In-depth understandings of charge carrier transfer dynamics in any artificial catalytic system are of critical importance for the future design of highly efficient photocatalysts. Herein, we synthesized sub-monolayer ZnSe partial-shell coated CdSe/CdS core/shell quantum dots in a controlled fashion. The ZnSe decorated quantum dots were employed as a model catalyst for photogeneration of H₂ under light illumination. Both theoretical calculations and experimental results unravel that the growth of ZnSe partial-shell would retard the photogenerated electron transfer, and meanwhile, accelerate the corresponding hole migration process during the H₂ photogeneration reaction in the artificial photocatalytic system. As such, the performance of the relevant photocatalytic system can be modulated and optimized, and accordingly, a plausible underlying mechanism is rationalized.