Substituent Regulation Improves Photocatalytic Hydrogen Evolution of Conjugated Polyelectrolytes

Polymeric photocatalysts for water splitting have received extensive attention recently. However, most polymeric photocatalysts suffer from an unexceptional hydrogen/oxygen evolution rate, primarily originating from less understanding of the molecular design of conjugated polymers for photocatalysis. Herein, we show that facile substituent regulation on conjugated polymers can boost the hydrogen evolution efficiency. Conjugated polyelectrolytes with different substituent groups (-F, -CN) were designed and synthesized. Compared to the unmodified polymer, the -F and -CN modified polymers showed 2.9- and 12-times improvements in the hydrogen evolution rate (3 mu mol h(-1) vs 8.8 mu mol h(-1) vs 38.3 mu mol h(-1)). Notably, -CN substituents in the polymer could reduce the exciton binding energy, induce closer packing and higher crystallinity, improve the charge transporting, and reduce the charge recombination. Moreover, higher efficient exciton generation and charge transfer efficiency to cocatalysts were observed in -CN modified polymers, indicating the great promise of using substituent regulation to achieve high-performance organic photocatalysts.