Dynamics of Electron Transfer in CdS Photocatalysts Decorated with Various Noble Metals

Abstract

To address charge recombination in photocatalysis, the prevalent approach involves the use of noble metal cocatalysts. However, the precise factors influencing this performance variability based on cocatalyst selection have remained elusive. In this study, CdS hollow spheres loaded with distinct noble metal nanoparticles (Pt, Au, and Ru) are investigated by femtosecond transient absorption (fs-TA) spectroscopy. A more pronounced internal electric field leads to the creation of a larger Schottky barrier, with the order Pt-CdS > Au-CdS > Ru-CdS. Owing to these varying Schottky barrier heights, the interface electron transfer rate (K_e ) and efficiency (η_e ) of metal-CdS in acetonitrile (ACN) exhibit the following trend: Ru-CdS > Au-CdS > Pt-CdS. However, the trends of K_e and η_e for metal-CdS in water are different (Ru-CdS > Pt-CdS > Au-CdS) due to the influence of water, leading to the consumption of photogenerated electrons and affecting the metal/CdS interface state. Although Ru-CdS displays the highest K_e and η_e , its overall photocatalytic performance, particularly in H₂ production, lags behind that of Pt-CdS due to the electron backflow from Ru to CdS. This work offers a fresh perspective on the origin of performance differences and provides valuable insights for cocatalyst design and construction.

Keywords: Schottky barrier; electron backflow; electron transfer dynamics; femtosecond transient absorption spectroscopy; noble metal.