Efficient Photocatalytic Hydrogen and Oxygen Evolution by Side-Group Engineered Benzodiimidazole Oligomers with Strong Built-in Electric Fields and Short-Range Crystallinity.

Abstract

The insufficient charge separation and sluggish exciton transport severely limit the utilization of polymeric photocatalysts. To resolve the above issues, we incorporate bountiful carboxyl substituents within a novel benzodiimidazole oligomer and assemble it into a crystalline semiconductor. The photocatalyst is polar, hydrophilic, short-range crystalline, and capable of both hydrogen and oxygen evolution. The introduction of carboxyl side-groups adds asymmetry to the local structure and increases the built-in electric field. Further, accelerated carrier transfer is enabled via the short-range crystallinity. The superior hydrogen and oxygen production rates of 18.63 and 2.87 mmol g-1 h-1 represent one of the best performances ever reported among dual-functional polymeric photocatalysts. Our work initiates studies on high-performance oligomer photocatalysts, opening a new frontier to produce solar fuel.