Living Biophotovoltaics Harnessing Green Algal Photosynthesis and Respiration for Simultaneous Photocurrent and Hydrogen Generation

This study presents a novel Living Biophotovoltaic (Living BPV) system designed to simultaneously generate photocurrent and hydrogen using metabolically active green algae ( Paulschulzia pseudovolvox sp). A photoanode was constructed by immobilizing green algae on a conductive polymer matrix of P(SNS‐Ph‐Pyr) and a calix[4]arene‐gold nanoparticle composite. The porous architecture of the platform enhanced algal adhesion and facilitated efficient electron transfer. The immobilized algae contributed to energy generation via both photosynthesis and respiration, enabling dual‐mode operation under light and dark conditions. Covalent bonding between calixarene carboxyl groups and algal amines ensured structural stability, while the gold nanoparticles supported rapid electron flow. A platinum nanoparticle‐based cathode enabled hydrogen evolution through proton reduction. The study uniquely explores the contribution of green algal respiration alongside photosynthesis in BPV applications. Electropolymerization and surface modification techniques were optimized to enhance system efficiency. The results demonstrate that the system maintains photocurrent stability over prolonged periods and enables reproducible hydrogen generation, even under PSII‐inhibited conditions. To our knowledge, this is the first report of a BPV system leveraging both photosynthetic and respiratory pathways of green algae for integrated electricity and hydrogen production. The findings highlight the potential of Living BPVs as sustainable, biohybrid platforms for next‐generation solar energy conversion.