Self-Assembled Zeolitic Imidazolate Framework/CdS Hollow Microspheres with Efficient Charge Separation for Enhanced Photocatalytic Hydrogen Evolution

Abstract

Enhanced interfacial charge separation is of great importance to high-efficiency photocatalytic hydrogen production. Herein, we successfully fabricated novel ZIF-67/CdS hollow sphere (HS) and ZIF-8/CdS HS heterostructures through an in situ self-assembly process, in which ZIF-67 and ZIF-8 are closely coated on CdS HSs to form “double-shell”-like structures. This hierarchical heterostructure with porous outer layers on the surface of CdS HSs can expose accessible active sites and possess close contact. Upon visible-light illumination, the optimal proportion of ZIF-67/CdS HS displays a hydrogen generation rate of 1721 μmol g–1 h–1, which is 11.9 and 3.1 times higher than that of a pure CdS HS (145 μmol g–1 h–1) and ZIF-8/CdS HS (555 μmol g–1 h–1), respectively. The proposed photocatalytic mechanism is explored: ZIF-8/CdS HS follows the type-II mechanism, and ZIF-67/CdS HS follows the Z-scheme mechanism. The reason for the higher photocatalytic activity of ZIF-67/CdS HS is that ZIF-67 not merely with a porous structure facilitates the diffusion of H2 gas, but with a well-matched band structure promotes charge transfer and separation.

Synthesis of Metal–Organic Framework-Based ZIF-8@ZIF-67 Nanocomposites for Antibiotic Decomposition and Antibacterial Activities

“…The reduced PL spectra of ZIF-67 following ZIF-8 incorporation are shown in Figure D confirming the improved charge separation. A decline in the PL response results in an increase in the degree of charge separation . The labeled sample 6ZIF-67/ZIF-8 had a low PL intensity, signifying that it is the most effective and active sample.…”

Charge-Transfer Modulation on CdS Artificial Leaf for Efficient Hydrogen Generation

“…The Zn 2p core level XPS spectra of CZ8@NiS are shown in Figure e. The binding energy of Zn 2p peaks at 1044.9 and 1021.7 eV correspond to Zn 2p 3/2 and Zn 2p 1/2 , respectively, indicating the coexistence of Zn 2+ . Meanwhile, the binding energy of Ni 2p peaks in Figure f at 856.5 and 864.3 eV correspond to Ni 2p 3/2 and Ni 2p 1/2 of Ni 2+ in CZ8@NiS, respectively .…”

“…The binding energy of Zn 2p peaks at 1044.9 and 1021.7 eV correspond to Zn 2p 3/2 and Zn 2p 1/2 , respectively, indicating the coexistence of Zn 2+ . 32 Meanwhile, the binding energy of Ni 2p peaks in Figure 5f at 856.5 and 864.3 eV correspond to Ni 2p 3/2 and Ni 2p 1/2 of Ni 2+ in CZ8@NiS, respectively. 42 The satellite peaks of Ni 2p are assigned to binding energies of 862.2 and 859.5 eV.…”

“…MOF-based heterostructures as photocatalysts have been proven to be beneficial in manipulating interfacial charge dynamics, directing the fate of photoexcited electron charge carriers and shaping the pathway of charge-transfer electrons. These intriguing photocatalytic properties of MOFs can be attributed to their structural flexibility and tunability, high surface area, well-defined porosity structure, and semiconductor-like properties. , For instance, Jiang et al successfully reported the CdS/UiO-66 photocatalyst heterojunction, which exhibited a significant performance of CdS due to UiO-66 acting as the support . Zhang and colleagues reported the use of the TiO 2 @ZIF-8 nanocomposite, a metal–organic framework, for water splitting, which produces hydrogen when exposed to UV radiation .…”

Deciphering ligand-controlled charge transfer from a metal–organic framework to cadmium sulfide for enhanced photocatalytic hydrogen evolution reaction

“…3,17,18 Recently, metal-organic frameworks (MOFs) have been explored as cocatalysts with various photocatalysts for photocatalytic energy conversion processes. 1,[19][20][21][22][23] For example, Prussian blue analogs (PBAs), a sub-class of MOF, have been demonstrated as cocatalysts for photocatalytic and photoelectrochemical water oxidation. [24][25][26][27][28][29] PBAs are well explored as electrocatalysts for water splitting and efficient materials for metal-ion batteries.…”