| Photocatalytic technology has played and will continue to play a key role in environmental protection and energy applications to satisfy current and future energy needs.Photocatalytic hydrogen production can be used to store inexhaustible solar energy,which can effectively solve the environmental problems arising from the use of fossil fuels.It is essential to seek highly active and stable catalysts for the sustainable development of photocatalytic hydrogen production technology.I-III-VI quantum dots?QDs?play an important role in visible-light-driven photocatalysis,owning to their unique optical properties,wide adjustable band gaps and no toxic elements.However,they also have some disadvantages can not be ignored,such as high electron-hole recombination rate,low photocatalytic stability and far lower photocatalytic activity than theoretical expectations.Based on Ag-In-Zn-S QDs,we studied the structure and performance of narrow band gap photocatalysts in this paper.Around the polysulfide QDs and carbon nanocomposite catalyst surface interface control.This leads to the surface defects of QDs are reduced,photogenerated carriers separation efficiency is enhanced and the photocatalytic efficiency is improved.The photocatalytic hydrogen production performance of QDs can be further improved by ligand modification,construction of 0D/2D heterojunctions and self-assembly structure of QDs/carbon dots,which provides an experimental basis for the wide application of photocatalysts in the future.The main contents of this paper are as follows:1.A series of mixed ligands modified Ag-In-Zn-S QDs were synthesized by a simple one-step hydrothermal method.We studied the structure,composition,optical properties and reaction mechanism of the samples.The experimental results show that the hydrogen yield of QDs is 2 times higher than MPA/Cys=5:5?Trimercaptopropionic acid/L-cysteine=5:5?.Using ascorbic acid as sacrificial agent and no co-catalyst,the hydrogen production rate of MPA/Cys-terminated QDs reach to 6.64 mmol·g-1·h-1.This shows the advantages of QDs mixed ligand method.Further mechanism studies show that the introduction of MPA leads to a significant increase in PL lifetime and a decrease in non-radiative attenuation,which can be attributed to the strong passivation effect of MPA.Without affecting charge transfer,our method provides a very simple strategy for surface defect state control of Ag-In-Zn-S QDs,and has important guiding significance for the development of high-efficiency quantum dot-based visible-light photocatalysts.2.A series of 0D/2D Ag-In-Zn-S/RGO heterojunctions were synthesized by simple in situ growth method.We studied the structure,morphology and photocatalytic hydrogen production performance of composite photocatalysts with different RGO content.When the amount of RGO is 30?L,the photocatalytic hydrogen production reaches the maximum of all samples,which is 3.1 times higher than that of pure Ag-In-Zn-S QDs and has good stability.Time-resolved fluorescence and electrochemical impedance spectroscopy?EIS?studies show that the improvement of photocatalytic efficiency can be attributed to the prolongation of photogenerated carrier lifetime and the improvement of charge separation efficiency.Our work provides a simple synthesis method for the construction of 0D/2D quantum dots/RGO heterojunction structure,and provides a good reference for further improving the activity and stability of I-III-VI sulfide QDs.3.The composite photocatalyst of 0D/0D Ag-In-Zn-S QDs/carbon dots were successfully constructed by simple in situ growth method,we studied the effects of preparation temperature on the interface structure and photocatalytic activity of the system.The results show that the introduction of carbon dots can improve the charge separation efficiency and hydrogen production rate of the system.The self-assembled Ag-In-Zn-S QDs/carbon dots after heating have excellent visible hydrogen production rate,up to 8.475 mmol·g-1·h-1,which is 3.57 times as much as that of unagglomerated Ag-In-Zn-S QDs/carbon dots,and 7.76 times higher than the pure Ag-In-Zn-S QDs.Further structural studies show that the interaction between Ag-In-Zn-S QDs and carbon dots increases with increasing temperature,resulting in many domain-partitioned microstructures,which can promote photoelectron transmission and inhibit charge recombination.The significant improvement of catalytic performance may be attributed to the amide bonding between Ag-In-Zn-S QDs and carbon dots at elevated temperatures,which enhanced interfacial interaction and facilitates carrier separation and transfer.Using the structural advantages of carbon dots and the enhanced regulation of interfacial interaction,it provides a new perspective and direction for the development and design of narrow bandgap 0D/0D QDs-based photocatalysts. |
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