Sponge-like inorganic-organic S-scheme heterojunction for efficient photocatalytic hydrogen evolution

Covalent organic frameworks (COFs)-based S-scheme heterojunction photocatalysts have gained considerable attention for photocatalytic hydrogen evolution. However, challenges such as limited interfacial contact and low stability persist, primarily due to uneven inorganic semiconductor coverage on the COFs surface. Therefore, constructing inorganic-organic S-scheme heterojunction photocatalysts via the in-situ growth of COFs on inorganic semiconductor surfaces shows great promise. Herein, we successfully developed a sponge-like TiO₂@BTTA S-scheme heterojunction with a tight contact interface by in-situ growing COF (referred to as BTTA) on the surface of sponge-like TiO₂ (referred to as ST). Density Functional Theory (DFT) calculations confirmed that the ST@BTTA hybrids exhibit the optimal adsorption and desorption capabilities for H₂O and H₂ molecules, respectively. Notably, the ST@BTTA-120 S-scheme heterojunction photocatalyst demonstrates an outstanding hydrogen production rate under simulated sunlight irradiation, surpassing pristine ST and BTTA by factors of 10.3 and 2.6, respectively. The enhanced photocatalytic performance is attributed to improved solar energy utilization efficiency, a larger specific surface area, and an increased interfacial contact area between ST and BTTA. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analyses further verify the S-scheme carrier transfer mechanism in the ST@BTTA hybrids. This research provides a valuable method for designing efficient S-scheme heterojunction photocatalysts with closely integrated interfaces for photocatalytic hydrogen production via water splitting.