NDLI: The kinetics and mechanism of photo-assisted Ag(I)-catalysed water oxidation with $S_{2}O

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Liu, Meiying Wang, Jidan You, Wansheng Li, Can Yu, Lihong Guo, Dan Zhang, Lancui
Description	Author Affiliation: Yu L ( Institute of Chemistry for Functionalized Materials, Liaoning Normal University, Dalian, 116029, P. R. China. wsyou@lnnu.edu.cn.)
Abstract	The kinetics of photo-assisted Ag(I)-catalysed water oxidation into $O_{2}$ with $S_{2}O_{8}^{2−}$ has been investigated. When the concentration of $Ag^{+}$ is less than 7.06 × $10^{−3}$ mol $L^{−1},$ $O_{2}-evolution$ under visible light illumination (λ ≥ 400 nm) obeys the first-order rate law with respect to the concentrations of $Ag^{+}$ and $S_{2}O_{8}^{2−},$ respectively. The rate law is expressed as $−dc(S_{2}O_{8}^{2−})/dt$ = $2dc(O_{2})/dt$ = $k_{L}c(S_{2}O_{8}^{2−})c(Ag^{+}),$ where $k_{L}$ is 12.4 ± 1 $mol^{−1}$ L $h^{−1}$ at 24.5 °C and the activation energy is 3.7 × $10^{4}$ J $mol^{−1}.$ It is found that visible light can improve the evolution of $O_{2}$ 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 $\{AgS_{2}O_{8}\}^{−},$ $Ag^{2+},$ OH˙, $Ag_{2}O_{3}$ 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 $S_{2}O_{8}^{2−}$ has been developed, in which the reaction $(AgO^{+}$ + $H_{2}O$ → $Ag^{+}$ + $H_{2}O_{2})$ is considered as the rate-determining step. The increase of the $O_{2}-evolution$ rate under visible light illumination results from the absorbance of the $AgO^{+}$ species at 375 nm, promoting the rate-determining step.
ISSN	14779226
Issue Number	2
Journal	Dalton Trans.
Volume Number	44
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2015-01-14
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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