Synthesis of bay-substituted perylene diimide as bifunctional photocatalyst for enhanced water oxidation and hydrogen peroxide generation

Rational design of semiconductor molecule structure is of significant importance for achieving the multifunctional photocatalysis. Herein, three end/bay-substituted perylenediimide (PDI) molecules, including bis(N-carboxymethyl) perylenediimide (H2PDI), 1,7-dibromo-substituted H2PDI (2Br-H2PDI) and 1,6,7,12-tetraether-substituted H2PDI (4CH3CH2O-H2PDI), are synthesized for photocatalytic oxygen evolution (POE) and oxygen reduction reaction (ORR). One-dimensional H2PDI nanorods, two-dimensional 2Br-H2PDI nanosheets, and zero-dimensional 4CH3CH2O-H2PDI nanoparticles are obtained. Under visible light, 4CH3CH2O-H2PDI as photocatalyst (5.31 mmol·g−1·h−1) exhibits the 1.8-times and 20-times POE rate of 2Br-H2PDI (2.93 mmol·g−1·h−1) and H2PDI (0.26 mmol·g−1·h−1) with AgNO3 as sacrificial agent. Additionally, the POE rate can be further improved to 9.34 mmol·g−1·h−1 with the Co2+ doping of 4CH3CH2O-H2PDI. With isopropanol as sacrificial agent, the H2O2 evolution rate of 657.4 μM·g−1·h−1 can be also achieved via photocatalytic ORR with 4CH3CH2O-H2PDI as catalyst, which is ∼3 and ∼4 times those of 2Br-H2PDI (220.8 μM·g−1·h−1) and H2PDI (160.0 μM·g−1·h−1), respectively. Especially, in the O2- or air- saturated aqueous solution without sacrificial agent, the H2O2 rate of 273.1 or 112.7 μM·g−1·h−1 can be also achieved. This work provides a promising way to design the PDI-based multifunctional photocatalysts.