Boosted Oxygen Evolution Reaction by Controllable Fluoridation on Porous Cobalt-Iron Nanoflakes

The design of a highly efficient OER electrocatalyst is important to improve the energy efficiency of hydrogen production by water electrolysis. Herein, porous cobalt-iron fluoride nanoflakes (CoFe-F) are prepared by hydrothermal and fluoridation treatment. A CoFe-F catalyst with a preserved nanoflake morphology and porous surface is obtained by an optimal degree of fluoridation, avoiding the aggregation of metal fluoride nanoparticles and exposing abundant active sites. Meanwhile, surface chemistry modification for the CoFe-F catalyst by forming ionic metal-F bonds can boost electrocatalytic performance, such as enhanced electrocatalytic activity, outstanding stability, and fast kinetics. CoFe-F-16 with optimal fluoridation only requires an overpotential of 252 mV with a Tafel slope of 52.1 mV dec(-1) at 10 mA cm(-2), which is smaller than the control samples with insufficient or overfluoridation, attributing to nanoflake morphology with a porous surface and the formation of ionic metal compounds by low-temperature fluoridation.