Ambient ammonia production via electrocatalytic nitrite reduction catalyzed by a CoP nanoarray

Industrial-scale ammonia (NH₃) production mainly relies on the energy-intensive and environmentally unfriendly Haber-Bosch process. Such issue can be avoided by electrocatalytic N₂ reduction which however suffers from limited current efficiency and NH₃ yield. Herein, we demonstrate ambient NH₃ production via electrochemical nitrite (NO₂^–) reduction catalyzed by a CoP nanoarray on titanium mesh (CoP NA/TM). When tested in 0.1 M PBS (pH = 7) containing 500 ppm NO₂^–, such CoP NA/TM is capable of affording a large NH₃ yield of 2, 260.7 ± 51.5 μg·h^–1·cm^–2 and a high Faradaic efficiency of 90.0 ± 2.3% at –0.2 V vs. a reversible hydrogen electrode. Density functional theory calculations reveal that the potential-determining step for NO₂^– reduction over CoP (112) is *NO₂ → *NO₂H.