Iron-doped novel Co-based metal–organic frameworks for preparation of bifunctional catalysts with an amorphous structure for OER/HER in alkaline solution

Abstract

A novel two-dimensional Co-MOF material {[Co(dptz)₂(oba)₂]·(DMF)₂}_n is prepared using mixed organic ligands, which exhibits both OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) catalytic performance. The integration of an Fe dopant and amorphous interface into Co-MOF to improving the electrocatalytic performance of pristine MOFs (metal–organic frameworks) is demonstrated and the origin of the remarkable electrocatalytic performance of the catalyst is elucidated. The comprehensive characterization data of Fe@Co-MOFs illustrate that there is a crystallinity transition during the doping of Co-MOF, which increases the electron transfer rate of the material and ensures increased exposure of the ligand unsaturated active site on the surface, and modulates the electronic structure of the Co center in a synergistic manner. As a result, the optimized catalytic Fe@Co-MOF-3 with an amorphous structure exhibits outstanding electrocatalytic performance for the OER, with only 248 mV at a current density of 50 mA cm⁻² and excellent stability after 11 h of testing in alkaline solution. Not only that, the HER was achieved with a low overpotential of 150 mV at 10 mA cm⁻². The present work indicates that the as-synthesized Co-MOF and Fe@Co-MOFs offer prospects in developing electrocatalysts for water splitting.