Catalytic decomposition of hydrogen peroxide on transition metal and lanthanide oxides

•H2O2 decomposition is reported for five oxides—transition metals and lanthanides.•The amount of interfacial HO• during decomposition of H2O2 is strongly catalyst dependent.•Mechanistic discussion for H2O2 on oxides of: Zr, Ti, Y, Fe, Cu, Ce, Gd, Hf and U.•Accurate kinetic/energetic data reported for H2O2 decomposition on these materials.

We have investigated the reactions of H2O2 with Fe2O3, CuO, HfO2, CeO2 and Gd2O3 in aqueous solution. The reactions rate constants at room temperature were determined. From the temperature dependence of the rate constants we extracted the Arrhenius parameters and the standard enthalpies of activation for the reactions. In addition, we studied the dynamics of formation of the intermediate species formed during decomposition of H2O2, the HO radical. The kinetic data for H2O2 reactivity and the yields of hydroxyl radical formation differ considerably between many of the materials studied. We compared the energetic and mechanistic data obtained in this work with literature data for a set of nine oxides in total. The Arrhenius pre-exponential factors normalized to surface area for the decomposition of H2O2 vary by nine orders of magnitude for some of the oxides investigated. This indicates that the surfaces of the oxides have very different catalytic capacity towards the decomposition of H2O2. The standard enthalpies of activation for H2O2 decomposition vary between 30 and 73 kJ mol−1, revealing also differences in the catalytic efficiency for the different materials. The mechanistic study consists of quantifying the HO radical scavenged by tris(hydroxymethyl)aminomethane (Tris) during the course of the decomposition of H2O2 for the whole set of oxides. The yields and dynamics of scavenging of HO• differ considerably between the oxides analyzed. Surprisingly, the time-independent plots of the amount of HO scavenged as a function of the conversion of H2O2 reveals that during the decomposition of H2O2 there are turnover points where the amount of HO scavenged by Tris suffers a sudden increase. The location of these points and the curvatures of the plots at the near-neighbours is considerably different for the different materials.

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