Tailoring the Electron Buffer in [Zn−S−Sm] Units via Gradient Orbital Hybridization for Efficient H ₂ O ₂ Photosynthesis

Solar-to-chemical conversion in H2O2 photosynthesis remains a formidable challenge due to the kinetic mismatch in timescales between charge carriers and sluggish surface reactions. Herein, we introduce a Samarium (Sm) catalyst anchored on ZnIn2S4 nanosheets (SmZIS) that accelerates H2O2 photosynthesis. The resulting catalyst demonstrates a marked increase in photocatalytic activity, achieving H2O2 production rates of 2447.45 and 1921.73 μmol g−1 h−1 in seawater and pure water, respectively. SmZIS-functionalized flow-type photocatalytic microreactors achieve 100% efficiency in bacterial sterilization. Theoretical calculations and spectroscopy results reveal that Sm induces electronic redistribution in the [Zn−S−Sm] units, which form an electron buffer for extending their survival lifetime by nearly sixfold (from 80 to 475 ps). The engineering of [Zn−S−Sm] units further increases the number of spin-down photogenerated electrons for filling into the antibonding orbitals of the oxygen molecules, thereby stabilizing the *OOH intermediate and accelerating the H2O2 photosynthesis. These findings justify that the rare-earth single atom opens up possibilities for H2O2 photosynthesis by inducing gradient d−p−f orbital hybridization to optimize the electronic density of states.