Efficient Ammonia Production Beginning from Enhanced Air Activation

Abstract Ammonia is considered to be a next‐generation clean energy carrier, and thus the green synthesis of NH 3 is of great importance. In this work, non‐thermal plasma oxidation is combined with electroreduction to achieve an efficient two‐step NH 3 synthesis. A Ti bubbler is introduced in the first step of plasma activation of air to effectively produce nitrate/nitrite (NO x − ) in an absorption solution, and the production rate achieves the highest value of 55.29 mmol h −1 ; the obtained NO x − aqueous solution is directly employed as catholyte for the second step of electroreduction with oxygen vacancy‐rich Co 3 O 4 nanoparticles as the catalyst. Density functional theory calculations reveal that the introduction of oxygen vacancies endows their adjacent Co atoms with improved activity, which promotes adsorption and hydrogenation of NO x − , meanwhile suppressing the hydrogen evolution reaction. Thus the oxygen vacancy‐rich Co 3 O 4 NPs present a significant NH 3 production rate of 39.60 mg h −1 cm −2 , high Faradaic efficiency of 96.08% and a large current density (376.48 mA cm −2 ), outperforming the previously reported ones including N 2 or NO x − electroreduction.