Exploring metal-free ionic covalent organic framework nanosheets as efficient OER electrocatalysts via cationic-π interactions

Abstract

Metal-free electrocatalysts play a crucial role in enabling practical water splitting for future clean energy production by facilitating the oxygen evolution reaction (OER). However, the preparation of such electrocatalysts presents significant challenges due to the limitations of the kinetically sluggish anodic half-cell reaction, which restricts the attainment of high energy inputs. In this study, we present a metal- and pyrolysis-free ionic covalent organic framework (COF) nanosheet, denoted as JUC-627-NS, and investigate its potential as an efficient electrocatalyst for OER by introducing cationic-π interactions. Notably, through the utilization of positively charged JUC-627-NS as cationic donors and π-conjugated graphene as electron donors for the first time, the JUC-627-NS@G-2 composite exhibits an exceptional ultralow overpotential of 275 mV at a current density of 10 mA cm−2, ranking among the top-performing metal- and pyrolysis-free electrocatalysts reported thus far. Combining theoretical calculations with in-situ infrared spectroscopy, we validate that the imidazolium salt moiety of JUC-627-NS serves as the active center of the electrocatalyst, while the robust cation-π interaction within the complex brings the reaction site closer to graphene, acting as a conductive agent. These findings highlight a novel strategy for advancing the development of metal-free OER electrocatalysts based on ionic COF materials, with promising applications in energy conversion and storage devices.