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

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 degrees 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 degrees 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 degrees C, Co-Fe2O4 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 degrees C showed the best overall performance for H2O2 decomposition.