Electrocatalytic nitrate reduction reaction (NO₃⁻RR) emerges as a highly efficient approach toward ammonia synthesis and degrading NO₃⁻ contaminant. In our study, CeO₂ nanoparticles with oxygen vacancies (V_O) decorated N-doped carbon nanorods on graphite paper (CeO_2−x@NC/GP) were demonstrated as a highly efficient NO₃⁻RR electrocatalyst. The CeO_2−x@NC/GP catalyst manifests a significant NH₃ yield up to 712.75 μmol·h⁻¹·cm⁻² at −0.8 V vs. reversible hydrogen electrode (RHE) and remarkable Faradaic efficiency of 92.93% at −0.5 V vs. RHE under alkaline conditions, with excellent durability. Additionally, an assembled Zn-NO₃⁻ battery with CeO_2−x@NC/GP as cathode accomplishes a high-power density of 3.44 mW·cm⁻² and a large NH₃ yield of 145.08 μmol·h⁻¹·cm⁻². Density functional theory results further expose the NO₃⁻ reduction mechanism on CeO₂ (111) surface with V_O.

NH₃ is an essential feedstock for fertilizer synthesis. Industry-scale NH₃ synthesis mostly relies on the Haber–Bosch method, however, which suffers from massive CO₂ emission and high energy consumption. Electrocatalytic NO₃^– reduction is an attractive substitute to the Haber–Bosch method for synthesizing NH₃ under mild conditions. As this reaction will produce a variety of products, it highly desires efficient and selective electrocatalyst for NH₃ generation. Here, we report in situ grown Fe₃O₄ particle on stainless steel (Fe₃O₄/SS) as a high-efficiency electrocatalyst for NO₃^– reduction to NH₃. In 0.1 M NaOH with 0.1 M NaNO₃, such Fe₃O₄/SS reaches a remarkable Faradaic efficiency of 91.5% and a high NH₃ yield of 10,145 μg·h^–1·cm^–2 at –0.5 V vs. reversible hydrogen electrode (RHE). Furthermore, it owns robust structural and electrochemical stability. This work provides useful guidelines to expand the scope of metallic oxide electrocatalysts for NH₃ synthesis. The catalytic mechanism is uncovered and discussed further by theoretical calculations.

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.