Nitrogen electrochemically reduced to ammonia with hematite: density-functional insights

Licht et al. ( Science , 2014, 345 , 637) recently proposed a procedure to synthesize NH 3 from N 2 and by steam electrolysis in molten hydroxide suspensions of nano-Fe 2 O 3 . This highly exciting investigation undoubtedly boosts the hope of the CO 2 -free and low-cost ammonia industry. To provide insights at the atomistic level into the reduction process of N 2 , we have carried out a density-functional study on the electrochemical formation of NH 3 molecules on hematite(0001) surfaces. By considering associative and dissociative mechanisms, we have identified a reaction path that requires an applied bias of −1.1 V to allow the proton transfer processes to occur downhill. The most energy-demanding step is the addition of the first proton to the adsorbed molecular nitrogen. The computed bias is in good agreement with experimental electrolysis potentials that activate the electric current. Licht et al. recently proposed a procedure to synthesize NH 3 from N 2 and steam electrolysis in molten hydroxide suspensions of nano-Fe 2 O 3 .