Energy efficient microwave synthesis of mesoporous Ce_0.5M_0.5O₂ (Ti, Zr, Hf) nanoparticles for low temperature CO oxidation in an ionic liquid – a comparative study

Abstract

Ce 0.5 M 0.5 O 2 (M = Ti, Zr, Hf) nanoparticles have been successfully synthesized by microwave irradiation in the ionic liquid [C 4 mim][Tf 2 N] (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide). The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N 2 -adsorption measurements. XRD and Raman spectroscopy analyses confirmed the formation of solid solutions with cubic fluorite structure. The catalytic activities of the Ce 0.5 M 0.5 O 2 (M = Ti, Zr, Hf) nanoparticles were investigated in the low-temperature oxidation of CO. Ce 0.5 Zr 0.5 O 2 nanospheres exhibit the best performance (100% conversion at 350 1C), followed by Ce 0.5 Hf 0.5 O 2 (55% conversion at 360 1C) and Ce 0.5 Ti 0.5 O 2 (11% conversion at 350 1C). Heating the as-prepared Ce 0.5 Zr 0.5 O 2 to 600 1C for extended time leads to a decrease in surface area and, as expected decreased catalytic activity. Depending on the ionic liquid the obtained Ce 0.5 Zr 0.5 O 2 exhibits different morphologies, varying from nano-spheres in [C 4 mim][Tf 2 N] and [P 66614 ][Tf 2 N] (P 66614 = trishexyltetradecylphosphonium) to sheet-like assemblies in [C 3 mimOH][Tf 2 N] (C 3 mimOH = 1-(3-hydroxypropyl)-3methylimidazolium). The microwave synthesis superiority to other heating methods like sonochemical synthesis and conventional heating was proven by comparative experiments where the catalytic activity of Ce 0.5 Zr 0.5 O 2 obtained by alternate methods such as conventional heating was found to be poorer than that of the microwave-synthesised material.

Controlled Synthesis of Polyions of Heavy Main-Group Elements in Ionic Liquids

“…Owing to the distinctive physicochemical properties of ILs (wide liquidus range, high redox and thermal stability, negligible vapor pressure, and tunable polarity) and their advantages over organic solvents, classic melts, or solid state reactions, their applications include separation techniques [7,8,9], lubrication [10], electrodeposition [11], acting as electrolytes in photovoltaic devices (e.g., solar cells) [12,13,14], catalysis for clean technology [15,16,17,18], polymerization processes [19], crystal engineering of a wide range of inorganic substances [20,21,22,23,24,25], and syntheses of new inorganic materials in general [23,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51]. Recently, several comprehensive reviews on syntheses of inorganic compounds in ILs have been published by Taubert [52], Feldmann [28], Dehnen [51], Janiak [42,53], Scrosati and Passerini [48], Morris [54], Mudring [55], Prechtl [56], Zhu [57], Dai [58], and Ruck [23,27,59] among others.…”

The Power of Ionic Liquids: Crystal Facet Engineering of SrTiO3Nanoparticles for Tailored Photocatalytic Applications

“…[ 23,24 ] In particular, they have proven to be well suited for the tailored synthesis of oxide nanoparticles (NPs) as they provide a tool to control the particle size, morphology, and crystalline phase. [ 17,25–28 ] Their potential can be even leveraged when combined with non‐classical synthesis techniques such as sonochemistry. [ 29–32 ] Sonochemistry has attracted over the past decade increasing interest of many researchers for the synthesis of inorganic nanomaterials.…”

The Intermetalloid Clusters [Ni2Bi12]4+and [Rh2Bi12]4+– Ionothermal Synthesis, Crystal Structures, and Chemical Bonding

“…Establishing ionic liquids (ILs) as reaction media for the (ionothermal) synthesis of inorganic materials has not only allowed their resource‐efficient production, but also lead to the discovery of new compounds . Among the latter are various new bismuth‐transition metal clusters, [RhBi 9 ] 4+ , [ M Bi 10 ] 4+ ( M = Pt, Pd), [Au(Bi 8 ) 2 ] 5+ , [CuBi 8 ] 3+ , and [(RhBi 7 )Br 8 ] (Figure ) , .…”