Interfacial engineering of an FeOOH@CoO heterojunction for efficient overall water splitting and electrocatalytic urea oxidation.

Constructing heterostructure is an efficient method to provide more active sites and optimize electronic structure for improving the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) performance. Herein, the 3D FeOOH@CoO heterostructure was constructed using FeOOH layer (10-20 nm) coated on the surface of CoO nanoneedles through the strong hydrolysis of Fe. The FeOOH@CoO heterostructure not only retains the nanoneedle structure with open frameworks, but also improves the specific surface area and expedites the charge transfer. The FeOOH@CoO-240 heterostructure affords a remarkable OER performance with low overpotential of 228 mV at 10 mA·cm in 1 M KOH solution. The symmetrical urea electrolyzer using FeOOH@CoO-240 as both anode and cathode delivers 10 mA/cm at 1.43 V. Density functional theory (DFT) calculations unveil that the FeOOH@CoO-240 heterostructure could adjust the electronic structure and strengthen the conductivity. This work offered a facile strategy for designing heterojunction catalysts in an economic way.