Colloidal Cd x Zn 1- x S nanocrystals as efficient photocatalysts for H 2 production under visible-light irradiation.

Cd x Zn 1- x S 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 H 2 production of the Cd x Zn 1- x S nanocrystals was investigated under visible-light irradiation ( λ ≥ 420 nm) with Na 2 SO 3 /Na 2 S as the electron donor. It was found that the Cd 0.8 Zn 0.2 S had the highest photoactivity with H 2 evolution rate of 6.32 mmol g -1 h -1 . By in situ adding Pt precursors into the reaction solution, inhomogenous Pt-Cd x Zn 1- x S nanoheterostructures were formed, which accounted for a 30% enhancement for the H 2 evolution rate comparing with that of pure Cd 0.8 Zn 0.2 S nanocrystals. This work highlights the use of facile organic synthesis in combination with suitable surface modification to enhance the activity of the photocatalysts.