Demystifying Multifunctional Electrocatalysis of 2D Monolayer Vanadium-Doped WS2 Transition Metal Dichalcogenide with Single-Atom Catalysts Toward Electrochemical O2 Reduction, O2 Evolution, and H2 Evolution Reactions

Designing cost-effective and efficient multifunctional electrocatalysts, especially single-atom catalysts (SACs), is essential for sustainable energy transformation. SACs have recently emerged as an important research area and have attracted great attention from the scientific community owing to their attractive properties allowing their application in different electrocatalytic processes, including O2 reduction reaction (ORR), O2 evolution reaction (OER), and H2 evolution reaction (HER). Herein, vanadium-doped WS2 (V-WS2) monolayers have been explored as a promising catalyst for O2 reduction (ORR), O2 evolution (OER), and H2 evolution (HER) reactions using first-principles based density functional theory (DFT) calculations. Notably, substitutional doping of W with V not only introduces 3d orbitals near the Fermi level, but also significantly reduces the band gap from 2.77 eV (pristine WS2) to 0.75 eV, which in turn improves the electrical conductivity. The ORR proceeds preferentially via the associative pathway, in which all proton-coupled electron-transfer steps following the initial O2 adsorption are exergonic (ΔG = −1.17 to −1.91 eV). For OER, the theoretical overpotential is calculated to be 0.40 V, which is ∼0.16 V lower than the benchmark IrO2 catalyst, indicating superior activity. In HER, the hydrogen adsorption free energy (ΔGH*) is close to thermoneutral values (0.17 eV at S-sites and 0.51 eV at V-sites), confirming excellent hydrogen evolution capability. Altogether, these results establish the 2D monolayer V-WS2 TMD as an efficient, earth-abundant, and multifunctional electrocatalyst for next-generation energy technologies, especially in the fuel cells as novel cathodic electrode material. This work provides a promising strategy for designing novel high-performance electrocatalysts with wide industrial applicability.