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Surface reactivity of hydroxyl radicals formed upon catalytic decomposition of H2O2 on ZrO2
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.ORCID iD: 0000-0003-0663-0751
2015 (English)In: Journal of Molecular Catalysis A: Chemical, ISSN 1381-1169, Vol. 400, 49-55 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2015. Vol. 400, 49-55 p.
Keyword [en]
Catalysis, Hydrogen peroxide, Hydroxyl radical, Oxide, Surface, Computer software, Methanol, Oxides, Surfaces, Catalytic decomposition, Concentration ranges, Hydroxyl radicals, Initial concentration, Kinetic simulation, Reaction system, Surface reactivity, Trishydroxymethylaminomethane, Zirconium alloys
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-167732DOI: 10.1016/j.molcata.2015.02.002ISI: 000353248000007ScopusID: 2-s2.0-84922771691OAI: diva2:815666

QC 20150601

Available from: 2015-06-01 Created: 2015-05-22 Last updated: 2015-08-26Bibliographically approved
In thesis
1. Radiation Induced Processes at Solid-Liquid Interfaces
Open this publication in new window or tab >>Radiation Induced Processes at Solid-Liquid Interfaces
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the thesis, the reactions between water radiolysis products—H2O2, HO• and O2—with metals and metal oxides utilized in nuclear industry are studied. The reactions include not only surface reactions, e.g. redox reactions and catalytic decomposition of H2O2, but also solution reactions (Haber-Weiss reactions). To study the interfacial reactions, it is crucial to monitor the dissolution of the solid material, reactivity of H2O2 and formation of the intermediate hydroxyl radicals.Hydroxyl radicals are captured by probe (Tris or methanol) to generate CH2O which can be quantified by the modified Hantzsch method. The results from γ-irradiation experiments on homogeneous system show that the conversion yield of CH2O from hydroxyl radicals is affected by O2 and pH. A mechanism of CH2O production from Tris is proposed.Besides, the consumption rate of H2O2 in the H2O2/ZrO2/Tris system is found to be influenced by Tris. A mechanism for the catalytic decomposition of H2O2 upon ZrO2 surface is proposed which includes independent surface adsorption sites for H2O2 and Tris. Moreover, it is demonstrated that the deviation of detected CH2O concentration by the modified Hantzsch method from actual concentration increases with increasing [H2O2]0/[CH2O]0.The inhibition of sulfide on the radiation induced dissolution of UO2 is confirmed and is dependent on sulfide concentration. And the inhibition of sulfide is independent to that of H2/Pd.It is found that the reactivity of H2O2 and dynamics of CH2O formation are different for the studied materials in the H2O2/MxOy/Probe system. The kinetic parameters, such as rate constant, activation energy, frequency factors are determined.Both surface and solution reactions are observed in the aqueous W(s)/H2O2/Tris system. It is also demonstrated that Haber-Weiss reactions which produce HO• continuously are dominating. Furthermore, it is found that hydroxyl radicals are formed simultaneously during the dissolution of W in aerobic aqueous system.The knowledge conveyed by the thesis is relevant to nuclear technological applications, as well as the applications related in photocatalysis, biochemistry, corrosion science, catalysis and optics/electronics.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xii, 74 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:39
National Category
Physical Chemistry
urn:nbn:se:kth:diva-172421 (URN)978-91-7595-656-5 (ISBN)
Public defence
2015-09-18, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20150826

Available from: 2015-08-26 Created: 2015-08-21 Last updated: 2015-08-26Bibliographically approved

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