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 (H 2 PDI), 1,7-dibromo-substituted H 2 PDI (2Br-H 2 PDI) and 1,6,7,12-tetraether-substituted H 2 PDI (4CH 3 CH 2 O-H 2 PDI), are synthesized for photocatalytic oxygen evolution (POE) and oxygen reduction reaction (ORR). One-dimensional H 2 PDI nanorods, two-dimensional 2Br-H 2 PDI nanosheets, and zero-dimensional 4CH 3 CH 2 O-H 2 PDI nanoparticles are obtained. Under visible light, 4CH 3 CH 2 O-H 2 PDI as photocatalyst (5.31 mmol·g −1 ·h −1 ) exhibits the 1.8-times and 20-times POE rate of 2Br-H 2 PDI (2.93 mmol·g −1 ·h −1 ) and H 2 PDI (0.26 mmol·g −1 ·h −1 ) with AgNO 3 as sacrificial agent. Additionally, the POE rate can be further improved to 9.34 mmol·g −1 ·h −1 with the Co 2+ doping of 4CH 3 CH 2 O-H 2 PDI. With isopropanol as sacrificial agent, the H 2 O 2 evolution rate of 657.4 μM·g −1 ·h −1 can be also achieved via photocatalytic ORR with 4CH 3 CH 2 O-H 2 PDI as catalyst, which is ∼3 and ∼4 times those of 2Br-H 2 PDI (220.8 μM·g −1 ·h −1 ) and H 2 PDI (160.0 μM·g −1 ·h −1 ), respectively. Especially, in the O 2 - or air- saturated aqueous solution without sacrificial agent, the H 2 O 2 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.