Fluoride-Induced Dynamic Surface Self-Reconstruction Produces Unexpectedly Efficient Oxygen-Evolution Catalyst

The oxygen-evolution reaction (OER) is a key process in water-splitting systems, fuel cells, and metal-air batteries, but the development of highly active and robust OER catalyst by simple methods is a great challenge. Here, we report an in situ dynamic surface self-reconstruction that can dramatically improve the catalytic activity of electrocatalysts. A fluoride (F^-)-incorporating NiFe hydroxide (NiFe-OH-F) nanosheet array was initially grown on Ni foam by a one-step hydrothermal method, which requires a 243 mV over-potential (η) to achieve a 10 mA cm^-2 current density with a Tafel slope of 42.9 mV dec^-1 in alkaline media. After the surface self-reconstruction induced by fluoride leaching under OER conditions, the surface of NiFe-OH-F was converted into highly mesoporous and amorphous NiFe oxide hierarchical structure, and the OER activity at η = 220 mV increases over 58-fold. The corresponding η at 10 mA cm^-2 decreases to 176 mV with an extreme low Tafel slope of 22.6 mV dec^-1; this performance is superior to that of the state-of-the-art OER electrocatalysts.