Facile synthesis of porous CoxFe1−xF2 microcubes derived from metal-organic frameworks for ultra-stable electrochemical oxygen evolution reaction

Fabricating efficient and low-cost noble-metal free electrocatalysts for the oxygen evolution reaction has been considered as a top priority for developing renewable energy devices. In this work, a series of CoxFe1−xF2 (x = 0.33, 0.50, 0.66, 0.75 and 0.80) with porous structure were prepared through low-temperature fluorination of MOFs precursors with controlled molar ratios of cobalt and iron and used as electrocatalysts for OER. Significantly, the Co0.66Fe0.33F2 exhibited the most excellent OER catalytic performance with a low overpotential of 260 mV at 10 mA cm−2 and a small Tafel slope of 54 mV dec−1. Moreover, it has an ultra-long durability of 50 h at current densities of 10 mA cm−2 and 50 mA cm−2, which is superior to most of non-noble metal and RuO2 electrocatalysts. The outstanding performance could be addressed to the porous structure and synergistic effect of CoF2 and FeF2 and in situ formed oxides, which could increase the active sites for electrochemical reactions and promote the proton transport and ion diffusion during the reaction process. This work proposes a brief and efficient way to design three-dimensional porous structure electrocatalyst. © 2021