Synthesis of a Library of Transition Metal Sulfide@MoS ₂ Core@Shell Nanostructures via Post‐Synthetic Cation Exchange

ABSTRACT 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@MoS ₂ core@shell heterostructures. Using Ag ₂ S@MoS ₂ as a template, we demonstrate a multi‐step transformation pathway via a highly reactive Cu _2‐x S@MoS ₂ intermediate. Critically, this approach successfully decouples the formation of the MoS ₂ shell from the final core composition, providing a universal route to three distinct classes of architectures—metal sulfide M _x S _y (M═Cd, Cu, Co, Ni, Mn, Zn), heterostructured (Cu _2‐x S/ZnS), and homogeneous solid‐solution (Ni _x Co _y S ₄ ) cores—while perfectly preserving the integrity of the monolayer MoS ₂ shell. The potential of these materials is highlighted by their electrocatalytic performance for the oxygen evolution reaction (OER). The Co ₉ S ₈ @MoS ₂ 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.