Enhancing the electrocatalytic activities of metal organic frameworks for the oxygen evolution reaction with bimetallic groups

Controlling the ratio of metals in bimetallic organic frameworks (MOFs) can not only alter the structures but also tailor the properties of MOFs. Herein, we report a series of electrocatalytically active CoxNiy-based bimetallic MOFs that are synthesized with the 3,5-pyridinedicarboxylic acid (3,5-H2pdc) ligand (where x : y = 20 : 1, 15 : 1, 10 : 1, 5 : 1, 1 : 1, and 1 : 20) and a facile, scalable, low temperature synthetic route. The materials have one-dimensional (1D), rod-like microstructures with different aspect ratios. While they all electrocatalyze the oxygen evolution reaction (OER) in alkaline solution (1 M KOH), their electrocatalytic performances vary substantially depending on their compositions. The CoxNiy-MOF with an optimal ratio of x : y = 15 : 1 (Co15Ni1-MOF) electrocatalyzes the OER with the highest maximum current density (92.2 mA cm-2 at 1.75 V vs. RHE) and the smallest overpotential (384 mV vs. RHE at 10 mA cm-2) in a 1 M KOH solution. It is also stable under constant current application during the electrocatalytic OER. This work demonstrates the application of bimetallic MOFs that are synthesized following a simple, low temperature synthetic route for the OER and their tailorable electrocatalytic properties for the OER by varying the ratio of two metals and the synthetic conditions used to produce them. Controlling the ratio of metals in bimetallic organic frameworks (MOFs) can not only alter the structures but also tailor the properties of MOFs, including their electrocatalytic properties.