Inorganic-bacterial biohybrids for efficient solar-driven nitrogen fixation

The integration of microbial nitrogen (N₂) fixation with photochemical processes using inorganic light-absorbing nanomaterials is a burgeoning field in sustainable energy production. Here, we explore the synergistic combination of inorganic semiconductor nanowires (NWs) with whole-cell microorganisms to create an inorganic-bacterial biohybrid system. Specifically, we employ Cu₂O@TiO₂ NWs with a core/shell structure to harness sunlight and generate photoexcited electrons. Azotobacter vinelandii, serving as a biocatalyst, adsorbs onto these NWs and facilitates the reception of photoexcited electrons, thereby enhancing the efficiency of the photoelectrochemical N₂ fixation reaction (PEC-NRR). The biohybrid system achieves an impressive ammonia (NH₃) yield of (1.49 ± 0.05) × 10^-9 mol s^-1 cm^-2 (5.36 ± 0.18 μmol h^-1 cm^-2). The enhancement in NH₃ synthesis within the Cu₂O@TiO₂ NWs/A. vinelandii biohybrid is attributed to the increased concentrations of nicotinamide adenine dinucleotide-hydrogen (NADH) and adenosine 5'-triphosphate (ATP), as well as the overexpression of N₂-fixing genes like nifH and nifD within the nitrogenase enzyme complex. This study underscores the potential of inorganic-bacterial biohybrid systems in solar-chemical conversion, paving the way for more diverse and functional approaches to harnessing solar energy for sustainable chemical production.