Unexpected effect of stacking manner of covalent triazine polymer on photocatalytic hydrogen production

Photocatalytic water splitting has been considered as a promising approach to generate H-2 for addressing energy crisis and environmental issues. Herein, we fabricated two novel covalent triazine polymers (CTP), the compact CTP-TG-1 (TG is abbreviation of Tiangong University) and incompact CTP-TG-2, to explore the effect of stacking manner of 2D semiconductor on photocatalytic H-2 production. The compact CTP-TG-1 shows excellent H-2 production rate of 7066.15 mu mol h(-1) g(-1). Meanwhile, the incompact counterpart, CTP-TG-2, which was constructed by tridimensional monomer, exhibits quite low H-2 production rate of 171.65 mu mol h(-1) g(-1). Although the two CTPs possess similar intrinsic features in visible-light absorbance, charge-carrier lifetime and energy level, the electrochemical measurements indicate that the compact CTP-TG-1 possesses faster charge-carrier transport, which is crucial for photocatalytic H-2 generation. For the compact CTP-TG-1, the hot pi-electrons in each 2D layer not only can migrate within the 2D plane, but also tunnel through 2D interlayer and then to Pt NPs on the surface for H-2 generation. In contrast, owing to the large distance of loose 2D interlayer, the incompact CTP-TG-2 shows much lower photocatalytic activity as a result of the suppressed hot pi-electrons tunneling. Furthermore, we designed and synthesized other three CTPs, including compact CTP-TG-4 and CTP-TG-5 and incompact CTP-TG-3. As expected, the compact CTP-TG-4 and CTP-TG-5 display one order of magnitude higher photocatalytic activity than that of the compact CTP-TG-3, further confirming the significant contribution of 2D stacking manner on photocatalytic hydrogen production. [GRAPHICS] .