Oxygen vacancy modulation in interfacial engineering Fe₃O₄ over carbon nanofiber boosting ambient electrocatalytic N₂...

The oxygen vacancy modulation of interface-engineered Fe₃O₄ nanograins over carbon nanofiber (Fe@CNF) was achieved to improve electrocatalytic nitrogen reduction reaction (NRR) activity and stability via facile electrospinning and tuning thermal procedure. The optimal catalyst calcined at 800 ℃ (Fe@CNF-800) was endowed with abundant nanograin boundaries and optimized oxygen vacancy (V_o) concentration of iron oxides, thereby affording 37.1 μg h^-1 mg_cat.^-1 (-0.2 V vs. reversible hydrogen electrode (RHE)) NH₃ yield and rational Faraday efficiency (10.2%), with 13.6 times atomic activity enhancement compared to of that commercial Fe₃O₄. The interfacial effect of assembled nanograins in particles correlated with the formation of V_o and more intrinsic active sites, which is conducive to the trapping and activation of nitrogen (N₂). The in-situ X-ray photoelectron spectroscopy (XPS) measurement revealed the real consumption of adsorbed oxygen when introducing N₂ by the trapping effect of V_o. Density-Functional-Theory (DFT) calculation validates the promotive hydrogenation effect and elimination of hydrogen intermediate (H*) interacted with N₂ transferring toward oxygen of the support. The optimal catalyst shows a lasting NRR activity at least 90 h, outperforming most reported Fe-based NRR catalysts.