Colloidal CdxZn1−xS nanocrystals as efficient photocatalysts for H2 production under visible-light irradiation

Abstract

Cd_xZn_1−xS nanocrystals with sizes ranging from 3–11 nm were synthesized by a simple organic solution method. The nanocrystals possess a cubic zinc-blende structure and the bandgap blue-shifts from 2.1 eV to 3.4 eV by increasing the composition of Zn ions in the solid solutions. After a facile ligand exchange process, the photocatalytic activity for H₂ production of the Cd_xZn_1−xS nanocrystals was investigated under visible-light irradiation (λ ≥ 420 nm) with Na₂SO₃/Na₂S as the electron donor. It was found that the Cd_0.8Zn_0.2S had the highest photoactivity with H₂ evolution rate of 6.32 mmol g⁻¹ h⁻¹. By in situ adding Pt precursors into the reaction solution, inhomogenous Pt–Cd_xZn_1−xS nanoheterostructures were formed, which accounted for a 30% enhancement for the H₂ evolution rate comparing with that of pure Cd_0.8Zn_0.2S nanocrystals. This work highlights the use of facile organic synthesis in combination with suitable surface modification to enhance the activity of the photocatalysts.