In Situ Preparation of 0D/2D Zn-Ag-In-S Quantum Dots/RGO Heterojunctions for Efficient Photocatalytic Hydrogen Production

Abstract

The creation of junctions between 0D and 2D materials can be an efficient strategy to enhance charge separation for solar hydrogen production. In this study, a simple in situ growth method has been used to synthesize a series of 0D/2D Zn-Ag-In-S quantum dots/reduced graphene oxide (ZAIS QDs/RGO) heterojunctions. The developed heterojunctions were characterized for structural characteristics, morphology, and photocatalytic performance, while varying the content of RGO. We observed that photocatalytic hydrogen production reached a maximum at an RGO content of 30 μL (342.34 µmol g−1 h−1), surpassing that of pure ZAIS QDs (110.38 µmol g−1 h−1) by 3.1 times, while maintaining excellent stability. To understand this enhancement, we performed time-resolved fluorescence and electrochemical impedance spectroscopy. The fluorescence lifetime of RGO loaded at 30 μL (417.76 ns) was significantly higher than that of pure ZAIS QDs (294.10 ns) and had the fastest charge transfer, which can be attributed to the charge transfer and storage capacity of RGO to extend the lifetime of photogenerated carriers and improve the charge separation efficiency. This study offers a simple synthesis method for constructing 0D/2D QDs/RGO heterojunction structures and provides a valuable reference for further enhancing the activity and stability of I-III-VI sulfide QDs.

Rational Design of MIL-68(In) Derived Multiple Sulfides with Well Confined Quantum Dots and the Promoted Photocatalytic Hydrogen Generation

“…Figure b shows that the high-resolution spectrum of O 1s could be fitted to three characteristic peaks at 530.4, 531.9, and 533.0 eV, corresponding to In–O, C–O, and CO in the QDs@MIL-68(In), respectively. While undergoing sulfurization and Zn(II) exchange, these three bonding energies shift toward the higher energy; for example, the energy of In–O upshifts to 531.4 eV by 1.0 eV, which may be due to the uncoordinated oxygen produced by the formation of In–S. , S 2– is responsible for two of the peaks at 161.3 eV ((S 2p 3/2 ) and 162.5 eV (S 2p 1/2 ) in Figure c, which shows the S 2p binding energy for QDs@MIL-68(In), and two further peaks at 168.6 eV(2p 3/2 ) and 169.7 eV(2p 1/2 ) come from the metal sulfide . In the S 2p profile of QDs@M-24h-Zn, the corresponding energies are slightly shifted to 161.6 eV (S 2p 3/2 ) and 162.8 eV (S 2p 1/2 ).…”

“…37,38 S 2− is responsible for two of the peaks at 161.3 eV ((S 2p 3/2 ) and 162.5 eV (S 2p 1/2 ) in Figure 3c, which shows the S 2p binding energy for QDs@ MIL-68(In), and two further peaks at 168.6 eV(2p 3/2 ) and 169.7 eV(2p 1/2 ) come from the metal sulfide. 39 In the S 2p profile of QDs@M-24h-Zn, the corresponding energies are slightly shifted to 161.6 eV (S 2p 3/2 ) and 162.8 eV (S 2p 1/2 ). In the high-resolution XPS spectra of In 3d orbitals (Figure 3d), for QDs@MIL-68(In), there are two obvious binding energies at 445.3 and 452.8 eV, which are attributed to 3d 3/2 and 3d 5/2 orbitals of In (III), respectively, while for QDs@M-24h-Zn, they are 445.0 and 452.5 eV with a negative shift of 0.3 eV.…”