High-Efficiency Electrochemical Ammonia Synthesis at Co-Catalytic Fe–Mo Dual-Atom Sites

Abstract

To tackle the challenge in electrochemical nitrogen fixing and reduction in aqueous electrolytes, the conventional approach has been to suppress the competitive hydrogen evolution reaction. Nonetheless, proton provision is a crucial step in the nitrogen reduction pathway to produce ammonia, and a single active site faces the daunting task in striking a balance between high nitrogen fixation efficiency and fast protonation kinetics. This work presents a harmonic strategy featuring atomically dispersed dual Fe–Mo sites anchored in an N-doped carbon (FeMoNC) substrate, where a low-spin Fe center with enriched empty d orbitals aids in nitrogen fixation and activation, and the adjacent Mo site accelerates the protonation kinetics of N-containing intermediates at the Fe site via a distal associative mechanism. Driven by this co-catalytic mechanism, the FeMoNC catalyst achieves a Faradaic efficiency of 37.42%, marking a significant improvement of 7.8- and 10.6-fold over Fe or Mo single-atom catalysts, respectively. Furthermore, an excellent NH₃ yield of 54.40 μg h^–1 mg_cat.^–1 is realized in a flow cell by enhancing mass transfer. This study provides valuable insights into diatomic co-catalytic mechanisms for electrochemical ammonia synthesis.