Nanoflower electrocatalysts derived from mixed metal (Fe/Co/Ni) organic frameworks for the electrochemical oxygen evolution reaction

Abstract

The development of high-performance and cost-effective electrocatalysts for the oxygen evolution reaction (OER) is critical to renewable energy conversion and storage technologies. Among of them, metal organic frameworks (MOFs) have been proved to be effective substitutes for precious metals. In this paper, a series of mixed NiCoFe-MOFs with low crystallinity were synthesized by a simple one-step solvothermal method, which can be used as a direct electrocatalyst for the OER. Notably, the flower-like nanocatalyst NiCoFe-MOF-2 exhibits a hierarchical pore network and a large specific surface area (149.6 m² g⁻¹), which results in an adjustable electronic structure, effective mass transfer, and abundant exposed active sites. In addition, due to the synergy between the three metals Fe, Co and Ni, NiCoFe-MOF-2 can exhibit excellent electrocatalytic OER performance, with a low overpotential of 321 mV at 10 mA cm⁻², superior to commercial RuO₂ (379 mV), a Tafel slope of 48 mV dec⁻¹ and long-term stability. The result may stimulate more designs of MOF-derived catalysts with multi-scale structures and multi-components designed for various electrochemical energy conversion devices.