Synergistic Effects of Fe ₂ O ₃ Clusters and Iron Phthalocyanine on Carbon Nanotubes for Enhanced Electrochemical Nitrate Reduction

The electrochemical nitrate reduction reaction (NO₃RR) has attracted considerable attention for the sustainable production of NH₃, urea, amino acids, and other value-added chemicals. Among these, NH₃ is particularly significant due to its large-scale industrial synthesis via the Haber-Bosch process. Herein, we report the design of an efficient NO₃RR catalyst prepared through a simple synthesis route. Fe₂O₃ clusters (2-5 nm) were uniformly deposited on iron phthalocyanine (FePc)-modified N-doped carbon nanotubes (Fe₂O₃/FePc/CNT), yielding a high NH₃ production rate of 58.67 mg h^-1 cm^-2 with a Faradaic efficiency (FE) of 81.89% at -1.0 V versus RHE. Comparative studies with FePc/CNT, Pc/CNT, and Fe₂O₃/CNT confirmed the synergistic effect between Fe₂O₃ clusters and FePc, with the optimized Fe₂O₃/FePc/CNT catalyst showing superior activity and selectivity. Furthermore, the optimized catalyst exhibited excellent stability for 24 h. A possible mechanism for NH₃ formation is proposed on the basis of the reaction intermediates identified by ex situ FTIR and x-ray photoelectron spectroscopy (XPS) analyses.