Construction of Carbon Nanotube-Supported CuO-Fe3O4 Dual-Site Catalysts for Ambient Electrosynthesis of Ammonia

Abstract

Electrocatalytic nitrate (NO3⁻) reduction reaction (NitRR) to ammonia (NH3) is considered a sustainable and environmentally friendly approach for synthesizing ammonia. However, the electrocatalyst encounters challenges related to the limited distribution of NO3⁻ and insufficient active hydrogen on the catalyst surface, which result from the high concentration of NO3⁻ and the difficulty of water splitting under ambient conditions. Here, by introducing Cu and Fe oxides onto carbon nanotube substrates (CuO-Fe3O4/CNT), a CuO-Fe3O4 dual-site synergistic catalytic mechanism is proposed to promote the adsorption and conversion of NO 3 ⁻ at CuO site and accelerate water splitting at Fe3O4 site, thereby significantly enhancing the performance of nitrate reduction reactions. The as-synthesized CuO-Fe3O4/CNT exhibits good activity for NitRR, achieving an NH3 yield rate of 39.2 ± 3.5 mg h-1 mg cat.-1 and a Faradaic efficiency of 90.5 ± 2.2% at -0.8 V (vs. RHE). Furthermore, different in-situ characterizations were employed to identify intermediates in the electrocatalytic NitRR process, confirming CuO-Fe3O4/CNT as a promising catalyst for NH3 electrosynthesis.