Uniform Formation of Amorphous Cobalt Phosphate on Carbon Nanotubes for Hydrogen Evolution Reaction†

Main observation and conclusion Tremendous efforts have been made to the development of highly active, stable hydrogen evolution reaction (HER) electrocatalysts based on earth‐abundant metal compounds. Recently, cobalt phosphorus (Co‐P) catalysts have received particular attention owing to their good performances for the HER. However, the reported Co‐P catalysts were not uniformly anchored on the substrates. Hence, developing Co‐P catalysts with a uniform surface structure for HER remains a major challenge. Herein, we utilized small molecule tris(4‐fluorophenyl)phosphane (PF) for preliminarily functionalizing carbon nanotubes (PF‐CNTs) via π–π stacking interactions. Using these as the substrate, amorphous cobalt phosphate (CoPi) catalysts could then be uniformly anchored on PF‐CNTs by electrodeposition method. These obtained CoPi/PF‐CNTs catalysts show an onset potential low to 29 mV, a low overpotential (105 mV in 0.5 mol/L H 2 SO 4 at a current density of 10 mA·cm –2 with a Tafel plot of 32 mV·dec –1 ) and an excellent stability for HER in acidic electrolyte, which is a promising noble‐metal‐free HER catalyst.