“…Spinels are materials with a particular crystalline structure, which widely exist in nature . Typically, spinels are concisely depicted as AB 2 O 4 , where A = Mg, Ca, Zn, Mn, Ni, Ba, Cu, Ge, Fe, Co, and so forth; B = Al, Ga, In, Cr, Fe, Ni, Mn, Co, and so forth . Their excellent characteristics such as the thermostabilized structure, low price, simple synthetic method, and environmental friendliness lead to many applications, especially in catalysis, because of the flexible adjustment of the atomic composition, structure, valence, and morphology .…”