Efficient nitrogen reduction to ammonia by fluorine vacancies with a multi-step promoting effect

Abstract

Improving the performance of catalysts by adjusting the vacancy engineering is currently one of the main ways to design effective catalysts. However, there are no reports in the literature on the influence that fluorine vacancies (FVs) have on the electronic structures of materials. In this work, we report the generation of FVs for the first time and discuss in depth their regulation mechanism on materials and their role in the electrochemical N₂ reduction reaction (NRR). The catalyst optimized by FVs showed good NRR performance in Li₂SO₄ solution. At 0 V vs. RHE, the faradaic efficiency (FE) reaches the highest value of 36.01%. When the potential is increased to −0.10 V vs. RHE, the highest ammonia yield is 7.99 μg h⁻¹ cm⁻². The specific activity of the FV-optimized LaF₃ nanosheets (NSs) is 9.5 times higher than that of the defect-free LaF₃ NSs. It is currently reported as the most effective non-noble metal catalyst in the nitrogen reduction process under low overpotential. In addition, this catalyst also demonstrates long-term structural stability. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) show that the LaF₃ NSs with the optimal defects have a multi-step promoting effect.