S-scheme heterojunction between donor-acceptor linear polymer and g-C3N4 via strengthened internal electric field for enhanced photocatalytic activity

The inherent sluggish photo-induced charge carrier separation and transport limit the efficiency of photocatalytic hydrogen evolution (PHE) of graphitic carbon nitride (g-C 3 N 4 ). To address this, polymer-based heterojunctions (PHJs) are designed by integrating a linear donor-acceptor type polymer (PTSO-T) with g-C 3 N 4 nanosheet at different feed ratios. The results demonstrate that the optoelectronic properties of the PHJs are significantly modulated by the intermolecular π-π stacking effect, resulting in a wide light absorption range, enhanced exciton dissociation rate and enhanced transport of charge carriers. Spectroscopic analysis and theoretical calculations confirmed the establishment of a highly efficient charge transfer pathway with an S -scheme and the formation of an internal electric field (IEF) within the PHJs. The optimized PTSO-T/g-C 3 N 4 -40 photocatalyst exhibits a remarkable hydrogen evolution rate (HER) of 85.51 mmol g −1 h −1 under visible light and with 0.3 % Pd as the co-catalyst. The photocatalyst shows improved HER, which is 1.3 and 83.0 times the HER values of PTSO-T and g-C 3 N 4 , respectively. The maximum apparent quantum efficiency (AQY) is 14.13 % at 475 nm for PTSO-T/g-C 3 N 4 -40. The performance of the PHJs reported in this study ranks the first class among the state-of-the-art PHJs. • PTSO was used to sensitize g-C 3 N 4 for the construction of polymer based heterojunctions (PHJs). • PTSO/g-C 3 N 4 -40 showed a hydrogen evolution rate of 85.51 mmol g −1 h −1 under visible light irradiation. • Intermolecular π-π stacking and band gap alignment promote the formation of PHJs. • The high photocatalytic performance is ascribed to the construction of S -scheme heterojunction.