Modifying the hygroscopic property of La 2 O 3  by Pr, Sm and Nd doping

Gangwar, Bhanu P.; Maiti, Sanat Chandra; Sharma, Sudhanshu

doi:10.1016/j.jssc.2017.08.036

Cited by 21 publications

(6 citation statements)

References 39 publications

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“…Considering the encouraging results of the two modification strategies in the above, one may intuitively think of combining them to construct codoped stepped La 2 O 3 to achieve even better performance. In fact, doping with metal ions is a mature technique in experiments and has also been widely evidenced to be applicable for the La 2 O 3 catalysts. ,,− However, our surface energy calculations showed a markedly higher energy cost of 1.07 J/m 2 to form the stepped (210) as compared with the flat (001) surface (surface energy = 0.59 J/m 2 ), which clearly signifies the difficulty in synthesizing the La 2 O 3 (210) surface and even more difficulty to dope it with different metal cations. Hence, we continued to focus on the Sr/Ce codoping strategy in the following and investigated the complete cycle of the OCM reactions on the Sr/Ce–La 2 O 3 (001) surface.…”

Section: Resultsmentioning

confidence: 78%

Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La₂O₃: A Density Functional Theory Study

Wang

Gong

2019

ACS Catal.

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Oxidative coupling of methane (OCM) holds the promise to achieve high-value-added products directly from methane, and the strategies to improve the catalytic performance of this process are highly desired. In this work, we performed extensive density functional theory (DFT) calculations to systematically study the activity and selectivity of the OCM reactions on several types of the La 2 O 3 and CeO 2 catalysts. We theoretically evidenced that the La 2 O 3 catalyst has high hydrocarbon selectivity but low activity, while the CeO 2 shows an opposite performance. These results can be largely rationalized by the calculated reaction energetics in generating the key CH 3 • intermediates and further protecting them from excessive oxidation on the surface. We then proposed two strategies to improve the OCM activity while maintaining the selectivity of the La 2 O 3 catalyst. Geometrically, by constructing the stepped La 2 O 3 (210) surface exposing lattice oxygens with low coordination numbers, both the heterolytic cleavage of the C−H bond in methane and the occurrence of the key CH 3 • intermediates could be promoted. Electronically, codoping of Sr and Ce into La 2 O 3 could favor the direct formation of CH 3 • and further avoid its deactivation on the surface, leading to the significantly improved OCM performance. By conducting further analyses on the thermostability of the catalysts and calculating catalytic energetics of the complete reaction cycle, we excluded the practical application of the high-Miller-index La 2 O 3 surfaces, but we theoretically predicted the Sr/Ce−La 2 O 3 catalyst with a proper doping concentration to be highly efficient for catalyzing the OCM reactions.

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Section: Resultsmentioning

confidence: 78%

Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La₂O₃: A Density Functional Theory Study

Wang

Gong

2019

ACS Catal.

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“…It is well known that Bi 2 O 3 is a non‐hygroscopic oxide. Hence, due to the formation of a non‐hygroscopic Bi 2 O 3 ‐type oxide in La 1.92 Bi 0.08 O 3 , hygroscopic properties decrease significantly …”

Section: Resultsmentioning

confidence: 99%

Effect of Bi³⁺ Ion Concentration on Physicochemical, Optical and Catalytic Properties of One‐Pot Combustion Synthesized Nanocrystalline Bi‐Doped La₂O₃

2020

Self Cite

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La 2-2x Bi 2x O 3 (x = 0-0.04) nanocrystalline powders are synthesized by one-pot single step solution combustion method. 4 atom% Bi doped La 2 O 3 reveals the presence of both Bi 3 + and metallic Bi. Temperature programmed reduction (TPR) of La 2 O 3 and La 2 À 2x Bi 2x O 3 (x = 0.005-0.04) indicates that the oxygen storage capacity changes with the dopant (Bi) concentration. La 2-2x Bi 2x O 3 (x = 0.04) has less hygroscopic behavior compared to La 2 O 3 and shown enhanced stability in an open atmosphere. The direct band gap of La 2 O 3 and La(OH) 3 decreases significantly after Bi doping. Further, PL studies of Bi doped compounds show a blue emission at 458 nm due to 3 P 1-1 S 0 transition of the Bi 3 + ion substituted in La 2 O 3. Emission intensity is maximum with 0.5 atom percent Bi doping, which decreases gradually with increasing Bi 3 + ion concentration. Bi doping also modifies the catalytic activity of La 2 O 3, resulting in higher CO oxidation activity than unsubstituted La 2 O 3 .

