Low Band Gap Benzimidazole COF Supported Ni₃N as Highly Active OER Catalyst

Abstract

Covalent organic frameworks (COFs) have structures and morphologies closely resembling graphenes, whose modular construction permits atomic‐level manipulations. This, combined with their porous structure, makes them excellent catalyst supports. Here, the high electrocatalytic activity of a composite, formed by supporting Ni 3 N nanoparticles on a benzimidazole COF, for oxygen evolution reaction is shown. The composite oxidizes alkaline water with a near‐record low overpotential of 230 mV @ 10 mA cm −2 ( η 10 ). This high activity is attributed to the ability of the COF to confine the Ni 3 N nanoparticles to size regimes otherwise difficult to obtain and to its low band gap character (1.49 eV) arising from the synergy between the conducting Ni 3 N nanoparticles and the π‐conjugated COF. The COF itself, as a metal‐free self‐standing framework, has an oxygen evolution reaction activity with η 10 of 400 mV. The periodic structure of the COF makes it serve as a matrix to disperse the catalytically active Ni 3 N nanoparticles favoring their high accessibility and thereby good charge‐transport within the composite. This is evident from the amount of O 2 evolved (230 mmol h −1 g −1 ), which, to the best of our knowledge, is the highest reported. The work reveals the emergence of COF as supports for electrocatalysts.