Synergistic Electrocatalytic N₂ Reduction over Asymmetric Heteronuclear Dual Ru-Fe Sites

The scaling relationship limit poses a significant challenge in single-atom catalysts (SACs) for reactions involving multi-intermediate interactions, such as the electrocatalytic nitrogen reduction reaction (eNRR) for ammonia synthesis. To overcome this limitation, a heteronuclear dual Ru-Fe sites on N,S-codoped Ti₃C₂T_x nanosheet (referred to as Fe₁-N^S-Ru₁/Ti₃C₂T_x) with precisely designed asymmetric coordination for eNRR is developed. Advanced characterizations verify the unique asymmetric coordination structure where Ru and Fe atoms are individually coordinated to N and S atoms, respectively, with the two metal centers interconnected via bridging N and S atoms. This catalyst achieves remarkable eNRR performance with an NH₃ yield rate of 32.8 µg h^-1 mg^-1 _cat at -0.55 V and 47.1% Faradaic efficiency at -0.25 V, surpassing its homonuclear analogues by 3.2- and 2.3-fold in activity and ≈3.0-fold in selectivity. Experimental and theoretical studies reveal a synergistic mechanism, in which Ru sites effectively dissociate H₂O to supply protons while the adjacent Fe sites selectively activate N₂, effectively decoupling proton supply from N₂ activation but also benefiting the formation of key intermediate ^*NNH. Additionally, the electronic interaction between Ru and Fe sites also lowers the energy barrier of the rate-determining step, thereby significantly enhancing catalytic activity and selectivity.