Accumulated photogenerated holes in type-II ZnSe/CdS nanotetrapods for efficient photocatalytic hydrogen evolution

Abstract

One-dimensional semiconductor nanorods have shown intrinsic advantages in photocatalytic H₂ evolution systems. However, the hole transfer and the subsequent oxidation reaction have been regarded as the rate-determining steps of the reaction. The introduction of only one single activity site per photocatalyst has great advantages for multi-electron reactions. Here, the ZnSe/CdS nanotetrapods (NTPs) with type-II band alignment are proposed and well designed. ZnSe is located at the center of the nanotetrapods, and its valence band is more negative than that of the CdS nanoarms. Therefore, the photogenerated holes of the four CdS nanoarms delocalize into a ZnSe core, and the electrons still reside in the nanoarms. The spatial separation of the photogenerated charges and accumulated holes accelerate the hole migration to the surface and the subsequent oxidation reaction. The ZnSe/CdS NTPs exhibit extraordinary photocatalytic H₂ evolution activity and stability. Specifically, a total of 8573.5 ± 249.0 μmol of H₂ gas is generated within 100 h of irradiation, giving the turnover number of (1.71 ± 0.05) × 10⁸ per ZnSe/CdS NTP.