One-step synthesis of amorphous transition metal sulfides as bifunctional electrocatalysts for the hydrogen evolution reaction and oxygen evolution reaction

Abstract

The search for efficient and stable bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is very important for the practical application of water splitting under alkaline conditions. Although transition metal-based sulfide catalysts have been widely studied as effective catalysts for the HER and OER in alkaline media, their electrocatalytic performances are much lower than those of noble metal catalysts, and their synthesis process is too cumbersome. Here, we report the synthesis of amorphous transition metal-based sulfides (NiSx, CuSx and FeSx) through facile one-step sulfuration of metal foam, exhibiting excellent bifunctional performance and durability towards alkaline hydrogen evolution and oxygen evolution reactions. Inspiringly, NiSx/NF only requires a low overpotential of 53 and 225 mV for the HER and OER to drive a current density of 10 mA cm⁻², and has high durability for the HER and OER for up to 100 hours at a current density of 100 mA cm⁻² in 1 M KOH solution. The superior catalytic activity is attributed to more exposed active sites, accelerated HER and OER kinetics and its unique amorphous structure. This important discovery opens a new possibility for the simple synthesis and demonstration of earth-abundant transition metal sulfide electrocatalysts for sustainable energy production.