Effect of defects and oxygen vacancies on the RTFM properties of pure and Gd-doped CeO2 nanomaterials through soft XAS

Soni, Swati; Dave, Mridula; Dalela, B.; Alvi, P. A.; Kumar, Shalendra; Sharma, Sathyashankara; Phase, D. M.; Gupta, Mukul; Dalela, S.

doi:10.1007/s00339-020-03777-y

Cited by 31 publications

(25 citation statements)

References 46 publications

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“…Even though we have found a trivalent form of Gd, its other valence state is not chemically stable, in contrast to the many valence states that have been described for other lanthanides. [ 72 ] The XANES spectra of the GZO samples and the XANES spectra of Gd 2 O 3 exhibit excellent agreement, as illustrated in Figure 18. The peak positions and intensity ratios are very consistent despite the fact that the M 5 peak's broadening reduces as dopant concentration increases.…”

Section: Resultsmentioning

confidence: 70%

Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd³⁺‐Substituted ZnO Nanoparticles

Sahu

Kumar

Vats

et al. 2022

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of ZnO has not yet been completely realized and explored despite two decades of rigorous research. It has a wide range of uses in photocatalysts, UV lasers, solar cells, photodiodes, sensors, optoelectronics, spintronic devices, and more. [1][2][3][4][5][6] Depending on the application, essential modifications have been made over time to increase the stability of ZnO nanostructures. High quantum confinement effect plays a significant role in the configuration of the electronic structure at the nanoscale. Also, factors such as doping, defects, and crystallinity affect various properties of the nanostructures. Doping ZnO with appropriate ions with varying sizes is great approach way to vary its properties for certain device applications. [7][8][9] According to Chaudhary et al., WO 3 -ZnO@rGO nanocomposites can be used for relevant photocatalytic applications and wastewater purification. [10] Additionally, Yousaf et al. have reported that the ZnO-NiO/rGO nanohybrid shows exceptional photocatalytic performance and is a reliable contender in the field of catalysis. [11] Transition metal (TM) and rare earth (RE)-doped metal oxides have been studied extensively under this regime. For optoelectronics and spintronic applications, ZnO doped with rare-earth ions is Undoped ZnO and Zn 1−x Gd x O nanoparticles are made using a sono-chemical co-precipitation approach. X-ray diffraction and transmission electron microscopy investigations verified the formation of a wurtzite structure with spherical geometry. All the samples are found to be nanocrystalline by transmission electron microscopy, with crystallite diameters ranging from 14 to 22 nm. The optical constants are calculated via diffuse reflectance spectroscopy. The Urbach energy and photoluminescence spectrum both showed that all doped nanoparticle samples contained defects and disorder due to vacancies. The band structure finding suggest that the forbidden gap of ZnO may change due to the conduction band shift, Burstein-Moss shift, and shrinkage effect. The near band emission in the ultraviolet region and deep level emission of the photoluminescence spectrum are both strong and decreased with increasing Gd 3+ concentration. Studies using X-ray absorption near edge spectroscopy revealed that the host nano-lattice Zn sites are substituted with Gd 3+ cations to preserve the symmetry with minor distortion. Investigations into charge transfer through the oxygen bands (Gd-O-Zn) are made using O K-edge spectra. The defect emission bands identified through Gd doping indicated that these emissions may be changed for ZnO samples, which could be advantageous for applications in phosphors and light-emitting devices.

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Section: Resultsmentioning

confidence: 70%

Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd³⁺‐Substituted ZnO Nanoparticles

Sahu

Kumar

Vats

et al. 2022

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“…[31] The oxidation state of metals at the B-site of a perovskite material can be correlated with the oxygen vacancy concentration. [32][33][34][35] Hence, X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) were used to investigate the valency of Co and Ce in BCCFZ nanocomposite. Figure 2a,b presents the X-ray absorption spectroscopy (XAS) of Co and Ce in BCCFZ relative to BCFZY and BCZYYb.…”

Section: Resultsmentioning

confidence: 99%

Electrokinetic Insights into the Triple Ionic and Electronic Conductivity of a Novel Nanocomposite Functional Material for Protonic Ceramic Fuel Cells

