Electrocatalytic Hydrogenation of N2 to NH3 by MnO: Experimental and Theoretical Investigations

NH 3 is a valuable chemical with a wide range of applications, but the conventional Haber–Bosch process for industrial-scale NH 3 production is highly energy-intensive with serious greenhouse gas emission. Electrochemical reduction offers an environmentally benign and sustainable route to convert N 2 to NH 3 at ambient conditions, but its efficiency depends greatly on identifying earth-abundant catalysts with high activity for the N 2 reduction reaction. Here, it is reported that MnO particles act as a highly active catalyst for electrocatalytic hydrogenation of N 2 to NH 3 with excellent selectivity. In 0.1 m Na 2 SO 4 , this catalyst achieves a high Faradaic efficiency up to 8.02% and a NH 3 yield of 1.11 × 10 −10 mol s −1 cm −2 at −0.39 V versus reversible hydrogen electrode, with great electrochemical and structural stability. On the basis of density functional theory calculations, MnO (200) surface has a smaller adsorption energy toward N than that of H with the *N 2 → *N 2 H transformation being the potential-determining step in the nitrogen reduction reaction.