Surface hydrophobic modification of MXene to promote the electrochemical conversion of N2 to NH3

Hydrophobic treatment of the catalyst surfaces can suppress the competitive hydrogen evolution reaction (HER) during the nitrogen reduction reaction (NRR). In this work, the surface of Ti3C2Tix MXene is modified by cetyltrimethylammonium bromide (CTAB) and trimethoxy (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) silane (FOTS) to increase the hydrophobicity of MXenes. The ammonia (NH3) production rate and faradaic efficiency (FE) are improved from 37.62 to 54.01 μg h−1 mg−1cat. and 5.5% to 18.1% at −0.7 V vs. RHE, respectively after surface modification. 15N isotopic labeling experiment confirms that nitrogen in produced ammonia originates from N2 in the electrolyte. The excellent NRR activity of surface hydrophobic MXenes is mainly due to surfactant molecules, which inhibit the entry of water molecules and the competitive HER, which have been verified by in situ FT-IR, DFT and molecular dynamics calculations. This strategy provides an ingenious method to design more active NRR electrocatalysts.