Photoelectrocatalytic‐Microbial Biohybrid for Nitrogen Reduction

Abstract Nitrogen (N ₂ ) conversion to ammonia (NH ₃ ) in a mild condition is a big chemical challenge. The whole‐cell diazotrophs based biological NH ₃ synthesis is one of the most promising strategies. Herein, the first attempt of photoelectrochemical‐microbial (PEC‐MB) biohybrid is contributed for artificial N ₂ fixation, where Azotobacter vinelandii ( A. vinelandii ) is interfaced directly with polydopamine encapsulated nickel oxide (NiO) nanosheets (NiO@PDA). By virtue of excellent bio‐adhesive activity, high conductivity, and good biocompatibility of PDA layer, abundant A. vinelandii are effectively adsorbed on NiO@PDA to form NiO@PDA/ A. vinelandii biohybrid, and the rationally designed biohybrid achieved a record‐high NH ₃ production yield of 1.85 µmol h ⁻¹ /10 ⁸ cells (4.14 µmol h ⁻¹ cm ⁻² ). In addition, this biohybrid can operate both under illumination with a PEC model or in dark with an electrocatalytic (EC) model to implement long‐term and successional NH ₃ synthesis. The enhancement mechanism of NH ₃ synthesis in NiO@PDA/ A. vinelandii biohybrid can be ascribed to the increase of nicotinamide adenine dinucleotide‐hydrogen (NADH) and adenosine 5‐triphosphate (ATP) concentrations and over expression of nitrogen‐fixing genes of nif H, nif D and nif K in nitrogenase. This innovative PEC‐MB biohybrid strategy sheds light on the fundamental mechanism and establishes proof of concept of biotic‐abiotic photosynthetic systems for sustainable chemical production.