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 Fe 3 O 4 and Al 2 O 3 nanoparticles to form a core–shell structure. Fe 3 O 4 -coated cells (DS@Fe 3 O 4 ) improve interfacial contact and electron transport, reducing internal resistance. At 2.0 mg mL –1 Fe 3 O 4 NPs, DS@Fe 3 O 4 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, SiO 2 -coated Fe 3 O 4 (Fe 3 O 4 @SiO 2 ) impaired performance, indicating the necessity of direct Fe 3 O 4 contact. These results establish Fe 3 O 4 nanoparticles as efficient electron collectors, offering a robust strategy to improve BPVs output and promote their application in sustainable energy systems.