Interfacial Engineering of Pillared Co(II) Metal–Organic Framework@NiMn-Layered Double Hydroxide Nanocomposite for Oxygen Evolution Reaction Electrocatalysis

Clean energy conversion and storage require simple, economical, and effective electrode materials to achieve promising results. The development of high-performance electrocatalysts with adequate stability and cost-effectiveness is essential to ensure low overpotentials toward the oxygen evolution reaction (OER). Herein, a cobalt-based metal-organic framework with 4,4,4-6T14 topology in combination with various ratios of NiMn-layered double hydroxide (Co-MOF@X%NiMn-LDH, X = 5, 10, 20, and 40%) is applied as an effective electrocatalyst for the oxidation of water. The optimum sample, Co-MOF@20%NiMn-LDH nanocomposite, showed an overpotential of 174 mV at a current density of 10 mA cm^-2 and a reduced Tafel slope of 64 mV dec^-1 in 1 M KOH, which makes it an excellent candidate, significantly superior to commercial IrO₂ and most MOF- and LDH-based electrocatalysts. Chronopotentiometry tests for the OER over several hours confirmed that these electrocatalysts have been sufficiently stable. Pillared MOFs can obstruct active entities from NiMn-LDH cubic agglomeration, thus facilitating mass transportation and ensuring the continuous exposure of active sites. Accordingly, the synthesized Co-MOF@20%NiMn-LDH composite demonstrates considerable electrocatalytic efficiency and stability toward the OER, as a consequence of the porous structure, external surface area, and synergistic effects among Co-MOF and NiMn-LDH samples.