Site-Specific Functioning of CuN₃-PdS₃ Janus Dual-Atom Sites Enable Near-Unity Faradaic Efficiency for Nitrate...

Electrochemical nitrate reduction reaction (NO₃RR) using renewable electricity offers a carbon-free and energy-saving route to remediating nitrate-polluted wastewater while producing ammonia (NH₃). However, conventional catalysts for NO₃RR suffer from strong adsorption of NO_x intermediates that hinders further hydrogenation, resulting in diminished selectivity and catalyst deactivation. Here we construct a Janus-type CuN₃-PdS₃ dual-atom catalyst featuring N/S dual bridging, namely CuPd-SNC, to enable decoupled NO_x species adsorption and hydrogen supply for hydrogenation on Cu and Pd sites, respectively. Excitingly, CuPd-SNC delivers a near-unity Faradaic efficiency of 99.58% for NH₃ synthesis and a production rate of 1.34 mmol h^-1 cm^-2. When integrated into a Zn-nitrate battery, CuPd-SNC achieves a maximum power density of 13.0 mW cm^-2 and demonstrates stable operation for >160 h. In situ spectroscopic and theoretical analyses reveal the site-specific functionalities of the CuN₃-PdS₃ Janus configuration, wherein Cu sites markedly enhance the adsorption/activation of NO_x ^- intermediates, Pd sites enable continuous proton supply and reduce the energy barriers for multi-step *NO_x hydrogenation, while N/S dual bridges serve as a proton reservoir. These findings highlight the site-specific but complementary functioning of dual-atom catalysts in synergistically pushing the limit of conventional electrocatalysts, offering fundamental insights into the rational catalyst design for NH₃ synthesis.