The synergy between electronic anchoring effect and internal electric field in CdS quantum dots decorated dandelion-like Fe-CeO2 nanoflowers for improved photocatalytic hydrogen evolution.

A series of dandelion-like Fe-CeO2/CdS (FeCex/Cdy) nanoflowers with different molar ratios of Fe-CeO2 to CdS are synthesized by solvothermal method for the first time. The FeCex/Cdy nanoflowers are assembled by a large number of nanoparticles with the diameter of about 3 nm, and the introduction of Fe ions and the couple of CdS quantum dots (QDs) efficiently enhanced the relative percentage of Ce3+ in CeO2. The as-obtained FeCe1/Cd1 heterostructure exhibits the highest photocatalytic H2 evolution ability of 108.9 µmol/h, which is 20.5, 6.1 and 7.1 times higher than CeO2, Fe-CeO2 and CdS, respectively. This significantly enhanced photocatalytic performance can be mainly attributed to the synergy between the electronic anchoring effect of Fe3+/Fe2+ and Ce4+/Ce3+ redox couples and the internal electric field constructed by the II-type heterojunction between Fe-CeO2 and CdS. This work provides a new idea for the design of efficient photocatalysts by combining the advantages of heterostructure and ion anchoring effect.

Stable 1T-phase MoS2 as an effective electron mediator promoting photocatalytic hydrogen production.

Coupling two semiconductors together to construct a Z-scheme type photocatalytic system is an efficient strategy to solve the serious recombination challenge of photogenerated electrons and holes. In this work, we develop a novel composite photocatalyst by sandwiching metallic 1T-phase MoS2 nanosheets between MoO3 and g-C3N4 (MoO3/1T-MoS2/g-C3N4) for the first time. The metallic 1T-phase MoS2 acts as an efficient electron mediator between MoO3 and g-C3N4 to construct an all-solid-state Z-scheme photocatalytic system, resulting in a highly-efficient spatial charge separation and transfer process. Benefiting from this, the newly developed MoO3/1T-MoS2/g-C3N4 exhibits a drastically enhanced photocatalytic H2 evolution rate of 513.0 µmol h-1 g-1 under visible light irradiation (>420 nm), which is nearly 12 times higher than that of the pure g-C3N4 (39.5 µmol h-1 g-1), and 3.5 times higher than that of MoO3/g-C3N4 (145.7 µmol h-1 g-1). More importantly, the originally unstable 1T-phase MoS2 becomes very stable in MoO3/1T-MoS2/g-C3N4 because of the sandwich structure where 1T-phase MoS2 is protected by MoO3 and g-C3N4, which endows the photocatalyst with excellent photostability. It is believed that this study will provide new insights into the design of efficient and stable Z-scheme heterostructures for photocatalytic applications.

Multiple carrier-transfer pathways in a flower-like In2S3/CdIn2S4/In2O3 ternary heterostructure for enhanced photocatalytic hydrogen production.

A novel flower-like In2S3/CdIn2S4/In2O3 (ICS) ternary heterostructure (HS) is rationally constructed for the first time by a series of carefully designed procedures. In2O3 nanoflakes are the main constituent units which assemble into a flower-like skeleton structure, and CdIn2S4 nanoparticles are in situ generated on the surface of In2O3 nanoflakes through the transformation of CdS quantum dots (QDs) while In2S3 nanoparticles are in situ produced at the region between CdIn2S4 nanoparticles and In2O3 nanoflakes resulting from a synchronous sulfuration procedure. As expected, the rationally designed ICS ternary HSs display significantly enhanced photocatalytic H2 production, especially ICS5 (sulfurized for 5 h) with the highest H2 evolution rate of 20.04 µmol h-1 (10 mg catalyst is used for photocatalytic reaction), which is 26.7 times and 2.6 times higher than that of pure In2O3 (0.75 µmol h-1) and In2S3/In2O3 binary HS (7.88 µmol h-1), respectively. The enhanced photocatalytic activity can be attributed to the multiple interfaces formed in the ICS HSs, including the CdIn2S4-In2O3 interface, the In2S3-In2O3 interface, and the CdIn2S4-In2O3-In2S3 interface, which construct multiple pathways for the transfer of photogenerated charge carriers, effectively promoting the photocatalytic hydrogen production.

WS2 /Graphitic Carbon Nitride Heterojunction Nanosheets Decorated with CdS Quantum Dots for Photocatalytic Hydrogen Production.

Two-dimensional/two-dimensional (2D/2D) stacking heterostructures are highly desirable in fabricating efficient photocatalysts because face-to-face contact can provide a maximized interfacial region between the two semiconductors; this largely facilitates the migration of charge carriers. Herein, a WS2 /graphitic carbon nitride (CN) 2D/2D nanosheet heterostructure decorated with CdS quantum dots (QDs) has been designed, for the first time. Optimized CdS/WS2 /CN without another cocatalyst exhibits a significantly enhanced photocatalytic H2 evolution rate of 1174.5 µmol h-1 g-1 under visible-light irradiation (λ>420 nm), which is nearly 67 times higher than that of the pure CN nanosheets. The improved photocatalytic activity can be primarily attributed to the highly efficient charge-transfer pathways built among the three components, which effectively accelerate the separation and transfer of photogenerated electrons and holes, and thus, inhibit their recombination. Moreover, the extended light-absorption range also contributes to excellent photocatalytic efficiency. In addition, the CdS/WS2 /CN photocatalyst shows excellent stability and reusability without apparent decay in the photocatalytic H2 evolution within 4 cycles in 20 h. It is believed that this work may shed light on specifically designed 2D/2D nanosheet heterostructures for more efficient visible-light-driven photocatalysts.