Pulse-Electrodeposited Single-Atom Alloys with Steered Surface Hydrogenation Dynamics for Air-to-Fertilizer Synthesis

Harnessing renewable electricity to transform abundant environmental resources into fertilizers is central to sustainable development. Electrochemical nitrate-to-ammonia conversion provides a promising route, yet its efficiency is constrained by the elusive surface hydrogenation dynamics governing multi-step *NO_x reduction. Here, a cooperative descriptor (Ψ) derived from large-language-models-assisted mining and energetic analysis successfully identifies NiCu single-atom alloys (SAAs) as optimal catalysts. Pulse electrodeposition delivers atomically dispersed alloys with tunable structures, achieving a maximum Faradaic efficiency (FE) of ∼95% and yield rate (YR) of ∼11.4 mg h^-1 cm^-2. In situ surface-interrogation scanning electrochemical microscopy (SI-SECM) provides quantitative information on the time-resolved surface-active hydrogen (*H) generation-consumption and *NO_x hydrogenation rate constants (NiCu > CoCu ≫ MnCu ≈ FeCu > Cu), directly aligning surface kinetics with selectivity. Theoretical investigations further confirmed that Ni doping lowers the barriers for *H formation and *NO_x hydrogenation. A plasma-electrochemical-CO₂ capture system demonstrated continuous "air-to-fertilizer" conversion with reduced energy consumption and potential net-negative emissions. These results establish a transferable design rule that bridges theoretical descriptors with operando hydrogenation dynamics, providing a mechanistic foundation and practical pathway toward scalable, zero-carbon fertilizer production.