Boron induced electron-rich single iron sites for boosted N2 electroreduction reaction

Abstract

Electrochemical N2 reduction to NH3 offers a mild and feasible alternative to Haber-Bosch NH3 synthesis. Designing a promising nitrogen reduction reaction (NRR) catalyst under alkaline condition is highly desirable due to the advantages of alkaline electrolyte in fast charge transfer and limiting the hydrogen evolution reaction. However, the ammonia yield rate of iron single-atom catalysts is lower, usually below 40 µg h−1 mg−1cat. Herein, the Fe sites supported on boron, nitrogen co-doped carbon with atomic dispersion (Fe-B/NC) catalyst was synthesized by the pre-polymerization and pyrolysis processes. This catalyst exhibits a NH3 yield 88.7 µg h−1 mg−1cat at −0.45 V (vs. RHE) an alkaline electrolyte, which is greater than the values reported in the literature. Combining experimental analysis with DFT calculations, we demonstrate that the introduction of B coordination breaks the symmetric electron distribution of the FeN4 strategy to regulate its N2 adsorption, activation and thus the NRR performance. The synergistic effect between B and Fe can effectively activate the adsorbed N2 molecules to achieve excellent NRR performance.