Co-degenerate doped WS₂ electrocatalyst with enriched CoS phase producing efficient hydrogen evolution at all pH conditions

Doping is a widely adapted method to modify the catalytic, magnetic, and electronic properties of transition metal dichalcogenides (TMDCs) semiconductor materials. Studies have revealed that doping improves the electrocatalytic hydrogen evolution reaction (HER) activity of WS₂ nanostructures and composite catalysts in an acidic environment. However, for practical use, high demand is appealing for the design of a catalyst able to produce efficient hydrogen in alkaline and neutral condition. Herein, we report the efficient HER performance of Co-degenerate-doped WS₂ electrocatalyst with enriched CoS phase under all pH conditions. The structural studies reveal that the CoS secondary phase emerged in WS₂ samples for higher Co doping (>4 %) concentrations. The prepared WS₂ possesses degenerate semiconductor nature at 17 % Co doping concentration, with high carrier density (4.5 × 10¹⁹/cm³), confirmed from the Mott-Schottky analysis and numerical simulations. The degenerate doped WS₂ (17 % Co-WS₂) electrocatalyst with CoS exhibits superior HER performance in 0.5M H₂SO₄ (pH = 0) electrolyte with a lower overpotential of 122 mV vs. RHE at a current density of 10 mA/cm² and a low Tafel slope of 69 mV/dec. In addition, the same catalyst also recorded 127 and 514 mV vs. RHE overpotential (@10 mA/cm²) with 70 and 90 mV/dec Tafel slope in 1M KOH (pH = 14) and 1M Na₂SO₄ (pH = 7) electrolytes, respectively. The abundant active sites with improved electrical conductivity of the degenerate doped WS₂ catalyst are responsible for the excellent HER activity in all pH condition.