| ?-?-? group quantum dots do not contain Cd and other highly toxic metal elements,band gap size and composition tunability,high defect tolerance and defect-related multiphoton absorption characteristics make it a development and high-performance photocatalytic hydrogen production system and a platform for discovering new physical effects.Due to the typical advantages of ternary quantum dots(QDs)and visible absorption band gap,CuInSe2(CISe)quantum dots have great potential applications in the field of photocatalysis.However,the low separation efficiency of photogenerated carriers and the unstable chemical performance of photocatalysts are still the main obstacles to the design of high performance CuInSe2-based photocatalytic hydrogen production system.Based on the research status,aiming at the main problems and challenges of ternary CuInSe2 QDs in the field of photocatalytic hydrogen production,ternary CuInSe2 QDs were studied from three aspects:surface defect control,surface ligand modification and heterojunction construction.The main contents are as follows:(1)CuInSe2(CISe)quantum dots have high defect tolerance,so catalysts can be designed by adjusting element ratio or defect distribution.In this work,a ligand-assisted aqueous two-step method for the preparation of defect-regulated CISe quantum dots is proposed for the first time.The absorption spectra confirm the typical double absorption edges of copper vacancy defects and indium substituted copper defects,which are formed by Cu/In ratio control and second step coarsening growth during the first step of initial synthesis.The steady-state-transient fluorescence spectra show that when the Cu/In ratio is1 CISe-1/4,the donor-receptor recombination dominates the CISe emission spectrum with the optimization of element composition,which leads to the prolongation of the fluorescence lifetime.The photocurrent response and electrochemical impedance spectroscopy of the samples show that the surface defects are beneficial to the separation and transport of carriers.The photocatalytic hydrogen evolution(PHE)rate of CISe-1/4 is722?mol·g–1·h–1,which is 23 times higher than that of CISe-1/4 crystal nucleus(31?mol·g–1·h–1),and the maximum apparent quantum efficiency is 1.3%.Based on the analysis of Raman spectra and Colombian interaction energy(Je/h),the surface defects lead to the decrease of Je/h of CISe-1/4,which is beneficial to improve the photoca talytic hydrogen evolution of CISe.This study provides a reference for the design of high-performance Imuri-VI photocatalyst through microstructure control to achieve efficient photocatalytic hydrogen production without precious metals.(2)The interaction between ligands and defects on the surface of quantum dots can significantly affect the kinetics of photocatalytic reaction.Using suitable surface ligands to modify the surface of quantum dots can improve the kinetic conditions of photocatalytic reaction and enhance their photocatalytic activity.In this work,Trithiocyanuric acid(TA)-modified CuInSe2 nanocrystals were prepared by aqueous synthesis for the first time,and the relationship between TA/Cu ratio,p H value or growth time and the luminescence properties of CuInSe2 quantum dots was studied to reveal the source of emission related to various defects.By studying the transient fluorescence spectra of the samples,it is found that the transfer of electrons related to the subband gap of CuInSe2(CISe)quantum dots to the corresponding TA,changes the traditional two-step one-electron photocatalytic hydrogen production process to an one-step reaction with the participation of two electrons.Under visible light irradiation,the hydrogen evolution rate of TA-modified CISe quantum dots reached 5832?mol·g–1·h–1 which was 2 times and 20.3 times higher than that of L-cysteine modified CISe quantum dots and ethylenediamine modified CISe quantum dots,respectively.It provides a new performance benchmark for the photocatalytic water splitting in I-III-VI quantum dots.Further p H treatment of the surface states of TA-CISe quantum dots confirmed the rationality of the photocatalytic one-step reaction mechanism of two electrons.By designing the surface ligand modification of quantum dots to regulate the charge transfer between the catalyst and the reaction interface,the photocatalytic performance is improved,which provides a new idea for designing efficient multicomponent quantum dots hydrogen production system from the surface state.(3)The heterojunction formed by two kinds of semiconductors with matched energy levels can promote the separation of photogenerated carriers and improve the photocatalytic activity.In this work,Zn S was grown on ultra-small CuInSe2 quantum dots by aqueous one-pot method,and CuInSe2-Zn S nanocrystalline heterostructures were obtained.XRD and TEM characterization confirmed that the prepared CuInSe2-Zn S nanocrystalline heterostructure.Absorption spectrum,fluorescence spectrum and electrochemical analysis show that the formation of heterojunction between CuInSe2 and Zn S is beneficial to the separation and transport of the carrier.The photocatalytic hydrogen evolution performance analysis showed that the photocatalytic hydrogen evolution activity of nanocrystalline heterojunction with Zn S/CuInSe2 ratio 4 was 8802?mol·g–1·h–1,which was 5.6 times higher than that of pure CuInSe2.The apparent quantum efficiency of Zn S/CuInSe2 nanocrystalline heterojunction was the highest at 415 nm,which was 2.3%.The heterojunction constructed by CuInSe2 and Zn S can significantly increase the photocatalytic hydrogen evolution rate of the photocatalyst,which can provide an effective reference for the design of I-III-VI photocatalyst heterojunction.To sum up,the photocatalytic performance of ternary CuInSe2 quantum dots was improved from the aspects of surface defect control,surface ligand modification and heterostructure construction.These studies confirmed that it is feasible to improve the photocatalytic activity of ternary CuInSe2 quantum dots by surface defect regulation,surface ligand modification and heterostructure construction.This work can provide an effective reference for the design of highly efficient visible light-driven multicomponent quantum dot photocatalysts from three aspects:surface defect regulation,surface ligand modification and heterostructure construction. |
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