Constructing tightly integrated CTF-2/TiO2 S-scheme heterojunction with enhanced charge separation for photocatalytic hydrogen evolution

Efficiently harnessing solar energy for hydrogen production remains a significant challenge, primarily dependent on the rational design of photocatalysts. In this work, an S-scheme heterojunction was constructed by integrating TiO 2 with a biphenyl-bridged covalent triazine framework (CTF-2). The extended π-conjugation in CTF-2 significantly enhances visible-light absorption and generates abundant delocalized electrons. The heterostructure was confirmed by characterizations, which revealed an increased specific surface area and enhanced redox capacity. Photoelectrochemical tests indicated a significant reduction in charge recombination, attributed to the newly formed Ti-N bonds that promote electron transfer from TiO 2 to CTF-2. The active species capture experiment and band structure analysis corroborated the S-scheme charge transfer route. The optimal 1.0 wt% CTF-2/TiO 2 achieved an H 2 evolution rate of 2.975 mmol·g -1 ·h -1 , 4.92 times higher than pristine TiO 2 , and retained 83% of its activity after five cycles. This study provides a practical approach to designing high-performance, stable heterostructures for solar energy conversion.