Construction of the donor–acceptor type conjugated porous polymer/g-C3N4 S-scheme heterojunction for efficient photocatalytic hydrogen production

Abstract

The rational design of charge transport mechanisms is crucial for constructing efficient catalysts with polymer heterojunctions (PHJs) for photocatalytic hydrogen production (PHP). In this study, a series of composites DBDSO/g-C₃N₄-x (x = 10, 15, 20, and 30) were synthesized by combining different proportions of g-C₃N₄ with DBDSO using the solvent dispersion method. The donor–acceptor (D–A) type conjugated porous polymer (CPP), named DBDSO, was synthesized through the Suzuki coupling reaction between dibenzothiophene-S,S-dioxide (DBTSO) and 4,8-di(thiophen-2-yl) benzo[1,2-b:4,5-b′] dithiophene (DBD). Optoelectronic measurements and theoretical simulations revealed that the formation of S-scheme PHJs facilitated efficient separation and transport of photo-generated carriers, resulting in a decrease in fluorescence lifetimes from 3.78 ns in pure g-C₃N₄ to 2.63 ns in the DBDSO/g-C₃N₄-15 composite. As a result, DBDSO/g-C₃N₄-15 exhibited significantly enhanced PHP performance compared to pure g-C₃N₄ catalysts without any precious metal co-catalyst addition, achieving an impressive hydrogen evolution rate (HER) of 80.75 mmol g⁻¹ h⁻¹. Additionally, DBDSO/g-C₃N₄-15 demonstrated good photocatalytic stability with an apparent quantum yield of 3.88% at a wavelength of 420 nm. This work presents a promising approach for enhancing the photocatalytic HER through rational structural design to regulate charge transfer.