Cell Surface-Coated Electron Collectors to Amplify Electron Transfer in Dunaliella-Based Photovoltaics

Microbial biophotovoltaics (BPVs) utilize photosynthetic microorganisms to generate electricity but are limited by low power densities due to inefficient electron transfer and restricted cell-electrode contact. This study enhances Dunaliella-based BPVs by coating cells with Fe₃O₄ and Al₂O₃ nanoparticles to form a core–shell structure. Fe₃O₄-coated cells (DS@Fe₃O₄) improve interfacial contact and electron transport, reducing internal resistance. At 2.0 mg mL^–1 Fe₃O₄ NPs, DS@Fe₃O₄ BPVs exhibit a 4.72-fold voltage increase and a 2.57-fold rise in power density (3658.41 ± 57.92 mW m^–2) compared to uncoated controls. These performances are all considerably higher than those of the best BPVs reported to date. In contrast, SiO₂-coated Fe₃O₄ (Fe₃O₄@SiO₂) impaired performance, indicating the necessity of direct Fe₃O₄ contact. These results establish Fe₃O₄ nanoparticles as efficient electron collectors, offering a robust strategy to improve BPVs output and promote their application in sustainable energy systems.