Effect of A2+ and B3+ substitution for Cobalt on low-temperature catalytic removal of formaldehyde over spinel AxB3-xO4 (A = Mg, Ni, Zn; B = Cr, Fe, Al)

Spinel Co3O4 catalysts were modified by A(2+) (A = Mg, Ni, Zn) and B3+ (B = Cr, Fe, Al) metal cation substitution respectively for low-temperature removal of formaldehyde. Among of those A(2+) substituted catalysts, Ni0.8Co2.2O4 was found to be the best low-temperature catalytic activity with T100 of 90 degrees C and 100% CO2 selectivity. However, B3+ substitution was found negative to improve the low-temperature catalytic performance for relatively weaker oxidation capacity of Cr3+, Fe3+ and Al3+. Results of XRD and Raman characterization confirmed that both A(2+) or B3+ cations substitution caused structural and surface electronic variation, and NiCo2O4 had been successfully synthesized. XPS analysis revealed that surface hydroxyl coming from Ni(OH)(2) was enriched by Ni2+ substitution. The active oxidant Co3+ and abundant hydroxyl were concluded to dominate the low-temperature activity of NixCo3-x catalysts.