable photocurrent densities and achieved a hydrogen yield that surpasses several benchmark inorganic photocatalysts. Electrochemical and biological analyses show that the engineered Gr CA scaffold enhances electron extraction from the microalgal cells and supports robust photoelectrochemical activity during prolonged operation. This study provides the first demonstration that microalgae originating from marine mucilage can function as effective photoactive catalysts in a bio hybrid photoanode, revealing a previously unexplored biological resource for solar driven hydrogen generation. The findings establish an indirect yet meaningful pathway for the valorization of marine mucilage as a biological resource and highlight its potential as a sustainable feedstock for next-generation bio-inspired solar to hydrogen energy conversion technologies.