Cobalt Nanodisks Anchored on Sulfur-Vacancy-Containing MoS₂ for the Hydrogen Evolution Reaction

Developing highly active and stable non-noble metal electrocatalysts is an imperious demand to achieve practical H₂ production via electrocatalytic water splitting. Herein, cobalt nanodisks (Co Nds) were synthesized on the basal plane of sulfur-vacancy-containing molybdenum disulfide (MoS_2-x), resulting in optimized active sites and improved conductivity of MoS_2-x without covering the original active sites, the sulfur vacancies, due to the unique nanodisk structure. In addition, the synergistic interaction between the Co Nds and sulfur vacancies further enhanced the catalytic performance of MoS_2-x. As a result, the Co Nds/MoS_2-x composite demonstrated outstanding electrocatalytic performance for the hydrogen evolution reaction (HER) in both acidic and alkaline solutions, exhibiting low overpotentials (179 mV in 0.5 M H₂SO₄ and 151 mV in 1.0 M KOH), relatively small Tafel slopes (62.5 mV dec^-1 in 0.5 M H₂SO₄ and 99.8 mV dec^-1 in 1.0 M KOH), and superior HER durability at the optimal Co/Mo molar ratio of 0.46. This work provides an innovative design strategy by introducing a sheeted non-noble metallic nanostructure to develop durable high-efficiency pH-universal transition metal dichalcogenide-based HER electrocatalysts.