Electrochemical oxygen evolution reaction efficiently catalyzed by a novel porous iron-cobalt-fluoride nanocube easily derived from 3-dimensional Prussian blue analogue

A three-dimensional porous architecture derived from FeCo Prussian blue analogue by low-temperature fluoridation etching is for the first time demonstrated with largely enhanced performances for oxygen evolution reaction. The morphology and structure for FeCo Prussian blue nanocubes are controlled by fluoride etching resulting in the formation of the porous structure with a lot of defects/voids as characterized by a series of spectroscopic techniques. Iron-cobalt-fluoride nanocubes obtained at 400 °C possess the optimal porous structure and morphology to guarantee the channels for mass transportation and ion diffusion. The increased electrochemical surface area, more exposure of the active sites and facile construction of metal oxide layer over the catalyst surface make this novel catalyst very active for the water oxidation reaction. The electrochemical measurements demonstrate this catalyst can drive the benchmark current density of 10 mA cm−2 at a low overpotential of 250 mV with a Tafel slope of 38.3 mV dec−1 and an excellent catalytic stability for 10 h in the long-term water electrolysis; the performance also outperforms most of the advanced analogous nonprecious catalysts and noble commercial IrO2 catalyst. This work provides an effective and convenient approach to design three-dimensional porous architecture catalysts for energy-relevant electro-catalysis reaction.