Achieving ultra-dispersed 1T-Co-MoS2@HMCS via space-confined engineering for highly efficient hydrogen evolution in the universal pH range

Abstract

The rational design and synthesis of noble-metal-free electrocatalysts for water splitting is always important for the future hydrogen economy. Therefore, it is necessary to design an effective transition metal sulfide down to a molecular level. In this work, a multi-level spatial confinement strategy was developed to fabricate Co-promoted 1T-MoS₂ (1T-Co-MoS₂) by employing Evans–Showell-type polyoxometalates (POMs) [Co₂Mo₁₀O₃₈H₄] as molecular precursor. Highly dispersed 1T-Co-MoS₂ nanoclusters with few layers (1–3 layers) and ultrasmall size (<5 nm) were synthesized within the hollow mesoporous carbon sphere (HMCS) by in situ vapor phase sulfurization. During the preparation, coordination bonds, organic cations and mesopores provide a triple-confinement environment to limit the growth of 1T-Co-MoS₂ from the atomic level, molecular level to mesoscopic scale. The obtained 1T-Co-MoS₂@HMCS exhibits remarkable electrocatalytic activity and excellent long-term durability for hydrogen evolution reaction (HER), with overpotentials of 220 and 245 mV to achieve the current density of 200 mA cm⁻² in 1 M KOH and 0.5 M H₂SO₄, respectively. The corresponding theoretical calculations indicate that Co–S edge sites are the most active sites of 1T-Co-MoS₂ for HER, reflecting the major significance of Co doping. The superior HER performance could be attributed to the high intrinsic activity from Co-doped 1T-MoS₂ sites, abundant exposed active sites from ultra-dispersed nanosheets, and enhanced charge and mass transfer within the HMCS substrate. This work provides a novel design concept via hierarchical multiple-level confinement for the synthesis of high-quality 1T-Co-MoS₂ and achieves outstanding performance in electrocatalytic HER.