Spinel‐Type Metal Oxides with Tailored Amorphous/Crystalline Heterointerfaces for Enhanced Electrocatalytic Water Splitting

Abstract Metal oxides with spinel structure have garnered increasing attention as promising alternatives to noble metal‐based electrocatalysts. However, these electrocatalysts often fail to simultaneously exhibit high activity and stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), limiting their applications in electrocatalytic water splitting. Herein, crystalline/amorphous heterogeneous interfaces are successfully introduced into spinel NiCo 2 O 4 nanosheets, which are grown in situ on carbon cloth (CC), denoted as NiCo 2 O 4 ‐B‐CC. The amorphous/crystalline heterostructures combine the advantages of both phases in electrocatalysts. The amorphous phase of the spinel NiCo 2 O 4 nanosheets modulates the electron density, provides abundant oxygen single vacancies as active sites, and enhances the corrosion resistance, while the crystalline phase improves conductivity. Density functional theory (DFT) calculations are performed to investigate the influence of surface oxygen single vacancy (SV O ) on the activity of the OER and HER processes. The NiCo₂O₄‐B‐CC exhibits overpotentials of only 26 mV for HER and 215 mV for OER at a current density of 10 mA cm −2 . It exhibits excellent electrocatalytic performance for water splitting, achieving a current density of 400 mA cm −2 at an applied voltage of 2.0 V. The construction of crystalline/amorphous heterogeneous interfaces in electrocatalysts provides novel approach for enhancing the electrocatalytic performance of metal oxides in water splitting.