Directional Electron and Hole Transfer Driven by Distinct Pd Sites in CdS Photocatalysts Revealed by Nonadiabatic Dynamics Simulations

Abstract

Photocatalysis offers a sustainable strategy for solar-driven redox transformations, yet its efficiency is often limited by rapid electron-hole recombination and the incomplete utilization of charge carriers at single catalytic sites. Atomically dispersed Pd sites with distinct coordination environments on CdS enable highly directional charge separation, providing a powerful strategy for enhancing photoredox performance. Using electronic structure calculations combined with nonadiabatic dynamics simulations at the HSE06 level, we reveal that photogenerated electrons and holes undergo ultrafast and directional transfer to Pd-S₃ and Pd-S₂ moieties, respectively. This site-specific carrier trapping arises from coordinationdependent electronic structures that energetically favor electron localization at substituted Pd-S₃ and hole localization at surface-loaded Pd-S₂. The resulting spatially separated charge carriers significantly suppress nonradiative recombination, enabling longer carrier lifetimes that are essential for efficient photocatalysis. These mechanistic insights highlight the critical role of coordination microenvironments in regulating photophysical properties and provide guiding principles for the rational design of dual-site catalysts capable of concurrently harvesting photogenerated electrons and holes.