NaBH4 reduced Mn-doped cobalt tetroxide R-MnxCo3−xO4 catalysts with plentiful oxygen vacancies for HCHO oxidation at low temperature

Abstract

Developing low-cost and efficient catalysts for the oxidation of formaldehyde (HCHO) is crucial for preservation of the environment. The main challenge of this study is how to develop an efficient, stable, and inexpensive catalyst that can oxidize HCHO at low temperatures. Herein, the reduced Mn-doped cobalt tetroxide R-Mn_xCo_3−xO₄ catalyst was prepared by simple co-precipitation and annealing treatment followed by reduction of NaBH₄. The prepared R-Mn_xCo_3−xO₄ showed remarkable enhanced activity for HCHO oxidation at low temperature. The R-MnCo₂O₄ catalyst can oxidize and decompose 79% of HCHO at a low temperature of 50 °C and exhibits excellent catalytic stability. The improved catalytic activity can be attributed to the increase in oxygen vacancy concentration and the improvement in redox performance. The TGA test shows that the content of oxygen vacancies in the R-MnCo₂O₄ catalyst can reach 5.77% (atomic ratio). The H₂-TPR, O₂-TPD and O₂-TPO tests indicated that the surface oxygen vacancies can promote oxygen mobility and facilitate the formation of reactive oxygen species during the formaldehyde catalytic oxidation process. This study reveals the importance of surface oxygen vacancies in improving the catalytic oxidation activity of catalysts, providing possibilities for the development of high-performance catalysts through atomic doping and reduction modification.