Charge transfer and vacancy engineering of Fe2O3 nanoparticle catalysts for highly selective N2 reduction towards NH3 synthesis.

The development of electrocatalysts for N2 reduction reaction (NRR) is significant for scalable and renewable NH3 synthesis, but calls for a technology innovation to overcome the specific problems of low efficiency and poor selectivity. Herein, we prepare a core-shell nanostructure by coating polypyrrole (PPy) onto sulfur-doped iron oxide nanoparticles (denoted as S-Fe2O3@PPy) as the highly selective and durable electrocatalysts for NRR under ambient conditions. Sulfur doping and PPy coating remarkably improve the charge transfer efficiency of S-Fe2O3@PPy, and the interactions between PPy and Fe2O3 nanoparticles produce abundant oxygen vacancies as active sites for NRR. This catalyst achieves an NH3 production rate of 22.1 μg h-1 mgcat-1 and a very-high Faradic efficiency of 24.6%, surpassing other Fe2O3 based NRR catalysts. Density functional theory calculations show that the S-coordinated iron site can successfully activate the N2 molecule and optimize the energy barrier during the reduction process, resulting in a small theoretical limiting potential.