Efficient Hydrogen and Oxygen Evolution from Degenerate-Doped Metallic WS₂ Bifunctional Electrocatalyst

The changes in electronic and structural properties of transition metal dichalcogenide (TMDC)-based electrocatalysts significantly affect the electrochemical water-splitting activity. Herein, we report the efficient electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) bifunctional activity of Ru degenerate-doped metallic WS₂ catalyst in alkaline electrolyte medium. WS₂ with a high percentage (14%) of Ru doping exhibits degenerate semiconductor nature with a structural phase transformation from the 2H-hexagonal into the 1T-octahedral phase. The 1T-WS₂ degenerate semiconductor (WS₂@Ru₁₄) catalyst demonstrates excellent bifunctional activity in 1 M KOH electrolyte with low overpotential (η₁₀ = 112 mV vs. reversible hydrogen electrode [RHE] and 470 mV vs. RHE) and low Tafel slope (b = 37 and 42 mV dec⁻¹) for HER and OER activity, respectively. Further, the symmetric full-cell electrolyzer constructed with a WS₂@Ru₁₄ catalyst used as an anode and cathode for overall water splitting requires a cell voltage of 1.68 V to deliver a 10 mA cm⁻² current density. The WS₂@Ru₁₄ catalyst with high carrier density and intrinsic conductivity activates the basal plane and promotes electrochemical activity with fast electron transfer kinetics in the degenerate-doped metallic WS₂ semiconductor. The density functional theory calculations throw light on understanding the phase stability and electronic band structure of the heavily doped WS₂ semiconductor. This work opens an avenue for rational design of doped TMDC electrocatalysts for clean energy generation.