Photoelectrocatalytic‐Microbial Biohybrid for Nitrogen Reduction

Abstract

AbstractNitrogen (N2) conversion to ammonia (NH3) in a mild condition is a big chemical challenge. The whole‐cell diazotrophs based biological NH3 synthesis is one of the most promising strategies. Herein, the first attempt of photoelectrochemical‐microbial (PEC‐MB) biohybrid is contributed for artificial N2 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 NH3 production yield of 1.85 µmol h−1/108 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 NH3 synthesis. The enhancement mechanism of NH3 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 nifH, nifD and nifK 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.