In Situ Soft X-Ray Absorption Spectroscopy Investigation on Charge Transfer Mechanism in COF/CdS S-Scheme Photocatalyst.

Abstract

Photocatalysis enabled by step-scheme (S-scheme) heterojunction has emerged as a promising strategy for addressing the global energy crisis and achieving carbon neutrality. However, mechanisms regulating the interfacial charge transfer dynamics of S-scheme heterojunctions remain elusive. Herein, the electron transfer mechanisms are elucidated for a model S-scheme heterojunction composed of cadmium sulfide and a covalent organic framework material using synchrotron-based in situ soft X-ray absorption spectroscopy, substantiating the well-established in situ irradiated X-ray photoelectron spectroscopy. The results, combined with theoretical calculations, reveal that interfacial Cd─N and Cd─S bonds act as the charge transfer channels within the heterojunction. The S-scheme heterojunction exhibits high charge separation efficiency, as demonstrated by femtosecond transient absorption spectroscopy, which contributed to enhanced photocatalytic performance in coupled H₂O₂ generation and organic transformation reactions. This study validates a new approach to characterizing S-scheme heterojunctions and can guide the design of inorganic-organic S-scheme heterojunctions for practical photocatalytic applications.