Surface reactivity of hydroxyl radicals formed upon catalytic decomposition of H2O2 on ZrO2

• Competition between H2O2 and Tris for surface bound HO was quantified.
• Competition is governed by the relative surface coverage.
• Competition between O2 and H2O2 for CH2OH (precursor for CH2O) was revealed.
• Site-specific mechanism of H2O2 decomposition on the surface of ZrO2 was proposed.
• Numerical simulations reproduce the experimental results.

In this work, the surface reactivity of hydroxyl radicals formed upon catalytic decomposition of H2O2 on ZrO2 in the presence of Tris(hydroxymethyl) aminomethane was studied experimentally. Two sets of competition experiments were performed: the competition between H2O2 and Tris for the surface bound hydroxyl radical (HO) and between O2 and H2O2 for the hydroxymethyl radical (CH2OH) (precursor for formaldehyde). A 5-fold increase in initial concentration of Tris or H2O2 does not lead to a 5-fold increase in CH2O formation (only by a factor of 2–3 in the studied concentration range). The O2-dependent enhancement of the final production of CH2O becomes weaker upon increasing the initial concentration of H2O2 from 0.5 mM to 5 mM. The final production of CH2O becomes independent of the concentration of Tris when [Tris]0 is above 100 mM, i.e., the surface is saturated with Tris at this concentration. Based on the experimental results, a site-specific mechanism of H2O2 decomposition on the surface of ZrO2 was proposed. This model was used for numerical simulations of the dynamics of the reaction system. The kinetics was simulated using the kinetic simulation software Gepasi 3.0 and the results are in good agreement with the experimental observations.

Figure optionsDownload high-quality image (219 K)Download as PowerPoint slide