Surface Amination for Site-Selective Activation of Cd Centers in High-Entropy Sulfide Photocatalysts

High-entropy sulfides offer exceptional compositional tunability for catalytic optimization, yet their photocatalytic hydrogen evolution activity is often limited by inefficient charge transfer and poorly activated surface metal sites. Here, we report a surface-functionalized Zn─Cd─Co─Cu─Mn high-entropy sulfide, in which amino (─NH₂) ligands selectively activate Cd centers, enabling efficient cocatalyst-free photocatalytic hydrogen evolution. Surface amination induces the formation of high-surface-area two-dimensional nanosheets and simultaneously modulates the local electronic structure of Cd sites. As a result, the aminated high-entropy sulfide exhibits a threefold enhancement in photocurrent density and a 16.25-fold increase in hydrogen evolution rate relative to the non-functionalized counterpart. Spectroscopic analyses combined with density functional theory calculations reveal that ─NH₂ coordination enhances the electronic accessibility of Cd 4d states, strengthens reactant-surface coupling, and substantially lowers the energy barriers for both water dissociation and hydrogen evolution. This work establishes surface coordination engineering as a general strategy to unlock the catalytic potential of high-entropy sulfides and provides a rational pathway toward efficient, cocatalyst-free photocatalysts.