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.