Insights into semiconductor heterojunctions for enhanced photocatalytic performance and applications

Semiconductor heterojunction combining with two or more photocatalytic materials has boosted a renovated interest in fields ranging from energy storage to environmental protection, resulting from the special synergistic preponderance in comparison of single-component photocatalysts. Generally speaking, the heterojunction formed at photocatalyst interface promotes the electrons rearrangement due to the discrepancy of Fermi lever, further inducing a robust internal electric field (IEF) which has a positive effect on the photogenerated charge separation and migration, enhancing the photocatalytic performance. The majority of extant research is oriented towards the design, characterization and application of specific heterojunctions, which lacks a comprehensive overview of all the common types of semiconductor heterojunctions. Thus, in order to better understand the photocatalytic mechanisms and construction methods of heterojunction photocatalysts, this review firstly summarizes basic categories of photocatalytic heterojunction systems, and simultaneously takes some typical examples to verify the important function of heterojunction. The design principle of heterostructures, as well as their synthesis methods, are summed up. Furthermore, the practical environmental applications of heterojunction photocatalysts are overall introduced, including environmental wastewater remediation, water splitting, CO₂ conversion, H₂O₂ synthesis and other applications, and the challenges associated with the construction method of heterojunction and the prospects that motivate future research are comprehensively discussed.