A 2D metal-organic framework/Ni(OH) ₂ heterostructure for an enhanced oxygen evolution reaction

2D metal-organic frameworks (MOFs) are widely regarded as promising electrocatalysts for the oxygen evolution reaction (OER). This results from their inherent properties such as a large portion of surface coordinatively unsaturated metal atoms, rapid mass transfer and enhanced conductivity. However, 2D MOFs have a strong tendency to aggregate, which severely limits their potential application in the OER. Here, novel 2D Ni-BDC/Ni(OH) ₂ (BDC stands for 1,4-benzenedicarboxylate, C ₈ H ₄ O ₄ ) hybrid nanosheets are synthesized via a facile sonication-assisted solution method. Because of the rational material design, the large surface area of Ni-BDC is maintained. Significantly, after coupling, the electronic structure of Ni atoms in the Ni(OH) ₂ component is well modified, leading to the generation of Ni cations with higher oxidation states, which are desirable for the OER. As-prepared Ni-BDC/Ni(OH) ₂ exhibits high activity, favorable kinetics and strong durability towards the OER. Specifically, the OER current density of Ni-BDC/Ni(OH) ₂ is 82.5 mA cm ^-2 at 1.6 V versus a reversible hydrogen electrode (RHE), which is significantly greater than those of Ni-BDC (5.5 times), Ni(OH) ₂ (20.6 times) and Ir/C (3.0 times). Moreover, the sonication-assisted method developed in this work can be readily adapted for the preparation of various 2D MOF-based hybrid functional materials.