Study of Plasma-Induced Surface Active Oxygen on Zeolite-Supported Silver Nanoparticles
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Study of Plasma-Induced Surface Active Oxygen on Zeolite-Supported Silver Nanoparticles Yoshiyuki Teramoto • Hyun-Ha Kim Atsushi Ogata • Nobuaki Negishi
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Received: 7 May 2013 / Accepted: 2 September 2013 / Published online: 25 September 2013 Ó The Author(s) 2013. This article is published with open access at Springerlink.com
Abstract Surface oxygen induced by non-thermal plasma at atmospheric pressure on silver nanoparticle-loaded zeolite was determined by a chemical probe based on the oxidation of NO. The amount of active oxygen fixed onto the catalyst surface by O2 plasma was approximately proportional to the square of the amount of supported silver. In dry air, its extraordinary long lifetime was confirmed for the first time. Keywords Plasma-driven catalysis Active oxygen Silver nanoparticle Atmospheric pressure
1 Introduction Environmental issues and especially atmospheric pollution are of great concern throughout the world. Atmosphericpressure non-thermal plasma (NTP) offers unique chemical environment that promotes the removal of air pollutants at low concentrations. On the other hand, the results of studies over the last 30 years have revealed several limitations of plasma-alone processes for practical use in industry. These include large energy consumption, low selectivity, and formation of unwanted byproducts. Plasmacatalyst hybrid technique is a promising technique to overcome these problems. Combinations of atmospheric pressure dielectric barrier discharge (DBD) with different types of catalyst are currently being studied to improve the process performance
Y. Teramoto (&) H.-H. Kim A. Ogata N. Negishi National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba West, 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan e-mail: [email protected]
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[1–3]. These combinations have been experimentally proved to provide better selectivity for plasma and lower working temperature for catalyst [4–6]. For example, it has been reported that the combination of DBD and manganese catalyst enhances TCE decomposition and CO2 selectivity [7, 8]. The loading of active metals not only enhances CO2 selectivity for various VOCs [9–11], but also extends plasma area over the surface on catalyst [12]. The mechanism of synergistic effect, however, is still barely understood. Roland et al. [13] experimentally studied the stabilization of plasma-formed oxidants on the surface of LaCoO3. When CO/N2 mixture was fed to the O2 plasma pretreated LaCoO3 catalyst, the temporal profiles of outlet CO concentration changed according to the O2 plasma pretreatment time. They concluded that the active oxygen formed by plasma treatment on the catalyst surface react with CO to produce CO2 and thus improves the CO2 selectivity, and that the active oxygen is the predominant active species for pollutant oxidation. The same group reported that oxygen atoms in the gas phase are available inside the nano-scale pores of c-Al2O3 and silica gel, and porosity and specific surface of catalysts are therefo
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