Construction of ZnIn2 S4 /CdS/PdS S-Scheme Heterostructure for Efficient Photocatalytic H2 Production.

It is facing a tremendous challenge to develop the desirable hybrids for photocatalytic H2 generation by integrating the advantages of a single semiconductor. Herein, an all-sulfide ZnIn2 S4 /CdS/PdS heterojunction is constructed for the first time, where CdS and PdS nanoparticles anchor in the spaces of ZnIn2 S4 micro-flowers due to the confinement effects. The morphology engineering can guarantee rapid charge transfer owing to the short carrier migration distances and the luxuriant reactive sites provided by ZnIn2 S4 . The S-scheme mechanism between ZnIn2 S4 and CdS assisted by PdS cocatalyst is testified by in situ irradiated X-ray photoelectron spectroscopy and electron paramagnetic resonance (EPR), where the electrons and holes move in reverse driven by work function difference and built-in electric field at the interfaces. The optimal ZnIn2 S4 /CdS/PdS performs a glaring photocatalytic activity of 191.9 µmol h-1 (10 mg of catalyst), and the largest AQE (apparent quantum efficiency) can reach a high value of 26.26%. This work may afford progressive tactics to design multifunctional photocatalysts.

Defected tungsten disulfide decorated CdS nanorods with covalent heterointerfaces for boosted photocatalytic H2 generation.

Owing to their intrinsic and pronounced charge carrier transport when facing the formidable challenge of inhibiting severe surface charge recombination, one-dimensional (1D) CdS nanostructures are promising for advancing high-yield hydrogen production. We herein demonstrate an efficient strategy of boosting interfacial carrier separation by heterostructuring 1D CdS with defective WS2. This process yields solid covalent interfaces for high flux carrier transfer that differ distinctively from those reported structures with physical contacts. As a nonnoble cocatalyst, WS2 can accept photogenerated electrons from CdS, and the sulfur vacancies existing at its edges can effectively trap electrons as active sites for H2 evolution. Moreover, due to its strong negative property, the H+ from the aqueous solution can gather around WS2. WS2 possesses a lower reaction barrier than CdS, which expedites the kinetic process for the reaction. The optimized sample exhibits a high photocatalytic H2 evolution rate of 183.4 µmol/h (10 mg photocatalyst), which is as far as we know among the top in the records for CdS-based photocatalysts. We believe this present work will be inspiring in addressing the interfacial charge carrier transfer by constructing covalent heterointerfaces.

PdS Quantum Dots as a Hole Attractor Encapsulated into the MOF@Cd0.5Zn0.5S Heterostructure for Boosting Photocatalytic Hydrogen Evolution under Visible Light.

Herein, a new photocatalyst PdS@UiOS@CZS is successfully synthesized, where thiol-functionalized UiO-66 (UiOS), a metal-organic framework (MOF) material, is used as a host to encapsulate PdS quantum dots (QDs) in its cages, and Cd0.5Zn0.5S (CZS) solid solution nanoparticles (NPs) are anchored on its outer surface. The resultant PdS@UiOS@CZS with an optimal ratio between components displays an excellent photocatalytic H2 evolution rate of 46.1 mmol h-1 g-1 under visible light irradiation (420∼780 nm), which is 512.0, 9.2, and 5.9 times that of pure UiOS, CZS, and UiOS@CZS, respectively. The reason for the significantly enhanced performance is that the encapsulated PdS QDs strongly attract the photogenerated holes into the pores of UiOS, while the photogenerated electrons are effectively migrated to CZS due to the heterojunction effect, thereby effectively suppressing the recombination of charge carriers for further high-efficiency hydrogen production. This work provides an idea for developing efficient photocatalysts induced by hole attraction.

Hydrogen spillover effect induced by ascorbic acid in CdS/NiO core-shell p-n heterojunction for significantly enhanced photocatalytic H2 evolution.

A new variety of CdS/NiO core-shell p-n heterojunction is synthesized by in-situ chemically depositing NiO shell on single-crystal CdS nanorods for the first time. With this method, the range of NiO shell thickness can be accurately controlled within a few nanometers. The optimized CdS/NiO sample (CSN0.5) with a NiO shell layer of 1.5 nm exhibits a highly efficient photocatalytic H2 evolution rate of 731.7 µmol/h (corresponding to 243.9 mmol/g/h) without using co-catalyst, which is among the highest value of all the CdS-based photocatalysts. The apparent quantum efficiency (AQE) of CSN0.5 at 365 nm wavelength reaches 28.19%. The remarkably enhanced photocatalytic performance can be attributed to a hydrogen spillover effect induced by ascorbic acid in CdS/NiO, which promotes the transmission of adsorbed H* from hydrogen-rich NiO (electron-poor region) to hydrogen-poor CdS (electron-rich region) where the adsorbed H* reacts in time with the photogenerated electron to produce H2, facilitating the H2 evolution reaction. This work provides a method to promote the photocatalytic H2 evolution reaction by using hydrogen spillover effect.

Thio linkage between CdS quantum dots and UiO-66-type MOFs as an effective transfer bridge of charge carriers boosting visible-light-driven photocatalytic hydrogen production.

Metal-organic frameworks (MOFs)/semiconductor hybrids have attracted attention in photocatalysis. Herein, we report a new strategy to use thiol-laced UiO-66 (UiO-66-(SH)2) as a porous and functional support for anchoring CdS quantum dots (QDs) (size: 0.5/3 nm). Cd2+ ions are firstly absorbed into the cavities of UiO-66-(SH)2 MOFs via coordinating to the thiol groups in the presence of a base to produce UiO-66-(S-Cd)2, then thiourea is added to form UiO-66-(S-CdS)2 (abbreviated as UiOS-CdS). It is clearly revealed by ultrafast transient absorption spectroscopy that the thio linkage between UiO-66 and CdS acts as an effective transfer bridge of charge carriers, which greatly promotes the interface transfer process of photogenerated electrons and holes, boosting the photocatalytic hydrogen production performance from water splitting. The optimized UiOS-CdS exhibits a photocatalytic H2 production rate of 153.2 µmol h-1 (10 mg of catalyst) under visible-light irradiation (λ > 420 nm) in the absence of nobel metal co-catalyst, corrsponding to an apparent quantum efficiency of 11.9% at 420 nm. This work may provide an effective strategy to construct QDs-linker-MOFs stylephotocatalysts for efficient energy conversion.