Plasma-assisted ammonia synthesis over Ni/LaOF: Dual active centers consisting of oxygen vacancies and Ni

Ammonia (NH3) is one of the most important chemicals and can also be used as an energy storage carrier. The catalytic synthesis of ammonia coupled with plasma can be achieved under mild conditions. Currently, the efficiency of the plasma catalytic ammonia synthesis is low. Herein we demonstrate the ammonia synthesis on nNi/LaOF (n = 0, 0.25, 0.5) containing dual active sites via atmospheric pressure packed-bed dielectric barrier discharge (AP-PBDBD). The 0.5Ni/LaOF sample resulted in an ammonia synthesis rate at least 30 times higher than that under the only plasma. The vibrationally-excited N2 in plasmas is activated and adsorbed by oxygen vacancy on Ni/LaOF surface. The adsorbed N2 and the H atoms on Ni gradually undergo a hydrogenation reaction to produce NH3. Our results illustrate the role of dual active centers, i.e., the oxygen vacancies and Ni, and introduce a design concept of the catalyst with dual active centers for plasma-assisted ammonia synthesis.