Transition Metal-Stabilized Lanthanide Sulfide Nanocrystal Libraries: A New Platform for Solar-to-Hydrogen Conversion

Lanthanide (Ln) sulfide semiconductor nanocrystals (NCs) have garnered considerable attention due to their unique optical properties associated with 4f-orbital participation. However, the scarcity of Ln sulfide-based NCs with well-controlled morphology, composition, and crystal phase, arising from the fairly poor affinity between Ln and S elements, has severely hindered their potential applications. Here, we demonstrate a monovalent transition metal cation-stabilized strategy for the general synthesis of a ternary Ln sulfide nanocrystal library, containing unconventional phases of Ag₂EuS₂ and AgLnS₂ (Ln = Nd, Sm, Gd, Tb, Dy, Ho) NCs with tunable size and composition via a colloidal thermal decomposition route. Additionally, this approach can be further extended to the synthesis of multicomponent high-entropy and heterostructured Ln sulfide-based NCs. As a proof-of-concept application, the as-constructed Ag₂EuS₂-CdS heteronanorods exhibit improved photocatalytic hydrogen evolution activity, which can be attributed to the interfacial type-II band alignment for efficient charge separation and transportation. This study expands the scope of rare earth-based semiconductor materials and provides promising candidates for solar energy conversion applications.