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

Abstract

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.