Cu-Fe-NH₂based metal-organic framework nanosheets: Via drop-casting for highly efficient oxygen evolution catalysts durable at ultrahigh currents

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.