Favorable Amorphous-Crystalline Iron Oxyhydroxide Phase Boundaries for Boosted Alkaline Water Oxidation

Interface engineering has proven an effective strategy for designing high-performance water-oxidation catalysts. Interface construction combining the respective advantages of amorphous and crystalline phases, especially embedding amorphous phases in crystalline lattices, has been the focus of intensive research. This study concerns the construction of an amorphous-crystalline FeOOH phase boundary (a-c-FeOOH) by structural evolution of iron oxyhydroxide-isolated Fe(OH)₃ precursors from one-step hydrothermal synthesis. a-c-FeOOH demonstrates superb electrocatalytic activity for the oxygen evolution reaction (OER) with overpotential of 330 mV to drive a current density of 300 mA cm^-2 in 1.0 m KOH, which is among the best OER catalysts and much better than the pristine amorphous or crystalline FeOOH alone. Density functional theory calculations reveal that the high-density a-c phase boundaries play a critical role in determining high OER activity.