Metal-free hydrophilic D-A conjugated polyelectrolyte dots/g-C3N4 nanosheets heterojunction for efficient and irradiation-stable water-splitting photocatalysis

The hydrophobic conjugated polymer-based photocatalysts suffer from long distance of excitons emigrating to the catalyst-water interface that restricts the photocatalytic efficiency. In this study, a hydrophilic conjugated polyelectrolyte (PFNBTBr) is obtained by quaternarization of a conjugated polymer (PFNBT) and further combined with g-C3N4 nanosheets to form PFNBTBr Pdots/g-C3N4 nanosheets heterojunction (PFNBTBr Pdots/CNNS). The PFNBTBr Pdots/CNNS can enhance the electron transfer as the suitable energy level difference and enhanced charge transfer effect of Br- ions, thus reducing charge-hole pairs recombination. Simultaneously, the hydrophilicity of PFNBTBr Pdots/CNNS can promote the surface wetting, facilitating the reaction between excitons and reactants. The PFNBTBr Pdots/CNNS exhibits a stable hydrogen revolution rate of 1200.9 mu mol.h(-1).g(-1) over 6 runs with an AQY of 7.71 % at 420 nm without co-catalysts, which is 1.55 times higher than that of Pt/CNNS-1%. This research points out a facile engineering method of metal-free polyelectrolyte-assisted heterojunction which can potentially substitute the metal-assisted photocatalysts.