Cu–Fe–NH2 based metal–organic framework nanosheets via drop-casting for highly efficient oxygen evolution catalysts durable at ultrahigh currents

Abstract

Synthesizing binder-free metal–organic frameworks (MOF) as thin films on a large scale to serve directly as electrodes for water electrolysis is challenging. Here, we report a simple and readily scalable strategy for fabricating binder-free Cu–Fe–NH₂ based MOF thin film-electrodes directly applicable as a catalyst for water electrolysis. Films composed of thin 2D-nanosheets of the MOF were deposited by dropping ink obtained from solvothermally synthesised bulk MOFs onto nickel foam substrates, or simply immersing the substrates in the ink. The Cu–Fe–NH₂ MOF electrodes demonstrated excellent oxygen evolution reaction (OER) performance, comparable or superior to recently reported state-of-the-art MOFs. Strikingly, the MOF electrodes exhibited a remarkably low OER overpotential of 330 mV at a high current density of 500 mA cm⁻², and excellent durability with a very minor chronopotentiometric decay loss of 1.26% at the end of a 24 h test at a high bias current of 500 mA cm⁻².