Iron-Doped Cobalt Phosphide Nanohoops for Electroreduction of Nitrate to Ammonia

Heteroatom doping can effectively tune the electronic structure of an electrocatalyst to accelerate the adsorption/desorption of reaction intermediates, which sharply increases their intrinsic electroactivity. Herein, we successfully prepare iron (Fe)-doped cobalt phosphide (CoP) nanohoops (Fe/CoP NHs) with different Fe/Co atomic ratios as highly active electrocatalysts for the nitrate electrocatalytic reduction reaction (NIT-ERR). Electrochemical measurements reveal that appropriate Fe doping can improve the electroactivity of cobalt phosphide nanohoops for the NIT-ERR. In a 1 M KOH electrolyte, the Fe/CoP NHs with the optimized chemical composition can achieve an efficient ammonia (NH₃) generation rate of 27.6 mg h^-1 mg_cat^-1 for the conversion of NO₃^- into NH₃ and a Faradaic efficiency of 93.3% at a -0.25 V potential, which exceed the values of various previously reported nanomaterials in an alkaline electrolyte.