An interfacially stacked covalent porous polymer on graphene favors electronic mobility: ensuring accelerated oxygen reduction reaction kinetics by an in situ study

Abstract

The oxygen reduction reaction (ORR) is largely influenced by material conductivity as well as electron transfer mobility. Usually, covalent porous polymers are fascinating in terms of the surface area and availability of abundant functionalities serving as active sites. However, this class of materials largely suffers from electronic conductivity issues, which limits their extensive application in electrocatalytic reactions. To overcome this long-standing issue, herein, we have developed a metallo [Fe(II)]-porphyrin-pyrene based pi-conjugated porous polymer (FePP), which was further modified with electrophoretically exfoliated graphene (FePP@G_30/3/7). The interfacing of these two units via π–π interaction introduces the flexibility of >C–C< bond rotation resulting in-plane flipping of the bridging –Ph ring from out of plane orientation. The ring flipping-induced co-planarity was investigated through experimental and computational studies. In situ FTIR and operando Raman studies reveal that the ORR process with the FePP@G_30/3/7 catalyst follows a 4e⁻ reduction pathway. This phenomenon drives axial as well as equatorial charge mobility within the system influencing the active FeN₄ site toward lowering the overpotential for the ORR.