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

Abstract

NH3 is a valuable chemical with a wide range of applications, but the conventional Haber–Bosch process for industrial‐scale NH3 production is highly energy‐intensive with serious greenhouse gas emission. Electrochemical reduction offers an environmentally benign and sustainable route to convert N2 to NH3 at ambient conditions, but its efficiency depends greatly on identifying earth‐abundant catalysts with high activity for the N2 reduction reaction. Here, it is reported that MnO particles act as a highly active catalyst for electrocatalytic hydrogenation of N2 to NH3 with excellent selectivity. In 0.1 m Na2SO4, this catalyst achieves a high Faradaic efficiency up to 8.02% and a NH3 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 *N2 → *N2H transformation being the potential‐determining step in the nitrogen reduction reaction.