Temperature-Tuned Cobalt-doped MoS2/WS2 heterojunction thin films for enhanced bifunctional electrocatalytic performance in water splitting

Transition metal dichalcogenides (TMDs), particularly WS₂ and MoS₂, have garnered significant attention as advanced energy materials due to their unique structural and electronic properties. This study reports the synthesis of cobalt-doped MoS₂/WS₂ (Co-MoS₂/WS₂) thin films using a two-step spin-coating technique, enabling the formation of a well-defined vertical interface between WS₂ and MoS₂ layers. Post-synthesis annealing at temperatures ranging from 700 to 900 °C under an argon-nitrogen atmosphere enhanced the bifunctional electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Cobalt doping improved the material's conductivity, optimized the hydrogen adsorption-free energy at the MoS₂/WS₂ interface, and introduced additional catalytic active sites for OER. The Co-MoS₂/WS₂ thin films exhibited competitive overpotentials comparable to state-of-the-art bifunctional catalysts, with the novelty residing in the simplicity and scalability of the spin-coating method and the synergistic effect of Co doping with the MoS₂/WS₂ heterostructure. This approach provides a cost-effective and scalable strategy for the development of bifunctional electrocatalysts for total water splitting.