Boosting Nitrogen Reduction Activity by Defect Engineering in 2D Iron Monochalcogenides FeX (X=S, Se)

Abstract

Large-scale ammonia synthesis under ambient environment is a highly demanding technology which is promising to replace the energy-consuming Haber–Bosch process. Motivated by the crucial iron–sulfur interaction in nitrogenase, the performance of 2D iron monochalcogenides (FeX, X=S, or Se) toward electrochemical nitrogen reduction reaction (e-N2RR) by means of density functional theory calculations is explored. It is confirmed that pristine 2D FeX is inert for even N2 adsorption while defective 2D FeX with single-anion-point vacancy (VX) demonstrates considerable activity for NRR. The enhancement is attributed to the interaction between defect-induced states and p-orbitals of nitrogen, which greatly alters the adsorption behavior of N2 molecule. Meanwhile, the relation between the N2 adsorption free energy and theoretical limiting potential (UL) agrees well with the previous report. Moreover, the 2D nature of FeX provides flexible adsorption sites for both N2 and proton, alleviating the competition between e-N2RR and hydrogen evolution reaction. As the existence of VS and VSe in tetragonal iron monochalcogenides has been validified by experiments, a facile strategy for designing practical and economical NRR electrocatalysts is provided and might be extended to the study of other species of defects in catalysis.