Phosphate ester functionalized fluorene-benzothiadiazole alternating copolymer/hydroxylated g-C3N4 heterojunctions for efficient hydrogen evolution under visible-light irradiation
Xulong Pang, Yong Li, Xiaofu Wu, Bingmiao Zhang, Ming Hao, Yan Zhu, Yi Zhang, Chuanjiang Qin, Chuanjiang Qin, Hongmei Zhan, Chuanli Qin, Chuanli Qin
Abstract
It is highly desirable to explore functionalized polymer semiconductor/g-C 3 N 4 heterojunction photocatalysts with the tight interfacial connection for promoting the photogenerated electron-hole pair separation, improving the hydrophilicity , extending the visible light response and achieving the efficient visible light-driven H 2 evolution. Herein, we synthesized novel poly[9,9-bis(3-ethyl phosphate propyl)fluorene- alt -benzothiadiazole] (PPFBT) with a phosphate ester on every repeating unit by the Suzuki polymerization and then fabricated PPFBT/hydroxylated g-C 3 N 4 (PPFBT/CN-OH) heterojunctions via a surface hydroxyl-induced assembly process. The ratio-optimized 5PPFBT/CN-OH shows the hydrogen evolution activity of 2662.4 μmol·g −1 ·h −1 , an 11.1-time enhancement compared to CN-OH. The improved photocatalytic activity is mainly attributed to the enhanced electron-hole pair separation due to the tight interfacial connection by hydrogen bond (P=O…H-O) and N…S interactions between PPFBT and CN-OH. It is verified that abundant phosphate ester groups of PPFBT improve the hydrophilicity and form coordination bonds with platinum (P=O:Pt) as a cocatalyst to facilitate water splitting for H 2 evolution. It is also confirmed that the enhanced electron-hole pair separation is mainly dependent on the excited high-energy level electron transfer from CN-OH to PPFBT. This work provides a rational molecular design strategy for constructing efficient functionalized polymer semiconductor/g-C 3 N 4 heterojunctions for sunlight-driven H 2 evolution.