Investigating the charge transfer mechanism of ZnSe QD/COF S-scheme photocatalyst for H2O2 production by using femtosecond transient absorption spectroscopy
Hydrogen peroxide(H2O2)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 H2O2 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 H2O2-production activity,and the optimal S-scheme composite with ethanol as the hole scavenger yields a H2O2-production rate of 1895 mol g 1 h-1.This study presents an example of a high-performance organic/inorganic S-scheme photocatalyst for H2O2 production.
ZnSe quantum dotCovalent organic frameworkS-scheme heterojunctionCarrier migration and separationH2O2 production
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