Abstract: Graphitic carbon nitride is flourishing in photocatalytic hydrogen production. However, the performance of traditional carbon nitride materials is limited by their scarcity of surface reactive sites and fast recombination of photogenerated electron-hole pairs. Herein, we introduce a simple ultrasonic synthesis method that exfoliates bulk carbon nitride into nanosheets while simultaneously forming S-scheme heterojunctions with in-situ grown thiophene-based polymer through π-π interactions. The obtained carbon nitride nanosheet/polymer S-scheme heterojunction possesses abundant surface active sites and exhibits suppressed recombination of photogenerated electron-hole pairs, resulting in a hydrogen production rate approximately double that of bulk carbon nitride and a superior apparent quantum yield of 5.00 %. The S-scheme charge transfer mechanism was proven by in-situ irradiated X-ray photoelectron spectroscopy, and time-resolved femtosecond-transient absorption analysis clarified the charge separation and transfer dynamics. This study demonstrates that combining organic semiconductors and hypercrosslinked polymers is a promising strategy for designing highly efficient S-scheme heterojunction photocatalysts.

Key words: Hydrogen production, Ultrasonic synthesis, Polymer semiconductor, S-scheme heterojunction, Femtosecond transient absorption, spectroscopy