Monitoring Electron Transfer Dynamics in WO <sub>3</sub> /CdS S‐Scheme Heterojunction by Near‐Infrared Femtosecond Transient Absorption Spectroscopy
Ziqing Yang, Songyu Yang, Hanjiao Yang, Jianjun Zhang, Jiaguo Yu
Abstract
Abstract To solve the problem of severe charge recombination in pure WO 3 , the construction of S‐scheme heterojunction is an effective approach. This work has successfully prepared WO 3 /CdS S‐scheme photocatalysts by electrostatic self‐assembly. In situ irradiated X‐ray photoelectron spectroscopy and in situ irradiated Kelvin probe force microscopy have provided evidence of steady‐state spectra of WO 3 /CdS S‐scheme heterojunction. To monitor the ultrafast S‐scheme interfacial electron transfer process, systematic femtosecond transient absorption spectroscopy (fs‐TAS) measurements are performed on pure WO 3 , CdS and WO 3 /CdS. Since pure WO 3 and CdS have similar negative fs‐TAS signals in the UV–vis wavelength range, it is difficult to resolve the electron dynamics of these two components in the WO 3 /CdS composite. To address this issue, this study effectively distinguishes the fs‐TAS signals of WO 3 and CdS by near‐infrared fs‐TAS for the first time. S‐scheme interfacial electron transfer mechanism is confirmed by resolving the quenching dynamics of trap state electrons in the WO 3 and CdS components of WO 3 /CdS composite. This work provides new ideas and references for systematic characterization of S‐scheme heterojunction photocatalysts.