Kinetics and mechanism of H/sub 2/O/sub 2/ decomposition catalyzed by Cu/sup 2+/ in alkaline solution

Journal Article · Wed Jul 13 04:00:00 EDT 1988 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00287a023· OSTI ID:6001478

Luo, Y; Kustin, K; Epstein, I R

The kinetics of the Cu/sup 2+/-catalyzed decomposition of hydrogen peroxide have been studied at pH 11-12. The disappearance of hydrogen peroxide and the appearance of dissolved dioxygen have been followed titrimetrically and potentiometrically. Alkaline decomposition in the presence of copper(II) is accompanied by formation of a superoxide-copper(I) complex, formally, (HO/sub 2/Cu(I)). The apparent complex formation constant K/sub app/ = (HO/sub 2/-Cu(I))/(H/sub 2/O)/sub f/(Cu/sup 2+/)/sub f/, where (H/sub 2/O/sub 2/)/sub f/ and (Cu/sup 2+/)/sub f/ are the concentrations of free hydrogen peroxide and free copper(II) ion, respectively, has been determined at several pH values. The results are consistent with a complex of molecular formula HO/sub 2/Cu(OH)/sub 2//sup /minus//, which has extinction coefficient /le/ 1600 M/sup /minus/1/ cm/sup /minus/1/ at 345 nm and acid dissociation constant K/sub e/ = (O/sub 2/Cu(OH)/sub 2//sup 2/minus//)(H/sup +/)/(HO/sub 2/Cu(OH)/sub 2//sup /minus//) = 3.55 /times/ 10/sup /minus/12/ M. The experimental time course of the reaction (graphs of (H/sub 2/O/sub 2/) vs time) can be obtained by integrating the rate law -dy/dt = wy/sup 2//(/upsilon/ + sy + uy/sup 2/), where y is (H/sub 2/O/sub 2/) and w, /upsilon/, s, and u are complicated constants composed of rate constants and initial concentrations. Computer simulations with a mechanism in which complex formation is accompanied by reactions involving OH/sup /center dot//, HO/sub 2//sup /center dot//, and O/sub 2//sup /center dot//minus// radicals give excellent agreement with a variety of experimental observations. The relevance of the proposed mechanism to the Cu/sup 2+/-catalyzed decomposition of H/sub 2/O/sub 2/ in acid solution and to the Fe/sup 3+/-catalyzed reaction is discussed briefly. 22 references, 7 figures, 3 tables.

• Research Organization: Brandeis Univ., Waltham, MS (USA)
• OSTI ID: 6001478
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 27:14; ISSN INOCA
• Country of Publication: United States
• Language: English

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CATALYSIS
CATALYTIC EFFECTS
CATIONS
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DATA
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EXPERIMENTAL DATA
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