Nitrogen Allotrope N6 Enables Electrocatalytic Ammonia Synthesis under Anodic Polarization

Electrocatalytic ammonia synthesis using N ₂ as reactant is hampered by the low Faradaic efficiency due to the competing hydrogen evolution reaction under cathodic potential conditions. This limitation can be overcome by exchanging N ₂ for the nitrogen allotrope N ₆ , which shifts the equilibrium potential for electrocatalytic ammonia formation by several hundred millivolts toward anodic conditions. Here we exemplify the electrochemical N ₆ reduction to ammonia using single-atom centers of molybdenum-based MXenes as a model electrocatalyst. Using a combination of different in silico methods, we demonstrate that electrocatalytic ammonia formation under positive bias is possible without concomitant hydrogen evolution. The application of allotropes for nitrogen conversion opens new avenues for the targeted synthesis of basic chemicals in electrochemical systems through the efficient use of green electrons and protons.