Recent advances of modification effect in CoO-based catalyst towards highly efficient photocatalysis.

Tricobalt tetroxide (CoO) has been developed as a promising photocatalyst material for various applications. Several reports have been published on the self-modification of CoO to achieve optimal photocatalytic performance. The pristine CoO alone is inadequate for photocatalysis due to the rapid recombination process of photogenerated (PG) charge carriers. The modification of CoO can be extended through the introduction of doping elements, incorporation of supporting materials, surface functionalization, metal loading, and combination with other photocatalysts. The addition of doping elements and support materials may enhance the photocatalysis process, although these modifications have a slight effect on decreasing the recombination process of PG charge carriers. On the other hand, combining CoO with other semiconductors results in a different PG charge carrier mechanism, leading to a decrease in the recombination process and an increase in photocatalytic activity. Therefore, this work discusses recent modifications of CoO and their effects on its photocatalytic performance. Additionally, the modification effects, such as enhanced surface area, generation of oxygen vacancies, tuning the band gap, and formation of heterojunctions, are reviewed to demonstrate the feasibility of separating PG charge carriers. Finally, the formation and mechanism of these modification effects are also reviewed based on theoretical and experimental approaches to validate their formation and the transfer process of charge carriers.