Recent progress in defective TiO2 photocatalysts for energy and environmental applications

In recent decades, TiO2 nanomaterial photocatalysts for energy and environmental applications have attracted extensive research interest. However, the main bottlenecks are the large bandgap (3–3.2 eV), which limits the amount of light absorption, and the relatively high charge-carrier recombination, which restricts the photocatalytic performance. Fortunately, recent reports indicate that engineering the defects of TiO2 could broaden the photoresponse and promote charge separation efficiency. To further promote the photocatalytic performance of solar energy, it is necessary to summarize the recent progress in defective TiO2 photocatalysts. In this review, various synthesis strategies for defective TiO2, especially black TiO2 nanomaterials, and their applications are summarized. The defect types and characteristics as well as the photocatalytic mechanism are reviewed and discussed in detail. This review is of great significance for environmental remediation and energy production in the field of photocatalysis.