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.