Abstract

Electrochemical nitrogen reduction reaction (eNRR) in aqueous media remains challenging due to the competing hydrogen evolution reaction (HER). Herein, we report an electrode with a synergistic combination of MoS2/FeS2 composite catalyst and ionic liquid surface coating to address this challenge. The electrodes are characterized by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). A small amount of ionic liquid coating ([BMPyrr][TFSI] or [P6,6,6,14][TFSI]) is incorporated into the catalyst inks to create a hydrophobic microenvironment on the catalyst surface to modulate HER/NRR selectivity and stability of nitrogen intermediates, as confirmed by differential electrochemical mass spectrometry (DEMS) and in situ Raman spectroscopy. Electrolysis results demonstrate a significant improvement in faradaic efficiency and ammonia yield from 1.4% and 0.7 & micro;g h-1 cm-2 for pristine MoS2 to 19.6% and 12.2 & micro;g h-1 cm-2, respectively, with [P6,6,6,14] [TFSI]-coated electrodes. Pressurized operation with a fixed gas volume (5 bar N2) produces a faradaic efficiency of 35.1% and ammonia yield of 10.1 & micro;g h-1 cm-2. 24 h continuous electrolysis confirms the stability of this platform for green ammonia synthesis.