CdS@Polydopamine@SnO2-x sandwich structure with electrostatic repulsion effect and oxygen deficiency: enhanced photocatalytic hydrogen evolution activity and inhibited photo-corrosion

Abstract

The activity and stability of photocatalysts are usually restricted to photo-corrosion issues. Here, an efficient electrostatic repulsion and anchor strategy via constructing a CdS@Polydopamine@SnO2-x sandwich structure with numerous oxygen vacancies through a simple chemical bath deposition approach. During the formation process, the CdS nanorods are wrapped by the catechol fragments from polydopamine (PDA) and display an electronegative surface. This strong electrostatic repulsion can effectively repel S2-, thereby effectively preventing S2- from being separated from CdS and being oxidized by holes or oxygen. Furthermore, the PDA employed as an interlayer of the heterojunction sandwich structure can fix the multivalent metal ions, such as Cd2+ and Sn4+ ions on CdS and SnO2-x, which can be used as a bridge for electronic transmission. More importantly, the as-prepared SnO2-x nanocrystals are found to possess a large amount of oxygen vacancies, which can effectively control the electronic structure of the catalyst, enhance the electron enrichment effect, promote the absorption of visible light and change the charge transfer ability. More importantly, the accumulation of CdS@PDA@SnO2-x (411.37 mmol) photocatalytic hydrogen evolution is 34.3 times than pristine CdS (12.0 mmol) within 5 h, and the catalytic activity remains stable after 10 cycles. Photoelectrochemical characterization, Scanning Kelvin Probe (SKP), Finite Difference Time Domain (FDTD) simulations verified the mechanism of enhanced photocatalytic activity. Herein, this work displays a novel structure and mechanism to enhance the stability of sulfide semiconductors, which may further open a new path in the structural control strategy of photocatalysts.