Amorphous Ni–Fe–Mo Oxides Coupled with Crystalline Metallic Domains for Enhanced Electrocatalytic Oxygen Evolution by Promoted Lattice‐Oxygen Participation

The crystalline/amorphous heterophase nanostructures are promising functional materials for biomedicals, catalysis, energy conversion, and storage. Despite great progress is achieved, facile synthesis of crystalline metal/amorphous multinary metal oxides nanohybrids remains challenging, and their electrocatalytic oxygen evolution reaction (OER) performance along with the catalytic mechanism are not systematically investigated. Herein, two kinds of ultrafine crystalline metal domains coupled with amorphous Ni-Fe-Mo oxides heterophase nanohybrids, including Ni/Ni_0.5-a Fe_0.5 Mo_1.5 O_x and Ni-FeNi₃ /Ni_0.5-b Fe_0.5-y Mo_1.5 O_x , are fabricated through controllable reduction of amorphous Ni_0.5 Fe_0.5 Mo_1.5 O_x precursors by simply tuning the amount of used reductant. Due to the suited component in metal domains, the special structure with dense crystalline/amorphous interfaces, and strong electronic coupling of their components, the resultant Ni-FeNi₃ /Ni_0.5-b Fe_0.5-y Mo_1.5 O_x nanohybrids show greatly enhanced OER activity with a low overpotential (278 mV) to reach 10 mA cm^-2 current density and ultrahigh turnover frequency (38160 h^-1 ), outperforming Ni/Ni_0.5-a Fe_0.5 Mo_1.5 O_x , Ni_0.5 Fe_0.5 Mo_1.5 O_x precursors, commercial IrO₂ , and most of recently reported OER catalysts. Also, such Ni-FeNi₃ /Ni_0.5-b Fe_0.5-y Mo_1.5 O_x nanohybrids manifest good catalytic stability. As revealed by a series of spectroscopy and electrochemical analyses, their OER mechanism follows the lattice-oxygen-mediated (LOM) pathway. This work may shed light on the design of advanced heterophase nanohybrids, and promote their applications in water splitting, metal-air batteries, or other clean energy fields.