Graphical Monodisperse submicrospheres : A one-pot method was developed for the preparation of monodisperse submicrospheres of core–shell CdS and its core–double shell derivative CdS@Zn x Cd 1− x S. Owing to its special semiconductor heterojunction, CdS@Zn x Cd 1− x S shows remarkably improved activity for H 2 evolution in comparison to bare CdS under visible-light irradiation (see figure). 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 x Cd 1− x S 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 x Cd 1− x S 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 x Cd 1− x S crystallites. The H 2 evolution rate over CdS@Cd x Zn 1− x S (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 x Cd 1− x S core–double shell structures exhibited excellent stability over 20 h of hydrogen production.
Yudong Guo,Xiya Chen,Yuxin Liu,Zhenjun Chen,Peiyuan Guo,Dongxiang Luo,Menglong Zhang,Xiao Liu
In a dual-functional lignin valorization system, a harmonious oxidation and reduction rate is a prerequisite for high photocatalytic performance. Herein, an efficient and facile ligand manipulating strategy to balance the redox reaction process is exploited via decorating the surface of the CdS@ZnxCd1–xS@ZnS gradient-alloyed quantum dots with both inorganic ligands of hexafluorophosphate (PF6–) and organic ligands of mercaptopropionic acid (MPA). Inorganic ion ligands in this system provide a promotion for intermediator reduction reactions. By optimizing the ligand composition on the quantum dot surface, we achieve precise control over the extent of oxidation and reduction, enabling selective modification of reaction products; that is, the conversion rate of 2-phenoxy-1-phenylethanol reached 99%. Surface engineering by regulating the ligand type demonstrates that PF6– and thiocyanate (SCN–) inorganic ion ligands contribute significantly toward electron transfer, while MPA ligands have beneficial effects on the hole-transfer procedure, which is predominantly dependent on their steric hindrance, electrostatic action, and passivation effect. The present study offers insights into the development of efficient quantum dot photocatalysts for dual-functional biomass valorization through ligand design.
Huakang Yang,Zining Zhang,Yudong Guo,Shuwen Yuan,Xiao Liu,Dongxiang Luo,Siyu Ye
Solar-driven photocatalytic CO 2 reduction coupled with the oxidation of organic compounds to value-added chemicals is a promising strategy, which can utilize both photogenerated electrons and holes. Here, a gradient alloyed CdS@Zn x Cd 1-x S@ZnS quantum dots (quasi-Type II band structure) capped with Cl − ligands demonstrate great potential in the simultaneous conversion of CO 2 and 1-phenylethanol into syngas and pinacol. The passivation with Cl − maximizes the exposure of surface-active sites and improves their electronic structure, providing a prerequisite for the efficient execution of redox reactions. More importantly, the p–π conjugation between chloride-ion ligands and the benzene ring provides a bridge for the ultrafast transfer of holes, which greatly promotes the activation of the Cα─H bond in 1-phenylethanol to release a mass of reactive free hydrogen. This process effectively lowers the thermodynamic energy barrier for CO 2 reduction, even as the excessively high kinetic energy barriers arising from the accumulation of excess protons also enable them to self-couple, leading to the generation of syngas (CO ≈ 75 mmol g −1 h −1 ; selectivity ≈ 69.86%). This work provides insights for future artificial photosynthesis to achieve high activity and cost-effective conversion of CO 2 into storable renewable resources and the co-production of value-added substances through synergistic organic oxidation.
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