Study of cobalt-iron mixed oxides and catalytic behavior for decomposition of hydrogen peroxide

Abstract

This work reports a comprehensive study on the iron incorporation in the lattice of cobalt-iron mixed oxides and its effect on physicochemical and catalytic properties. Catalysts with different Co:Fe molar ratio (Co:Fe = 2:1, 1:1, and 1:2) and different synthesis temperatures (400, 500, and 600 °C) were prepared by the citrate method. The catalysts were characterized by several techniques (TGA, DSC, FAAS, SEM-EDS, XPS, FTIR, XRD, Rietveld refinement, nitrogen sorptometry, and TPR) and the catalytic behavior was evaluated in terms of the H2O2 decomposition. The characterization results showed that Co-Fe mixed oxides with spinel structure were obtained. For the catalysts calcined at 400 °C, the iron incorporation in the Co3O4 lattice increased the unit cell size, induced the spinel partial inversion, increased the specific area, and affected the reducibility. The Co-Fe mixed oxides were slightly less active than Co3O4, but they showed greater leaching resistance under reaction conditions. The increase of the calcination temperature caused strong sintering and at 600 °C, CoFe2O4 segregated. The catalytic activity decreased with the increasing of calcination temperature and the leaching resistance did not improve. Thus, the catalyst with Co:Fe = 2:1 molar ratio calcined at 400 °C showed the best overall performance for H2O2 decomposition.