Synthesis of a Library of Transition Metal Sulfide@MoS₂ Core@Shell Nanostructures via Post-Synthetic Cation Exchange

The rational synthesis of compositionally diverse and structurally well-defined inorganic heterostructures remains a substantial challenge. Herein, we report a post-synthetic cation exchange strategy for the programmable construction of a library of transition metal sulfide@MoS₂ core@shell heterostructures. Using Ag₂S@MoS₂ as a template, we demonstrate a multi-step transformation pathway via a highly reactive Cu_2-xS@MoS₂ intermediate. Critically, this approach successfully decouples the formation of the MoS₂ shell from the final core composition, providing a universal route to three distinct classes of architectures-metal sulfide M_xS_y (M═Cd, Cu, Co, Ni, Mn, Zn), heterostructured (Cu_2-xS/ZnS), and homogeneous solid-solution (Ni_xCo_yS₄) cores-while perfectly preserving the integrity of the monolayer MoS₂ shell. The potential of these materials is highlighted by their electrocatalytic performance for the oxygen evolution reaction (OER). The Co₉S₈@MoS₂ catalyst exhibits exceptional activity, achieving a low overpotential of 253 mV at 10 mA cm^-2 and remarkable long-term stability. This work establishes cation exchange within a 2D shell as a powerful and general platform for engineering complex hybrid architectures for advanced energy applications.