Construction of 2D-layered quantum dots/2D-nanosheets heterostructures with compact interfaces for highly efficient photocatalytic hydrogen evolution.

Construction of 2D-layered quantum dots/2D-nanosheets heterostructures with compact interfaces for highly efficient photocatalytic hydrogen evolution

The introduction of impure atoms or crystal defects is a promising strategy for enhancing the photocatalytic activity of semiconductors. However, the synergy of these two effects in 2D atomic layers remains unexplored. In this case, the preparation of molybdenum-doped thin ZnIn2S4-containing S vacancies (Mo-doped Sv-ZnIn2S4) is conducted using a one-pot solvothermal method. The coordination of Mo doping and S vacancies not only enhances visible light absorption and facilitates the separation of photogenerated carriers but also provides many active sites for photocatalytic reactions. Meanwhile, the Mo-S bonds play function as high-speed channels to rapidly transfer carriers to the active sites, which can directly promote hydrogen evolution. Consequently, Sv-ZnIn2S4 with an optimized amount of Mo doping exhibits a high hydrogen evolution rate of 5739 μmol g−1 h−1 with a corresponding apparent quantum yield (AQY) of 21.24% at 420 nm, which is approximately 5.4 times higher than the original ZnIn2S4. This work provides a new strategy for the development of highly efficient and sustainable 2D atomic photocatalysts for hydrogen evolution.

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Highly Efficient Photocatalytic Hydrogen Evolution over Mo-Doped ZnIn2S4 with Sulfur Vacancies

The design of photocatalyst with excellent light-harvesting and charge-separation abilities is quite important for high-performance photocatalysis. Herein, narrow-bandgap PbS, wide-bandgap WO3–x, and Au nanoparticles were combined to form a plasmon-mediated Z-scheme nanostructure for the first time. Particularly, PbS nanoparticles were deposited on oxygen-abundant WO3–x nanobricks, then Au nanoparticles were grown on the hybrids to form WO3–x/PbS/Au ternary nanostructures. Because of the cooperation of wide and narrow bandgaps as well as the oxygen vacancies and plasmon, the ternary hybrids displayed wide light absorption ranging from ultraviolet to near-infrared region. Meanwhile, the energy band arrangement of PbS and WO3–x provides a direct Z-scheme pathway and built-in electric field for charge transfer and separation. As a result, WO3–x/PbS hybrids displayed a large enhancement on photocatalytic hydrogen generation activity compared with the components under visible light irradiation, which is 9.2 and 9.8 times of WO3–x and PbS, respectively. Furthermore, the WO3–x/PbS/Au ternary hybrids showed the best photocatalytic performance that is 21.8 and 2.4 times of WO3–x and WO3–x/PbS hybrids. Meanwhile, the ternary photocatalysts possessed prominent apparent quantum efficiency under near-infrared light irradiation. The prominent photocatalytic performance can be attributed to the broadband light absorption, enhanced specific surface area, efficient charge transfer and separation induced by the oxygen-vacancy and plasmon-mediated Z-scheme band energy structure. 

WO3–x/PbS/Au Ternary Heterojunction Nanostructures for Visible-Light-Driven Photocatalytic Hydrogen Generation

Spatial confinement: A green pathway to promote the oxidation processes for organic pollutants removal from water.

Photocatalytic hydrogen evolution from water is a promising approach for renewable energy generation and storage. However, traditional photocatalysts suffer from limited hydrogen evolution rates due to the lack of active sites. In this work, we demonstrate that a plenty of active sites can be provided by the surface autocatalytic effect and quantum confinement of ultrasmall SiC nanocrystals (NCs). A metal-free photocatalyst is constructed by anchoring the ultrasmall SiC NCs on carbon nitride (CN) nanosheets for efficient and durable hydrogen generation. Moreover, the optical absorption in the visible range and the separation of electrons and holes are significantly improved by the heterojunction band alignment. As a consequence, the CN/SiC NC composite exhibits a high hydrogen evolution rate up to 1889 μmol g−1 h−1 under visible light irradiation with an apparent quantum yield (AQY) of 9.8% at 420 nm. And the photocatalyst shows high stability in the cyclic test. This work provides a new strategy to develop highly efficient photocatalysts for hydrogen generation via the surface autocatalytic effect and quantum confinement.

Qingfeng Gui

Papers

Active sites provided by the surface autocatalytic effect and quantum confinement for stable and efficient photocatalytic hydrogen generation