Ammonia Synthesis under Ambient Conditions: Insights into Water-Nitrogen-Magnetite Interfaces

Abstract

New routes for transforming nitrogen into ammonia at ambient conditions would be a milestone toward an energy efficient and economically attractive production route in comparison to the traditional Haber-Bosch process. Recently, the synthesis of ammonia from water and nitrogen at room temperature and atmospheric pressure has been reported to be catalyzed by Fe3O4 at the air-water interface. By integrating ambient pressure X-ray photoelectron spectroscopy and ab initio molecular dynamics and free energy calculations, we investigate the underlying thermodynamic mechanisms governing ammonia and hydrazine formation at the water-Fe3O4-nanoparticle interface. We find that, unlike pure Fe3O4 where N2 can only interact with a limited number of Fe sites, hydroxylated species introduce large and diverse adsorption geometries where N2 can bind through either Fe sites or Fe-OH groups, each of which are capable of independently facilitating proton-coupled electron transfer.