Metal complexes of bipyridine‐functionalized covalent organic frameworks as efficient electrocatalysts for oxygen evolution reaction

Abstract

Abstract Electrocatalytic water splitting is considered a clean and practical method for producing energy. In this study, COF‐Bpy, a bipyridine‐functionalized covalent organic framework (COF), was prepared via post‐synthetic modification, after which electrocatalysts for the oxygen evolution reactions (OER) were formed through coordination to single‐ or double‐transition metals (Fe, Co, Ni, FeCo, FeNi or CoNi). COF‐Bpy@FeNi delivered the best OER performance among the studied electrocatalysts, with an overpotential of 399 mV at 10 mA·cm −2 in an alkaline electrolyte (1.0 mol·L −1 KOH aqueous). Notably, the electrocatalytic performance of COF‐Bpy@FeNi showed slight degradation during durability testing, which is ascribable to its irreversible benzoquinoline structure and strong metal coordination. As expected, COF‐Bpy@FeNi exhibited a low overpotential of 347 mV at a turnover frequency (TOF) of 0.1 s −1 , which suggests that COF‐Bpy@FeNi possesses excellent intrinsic electrocatalytic OER activity. Finally, density functional theory (DFT) calculations reveal that the Ni site plays a major role, while the Fe site adjusts the electronic structure of the Ni ions, which rationalizes the excellent OER properties of COF‐Bpy@FeNi. This study not only provides a simple and efficient method for complexing COFs with transition metals, but also offers a novel strategy for designing porous organic polymer electrocatalysts.