CQDs-interspersed floral CdS/NiAl-LDH heterojunction towards efficient photoreduction of CO2-to-CO

Abstract

A series of hierarchical flower-like CdS/carbon quantum dots/NiAl-LDH (CCL) photocatalyst have been successfully prepared to achieve efficient conversion of CO2-to-CO via a simple yet effective hydrothermal method. In the CCL, interspersed-CQDs not only increase the number of reactive sites but also reduce inner electronic impedance with the assistance of light reflecting-scattering effect. This significantly improves electron migration efficiency and inhibits the recombination of photoinduced electron-holes pairs. Without any sacrificial agent or photosensitizer, the sample of CCL-1 exhibits the highest CO evolution rate of 7.04 μmol·g−1·h−1 in water under simulated sunlight illumination with a large specific surface area (129.15 m2 g−1) and an appropriate CQDs content of 15.2 wt%, which is 12.8- and 11.2-fold higher than those of pristine LDH, pure CdS, and many previously reported LDH-based counterparts. A type-Ⅱ interfacial charge transfer mechanism is proposed, where electrons migrate rapidly from CdS to LDH with highly-interspersed CQDs as unhindered electron conduction bridges. The present work outlines a simple and controllable LDH-based heterojunction, which give rise to superior photocatalytic activity for CO2 photoreduction.