Heterointerface Engineering of Hierarchical CoO@NiO Nanoarrays: Low-Cost and Highly Efficient Electrocatalysts for Oxygen Evolution.

Transition metal oxides (TMOs) have great potential application in oxygen evolution reaction (OER). However, the inferior electrical conductivity and limited active sites of TMOs lead to their sluggish electrocatalytic efficiency. Herein, we adopted a two-step solvothermal approach to fabricate hierarchical CoO@NiO porous core–shell nanoarrays on carbon paper (denoted as CoO@NiO/CP). We found that numerous NiO nanofibers were uniformly coated over the surface of CoO nanosheets, forming a well-defined integrated interfacial nanocomposite. When acting as a catalyst for the OER, CoO@NiO/CP showed enhanced electroactivity with lower overpotential (323 mV at 10 mA cm⁻²), outstripping both pure CoO nanosheet array and NiO nanofiber array. Furthermore, it displayed outstanding OER stability, and the potential attenuation was only 3.4% after a 24 h chronopotentiometry test. The remarkable OER properties of CoO@NiO/CP were mainly due to its unique heterointerface between CoO and NiO, which promoted electron/charge transfer, increased electrocatalytic reactive sites, and improved electrical conductivity. Our presented findings provide a rational and practical interface-engineering approach for fabricating an advanced OER electrocatalyst. [ABSTRACT FROM AUTHOR]