Orbital-orthogonality-mediated active-site decoupling for ammonia electrosynthesis

Electrocatalytic nitrogen reduction (NRR) offers a promising route for sustainable ammonia production but suffers from low efficiency due to the competitive hydrogen evolution reaction (HER) and inadequate N₂ mass transfer in conventional aqueous systems. Here, we propose a rational strategy of orbital orthogonality to reconfigure lattice-intrinsic orbital hybridization, effectively decoupling HER and NRR onto distinct frontier orbital domains. Using non-stoichiometric MoS_x as a model platform, we identify two mechanistic paradigms: while terminal S^2- species in MoS_2-x lead to single-site competition, the bridging S₂^2- species in MoS_2+x force S 3p orbitals to be spatially orthogonal to Mo‑d orbitals. This orthogonal configuration segregates proton capture (S-p states) from N₂ activation (Mo-d states), thereby eliminating direct electronic competition. Furthermore, an integrated “water-in-nitrogen” reactor was implemented to overcome mass-transport limitations. The optimized MoS_2.57 catalyst achieves a peak NH₃ yield rate of 303.63 ± 3.49 μg h⁻¹ mg⁻¹ and 100-hour durability. This work establishes orbital orthogonality as a generalizable strategy for managing competing reactions and demonstrates a versatile co‑design approach from active sites to system architecture for ammonia synthesis. © 2026 The Authors