Mn ⁴ T ₁ Electronic State Mediated Carrier Dynamics in Heavy Metal‐Free Core/Shell Quantum Dots for Boosting Photoelectrochemical Hydrogen Evolution

Colloidal core/shell quantum dots (QDs) have garnered significant attention as photon‐harvesting materials in photoelectrochemical (PEC) hydrogen evolution, leveraging their high absorption coefficient, tunable bandgap, and solution processability. Nevertheless, several major challenges impede its further application, such as limited photo‐induced electron‐hole separation, undesirable carrier recombination, and environmental hazards from heavy metal elements. Herein, a strategy that Mn 4 T 1 electronic state enhances carrier dynamics in heavy metal‐free Mn‐doped ZnSe/ZnS core/shell QDs is proposed for boosting PEC hydrogen evolution. It is found that the photoluminescence lifetime for Mn‐doped ZnSe/ZnS QDs increases by five orders of magnitude compared to ZnSe/ZnS QDs counterparts. As a proof‐of‐concept, the as‐prepared Mn‐doped core/shell QDs were employed as light harvesting materials in PEC devices for hydrogen evolution, demonstrating a saturated photocurrent density as high as 8.0 mA·cm −2 and hydrogen evolution of 133.8 µmol·cm −2 in 2 h (approximately 4 times and 5.2 times higher than those of the undoped ZnSe/ZnS QDs PEC system). The enhancement is attributed to the consequence of Mn 2+ electron “storage” center, which significantly optimizes the kinetics of carrier separation and transfer processes. These findings demonstrate the availability of the strategy regulating carrier dynamics of environmentally friendly QDs by Mn 4 T 1 electronic state for high‐performance PEC systems.