Palladium-Doping-Enabled Interface Synergy for Superb Ampere Level Ammonia Electrosynthesis From Nitrate

The practical electrocatalytic nitrate-to-ammonia conversion suffers from insufficient performance at industrial current densities. Here, we report an electrochemically reconstructed Pd-doped Co catalyst that achieves > 98.0% ammonia Faradaic efficiency at an ultrahigh partial current density of ‒1.43 A cm^-2 and operates stably for over 170 h. Integrated in situ spectroscopy and theoretical simulations reveal a dual-enhancement mechanism, in which Pd doping lowers the energy barrier of the rate-determining *NO hydrogenation step and reconstructs the interfacial microenvironment. This restructuring promotes cation enrichment and establishes a dynamic hydrogen-down-oriented water network, facilitating proton transfer and intermediate stabilization under high-flux conditions. Unlike its role in Cu-based systems, Pd in the Co matrix distinctly optimizes the kinetics of surface intermediates, enhances the local interfacial electric field, and increases the flexibility of the hydrogen-bond network. This work demonstrates the critical synergy between atomic-site engineering and microenvironment control for achieving high-rate electrocatalysis beyond conventional electronic modulation.