The paper reviews the state of the art in the synthesis of multinary (ternary, quaternary and more complex) metal chalcogenide nanocrystals (NCs) and their applications as a light absorbing or an auxiliary component of light-harvesting systems. This includes solid-state and liquid-junction solar cells and photocatalytic/photoelectrochemical systems designed for the conversion of solar light into the electric current or the accumulation of solar energy in the form of products of various chemical reactions. The review discusses general aspects of the light absorption and photophysical properties of multinary metal chalcogenide NCs, the modern state of the synthetic strategies applied to produce the multinary metal chalcogenide NCs and related nanoheterostructures, and recent achievements in the metal chalcogenide NC-based solar cells and the photocatalytic/photoelectrochemical systems. The review is concluded by an outlook with a critical discussion of the most promising ways and challenging aspects of further progress in the metal chalcogenide NC-based solar photovoltaics and photochemistry.

Solar light harvesting with multinary metal chalcogenide nanocrystals

It is highly desirable to develop efficient visible-light-driven photocatalysts for hydrogen production from water splitting. We herein report a rational design for reliable and convenient fabrication of a set of nanocomposites with ZnIn2S4 nanosheets encapsulated UiO-66 octahedral nanoparticles (UiO-66@ZnIn2S4). The comprehensive characterizations verify ZnIn2S4 nanosheets are uniformly decorating on UiO-66 octahedral nanoparticles. The systematic studies demonstrate the UiO-66@ZnIn2S4 (U@Z) holds favorable features to facilitate effective separation and transfer of photochemical charges, thanks to intimate contact interfaces and a well-matched band structure between UiO-66 and ZnIn2S4. The optimal nanocomposite exhibits high photocatalytic activity for hydrogen production under visible light illumination, generating hydrogen at an impressive rate of up to 3061.61 μmol h−1 g−1, with an apparent quantum efficiency of 9.84% under the incident monochromatic light of 420 nm.

Nanohybrid photocatalysts with ZnIn2S4 nanosheets encapsulated UiO-66 octahedral nanoparticles for visible-light-driven hydrogen generation

ZnIn2S4-Based Photocatalysts for Energy and Environmental Applications

The relatively low charge transfer efficiency remains the critical limiting factor for the practical application of solar-driven water splitting. In this work, a promising photocatalyst intensified by dual cocatalysts was developed via separately loading Au nanoparticles and CoP nanosheets onto the inside and outside surface of three dimensionally ordered macroporous (3DOM) g-C3N4 framework to significantly facilitate the ordered transfer of charges. The spatial positioning of dual cocatalysts and average wall thickness of 3DOM g-C3N4 framework were precisely controlled to reveal the optimal distribution position of Au and CoP as well as the most appropriate transfer distance for charges (from 3DOM g-C3N4 walls to the surface of cocatalysts), respectively. The results show that the spatial positioning effect of dual cocatalysts and optimization of charge transfer distance can endow the CoP/3DOM g-C3N4/Au photocatalyst with an excellent charge transfer efficiency, thereby contributing to high apparent quantum efficiency (AQE, 27.6% at 435 nm and 29.9% at 550 nm) and photocatalytic H2 evolution activity of 11,820.1 μmol h−1 g−1, which is up to 619.9, 6.5 and 5.6 times than that of 3DOM g-C3N4, CoP/3DOM g-C3N4 and 3DOM g-C3N4/Au, respectively. This work would provide a new platform to design high-performance artificial photocatalysts with superior charge transfer capacity.

Spatial positioning effect of dual cocatalysts accelerating charge transfer in three dimensionally ordered macroporous g-C3N4 for photocatalytic hydrogen evolution

In some oxide photocatalysts, changing their surface structure rather than crystal structure by introducing some defects (such as oxygen vacancies) has been proven to be effective in enhancing the separation efficiency of photogenerated carriers and thus photocatalytic activity. To the best of our knowledge, however, such a surface defect engineering strategy for sulfide photocatalysts has rarely been verified. The present work shows the first case of employing pressure hydrogenation to prepare hydrogenated ZnIn2S4 (H-ZIS) microspheres with surface-deficient porous structures, which are favorable for furnishing sufficient surface sulfur vacancies to realize excellent photocatalytic hydrogen evolution reactions. The hydrogen evolution rate (HER) of H-ZIS is as high as 1.9 mmol h-1 g-1 (nearly 8.6 times that of the pristine ZIS sample), which rivals or exceeds those of previously-reported ZIS-based photocatalysts under visible light irradiation. Meanwhile, the inherent correlation between surface sulfur vacancies and photocatalytic activities of H-ZIS is also explored. Thus, this work demonstrates the feasibility of enhancing the hydrogen evolution capability of sulfide photocatalysts by the formation of sulfur vacancies through a pressure hydrogenation process.

