The effect of the phase structure on physicochemical properties of TMO materials: A case of spinel to bunsenite

It is worthwhile to comprehensively investigate the relationship between different phase structures and physicochemical properties of TMO materials. For investigating the phase structure effect, spinel Co₃O₄, NiCo₂O₄, and bunsenite NiO microflowers were rationally synthesized through a facile solvothermal method combined with a post-annealing process. The phase structures of final products were controlled by adjusting the Ni/Co addition ratio. The SEM and TEM results revealed that these Ni/Co oxides exhibited similar flower-like morphology; this provided convenience for investigation of their physicochemical properties in view of their phase structure. Compared with Co₃O₄ that exhibited superparamagnetic behavior, NiCo₂O₄ exhibited ferromagnetic characteristics because of the incorporation of nickel into the spinel structure. Co₃O₄ and NiCo₂O₄ demonstrated thermal catalytic ability higher than that of bunsenite NiO due to the more efficient electron transfer ability of the spinel structure. In view of the phase structures, this study provided a prospective case of research on the physicochemical properties of transition-metal oxide (TMO) materials.