Highly efficient metal–organic-framework catalysts for electrochemical synthesis of ammonia from N2 (air) and water at low temperature and ambient pressure

Abstract

Metal–organic-frameworks (MOFs) (i.e., MOF(Fe), MOF(Co) and MOF(Cu)) were synthesized by a hydrothermal process. The prepared MOFs were characterized using X-ray diffraction, Fourier transform infrared spectroscopy and N2 adsorption–desorption. The catalytic activities of the MOFs for the electrochemical synthesis of ammonia were evaluated when using N2 (air) and water as raw materials at low temperature and ambient pressure. The results indicated that the prepared MOFs have fine crystalline structures, abundant micropores, and large specific surface areas. The prepared MOFs showed excellent catalytic activity for the electrochemical synthesis of ammonia at low temperature and ambient pressure. Among these MOFs, the MOF(Fe) displayed the best catalytic activity, and the highest ammonia formation rate and the highest current efficiency reached 2.12 × 10−9 mol s−1 cm−2 and 1.43%, respectively, at 1.2 V and 90 °C, when using pure N2 and water as raw materials. The prepared MOFs in this work showed remarkable catalytic activities for the electrochemical synthesis of ammonia at low temperature and ambient pressure among the non-noble metal catalysts. It was the first exploration to apply MOFs as the electrocatalysts for the electrochemical synthesis of ammonia at low temperature and ambient pressure.