Comparison between Fe₂O₃/C and Fe₃C/Fe₂O₃/Fe/C Electrocatalysts for N₂ Reduction in an Alkaline Electrolyte

Abstract

Cost-effective and nonprecious iron-based catalysts were synthesized, evaluated, and compared for electrocatalytic N2 reduction reaction (NRR) under alkaline conditions in the potential range from −0.4 to 0.1 V [vs reversible hydrogen electrode (RHE)] at low temperature (≤60 °C) and atmospheric pressure. The tested H-type cell was separated by an anion exchange membrane in 6 M KOH alkaline electrolyte (pH = over 14) in order to minimize hydrogen evolution reaction and to directly form NH3 gas. The amount of ammonia synthesized was quantified using an indophenol blue method and cross-checked with 1H nuclear magnetic resonance spectroscopy and ion chromatography using both 14N2 and 15N2 gases. Because of the synergistic effect between the Fe3C, Fe2O3, and Fe composites in the NRR, both the ammonia formation rate and faradaic efficiency in Fe3C/Fe2O3/Fe/C were approximately fourfold higher than those in Fe2O3/C at 60 °C and 0.1 V (vs RHE). These results can provide insights into designing Fe-based electrocatalysts for NRR at atmospheric pressure.

Cu-Doped Fe2O3 Nanorods for Enhanced Electrocatalytic Nitrogen Fixation to Ammonia

“…–1 and 16.4%, respectively. This optimum performance of Cu–Fe 2 O 3 -1 is comparable to or even exceeds those of recently reported Fe oxide-based electrocatalysts, ,− ,− ,− and the marked FE is higher than that of Zn-doped Fe 2 O 3 , as expected in the Introduction. Upon shifting the applied potential in a negative direction beyond −0.20 V, both NH 3 formation rate and FE gradually decreased because of the competing HER process (Figure S14), whereas the smaller FE observed at −0.10 V is likely due to uncontrollable experimental error and the capacitance of the carbon support. , The durability of Cu–Fe 2 O 3 -1 was evaluated by conducting a consecutive cycling test and a long-term chronoamperometry measurement.…”

Revisiting the Electrochemical Nitrogen Reduction on Molybdenum and Iron Carbides: Promising Catalysts or False Positives?

“…The peaks between 45 and 60° in Figure b correspond to orthorhombic iron carbide (θ-Fe 3 C, PDF 00-035-0772). The formation of other Fe oxidation states, such as reduced Fe (53.3°), Fe 3 O 4 (41.3, 35, and 74.2°), and Fe 2 O 3 (38.6°) are inevitable by-products of the carburization process. , Also, small fractions of Fe 3 O 4 (41.4° and 74°) were identified in Figure c after the thermal decomposition of Fe(CO) 5 , while the multiplet between 49 and 55° is very typical for χ-Fe 5 C 2 (PDF 01-080-4102). The average crystallite size was calculated with the Scherrer equation (eq ) and summarized in Table S1.…”

Electrochemical nitrogen reduction to ammonia using mesoporous iron oxide with abundant oxygen vacancies

“…15 For these reasons, a variety of Fe oxides have been extensively studied as NRR electrocatalysts. 16–29…”