Preparation and Electrocatalytic Property of Triuranium Octoxide Supported on Reduced Graphene Oxides

Nano Research 1 DOINano 10.1007/s12274Res -014-0668-8 Preparation and Electrocatalytic Property of Triuranium Octoxide Supported on Reduced Graphene Oxides Dongliang Gao1, 2, Zhenyu Zhang1, Li Ding1, Juan Yang1, and Yan Li1, 2 () Nano Res., Just Accepted Manuscript • DOI: 10.1007/s12274-014-0668-8 http://www.thenanoresearch.com on December 2 2014 © Tsinghua University Press 2014 Just Accepted This is a “Just Accepted” manuscript, which has been examined by the peer-review process and has been accepted for publication. A “Just Accepted” manuscript is published online shortly after its acceptance, which is prior to technical editing and formatting and author proofing. Tsinghua University Press (TUP) provides “Just Accepted” as an optional and free service which allows authors to make their results available to the research community as soon as possible after acceptance. 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TABLE OF CONTENTS (TOC) Preparation and Electrocatalytic Property of Triuranium Octoxide Supported on Reduced Graphene Oxides Dongliang Gao1, 2, Zhenyu Zhang1, Li Ding1, Juan Yang1, and Yan Li1, 2* 1 Key Laboratory for the Physics and Chemistry of Nanodevices, Beijing National Laboratory for Molecular Science, College of Chemistry and Molecular Engineering, State Key Laboratory of Rare Earth Materials Chemistry and Applications, Peking University, Beijing100871, China A two-step solution-phase method was used to prepare triuranium octoxides-reduced graphene oxides hybrids, which exhibited superior electrocatalytic activity for oxygen 2 Academy for Advanced Interdisciplinary reduction reaction. Studies, Peking University, Beijing100871, China Provide the authors’ webside if possible. Author 1, webside 1 Author 2, webside 2 Nano Research DOI (automatically inserted by the publisher) Research Article Preparation and Electrocatalytic Property of Triuranium Octoxide Supported on Reduced Graphene Oxides Dongliang Gao1, 2, Zhenyu Zhang1, Li Ding1, Juan Yang1, and Yan Li1, 2 () Received: day month year ABSTRACT Revised: day month year Triuranium octoxides-reduced graphene oxides (U3O8/rGO) hybrids were Accepted: day month year prepared by a two-step solution-phase method. The presence of GO is essential (automatically inserted by for obtaining pure phase U3O8. The U3O8/rGO hybrids exhibited superior the publisher) electrocatalytic activity for oxygen reduction reaction. The electron transfer number was calculated to be ~3.9 at -0.7 V (v.s. Ag/AgCl) from the slope of © Tsinghua University Press Koutecky-Levich plots. The U3O8/rGO hybrids were more stable than the and Springer-Verlag Berlin commercial Pt/C catalysts. When methanol existed, the U3O8/rGO hybrids still Heidelberg 2014 kept high activity. Besides, the U3O8/rGO hybrids can also catalyze the reduction of hydrogen peroxide. KEYWORDS Triuranium Octoxide, Reduced Graphene Oxides, Oxygen Reduction Reaction, Electrocatalysis of 99.275%, 0.720%, and 0.005%, respectively [1]. 1 Introduction Uranium-dioxide with enriched 235U is normally used as a fuel in the nuclear reactors. So large amount of 238U, which has a very long half-life period of ~4.5 Uranium is an important element in nuclear industry. billion years and hence is safe to be used Uranium consists of several natural isotopes conventionally [2], is left. Therefore, the application including 238U, 235U, and 234U, with natural abundance Address correspondence to Yan Li, [email protected] Nano Res. 2 of residual 238U is of great importance. [19]. In these studies, it is always difficult to avoid the formation of impurity uranium oxides with Uranium is an actinide element which has 5f different valence. The introducing of different electrons. The 5f-orbital can hybridize with the organic molecules which act as reductants or capping 6d-orbital, giving the actinides a broader range of agents is also a big problem, which depresses the oxidation states. Thus uranium possesses +2, +3, +4, catalytic performance of uranium oxides [20]. +5, and +6 valence [3-9]. Besides the most outside orbitals in the 7th shell, both 5f and 6d orbitals can Graphene oxide (GO) presents high specific also partake in chemical bonding, therefore, the surface area and contains carboxylic, hydroxyl, bonding of uranium is quite complicated. In addition, epoxide and other hydrophilic functional groups on chemical bonds consisting of uranium ions are often the surface. Therefore, GO has been widely used as less ionic due to the large radius and high charge substrates to prepare inorganics-GO hybrids. Dai’s number [10]. So uranium has different coordination group has developed a general two-step method to numbers and bonding modes from the lanthanide or prepare hybrids of inorganic nanomaterials and transition elements [11]. Owing