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; Hongmei Zhan; Chuanli Qin

doi:10.1016/j.jcis.2023.08.153

Phosphate ester functionalized fluorene-benzothiadiazole alternating copolymer/hydroxylated g-C₃N₄ heterojunctions for efficient hydrogen evolution under visible-light irradiation

J Colloid Interface Sci. 2023 Dec 15;652(Pt B):1405-1416. doi: 10.1016/j.jcis.2023.08.153. Epub 2023 Aug 26.

Authors

Xulong Pang¹, Yong Li¹, Xiaofu Wu², Bingmiao Zhang¹, Ming Hao¹, Yan Zhu¹, Yi Zhang¹, Chuanjiang Qin², Hongmei Zhan², Chuanli Qin³

Affiliations

¹ Key Laboratory of Functional Inorganic Material Chemistry (Ministry of Education), School of Chemistry and Materials Science, International Joint Research Center for Catalytic Technology, Heilongjiang University, Harbin 150080, People's Republic of China.
² State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, People's Republic of China.
³ Key Laboratory of Functional Inorganic Material Chemistry (Ministry of Education), School of Chemistry and Materials Science, International Joint Research Center for Catalytic Technology, Heilongjiang University, Harbin 150080, People's Republic of China. Electronic address: qinchuanli@hlju.edu.cn.

PMID: 37659309
DOI: 10.1016/j.jcis.2023.08.153

Abstract

It is highly desirable to explore functionalized polymer semiconductor/g-C₃N₄ 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 H₂ 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-C₃N₄ (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 H₂ 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-C₃N₄ heterojunctions for sunlight-driven H₂ evolution.

Keywords: Graphitic carbon nitride; H(2) evolution; Hydrophilic fluorene-benzothiadiazole alternating copolymer; Phosphate ester group; Visible light catalysis.