Abstract: Dual co-catalyst loading is a viable strategy to enhance charge carrier separation in photocatalysis. However, conventional randomly-loaded dual co-catalysts often fail to effectively direct charge transfer. In this study, a strategically designed spatially separated dual co-catalyst system (MnO_x/CdS/Pt) optimizes redox site orientation to address the challenge of disordered carrier transfer. This configuration maximizes the utilization of both electrons and holes while establishing ultrafast electron transfer channels between CdS and Pt. The ultrafast electron transfer channels between spatially separated redox sites are demonstrated by femtosecond transient absorption (fs-TA) spectroscopy and in situ characterization. The average lifetime of MnO_x/CdS/Pt (MCSP) in a real reaction environment reduced from ∼ 1352.6 to ∼ 996.6 ps, compared to CdS alone. The interfacial electron transfer rate is accelerated to ∼ 2.6 × 10⁸ s^-1, a substantial improvement over the CdS/Pt (∼ 6.0 × 10⁷ s^-1). Consequently, this system achieves efficient hydrogen production coupled with fine chemical synthesis. This work underscores the potential of rational dual co-catalyst design with spatially separated redox sites as a promising strategy for developing high-performance photocatalytic platforms for solar fuel production.

Key words: Dual co-catalysts, Hydrogen production, Separated sites, Femtosecond transient absorption spectroscopy