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Novel Inorganic and Metal Nanoparticles Prepared by Inverse Microemulsion
Published in Victor M. Starov, Nanoscience, 2010
Lots of synthesis of rare-earth oxide nanomaterials with different morphologies has been reported, especially for ceria nanostructures. Ceria is one of the most reactive rare-earth composites, which is being currently used as a promoter or support in three-way catalysts for automobile exhaust gases, fluid catalytic cracking, and dehydrogenation of ethylbenzene to styrene. Ceria is also used in the fields of optical materials, high-temperature ceramics, and fuel cells. A reverse micelle method (TX-100 “soft template”) was used for the formation of 1D mesoporous crystalline ceria nanomaterials. Mesoporous crystalline ceria nanofibers were obtained by calcination of the Ce2(CO3)3 nanofibers. If the temperature is high enough, most of the surfactant molecules will desorb and the surfaces of the NCs will be exposed. Simultaneously, the motion rate of micelles became faster and thermal disturbance turbulent. These reasons may account for the morphological changes of the NCs when the aging temperature is 50◦C [from Ce2(CO3)3 to CeO2]. The UV–vis absorption spectra confirmed the formation of nanofibers, nanobelts, and rod-like CeO2 NPs. Cerium oxide NPs with spherical shapes of high purity, uniform size distribution, and lower aggregation were synthesized using CTAB as surfactant, n-butyl alcohol as cosurfactant, and CH as oil by the w/o microemulsion method at room temperature.
Investigation on the Effect of Method of Synthesis on the Thermal Decomposition of Ceria Nanostructures
Published in Satya Bir Singh, Prabhat Ranjan, A. K. Haghi, Materials Modeling for Macro to Micro/Nano Scale Systems, 2022
The design and synthesis of versatile ceria nanostructures have substantial interest in material synthesis field. The morphological and dimensional aspects of ceria differentiate its performance. Ceria is one of the major components of three-way catalysts for the removal of toxic automobile exhaust gases (CO, NO, etc.) [1–3]. It can act as the oxygen sensors [4, 5], humidity sensors [6], etc. Ceria performs as excellent ultraviolet (UV) absorbent and filter [7]. It can be utilized as the good absorbent for the removal of fluoride-ion- and arsenic-based compounds [8]. Ceria with controlled morphology exposes different crystal planes on the solid crystallites, which exhibits interesting chemical and physical properties. Ceria having different morphologies is synthesized and studied, which involves nanorods, nano-cube, octahedron or polyhedron, etc. [9]. Surfaces of ceria can be activated by different factors such as surface area, elemental composition, defects, and reactive facets [10–13]. Ceria nanosystems such as nanowire, nanorod, and nanoparticle have different redox behavior toward CO oxidation. This occurs due to the distinguishing exposed crystal plane on the surface of ceria nano-structures [14]. Ceria nanorods and nanowires expose (1 0 0) and (1 1 0) as the performing crystal plane, whereas nanocubes have (1 0 0) and nanoparticle and polyhedron have (1 1 1) [9]. It was explored that ceria nanorods selectively exhibit higher activity for CO oxidation and NO reduction [15, 16], whereas nanocubes show superior properties in soot combustion [17], hydrogen oxidation [18], and preferential oxidation of CO [19]. But the existence of large proportion of reactive planes on the surface of ceria nanowire made it as potential redox catalyst for CO oxidation. Presence of oxygen vacancies and mobility of oxygen in the lattices are significantly altered with morphological parameters [14]. For water gas shift reaction processes [20], gold-supported ceria nanorod performed as the best catalyst, while Cu-based ceria polyhedral nanoparticles contributed to the best structural support [21, 22]. 3D flower-like ceria has owned enhanced catalytic activity toward oxidation of CO for the removal of As(V) and Cr(VI) [23].
Ceria-Based Nanocrystalline Oxide Catalysts: Synthesis, Characterization, and Applications
Published in Nandakumar Kalarikkal, Sabu Thomas, Obey Koshy, Nanomaterials, 2018
Anushka Gupta, v. Sai Phani Kumar, Manjusha Padole, Mallika Saharia, K. B. Sravan Kumar, Parag A. Deshpande
One of the most popular supports investigated for numerous redox reactions is the ceria-based materials. Ceria due to its oxygen storage capacity (OSC) offers active lattice oxygen for the oxidation steps and due to the presence of oxide ion vacancies, new adsorption sites are formed in the solid thereby making the catalyst more active. Substitution of a metal ion, rather than its impregnation in metallic form, increases both adsorption of gases and creation of oxide ion vacancies in the material. Several methods have been reported for the synthesis of ceria-based solid solutions viz., sol-gel method, co-precipitation, wet impregnation, electrochemical deposition, hydrothermal treatment, dry mixing method, etc.4–11 The activity of the catalyst depends on the synthesis method, composition of precursors and reaction conditions used. The solid solutions synthesized from co-precipitation method form aggregates easily and they are difficult to be re-dispersed in any solvent.12 The drawbacks of conventional synthesis techniques are limited control over the composition, grain size, and crystallinity of the nanoparticles formed.12 Solution combustion technique has made the synthesis of such compounds feasible with high purity and crystallinity. It is a simple process and it produces highly sinterable ceramic powders.5 As a result, numerous studies have appeared recently reporting the synthesis, characterization, and applications of ceria-based materials for heterogeneous catalysis synthesized by solution combustion technique.4–6, 10, 14–19 The catalysts have been tested and found active for reactions like CO oxidation, NOx reduction, the water-gas shift reaction, hydrogen combustion, hydrocarbon combustion, and C—C coupling reaction. Ceria can also be used as an electrolytic material in solid oxide fuel cells (SOFC’s) to generate electric energy from the chemical energy of a fuel.5 Transition or rare earth metals doped ceria serves as an effective material for the SOFC electrolyte due to its oxygen ion conductivity character. This is due to the oxygen ion vacancy formation ability and the reducibility of Ce4+ to Ce3+.5, 6 This chapter focuses on detailing the recent development of such systems including their synthesis, characterization, applications, computational modeling, and mechanistic investigations with particular focus on the systems synthesized by solution combustion technique.
