Hofmann-Type Metal–Organic Framework Nanosheets for Oxygen Evolution

Developing an efficient and low-cost electrocatalyst is important in energy conversion and storage, while it is challenging especially in the oxygen evolution reaction (OER) owing to the sluggish kinetic process. Hofmann-type metal–organic frameworks (MOFs) are layer-structured materials, and if they are synthesized in the form of regular-shaped and slim nanosheets, a higher density of exposed active sites and easier electron and mass transport will be expected. In the current study, we prepared such a type of Hofmann MOFs plus Ni site tuning for the OER. The characterizations verified the successful material synthesis and characteristics. Density functional theory (DFT) simulations proved that the Ni site modified by Fe atom is more efficient for the critical OH* as well as O* intermediate formation. Taking advantage of the designed unique structure configuration, the as-obtained Fe–Ni Hofmann-type MOF showed the OER activity with an overpotential of 290 mV at the current density of 10 mA cm–2 and a Tafel slope of 44 mV dec–1, the very best performance plus outstanding durability among the Hofmann-type MOFs for the OER known to date.