FeCoS2/Co4S3/N-doped graphene composite as efficient electrocatalysts for overall water splitting

Abstract

Transition metal sulfide is a kind of electrocatalyst with appropriate cost, high efficiency, and stability. However, introducing additional metal atoms into transition metal complexes to form ternary compounds can more effectively optimize the electronic structure and improve its catalytic performance. In this work, FeCoS2/Co4S3 nanoparticles were groundbreakingly synthesized and loaded on nitrogen-doped graphene foam (NGF) with a 3D network structure by facile hydrothermal synthesis and simple chemical vapor deposition (CVD) process. The transition metal sulfide nanoparticles were uniformly distributed on the surface of NGF substrates. The transition metal sulfide nanostructures can provide a larger surface area, enhance the interaction with the medium, and improve the electrocatalytic performance. The synthesized FeCoS2/Co4S3/NGF catalyst exhibits enhanced HER and OER catalytic performance in 1 M KOH, with overpotentials of 172 mV for the HER and 276 mV for the OER at a current density of 10 mA·cm−2. The performance of the FeCoS2/Co4S3/NGF hybrid catalyst could match the best Fe-Co-S bifunctional electrocatalysts reported in the literature. Strong evidence supports that the FeOOH/CoOOH species in situ formed on the surface of FeCoS2/Co4S3/NGF catalyst was the actual catalytic active substance towards OER. In addition, the Tafel slope, TOF, EIS, and stability test results collaboratively support that Fe-Co-S/NGF shows great potential to be used as a bifunctional electrocatalyst for large-scale overall water electrolysis.