Surface decoration of ceria nanoparticles as propane/air partial oxidation catalyst integrated in a micro-tubular solid oxide fuel cell
Published in International Journal of Green Energy, 2023
Jin Guo, Yue Yao, Wenhuan Yang, Yue Ma, Chengpeng Wang, Yingbang Yao, Tao Tao, Shengguo Lu, Xiaobo Zhao, Chao Wang, Bo Liang
Ni-based catalysts have been widely employed for the partial oxidation (POX) of propane (Nikolaidis and Poullikkas 2017). The high catalytic activity of nickel and its relatively low cost, compared to noble metals, make it a suitable active phase for POX reactions. However, Ni-based catalysts have a strong tendency to sinter and produce carbon deposits in reforming reactions, particularly at high temperatures. The nature of the support is crucial to catalytic performance of supported metal catalysts. Ceria (CeO2) has been widely used as a catalysis support due to its unique properties (Montini et al. 2016). Through a reversible redox cycle between Ce4+ and Ce3+ ions, oxygen vacancies are intrinsically generated. This allows ceria to either release or store oxygen depending on the surface demand; this property is called oxygen storage capacity (OSC) (Trovarelli 1996). Overall, CeO2 functions as the support of the active metal particles and as an oxygen reservoir, helping to oxidize carbonaceous species deposited over the catalyst during reactions.
Hydrogen production by Co-based bimetallic nano-catalysts and their performance in methane steam reforming
Published in Petroleum Science and Technology, 2020
Qiuwan Shen, Yuhang Jiang, Feihong Xia, Biao Wang, Xinrong Lv, Weiqiang Ye, Guogang Yang
The support is one of the essential components of the catalyst. It plays a very important role for catalytic performance of the catalyst. One of its basic functions is to support the active component. The nature of the support is crucial in the catalytic performance of supported metal catalysts. For some specific reactions, besides influencing metal dispersion and providing stability to the metal particles, the support may participate in the reaction (Cargnello, Fornasiero, and Gorte 2012). Commonly used supports are γ-Al2O3, CeO2, ZrO2, SiO2 and the so on. The support is required to have high mechanical strength, large specific surface area and strong anti-sintering ability. In general, ceria has been widely used in heterogeneous catalysis due to its unique properties (Montini et al. 2016).
Atomic and nanocluster Ce species on graphene oxides for selective catalytic reduction of NO with NH3
Published in Petroleum Science and Technology, 2019
Xiaowei Huang, Haoyang Wang, Zhiling Xin, Kang Zheng, Shaocen Xu, Tsungwu Lin, Yuejia Sun, Xing Huang, Lidong Shao
The most common carriers include metal oxides such as ZnO, molecular sieves, and carbon-based materials. Among these, carbon-based materials have been widely studied and used in various fields. Moreover, the use of carbon-based catalysts in the selective catalytic reduction of NO with ammonia has also been reported, including materials such as CeOx/AC, V2O5/CNTs, and Co3O4/CNTs. Relative to AC, CNTs, and other carbon-based materials, two-dimensional graphene oxide (GO) has a high specific surface area and excellent electron transport capability (Shao et al. 2014), making it an ideal candidate for supports of NH3-SCR. Ceria is reported to be active SCR catalyst due to its non-toxicity, excellent oxygen storage capacity, and redox property (Athappan, Sattler, and Sethupathi 2015). You et al. synthesized MnOx-CeO2/graphene and pointed out that the introduction of graphene can change the valence of surface Mn atoms and promote catalytic activity (You et al. 2017). Lu et al. prepared a CeOx-MnOx/TiO2-GE catalyst to demonstrate that the amount of surface active component is increased after the introduction of Ce, resulting in increased SCR activity (Lu et al. 2015). In these works, the roles of morphologies (geometric properties) and surfaces (electronic properties) of Ce3+ or Ce4+ species in affecting SCR activities remains unclear. Therefore, aided by GO, we aim at fabricating CeOx in regulated size distributions (atomic and nanocluster) with tuned surfaces (high proportion Ce3+) as catalysts for NO conversion.