The kinetics of hydrogen peroxide decomposition catalyzed by cobalt-iron oxides
1974; Elsevier BV; Volume: 32; Issue: 3 Linguagem: Inglês
10.1016/0021-9517(74)90096-7
ISSN1090-2694
Autores Tópico(s)Advanced oxidation water treatment
ResumoThe kinetics, in alkaline solution, of heterogeneous H2O2 decomposition by the cobalt-iron spinel oxide system, CoxFe3 − xO4, (0 ≤ x ≤ 3), were studied with a view to defining the intrinsic and microstructural factors influencing the catalytic activity. The activity order for two catalyst series, prepared by hydroxide and oxalate coprecipitation routes, was found to be (considering x values) 1.0 > 1.5 > 2.0 > 2.4 > 3.0 > 0.6 > 0.0 on the basis of diffusion-free activation energies for the decomposition reaction. This order agreed with results obtained by measuring the initial rates of H2O2 decomposition, provided the rates were normalized for the available area of reaction at the catalyst surface. The activity order can be interpreted in terms of the electronic structure of cobalt-iron oxides, and a key factor is the presence of CoII ions on the octahedral lattice sites, which can initiate a cyclic electron transfer process (redox reaction) on the catalyst surface. Maximum activity, and lowest activation energy for the reaction, occurs at x = 1, since the greatest availability of octahedral CoII occurs at this composition.
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