Alkylthiol surface engineering: an effective strategy toward enhanced electrocatalytic N2-to-NH3 fixation by CoP nanonarray

Electrosynthesis of NH3 from N2 addresses the need for renewable electricity storage and provides a promising alternative to the Haber–Bosch process. Unfortunately, it is hindered by sluggish kinetics and low faradaic efficiency (FE) due to the strong NN triple bond and competing proton reduction. Herein, we propose that the surface engineering of a CoP nanoarray supported on a titanium mesh using hydrophobic octadecanethiol (C18@CoP/TM) is an effective strategy to enhance the electrocatalytic activity of the CoP nanoarray supported on a titanium mesh for ambient N2-to-NH3 conversion. Such C18@CoP/TM offers an NH3 yield of 1.44 × 10−10 mol s−1 cm−2 and a FE of 14.03% in 0.1 M Na2SO4, surpassing its CoP/TM counterpart (0.783 × 10−10 mol s−1 cm−2, 5.83%). Moreover, C18@CoP/TM also shows steady NH3 yield and FE in a six-cycle test with high durability. Density functional theory calculations reveal that modifying CoP with a C18 layer leads to a regulated surface electronic structure, which further promotes the catalytic formation of NH3.