Controllable synthesis of multidimensional carboxylic acid-based NiFe MOFs as efficient electrocatalysts for oxygen evolution

Abstract

The oxygen evolution reaction (OER), an essential half reaction of water splitting to produce green hydrogen, has been subject to high overpotentials and restrictions on the use of noble metal catalysts. Metal–organic frameworks (MOFs) are a class of structure-adjustable novel material composed of metal nodes and organic ligands, and their unique physical and chemical properties endow them with adjustable catalytic properties and make them potentially alternate to noble metal catalysts for the OER. However, the controllable synthesis of MOFs with a favorable structure for the OER is still a great challenge. Here, we report a simple solvent-assisted strategy to realize the synthesis of NiFe MOFs with controllable morphology and electronic structure. Owing to the highly exposed active sites and optimized electronic structure for the active sites, the obtained two-dimensional carboxylic acid-based MOFs (2D-NiFe-BDC) show an excellent OER activity in 1.0 M KOH, the overpotential for oxygen evolution is as low as 223 mV at 10 mA cm⁻², and the Tafel slope is 37.3 mV dec⁻¹, together with a decent stability of at least 70 h under a large current density of 100 mA cm⁻². Moreover, we also investigate and prove the universality of this synthesis method for other carboxylic acid-based MOFs. This work not only provides a universal route to design 2D MOFs but also demonstrates the superiority of the method to adjust the performance of highly efficient OER catalysts for related energy conversion and storage technologies.