K alpha

The phase structure was characterized by X-ray diffraction (XRD) using a Rigaku D/max-3C. The morphologies and microstructures were analyzed by a scanning electron microscope (SEM, JSM-7610F, Japan) and a transmission electron microscope (TEM, TF20), respectively. The composition and valence of elements of the prepared NiCo₂O₄ nanomaterials were determined by X-ray photoelectron spectrometer (XPS, Thermo Scientific K-Alpha), Raman spectrometer (Horiba LabRAM HR Evolution), and TGA/DSC system (Netzsch STA 449 F3). The magnetic characters of the as-prepared samples were observed via a vibrating sample magnetometer (VSM, LakeShore7404, USA) at room temperature. The specific surface and pore size distribution were analyzed by nitrogen adsorption–desorption isotherms (ASAP 2460). To demonstrate the presence of oxygen vacancies, the samples were tested using electron paramagnetic resonance spectroscopy (EPR, Bruker EMXplus-6/1, Germany).

The phase structure was characterized by X-ray diffraction (XRD) using a Rigaku D/max-3C. The morphologies and microstructures were analyzed by a scanning electron microscope (SEM, JSM-7610F, Japan) and a transmission electron microscope (TEM, TF20), respectively. The composition and valence of elements of the prepared NiCo₂O₄ nanomaterials were determined by X-ray photoelectron spectrometer (XPS, Thermo Scientific K-Alpha), Raman spectrometer (Horiba LabRAM HR Evolution), and TGA/DSC system (Netzsch STA 449 F3). The magnetic characters of the as-prepared samples were observed via a vibrating sample magnetometer (VSM, LakeShore7404, USA) at room temperature. The specific surface and pore size distribution were analyzed by nitrogen adsorption–desorption isotherms (ASAP 2460). To demonstrate the presence of oxygen vacancies, the samples were tested using electron paramagnetic resonance spectroscopy (EPR, Bruker EMXplus-6/1, Germany).