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. 2023:6:0073.
doi: 10.34133/research.0073. Epub 2023 Mar 10.

Heterostructure-Engineered Semiconductor Quantum Dots toward Photocatalyzed-Redox Cooperative Coupling Reaction

Lin-Xing Zhang  1 , Ming-Yu Qi  1 , Zi-Rong Tang  1 , Yi-Jun Xu  1
Affiliations

Heterostructure-Engineered Semiconductor Quantum Dots toward Photocatalyzed-Redox Cooperative Coupling Reaction

Lin-Xing Zhang et al. Research (Wash D C). 2023.

Abstract

Semiconductor quantum dots have been emerging as one of the most ideal materials for artificial photosynthesis. Here, we report the assembled ZnS-CdS hybrid heterostructure for efficient coupling cooperative redox catalysis toward the oxidation of 1-phenylethanol to acetophenone/2,3-diphenyl-2,3-butanediol (pinacol) integrated with the reduction of protons to H2. The strong interaction and typical type-I band-position alignment between CdS quantum dots and ZnS quantum dots result in efficient separation and transfer of electron-hole pairs, thus distinctly enhancing the coupled photocatalyzed-redox activity and stability. The optimal ZnS-CdS hybrid also delivers a superior performance for various aromatic alcohol coupling photoredox reaction, and the ratio of electrons and holes consumed in such redox reaction is close to 1.0, indicating a high atom economy of cooperative coupling catalysis. In addition, by recycling the scattered light in the near field of a SiO2 sphere, the SiO2-supported ZnS-CdS (denoted as ZnS-CdS/SiO2) catalyst can further achieve a 3.5-fold higher yield than ZnS-CdS hybrid. Mechanistic research clarifies that the oxidation of 1-phenylethanol proceeds through the pivotal radical intermediates of •C(CH3)(OH)Ph. This work is expected to promote the rational design of semiconductor quantum dots-based heterostructured catalysts for coupling photoredox catalysis in organic synthesis and clean fuels production.

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Figures

Fig. 1.
Fig. 1.
Synthetic process diagram and morphological characterization. (A) Schematic diagram of ZnS-CdS hybrid prepared via self-assembly process. (B) TEM image of CdS QDs. HRTEM images of (C) CdS QDs and (D) ZnS QDs. (E) TEM image, (F) HRTEM image, and (G) high-angle annular dark field (HAADF) and corresponding elemental mapping results of ZnS-CdS hybrid.
Fig. 2.
Fig. 2.
Physicochemical properties. (A) FTIR spectra of MPA-capped CdS QDs, ZnS QDs, and ZnS-CdS hybrid. (B) XRD patterns and (C) DRS spectra of CdS QDs, ZnS QDs, and ZnS-CdS hybrids. XPS spectra for CdS QDs, ZnS QDs, and ZnS-CdS hybrid: (D) Cd 3d, (E) S 2p, and (F) Zn 2p. a.u., arbitrary units; JCPDS, Joint Committee on Powder Diffraction Standards.
Fig. 3.
Fig. 3.
Photocatalyzed-redox 1-phenylethanol paired with H2 evolution reaction. (A) The formula for coupling photocatalyzed-redox 1-phenylethanol to acetophenone/pinacol integrated with H2 evolution. (B) Photocatalytic activities of CdS QDs, ZnS QDs, and ZnS-CdS hybrids. (C) DRS spectrum of 5%ZnS-CdS hybrid and AQYs of H2 under various monochromatic lights. (D) Long-term photocatalytic activity tests and (E) recycling photocatalytic activity tests over 5%ZnS-CdS hybrid.
Fig. 4.
Fig. 4.
The performance of the charge separation. (A) Transient photocurrent spectra, (B) EIS Nyquist plots, (C) polarization curves, (D) cyclic voltammetry curves, (E) steady-state PL emission spectra, and (F) time-resolved PL decay plots of CdS QDs, ZnS QDs, and 5%ZnS-CdS hybrid.
Fig. 5.
Fig. 5.
The mechanism of photocatalyzed-redox reaction. (A) EPR spectroscopy in an Ar-saturated 1-phenylethanol solution of CdS QDs, ZnS QDs, and 5%ZnS-CdS hybrid suspensions with or without light illumination (300 nm ≤ λ ≤ 800 nm) and (B) corresponding quantitative analysis results of 5%ZnS-CdS hybrid. (C) Tauc plots and (D) Mott-Schottky plots of CdS QDs and ZnS QDs. (E) Proposed type-I reaction mechanism for coupling photocatalyzed-redox reaction over heterostructured ZnS-CdS hybrid.
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