Hydrogen peroxide(H_(2)O_(2))has gained widespread attention as a versatile oxidant and a mild disin-fectant.Here,an electrostatic self-assembly method is applied to couple ZnSe quantum dots(QDs)with a flower-like cov...Hydrogen peroxide(H_(2)O_(2))has gained widespread attention as a versatile oxidant and a mild disin-fectant.Here,an electrostatic self-assembly method is applied to couple ZnSe quantum dots(QDs)with a flower-like covalent organic framework(COF)to form a step-scheme(S-scheme)photocata-lyst for H_(2)O_(2)production.The as-prepared S-scheme photocatalyst exhibits a broad light absorption range with an edge at 810 nm owing to the synergistic effect between the ZnSe QDs and COF.The S-scheme charge-carrier transfer mechanism is validated by performing Fermi level calculations and in-situ X-ray photoelectron and femtosecond transient absorption spectroscopies.Photolumi-nescence,time-resolved photoluminescence,photocurrent response,electrochemical impedance spectroscopy,and electron paramagnetic resonance results show that the S-scheme heterojunction not only promotes charge carrier separation but also boosts the redox ability,resulting in enhanced photocatalytic performance.Remarkably,a 10%-ZnSe QD/COF has excellent photocatalytic H_(2)O_(2)-production activity,and the optimal S-scheme composite with ethanol as the hole scavenger yields a H_(2)O_(2)-production rate of 1895 mol g^(-1)h^(-1).This study presents an example of a high-performance organic/inorganic S-scheme photocatalyst for H_(2)O_(2)production.展开更多
The fabrication of S-scheme heterojunctions has received considerable attention as an effective approach to promote the separation and migration of photoexcited electron/hole pairs and retain strong redox abilities.He...The fabrication of S-scheme heterojunctions has received considerable attention as an effective approach to promote the separation and migration of photoexcited electron/hole pairs and retain strong redox abilities.Herein,an imine-based porous covalent organic framework(COF-LZU1)is integrated with controllably fabricated Cd S hollow cubes,resulting in the formation of an S-scheme heterojunction.When the COF content reaches 1.5 wt%,the COF/Cd S heterostructure(1.5%COF/Cd S)achieves the highest hydrogen generation rate of 8670μmol·h^(-1)·g^(-1),which is approximately 2.1 times higher than that of pure Cd S.The apparent quantum efficiency(AQE)of 1.5%COF/Cd S is approximately 8.9%at 420 nm.Further systematic analysis shows that the intimate contact interface and suitable energy band structures between Cd S and COF can induce the formation of an internal electric field at the heterojunction interface,which can effectively drive the spatial separation of photoexcited charge carriers and simultaneously maintain a strong redox ability,thus enhancing the photocatalytic H_(2) evolution performance.展开更多
Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separati...Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separation.Therefore,investigating highly effective COF-based photocatalysts is crucial.For the first time,conjugated COF/perylene diimide urea polymer(PUP)all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF(denoted as TATF-COF)with PUP.The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h^(-1) g^(-1) for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts,resulting in an apparent quantum efficiency of up to 19.7%at 420 nm.The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H_(2) evolution.Experiments and theoretical studies reveal plausible H_(2) evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation.This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.展开更多
文摘Hydrogen peroxide(H_(2)O_(2))has gained widespread attention as a versatile oxidant and a mild disin-fectant.Here,an electrostatic self-assembly method is applied to couple ZnSe quantum dots(QDs)with a flower-like covalent organic framework(COF)to form a step-scheme(S-scheme)photocata-lyst for H_(2)O_(2)production.The as-prepared S-scheme photocatalyst exhibits a broad light absorption range with an edge at 810 nm owing to the synergistic effect between the ZnSe QDs and COF.The S-scheme charge-carrier transfer mechanism is validated by performing Fermi level calculations and in-situ X-ray photoelectron and femtosecond transient absorption spectroscopies.Photolumi-nescence,time-resolved photoluminescence,photocurrent response,electrochemical impedance spectroscopy,and electron paramagnetic resonance results show that the S-scheme heterojunction not only promotes charge carrier separation but also boosts the redox ability,resulting in enhanced photocatalytic performance.Remarkably,a 10%-ZnSe QD/COF has excellent photocatalytic H_(2)O_(2)-production activity,and the optimal S-scheme composite with ethanol as the hole scavenger yields a H_(2)O_(2)-production rate of 1895 mol g^(-1)h^(-1).This study presents an example of a high-performance organic/inorganic S-scheme photocatalyst for H_(2)O_(2)production.
文摘The fabrication of S-scheme heterojunctions has received considerable attention as an effective approach to promote the separation and migration of photoexcited electron/hole pairs and retain strong redox abilities.Herein,an imine-based porous covalent organic framework(COF-LZU1)is integrated with controllably fabricated Cd S hollow cubes,resulting in the formation of an S-scheme heterojunction.When the COF content reaches 1.5 wt%,the COF/Cd S heterostructure(1.5%COF/Cd S)achieves the highest hydrogen generation rate of 8670μmol·h^(-1)·g^(-1),which is approximately 2.1 times higher than that of pure Cd S.The apparent quantum efficiency(AQE)of 1.5%COF/Cd S is approximately 8.9%at 420 nm.Further systematic analysis shows that the intimate contact interface and suitable energy band structures between Cd S and COF can induce the formation of an internal electric field at the heterojunction interface,which can effectively drive the spatial separation of photoexcited charge carriers and simultaneously maintain a strong redox ability,thus enhancing the photocatalytic H_(2) evolution performance.
文摘Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separation.Therefore,investigating highly effective COF-based photocatalysts is crucial.For the first time,conjugated COF/perylene diimide urea polymer(PUP)all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF(denoted as TATF-COF)with PUP.The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h^(-1) g^(-1) for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts,resulting in an apparent quantum efficiency of up to 19.7%at 420 nm.The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H_(2) evolution.Experiments and theoretical studies reveal plausible H_(2) evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation.This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.
