Enhancing electrocatalytic N2-to-NH3 fixation by suppressing hydrogen evolution with alkylthiols modified Fe3P nanoarrays

Electrocatalytic N2 reduction provides an attractive alternative to Haber-Bosch process for artificial NH3 synthesis. The difficulty of suppressing competing proton reduction, however, largely impedes its practical use. Herein, we design a hydrophobic octadecanethiol-modified Fe3P nanoarrays supported on carbon paper (C18@Fe3P/CP) to effectively repel water, concentrate N2, and enhance N2-to-NH3 conversion. Such catalyst achieves an NH3 yield of 1.80 × 10−10 mol·s−1·cm−2 and a high Faradaic efficiency of 11.22% in 0.1 M Na2SO4, outperforming the non-modified Fe3P/CP (2.16 × 10−11 mol·s−1·cm−2, 0.9%) counterpart. Significantly, C18@Fe3P/CP renders steady N2-fixing activity/selectivity in cycling test and exhibits durability for at least 25 h. First-principles calculations suggest that the surface electronic structure and chemical activity of Fe3P can be well tuned by the thiol modification, which facilitates N2 electroreduction activity and catalytic formation of NH3.