Environmental application of versatile Bi-based perovskite photocatalysts and their Z-scheme and S-scheme heterojunctions

Bi-based perovskites (Bi2WO6, Bi2MoO6, BiFeO3, Bi4Ti3O12, etc.) have been documented as promising visible-light responsive materials for different photocatalytic applications (wastewater treatment, water splitting, CO2 reduction, and oxidation of hydrocarbons and alcohols to produce valuable chemicals). However, the main disadvantage of pure perovskites is the rapid recombination of photoinduced charge carriers and, therefore, low activity. Among different methods developed, creating heterojunctions, especially Z-scheme and S-scheme, is considered as the most effective approach to improve the photocatalytic performances of materials due to increased light absorption, improved separation of electrons-hole pairs, combination of different favorable properties of each component of a hybrid, possibility to use a wide range of semiconductors to construct an ideal composite. This critical review reports progress over the last 5 years in creating Z-scheme and S-scheme composites based on Bi-containing perovskites in photocatalysis for environmental remediation, hydrogen evolution, reduction of CO2 to CO and CH4, and production of industrially important organic chemicals by oxidation of hydrocarbons and alcohols. Moreover, challenges and opportunities are considered into developing new photocatalytic materials with their possible future commercialization. The critical review suggests strategies to improve the photocatalytic activity and stability of Z-scheme and S-scheme heterojunctions.