CdS nanocrystals were synthesized by a hydrothermal method using ethylenediamine (en) as the template agent and coordination agent, and characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), BET, and UV−vis absorption spectroscopic techniques. Their photoactivity was evaluated by hydrogen evolution from aqueous solution containing formic acid as a hole scavenger under visible light (λ ≥ 420 nm) irradiation. The nanocrystals display rodlike and granular shapes, and their amount and morphology depend on the hydrothermal temperature and the added content of en. Photoactivity of the nanorods is higher than that of the nanograins. The effect of deposited Pt as cocatalyst on photoactivity for hydrogen evolution has been investigated. Pt can be dispersed highly on CdS so that the Pt content for effective hydrogen evolution is very low. 0.050 wt % Pt-loaded CdS shows the highest activity for hydrogen evolution under visible light irradiation, and the apparent quantum yield amounts to 13.9%. A possible mechanism was discussed.

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