Constructing bifunctional Fe7S8/CoS heterostructures for efficient water electrolysis

Pyrrhotite Fe7S8 has inferior catalytic performance in electrochemical water splitting due to its poor electrical conductivity. The construction of interface-type materials results in exposing more active sites, in turn, boosting the conductivity and electrochemical activity. Herein, we successfully fabricate Fe7S8/CoS heterostructures to mediate the reactivity in water electrolysis. The formation of heterointerfaces between Fe7S8 and CoS is confirmed by structural characterization. The as-prepared Fe7S8/CoS heterostructures exhibit remarkable activity in water oxidation reaction with 241 mV at 10 mA/cm2, superior to RuO2. Compared with Fe7S8, the heterointerfaces in Fe7S8/CoS heterostructures significantly enhance water reduction reaction activity. Moreover, Fe7S8/CoS heterostructures require 1.68 V to reach 10 mA/cm2 in water electrolysis reaction, which outperforms most the reported Fe7S8-based materials. The interface structures between Co-S and Fe-S provide the rich active sites and accelerate the electron diffusion rate, resulting in the excellent water electrolysis activity. Our work offers a one-pot method for the fabrication of heterostructures to tailor intrinsic catalytic activity of Fe7S8 by interface engineering.