Fe-Based Metal–Organic Framework-Ni3S2 Heterostructure Nanocomposites for Efficient Oxygen Evolution Reaction at High Current Densities

Hydrogen, carrying a high energy density and emitting zero greenhouse gases when in use, is particularly promising as an alternative for traditional fossil fuels. Electrochemical water splitting is an economical technology for producing sustainable and high-purity hydrogen gas. However, the intrinsically sluggish kinetics of the anode oxygen evolution reaction (OER) always decreases the efficiency of hydrogen production; the development of highly active and durable electrocatalysts with improved OER kinetics is thus desirable and crucial. Herein, Fe-based metal–organic framework (MOF)-Ni3S2 heterostructure nanocomposites are synthesized on a nickel foam (NF) substrate. The self-supporting Fe MOF-Ni3S2/NF catalyst shows excellent catalytic activities for OER. In alkaline media (1.0 M KOH), only 243 mV of overpotential is needed to reach the current density of 100 mA·cm–2. Even at the commercially viable high current densities of 500 and 1000 mA·cm–2, ultralow overpotentials of 283 and 309 mV are required, respectively. The catalytic activity of Fe MOF-Ni3S2/NF far exceeds that of the noble metal catalysts (e.g., RuO2) and most non-noble metal OER catalysts reported in the literature. In addition, the Fe MOF-Ni3S2/NF nanocomposite exhibits ultrahigh long-term stability at high current densities, with almost no activity attenuation in the chronopotentiometry test conducted at 100 mA·cm–2 and a negligible attenuation (23 mV) at 500 mA·cm–2 for 20 h. Our findings provide insights into designing and preparing cost-effective, highly active, and durable electrocatalysts for OER at high current densities.