One-Pot Synthesis of Size-Controllable Core–Shell CdS and Derived CdS@Zn_xCd_1−xS Structures for Photocatalytic Hydrogen Production

Chalcogenide micro/nanocomposite structures have been attracting worldwide attention due to prospective applications in photocatalytic hydrogen production. Well-defined micro/nanostructures with pronounced properties are of extraordinary importance. Herein, a facile one-pot method for the synthesis of monodisperse, size-controllable CdS core–shell and CdS@Zn_xCd_1−xS core–double shell submicrospheres, which were engineered with respect to structure and size, is reported. CdS core–shell submicrospheres with different sizes were selectively prepared for the first time. The growth mechanism was investigated in detail by monitoring the time-dependent morphology of intermediates by TEM. By introduction of a zinc precursor in the synthetic system, CdS@Zn_xCd_1−xS core–double shell submicrospheres were obtained by cation exchange of CdS with zinc ions, with a process of diffusion of CdS towards the outside and transformation of Zn_xCd_1−xS crystallites. The H₂ evolution rate over CdS@Cd_xZn_1−xS (5.17 mmol h⁻¹ g⁻¹) is 12.3 times that of CdS core–shell structures (0.42 mmol h⁻¹ g⁻¹) under visible light, owing to the efficient charge separation, as demonstrated by electrochemical impedance and transient-state time-resolved photoluminescence spectroscopy. Furthermore, CdS@Zn_xCd_1−xS core–double shell structures exhibited excellent stability over 20 h of hydrogen production.