Metal-free corrole-based donor–acceptor porous organic polymers as efficient bifunctional catalysts for hydrogen evolution and oxygen reduction reactions

Abstract

Porous organic polymers (POPs) are promising candidates for catalyzing the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR) owing to their tunable porous structures and abundant chemical reaction channels/active centers. However, insufficient conductivities limit their practical applications in the HER/ORR. The challenge is to construct conductive POPs with highly efficient HER/ORR performance. Herein, a series of metal-free corrole-based donor–acceptor POPs (Cor-D–A-POPs) as bifunctional HER/ORR catalysts have been designed and constructed from 5,10,15-tris(p-aminophenyl)corrole (TPAPC) and 2,2′-bithiophene-5,5′-dialdehyde (BTDA) or 2,5-thiophenedialdehyde (TDA) with a donor–acceptor method. Compared with Cor-D–A-POPs using TDA as an electron donor (Cor-TDA-D–A-POPs), Cor-D–A-POPs using BTDA as an electron donor (Cor-BTDA-D–A-POPs) exhibit higher HER/ORR activities due to their more favorable charge transfer ability from the BTDA donor to the TPAPC acceptor. The integration of high surface area, rich accessible catalytic sites, and high conductivity makes Cor-BTDA-D–A-POP-1 constructed in a mixed solvent of n-butanol/mesitylene (1 : 1) exhibit optimal HER/ORR activities in alkaline solution, with a comparable HER overpotential of 0.10 V at 10 mA cm⁻² and an ORR Tafel slope of 90.0 mV dec⁻¹ to Pt/C (0.09 V and 88.0 mV dec⁻¹). Moreover, its HER/ORR stability is superior to that of Pt/C. The experimental results are consistent with density functional theory calculations. Therefore, the combination of suitable electron donors and electron acceptors can promote charge transfer within POPs and generate high activities for the HER/ORR.