Impact of Aspect Ratio on Charge Carrier Dynamics and Efficiency Enhancement in CdSe/CdS Dot-in-Rod Nanostructures for Photocatalytic Hydrogen Evolution

We demonstrated that the aspect ratio (AR)-tunable CdSe/CdS dot-in-rod (DiR) nanostructures with quasi-type-II band structure were successively synthesized using the hot injection method. When the AR of CdSe/CdS DiR was tuned from 10 to 37, the exciton localization efficiency along the longitudinal CdS rod shell decreased from 57.9 to 15.1%, resulting in a 5-fold improvement in the efficiency of photocatalytic hydrogen (H₂) evolution. The optimal CdSe/CdS DiR exhibited the highest H₂ evolution rate of 2.11 mmol·g^-1·h^-1 at an AR of 29 without any cocatalyst assistance. In situ transient absorption spectroscopy was employed to investigate the interfacial charge carrier dynamics of CdSe/CdS DiR during practical photocatalytic H₂ evolution. The findings indicated that the half-life of delocalized electrons on the conduction band along the longitudinal CdS rod shell increases from 11.5 to 20.1 μs as the AR increased, demonstrating that the AR-dependent charge carrier dynamics significantly influences the photoactivity of CdSe/CdS DiR. This study provides valuable and novel insights into the tunability of charge carrier dynamics through AR manipulation in one-dimensional semiconductor nano-heterostructures for solar fuel generation.