Elsevier

Journal of Hazardous Materials

Volume 293, 15 August 2015, Pages 1-6
Journal of Hazardous Materials

Room-temperature cataluminescence from CO oxidation in a non-thermal plasma-assisted catalysis system

https://doi.org/10.1016/j.jhazmat.2015.03.029Get rights and content

Highlights

  • Room-temperature CTL emission from CO oxidation was firstly observed.

  • A non-thermal plasma-assisted catalysis system was fabricated for CO oxidation.

  • Low-cost catalysts were synthesized and used for CTL emission at room temperature.

  • Plasma assistance contributed to the reactivity of catalysts.

  • New optical sensing system was fabricated for CO detection.

Abstract

Cataluminescence (CTL) is a kind of chemiluminescence during catalytic reaction on surface of catalysts under a heated condition. Due to the low catalytic reactivity of CO, normally low intensity of CTL is obtained during heterogeneously catalytic oxidation of CO under heated conditions (normally higher than 150 °C), even catalyzed by precious-metal-based catalysts. Therefore, seeking enhanced CTL of CO at room temperature and using low-cost catalysts becomes significant. Here, CTL generated from CO oxidation was firstly reported at room temperature, which was carried out in a non-thermal plasma-assisted (NTPA) catalysis system. With air acting as discharge gas, carrier gas as well as oxidant, a Mn/SiO2 nanomaterials-based NTPA catalysis system was fabricated for CO catalytic oxidation at room temperature, whose temperature was much lower than previous CTL methods. Relatively high and selective CTL responses were acquired during CO oxidation on surface of Mn/SiO2 nanomaterials, whereas no significant CTL signal was recorded without plasma assistance or on other metals-doped SiO2 catalysts. Without any excitation light source or heating element, a low cost and simple CO sensor was fabricated by using common and easily synthesized catalysts. The present work has greatly simplified the constructions, and enlarged CTL applications.

Graphical abstract

The cataluminescence generated from CO oxidation was firstly reported at room temperature, which was carried out in a non-thermal plasma-assisted catalysis system.

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Introduction

Heterogeneously catalytic oxidation of carbon monoxide (CO) at low temperature has obtained much attention due to the potentials in the industrial controls [1]. As reported, performance for CO oxidation has been exhibited through the catalytic oxidation of CO catalyzed by precious-metal-based catalysts including Au [2], [3], Ag [4], Pt [5], Pd [6], [7] or Ru [8] supported catalysts. However, the greater interest in non-precious-metal catalysts (NPMCs) is coming to be aroused by their low price as well as abundant reserves [9]. For example, Cu [10], Co [11] or Mn-based [12] NPMCs supported on some oxides supports such as SiO2 [13], [14], Al2O3 [15] and TiO2 [9] have obtained much attention for low-temperature oxidation of CO. However, the synthesis of these catalysts is normally complicated, whose catalytic performance would depend on the special characteristics of the catalysts. Therefore, to promote the application of these catalysts in CO industry, more green catalysts with low cost, easy preparation procedures are still needed.

Interestingly, the cataluminescence (CTL) emitted during catalytic oxidation on surface of nanomaterials has many applications in sensing or catalysts evaluation [16], [17], [18], which has also been recorded during the catalytic oxidation of CO on surfaces of some precious-metal-based catalysts such as Au and Pt supported nano-oxides [19], [20]. This offers a new approach for seeking more green catalysts, and would awake the new optical application of CO catalytic oxidation after the finding of electrical [21] and infrared characteristics [22] along with CO catalytic oxidation. Without any excitation light source, the emission of CTL signals relies on the catalytic oxidation on the surface of nanomaterials [23], [24], which simplifies the construction. For catalysts’ non-consumption, the CTL signals have long lifetime, together with intuitional change in signals and absence of electromagnetic interferences. However, due to the poor CTL reactivity of CO, the CTL responses acquired were still relatively low despite the adopting of high operating temperatures (higher than 150 °C) and precious-metal-based catalysts. Although great efforts have been devoted to seeking catalysts that could emit CTL at low temperature [4], [25], few reports were in terms of CO. Recently, we have utilized plasma, a sort of chemically active gas consisting of excited species and activated particles, for the activation of analytes with low CTL activities for CTL emission [26], [27]. But considering the quite low activity of hydrocarbons, a relatively high operating temperature above 100 °C was still needed [27]. Recently, with plasma assistance, a low temperature CTL sensor of CO was also fabricated by our group, but the adopting of Ag doped alkaline-earth catalyst is of high cost and a heating element is still needed to guarantee a working temperature about 50 °C [28]. Therefore, it is still crucial to find a low-cost and easy pathway for the emission of CTL during CO oxidation at room temperature, which is of much importance in further applications.

In this work, with the assistance of low-temperature plasma, CTL emission (NTPA–CTL) was firstly observed during room-temperature oxidation of CO catalyzed by Mn/SiO2 nanomaterials. Different from the previous CTL-based methods, this technique needs not any heating element, and relatively high CTL responses were obtained at room temperature for CO oxidation on surface of Mn/SiO2 nanomaterials. Then, without any excitation light source or heating element, this has evoked the low cost and simple sensing of CO based on the intuitional optical signals at room temperature. Due to the simply prepared sensing elements, and low-cost setup with the absence of heating elements, this will show potential in the development of hand-held and mobile devices for CO detection, enlarging applications of cataluminescence and CO oxidation.

Section snippets

Chemicals

All reagents were of analytical reagent grade. The reagents of manganese acetate tetrahydrate (Mn(CH3COO)2·4H2O), cobalt(II) chloride hexahydrate (CoCl2·6H2O), chromium(III) chloride hexahydrate (CrCl3·6H2O), iron(III) nitrate nonahydrate (Fe(NO3)3·9H2O), absolute methanol, absolute ethanol and acetic acid (HAc) were obtained from Beijing Co., Ltd. Tetraethyl orthosilicate (TEOS) was purchased from Sinopharm Chemical Reagent Co., Ltd. SiO2 nanomaterial was supplied by Nanjing Haitai Nano Co.,

Fabrication of NTPA–CTL system.

As shown in Fig. 1, the NTPA–CTL system consisted of three parts: the low-temperature plasma generator, the non-thermal CO oxidation cell and ultraweak chemiluminescence analyzer (BPCL-2-JZ-TGC) for recording CTL signals. Based on dielectric barrier discharge [27], a commercial ozonizer (JR-A2-1G, Jinrun Electronics Co., Ltd., China) combined with an 8 W of power acted as the low-temperature plasma generator. The non-thermal CO oxidation cell was simply a catalysts-coated glass rod in a glass

Conclusions

In summary, the room-temperature CTL emission was first observed during CO oxidation. With the assistance of the plasma, reactivity of analytes or the catalytic activity of catalysts could be increased for CO oxidation at room temperature, which combined with the emission of significant CTL signals without any excitation light source or heating element. This has evoked the simple sensing of CO based on the intuitional optical signals at room temperature, which will enlarge the application of CO

Acknowledgments

The authors gratefully acknowledge the support from the National Nature Science Foundation of China (21422503, 21475011), A Foundation for the Author of National Excellent Doctoral Dissertation of PR China (201221), and the Fundamental Research Funds for the Central Universities.

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