Structural and Electronic Modulation of Iron-Based Bimetallic Metal–Organic Framework Bifunctional Electrocatalysts for Efficient Overall Water Splitting in Alkaline and Seawater Environment

Metal-organic frameworks (MOFs) are considered potential electrocatalysts for efficient water splitting. However, the structure-activity relationship of most MOFs is not systematically analyzed for electrocatalysis for anodes and cathodes. In this paper, we provide a strategy to modulate the electronic microstructure of iron-based bimetallic MOFs (MFe-BDC (M: Mg, Zn, Cd)) grown on the nickel foam (NF) as bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The optimal bimetallic CdFe-BDC via modulating appropriate metal cations of IIA and IIB possesses excellent OER and HER performance with the lowest overpotentials of 290 mV at 100 mA cm-2 and 148 mV at 10 mA cm-2, respectively. The overall water splitting performance of the as-prepared CdFe-BDC requires 1.68 V to achieve a current density of 10 mA cm-2 in the real seawater media, and it exhibits the competitive H2 and O2 production rates of 6.4 and 3.1 μL s-1, respectively, in ambient alkaline conditions, suggesting its potential practical applications. Density functional theory (DFT) calculations demonstrate the relationship between microstructure and electrocatalytic performance of bimetallic MFe-BDC. This work emphasizes the significance of tailoring the electronic microstructure of bimetallic MOFs for efficient overall water splitting in alkaline and seawater environment.