Electrocatalytically Active Fe-(O-C₂ )₄ Single-Atom Sites for Efficient Reduction of Nitrogen to Ammonia

Single-atom catalysts have demonstrated their superiority over other types of catalysts for various reactions. However, the reported nitrogen reduction reaction single-atom electrocatalysts for the nitrogen reduction reaction exclusively utilize metal-nitrogen or metal-carbon coordination configurations as catalytic active sites. Here, we report a Fe single-atom electrocatalyst supported on low-cost, nitrogen-free lignocellulose-derived carbon. The extended X-ray absorption fine structure spectra confirm that Fe atoms are anchored to the support via the Fe-(O-C₂ )₄ coordination configuration. Density functional theory calculations identify Fe-(O-C₂ )₄ as the active site for the nitrogen reduction reaction. An electrode consisting of the electrocatalyst loaded on carbon cloth can afford a NH₃ yield rate and faradaic efficiency of 32.1 μg h^-1  mg_cat. ^-1 (5350 μg h^-1  mg_Fe ^-1 ) and 29.3 %, respectively. An exceptional NH₃ yield rate of 307.7 μg h^-1  mg_cat. ^-1 (51 283 μg h^-1  mg_Fe ^-1 ) with a near record faradaic efficiency of 51.0 % can be achieved with the electrocatalyst immobilized on a glassy carbon electrode.