Preparation of a Dual-MOF Heterostructure (ZIF@MIL) for Enhanced Oxygen Evolution Reaction Activity

Graphical A ZIF@MIL heterostructure was successfully prepared by an in situ solvothermal method. Compared to pure ZIF-67 and MIL-100, the heterostructure possesses a larger electrochemical surface area and exhibits a remarkable catalytic performance with a low overpotential of 232 mV and a small Tafel slope of 57 mV dec −1 at 10 mA cm −2 . Although metal-organic frameworks have proven to be excellent electrocatalytic materials, their application as electrode materials remains limited. The preparation of heterostructures is considered an effective method to improve catalytic activity. Herein, we describe the design and assembly of a dual-MOF heterostructure (CoNi−ZIF-67@Fe−MIL-100, denoted ZIF@MIL). Specifically, we grew a layer of MIL-100 in situ on a bimetallic ZIF-67 surface using a solvothermal method. We demonstrate that the ZIF@MIL has remarkable OER electrocatalytic performance, requiring a low overpotential and showing a small Tafel slope, compared to pure ZIF-67 and MIL-100 in 1.0 m KOH. More importantly, it has excellent operational durability for 50 h at 100 mA cm −2 . The high catalytic activity of ZIF@MIL can be attributed to the heterostructure that can expose more active sites, the synergistic effect between ZIF-67 and MIL-100, and improvement of electron transfer ability. Our work provides a new way to design and prepare dual-MOF crystals with different structures as electrocatalysts.