Building Asymmetric B Vacancy Coupled FeB ₂ N ₃ Associate Site by Joule Heating Metal‐Based Ionic Liquid for Enhanced Full Wavelength Photosynthesis of Ammonia

ABSTRACT Building an asymmetric active site has been regarded as an effective strategy to boost photocatalytic ammonia synthesis. However, there is a lack of effective and controllable methods for rapidly constructing asymmetric sites. Herein, Fe single atoms are engineered onto BCN atomic layer (Fe‐BCN) using a metal‐based ionic liquid through a rapid joule heating method. A FeB 2 N 3 coordination structure coupled with B vacancy can be created in Fe‐BCN, forming an asymmetric associate site. This asymmetric configuration leads to the generation of local charge redistribution and a polarized electric field at the interface, promoting the photo‐generated charge separation. Moreover, the synergy between B vacancies and FeB 2 N 3 sites transforms the interfacial electronic interaction with key *NO 2 intermediate from p–p to d–p interaction, enhancing orbital hybridization between the 3d z2 orbitals of Fe and the 2b1 antibonding orbitals of *NO 2 , significantly accelerating the conversion of *NO 2 . The key reaction intermediates are verified by 15 N isotope in‐situ FTIR. Benefiting from these features, the optimized Fe‐BCN shows 8.8 and 58.5 times enhanced NH 3 production activity than BCN and BN, respectively, while the NH 3 production rate over Fe‐BCN‐2 device arrives 1182.5 µmol g −1 h −1 . This study provides new ideas for the fast construction of asymmetric active sites and the key role of intermediate interaction regulation.