Efficient electrocatalytic nitrogen reduction to ammonia with FeNi-Co/carbon mat electrodes

Abstract

Electrochemical nitrogen reduction reaction has recently received increasing attention due to its ability to synthesize ammonia under ambient conditions. However, the low ammonia yields and Faradaic efficiency hinder its further development, which necessitates the use of high-performance catalysts. Hence, in this study, a self-supporting carbon mat with FeNi-doped Co catalysts (Fe1Ni0.2Co145) fabricated by electrospinning was used as an electrode (FeNi-Co@CM) for electrochemical ammonia synthesis. The electrochemical performance of the FeNi-Co@CM electrode is evaluated in a three-electrode setup with FeNi-Co@CM as working electrode, a platinum mesh as counter electrode, and a Ag/AgCl electrode as reference electrode. The experimental investigations produce an ammonia yield rate of 27.9 μg h−1 mg−1 and a Faradaic efficiency of 1.52 % in 1.0 M KOH, which is higher than most of the reported data where iron-group-based electrocatalysts were employed. The verification results from multiple sets of control experiments indicated that the ammonia detected is generated by the nitrogen reduction reaction rather than the contaminants in the surrounding environment. In addition, the results of the stability test show that the FeNi-Co@CM electrode can maintain a high level of ammonia production for more than ten cycles. The working mechanism of nitrogen reduction reaction based on FeNi-Co@CM electrode is also discussed at various scales, including the electrode scale, the catalyst scale, and the atomic scale. This study therefore provides an in-depth understanding of the nitrogen reduction reaction from various perspectives, such as mass transport, reaction interfaces, and reaction intermediates.