Triangular nanosheet arrays of O-doped Co/Fe disulfides as highly efficient electrocatalysts for the hydrogen evolution reaction

Abstract

The development of inexpensive and efficient electrocatalysts is of significance for the hydrogen evolution reaction (HER) involved in water splitting. In this work, we report triangular nanosheet arrays of O-doped Co/Fe disulfides (labelled O-(CoFe)S2-x-y, in which x is the Fe concentration and y is the sulfurization temperature) grown on carbon cloth (CC). With the Co-MOF as precursor, Fe was introduced by ligand exchange, and O-doped metal sulfides were achieved via calcination followed by sulfurization. An optimized sample of CC@O-CoFeS-0.025–500 exhibited an outstanding electrocatalytic HER performance, and it showed strong durability (≥ 24 h) and a very low overpotential of 105 mV at a current density of 10 mA cm−2 (η10 = 105 mV) in 0.5 M H2SO4. The interspaces-rich nanosheet array morphology of O-CoFeS-0.025–500 enabled maximum exposure of the electrocatalytically active sites. O doping effectively modulated the electronic structure, promoted charge redistribution of the catalyst and significantly increased the intrinsic catalytic activity. Density functional theory (DFT) calculations indicated that the Co atoms in pure CoS2 were the catalytically active sites, and the Gibbs free energy for hydrogen adsorption (ΔGH*) was 0.38 eV. Most notably, Fe/O codoping changed the active sites of O-CoFeS-0.025–500 from Co to S with a markedly reduced ΔGH* of 0.22 eV at the S sites. This work provides a novel perspective for designing outstanding electrocatalysts through element doping to realize highly effective water splitting and produce hydrogen.