LAUSR

The metal-modified Co3O4 sample (metal: Zn or Cr, Zn and Cr) was prepared through hydrothermal approach, and applied in low concentration of HCHO removal under room temperature. The Cr/Zn/Co3O4 exhibited the best formaldehyde removal activity and stability. The effect of dopants on the physicochemical properties of the Co3O4 samples was characterized by X-ray diffraction, Raman, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, thermogravimetric (TG-DTG) and X-ray photoelectron spectroscopy, resulting that the Cr/Zn/Co3O4 sample possessed the optimal specific surface area (177.53 m2/g, 3.4 times that of pure Co3O4). Meanwhile, Cr and Zn incorporated into Co3O4 lattice simultaneously and promoted the formation of defects, which is the prerequisite for increasing the reactive oxygen species of Cr/Zn/Co3O4. In addition, Cr6+/Cr3+ ion pairs in the sample could be an important role in the removal of formaldehyde. It is concluded that the ideal HCHO removal performance and stability of Cr/Zn/Co3O4 were associated with its high vacancy oxygen content, excellent specific surface area and the promotion of Cr6+/Cr3+ ion pairs.