to the special graphene oxides. First, metal ions absorb onto GO structural features and chemical properties, uranium and hydrolyze in situ; then the pre-products are oxides may be used as good catalysts for different treated under hydrothermal or solvothermal kinds of reactions [10, 12-16]. conditions to obtain the final hybrids [22-30]. This method may be used to prepare hybrids of uranium It is found that the oxidation state of uranium is a oxides and GO. crucial factor influencing its catalytic performance. For instance, U3O8 can catalyze the aldolization With the outstanding properties of high electrical reaction of acetaldehyde to form crotonaldehyde. conductivity, surface area, flexibility, thermal However, when β-UO3 was used as catalysts, conductivity, and mechanical strength, graphene can acetaldehyde conducted condensation reaction to be used as electrode materials or supports for form furan [17]. U3O8 nanocrystals have a better electrocatalysts [31-33]. Due to the scarcity and high catalytic performance for benzyl alcohol conversion price of Pt for large scale application of fuel cells, to benzadlehyde than UO2 nanocrystals [18]. electrocatalysts without Pt have attracted much Nanoplates of uranium oxide hydroxide hydrate attention [34-36]. Very recently, M. Pumera et al. exhibit a higher catalytic activity than U3O8 for reported that uranium doped graphene hybrids benzyl alcohol oxidation [15]. The oxygen-defected exhibited electrocatalytic properties towards oxygen UO2 (111) single crystal reduces coupling of CO reduction [37]. They found UO3 and U3O8 co-exist in molecules to acetylene and ethylene compounds on their catalysts. It is unclear which component acts as its surface [12]. the catalytic species and the performance of the catalysts is not optimized. In this paper, we prepared Thus synthesis of pure phase uranium oxides with hybrids of pure phase triuranium octoxide and different oxidation states is very important for reduced GO (U3O8/rGO) and studied their studying their catalytic property. A few literatures electrocatalytic property. It was found that the have reported about the preparation of uranium U3O8/rGO hybrids showed very good activity toward oxides nanomaterial [15, 18-21]. For instance, using oxygen reduction reaction (ORR) and were more different organic amines as reducing reagents, UO2 stable than the commercial Pt/C catalysts. U3O8/rGO nanospheres and U3O8 nanorods have been hybrid catalysts might be used as a substitute of Pt/C synthesized [18]. By the addition of hydrazine, electrocatalyst for oxygen reduction reaction in fuel spherical UO2 nanoparticles with diameter from 30 to cells. 250 nm and U3O8 nanocuboids have been synthesized | www.editorialmanager.com/nare/default.asp Nano Res. 3 voltammetry. The catalyst-modified electrode was 2 Experimental prepared by transferring 20 μl of 2 mg/ml suspension of the samples onto the glassy carbon 2.1 Preparation of U3O8/rGO nanocrystals electrode with a diameter of 5.0 mm. A thin layer of Nafion was added to cover the electrode when it GO was synthesized by an improved hummers was dried. ORR was carried out in O2-saturated 0.1 method [38] (see details in the supporting M KOH aqueous solution at room temperature. information). Typically, 6 mg GO was dispersed in Hydrogen peroxide reduction was carried in 10 ml ethanol. 1 ml of 30 mg/mL UO2(NO3)2 N2-saturated 50 mM phosphate buffer saline (PBS) aqueous solution and 0.9 mL of concentrated aqueous solution at room temperature. NH3·H2O was injected into the suspension at 60 ºC, respectively. After stirring at 60 ºC for 6 hours, the 3 Results and discussion precipitates were collected by centrifugation and washed with water. Then the precipitates were Figures 1 (a) & (c) shows the TEM and SEM images re-dispersed in 10 ml water and transferred into a of the products obtained under typical conditions 20 ml Teflon-lined stainless steel autoclaves to carry with the hydrolysis temperature of 60 ºC. HRTEM out hydrothermal reaction at 200 ºC for 4 hours. The image in Fig. 1(b) clearly exhibits the fringes with product was collected by centrifugation, washed the inter-plane distance of (0 0 1) plane of U3O8 (0.42 with water, frozen by liquid nitrogen and nm). The selected area electron diffraction (SAED) lyophilized overnight. Using lyophilization process pattern also matches the structure of single crystal other than normal drying can avoid the aggregation U3O8 well. So the product we obtained is U3O8/rGO. of the products. The morphologies of the U3O8 nanoparticles are approximately cuboid with the dimensions of 2.2 Characterization 100-200 nm in length and 20-100 nm in width. X-ray diffraction (XRD) measurements were performed on a Rigaku Dmax-2400 diffractometer using Cu-Kα radiation (λ = 1.5406 Å ) with an accelerating voltage of 40kV.

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