Enhanced N₂ electroreduction activity of single-atom catalysts: Modulating the linear scaling relationship by coordination engineering and dual-site strategies

The volcano plot is widely used to elucidate the activity trends among different catalysts, thereby effectively screening and guiding catalyst design. However, the inherent linear scaling relationship (LSR) constrains the breakthrough in the activity of catalysts, and the understanding of the activity limit in volcano plot is still ambiguous. In this work, by employing first-principles calculations and microkinetic modeling, we proposed coordination engineering (CE) and dual-site (DS) strategies to surpass the Sabatier’s limitation of WS₂-supported TM (TM@WS₂) single-atom catalysts (SACs) for electrocatalytic nitrogen reduction reaction (eNRR). We found that the LSR between ΔG(*N₂→*N₂H) and ΔG(*NH₂→*NH₃) was optimized to be closer to the ideal space of eNRR activity after modulating TM@WS₂ SACs by these two design strategies. By combining the reaction selectivity trend plot, we picked out N-Os@WS₂, C-Ir@WS₂, Fe₂@WS₂, and Ru₂@WS₂ as optimal eNRR catalysts with low limiting potential (U_L), and N-Os@WS₂ SAC (U_L: –0.28 V) outperforms the best eNRR catalyst among TM@WS₂ SACs. By constructing explicit solvent models, we conducted a detailed study on the reaction kinetics of proton transfer over these four catalysts. We propose that the activity enhancement in TM@WS₂ SACs for eNRR can be attributed to the ligand effect and geometric effect brought about by CE and DS strategies, improving the donation-backdonation process of electron transfer between N₂ and the active sites. The designed catalyst has certain resistance to demetallization and agglomeration under simulated solvent environment. This work provides a feasible design strategy for the activity enhancement of SACs and brings a new perspective to deeply understanding the volcano plot in heterogeneous catalysis.