Hydrogenated ZnIn2S4 microspheres: boosting photocatalytic hydrogen evolution by sulfur vacancy engineering and mechanism insight

A binary noble-metal-free cocatalyst consisting of ZnIn2S4 and In(OH)3 was developed via a facile one-step hydrothermal method The ZnIn2S4/In(OH)3 modified ZnWO4 nanocomposite exhibited enhanced photocatalytic H2 evolution activity compared to all the related pure samples and binary composite photocatalysts under visible light irradiation The enhanced photocatalytic hydrogen production activities can be attributed to the synergistic effects of the favorable light trapping ability and efficient spatial charge separation The photocatalytic hydrogen evolution activity over other semiconductors, such as Zn2SnO4 and TiO2, can also be significantly increased by loading ZnIn2S4/In(OH)3 as a cocatalyst The results clearly demonstrated that ZnIn2S4/In(OH)3 is discovered as a new class of earth-abundant cocatalyst for water-splitting under visible light irradiation It is expected that our work could provide a new strategy to improve the visible light response of semiconductors and facilitate their application in water splitting

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Cocatalyst designing: a binary noble-metal-free cocatalyst system consisting of ZnIn2S4 and In(OH)3 for efficient visible-light photocatalytic water splitting

A novel in situ hydrolysis reaction method has been developed for the controllable synthesis of ternary CdIn2S4/In(OH)3/Zn2GeO4 nanocomposite. The CdIn2S4 and In(OH)3 content in the ternary system can be conveniently tuned by varying the pH value of the reaction system. The ternary CdIn2S4/In(OH)3/Zn2GeO4 (pH = 6.5) nanocomposite sample exhibited the highest photocatalytic H2 production rate of 1426.90 μmol h−1 g−1, without the assistance of a noble metal. A possible mechanism of H2-production activity was proposed. The photo-generated electrons in the CB of CdIn2S4 can transfer to the CB of In(OH)3 and Zn2GeO4, resulting in a rapid separation of photo-generated electrons and holes. This work can not only provide an excellent candidate for visible-light H2 evolution, but also provide an efficient strategy for designing of new system with high activity for solar hydrogen generation.

Facile synthesis of ternary CdIn2S4/In(OH)3/Zn2GeO4 nanocomposite with enhanced visible-light photocatalytic H2 evolution

The invention discloses a preparation method of a photocatalytic water splitting hydrogen production material In(OH)3-ZnIn2S4 compound. The method comprises the following steps: dissolving 0.2975 g ofZn(NO3)2.6H2O, 0.6017 g of In(NO3)3.(4.5H2O) and 0.6090 g of thiourea into distilled water for mixing, dropwise adding 0.2 mol/L of NaOH into a solution by continuous stirring and adjusting the pH to4 to 6; after stabilizing for half an hour, transferring mixed liquid to 100 ml of polytetrafluoroethylene-lined high-temperature high-pressure reactor, and carrying out a reaction at the reaction temperature of 160 to 180 DEG C for 10 to 14 hours; transferring the reaction liquid into a suction flask for suction filtration, respectively washing with distilled water and ethanol for three times and drying at 60 to 100 DEG C for 3 to 5 hours to obtain the In(OH)3-ZnIn2S4 compound. According to the preparation method disclosed by the invention, a composite material consisting of two semiconductors with matching strip edge potential can greatly promote the separation of photo-generated carrier pairs and improve the photocatalytic activity.

Xiaoming Yan

Papers

Cocatalyst designing: a binary noble-metal-free cocatalyst system consisting of ZnIn2S4 and In(OH)3 for efficient visible-light photocatalytic water splitting

Facile synthesis of ternary CdIn2S4/In(OH)3/Zn2GeO4 nanocomposite with enhanced visible-light photocatalytic H2 evolution

Method for preparing In(OH)3-ZnIn2S4 hydrogen production material