Directional Electron Transfer in Enzymatic Nano‐Bio Hybrids for Selective Photobiocatalytic Conversion of Nitrate

Abstract

Semi‐artificial photosynthetic system (SAPS) that combines enzymes or cellular organisms with light‐absorbing semiconductors, has emerged as an attractive approach for nitrogen conversion, yet faces the challenge of reaction pathway regulation. Herein, we find that photoelectrons can transfer from the ‐C≡N groups at the edge of cyano‐rich carbon nitride (g‐C3N4‐CN) to nitrate reductase (NarGH), while the direct electron transfer to nitrite reductase (cd1NiR) is inhibited due to the physiological distance limit of active sites (> 14 Å). By means of the directional electron transfer between g‐C3N4‐CN and extracted biological enzymes, the product of the denitrification reaction was switched from inert N2 to usable nitrite with an unprecedented selectivity of up to 95.3%. The converted nitrite could be further utilized by anammox microbiota and dissimilatory nitrate reduction to ammonia (DNRA) microorganisms, doubling the efficiency of total nitrogen removal (96.5 ± 2.3 %) for biological nitrogen removal and ammonia generation (12.6 mg NH4+‐N L‐1 h‐1), respectively. Thus, our work paves an appealing way for the sustainable treatment and utilization of nitrate for ammonia fuel production by strategically regulating the electron transfer pathway across the biotic‐abiotic interface.