A composite material of vacuum heat-treated CQDs/Ce0.7Zr0.3O2 with enhanced charge separation for efficient photocatalytic degradation

In this study, Ce x Zr 1−x O 2 solid-solution oxide (x = 0.7) was prepared using hydrothermal method , and the obtained Ce 0.7 Zr 0.3 O 2 nanoparticles were modified with wood–based carbon quantum dots (CQDs). Furthermore, we report a composite photocatalyst of vacuum heat-treated CQDs/Ce 0.7 Zr 0.3 O 2 for degrading methylene blue. The structural properties and photocatalytic activity of CQDs/Ce 0.7 Zr 0.3 O 2 were systematically studied after vacuum heat treatment. Herein, a part of the functional groups present on CQD surfaces changed through high–temperature heating during vacuum heat treatment. The dominant structures sp 2 hybrid carbon atoms and amorphous carbon were transformed to defect states of sp 3 hybrid oxygen atoms, thus increasing the surface oxygen vacancy concentration. The high activity and excellent stability of vacuum heat-treated CQDs/Ce 0.7 Zr 0.3 O 2 system can be attributed to increased surface oxygen vacancy concentration, modification of CQDs, and the protruding structure of Ce 0.7 Zr 0.3 O 2 , contributing to efficient charge transfer. This study provides potential systems of CQD-modified photocatalysts and also reveals the substantial effect of vacuum heat treatment on enhancing the photocatalytic properties of composites.