Efficient Ammonia Production Beginning from Enhanced Air Activation

摘要

Ammonia is considered to be a next-generation clean energy carrier, andthus the green synthesis of NH_3 is of great importance. In this work, nonthermalplasma oxidation is combined with electroreduction to achieve anefficient two-step NH_3 synthesis. A Ti bubbler is introduced in the first stepof plasma activation of air to effectively produce nitrate/nitrite (NO_x~?) in anabsorption solution, and the production rate achieves the highest value of55.29 mmol h~(?1); the obtained NO_x~? aqueous solution is directly employed ascatholyte for the second step of electroreduction with oxygen vacancy-richCo_3O_4 nanoparticles as the catalyst. Density functional theory calculationsreveal that the introduction of oxygen vacancies endows their adjacent Coatoms with improved activity, which promotes adsorption and hydrogenationof NO_x~?, meanwhile suppressing the hydrogen evolution reaction. Thus theoxygen vacancy-rich Co_3O_4 NPs present a significant NH3 production rateof 39.60 mg h~(?1) cm~(?2), high Faradaic efficiency of 96.08 and a large currentdensity (376.48 mA cm~(?2)), outperforming the previously reported onesincluding N_2 or NO_x~? electroreduction.