Strategies for enhancing interfacial built-in electric field strength in S-scheme heterojunction photocatalysts: A review

S-scheme heterojunctions, regarded as high-performance photocatalysts, have gained increasing attention in various applications due to their effective charge separation and migration, enhanced visible light absorption, high redox capacity, and remarkable stability. However, despite achieving effective charge separation, the built-in electric field (BIEF) driving charge separation process often lacks the desired strength. The BIEF strength is influenced by the Fermi level difference between the constituent semiconductors in an S-scheme heterojunction. Several emerging strategies have been explored to increase charge separation by enhancing the BIEF, particularly through modulation of band structure and Fermi levels. Despite significant progress in strengthening the BIEF, a review addressing these strategies is still lacking. This review consolidates recent advances in strategies to increase BIEF strength in S-scheme photocatalysts. Finally, the challenges and future perspectives for increasing BIEF strength through these strategies are discussed. This review provides valuable insights for researchers aiming to optimize charge separation and overall photocatalytic performance in S-scheme photocatalysts.