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

In this study, CexZr1-xO2 solid-solution oxide (x = 0.7) was prepared using hydrothermal method, and the obtained Ce0.7Zr0.3O2 nanoparticles were modified with wood-based carbon quantum dots (CQDs). Furthermore, we report a composite photocatalyst of vacuum heat-treated CQDs/Ce0.7Zr0.3O2 for degrading methylene blue. The structural properties and photocatalytic activity of CQDs/Ce0.7Zr0.3O2 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(2) hybrid oxygen atoms, thus increasing the surface oxygen vacancy concentration. The high activity and excellent stability of vacuum heat-treated CQDs/Ce0.7Zr0.3O2 system can be attributed to increased surface oxygen vacancy concentration, modification of CQDs, and the protruding structure of Ce0.7Zr0.3O2, 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.