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“…This material is capable of exhibiting partially hygroscopic properties upon exposure to humidity. According to Gangwar et al, (21) La 2 O 3 reacts hygroscopically upon the adsorption of water molecules onto molecular bonds before the hydroxylation reaction obtained from zinc chloride precursor sol-gel, (17) (b) short hexagonal zinc oxide rods obtained from zinc acetate precursor sol-gel, (17) (c) hexamethylenetetramine (HMTA)-enhanced zinc oxide nanoflakes obtained by hydrothermal method, (18) (d) zinc oxide crystal islands directly deposited via e-beam deposition from zinc metal precursor (no synthesis route), (19) and (e) zinc oxide microflowers obtained through wet-chemical-based synthesis with NaOH. (20) begins.…”

Section: Lanthanum Oxidementioning

confidence: 99%

“…Being a metal oxide, the hygroscopic behavior of La 2 O 3 can be enhanced by doping other metal elements, as reported elsewhere. (21) This material can be implemented in fiber sensors provided that the La(OH) 3 can undergo a reversible reaction back to its original molecule (La 2 O 3 ) or the hydroxylation reaction upon the uptake of water by La 2 O 3 can be prevented from occurring.…”

Section: Lanthanum Oxidementioning

confidence: 99%

Hygroscopic Materials and Characterization Techniques for Fiber Sensing Applications: A Review

Riza¹,

Go²,

Maier³

et al. 2020

Sensors and Materials

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Various characterization techniques are used in the study of materials in order to understand their properties. Data and observation recording characterization of a material is done by researchers for various properties within various environments. One of the many properties that make a material attractive for use in certain devices is hygroscopicity. Various techniques for characterizing hygroscopicity have been developed and utilized. However, since these techniques are not usually the highlights of studies, there has been limited acknowledgement of the usefulness of hygroscopicity testing. This review introduces several established characterization techniques allowing researchers to fully characterize materials in terms of their hygroscopicity. The full potential of hygroscopic materials can be seen in their use in various fiber sensors. The deformation of materials upon exposure to water molecules can be utilized to perturb sensing elements in fiber sensors, allowing the user to take full advantage of the hygroscopicity of the material.

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Modifying the hygroscopic property of La 2 O 3 by Pr, Sm and Nd doping

Cited by 21 publications

References 39 publications

Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La₂O₃: A Density Functional Theory Study

Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La₂O₃: A Density Functional Theory Study

Effect of Bi³⁺ Ion Concentration on Physicochemical, Optical and Catalytic Properties of One‐Pot Combustion Synthesized Nanocrystalline Bi‐Doped La₂O₃

Hygroscopic Materials and Characterization Techniques for Fiber Sensing Applications: A Review

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Modifying the hygroscopic property of La 2 O 3 by Pr, Sm and Nd doping

Cited by 21 publications

References 39 publications

Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La2O3: A Density Functional Theory Study

Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La2O3: A Density Functional Theory Study

Effect of Bi3+ Ion Concentration on Physicochemical, Optical and Catalytic Properties of One‐Pot Combustion Synthesized Nanocrystalline Bi‐Doped La2O3

Hygroscopic Materials and Characterization Techniques for Fiber Sensing Applications: A Review

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Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La₂O₃: A Density Functional Theory Study

Strategies To Improve the Activity While Maintaining the Selectivity of Oxidative Coupling of Methane at La₂O₃: A Density Functional Theory Study

Effect of Bi³⁺ Ion Concentration on Physicochemical, Optical and Catalytic Properties of One‐Pot Combustion Synthesized Nanocrystalline Bi‐Doped La₂O₃