In Situ Irradiated X‐Ray Photoelectron Spectroscopy Investigation on a Direct Z‐Scheme TiO2/CdS Composite Film Photocatalyst

Abstract Inspired by nature, artificial photosynthesis through the construction of direct Z‐scheme photocatalysts is extensively studied for sustainable solar fuel production due to the effectiveness in enhancing photoconversion efficiency. However, there is still a lack of thorough understanding and direct evidence for the direct Z‐scheme charge transfer in these photocatalysts. Herein, a recyclable direct Z‐scheme composite film composed of titanium dioxide and cadmium sulfide (TiO2/CdS) is prepared for high‐efficiency photocatalytic carbon dioxide (CO2) reduction. In situ irradiated X‐ray photoelectron spectroscopy (ISI‐XPS) confirms the direct Z‐scheme charge‐carrier migration pathway in the photocatalytic system. Furthermore, density functional theory simulation identifies the intrinsic cause for the formation of the direct Z‐scheme heterojunction between the TiO2 and the CdS. Thanks to the significantly enhanced redox abilities of the charge carriers in the direct Z‐scheme system, the photocatalytic CO2 reduction performance of the optimized TiO2/CdS is 3.5, 5.4, and 6.3 times higher than that of CdS, TiO2, and commercial TiO2 (P25), respectively, in terms of methane production. This work is a valuable guideline in preparation of highly efficient recyclable nanocomposite for photoconversion applications.