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Issue 2, 2015
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The kinetics and mechanism of photo-assisted Ag(I)-catalysed water oxidation with S2O82−

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Abstract

The kinetics of photo-assisted Ag(I)-catalysed water oxidation into O2 with S2O82− has been investigated. When the concentration of Ag+ is less than 7.06 × 10−3 mol L−1, O2-evolution under visible light illumination (λ ≥ 400 nm) obeys the first-order rate law with respect to the concentrations of Ag+ and S2O82−, respectively. The rate law is expressed as −dc(S2O82−)/dt = 2dc(O2)/dt = kLc(S2O82−)c(Ag+), where kL is 12.4 ± 1 mol−1 L h−1 at 24.5 °C and the activation energy is 3.7 × 104 J mol−1. It is found that visible light can improve the evolution of O2 remarkably. Compared with those without illumination, the rate constants under visible light are increased by ca. 3.8 mol−1 L h−1 at 4.5, 11.5, 17.5 and 24.5 °C, which are hardly affected by the reaction temperature. Employing MS/MS, ESR, XRD and UV-visible spectroscopy, the intermediate species {AgS2O8}, Ag2+, OH˙, Ag2O3 and AgO+ in the process of water oxidation have been detected. Based on the experimental evidence, the mechanism of Ag(I)-catalysed water oxidation with S2O82− has been developed, in which the reaction (AgO+ + H2O → Ag+ + H2O2) is considered as the rate-determining step. The increase of the O2-evolution rate under visible light illumination results from the absorbance of the AgO+ species at 375 nm, promoting the rate-determining step.

Graphical abstract: The kinetics and mechanism of photo-assisted Ag(i)-catalysed water oxidation with S2O82−

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Publication details

The article was received on 24 Jul 2014, accepted on 27 Oct 2014 and first published on 03 Nov 2014


Article type: Paper
DOI: 10.1039/C4DT02254H
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Citation: Dalton Trans., 2015,44, 710-717
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    The kinetics and mechanism of photo-assisted Ag(I)-catalysed water oxidation with S2O82−

    L. Yu, J. Wang, D. Guo, W. You, M. Liu, L. Zhang and C. Li, Dalton Trans., 2015, 44, 710
    DOI: 10.1039/C4DT02254H

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