Bello

Song

et al. 2022

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Triple ionic and electronic conductivity (TIEC) in cathode materials for protonic ceramic fuel cells (PCFCs) is a desirable feature that enhances the spatial expansion of active reaction sites for electrochemical oxygen reduction reaction. The realization of optimal TIEC in single‐phase materials, however, is challenging. A facile route that facilitates the optimization of TIEC in PCFC cathodes is the strategic development of multiphase cathode materials. In this study, a cubic‐rhombohedral TIEC nanocomposite material with the composition Ba(CeCo)0.4(FeZr)0.1O3−δ (BCCFZ) is designed via self‐assembly engineering. The material consists of a mixed ionic and electronic conducting phase, BaCo1−(x+y+z)CexFeyZrzO3−δ (M‐BCCFZ), and a dominant proton‐conducting phase, BaCe1−(x+y+z)CoxZryFezO3−δ (H‐BCCZF). The dominant cerium‐rich H‐BCCFZ phase enhances the material's oxygen vacancy concentration and the proton defects formation and transport with a low enthalpy of protonation of −30 ± 9 kJ mol−1. The area‐specific resistance of the BCCFZ symmetrical cell is 0.089 Ω cm2 at 650 °C in 2.5% H2O‐air. The peak power density of the anode‐supported single cell based on BCCFZ cathode reaches 1054 mW cm−2 at 650 °C with good operation stability spanning over 500 h at 550 °C. These promote BCCFZ as a befitting cathode material geared toward PCFC commercialization.

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“…After the addition of Gd 3+ ions (Figure 5b), the electrons captured by the oxygen vacancy occupy an orbital that overlaps with the 4 f 1 shell of the neighboring Ce 3+ and Gd 3+ ions, resulting in the spin polarization of Ce ions. [ 31 ] This finding provides a reference value for how to design efficient defect catalysts. Except for the effect on the magnetic moments, as for the content of Gd dopant is greater than 0.01, lattice parameters are also changed, which is attributed to the increase of the amount of both Gd 3+ doping and oxygen vacancies [40a] .…”

Section: Strategies For Introducing Defectsmentioning

confidence: 92%

“…In addition to those mentioned previously, XAS has attracted more attention in the characterization of defects in recent years. [ 31 ] As shown in the X‐ray absorption near‐edge structure (XANES) spectra fitting of the CeO 2 and M/CeO 2 of Figure 3f,g, Zhao et al used XAS to analyze the species corresponding to each peak and verified the existence of oxygen vacancies in CeO 2 and transition‐metal‐doped CeO 2 . For pure CeO 2 and Co/CeO 2 samples, the concentration of Ce 3+ increased from 29.4% to 38.7%.…”

Section: Characterization Of Defectsmentioning

confidence: 99%

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Defect Engineering on CeO₂‐Based Catalysts for Heterogeneous Catalytic Applications

et al. 2021

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With abundant crystal defects, cerium oxide (CeO2), widely used in heterogeneous catalysis, has attracted extensive attention. In recent years, researchers have investigated that the defect chemistry of CeO2 plays a vital role in its catalytic activity and have developed various defect introduction methods to synthesize stable and efficient defective CeO2‐based catalysts. Herein, the understanding, introduction, and applications of defect chemistry in CeO2‐based heterogeneous catalysis are reviewed, and the structure–activity relationship between defect engineering and catalytic performance is recommended with great emphasis. Interests are put into the investigation of how defects influence the activity and stability of defective CeO2 catalysts and effective strategies for fabricating efficient, stable, and defective CeO2 catalysts. Finally, the existing problems and perspectives of CeO2 defect chemistry for heterogeneous catalysis are displayed. This review provides a reference for in‐depth understanding and the design of more efficient CeO2‐based catalysts for heterogeneous catalysis.

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Effect of defects and oxygen vacancies on the RTFM properties of pure and Gd-doped CeO2 nanomaterials through soft XAS

Cited by 31 publications

References 46 publications

Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd³⁺‐Substituted ZnO Nanoparticles

Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd³⁺‐Substituted ZnO Nanoparticles

Electrokinetic Insights into the Triple Ionic and Electronic Conductivity of a Novel Nanocomposite Functional Material for Protonic Ceramic Fuel Cells

Defect Engineering on CeO₂‐Based Catalysts for Heterogeneous Catalytic Applications

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Effect of defects and oxygen vacancies on the RTFM properties of pure and Gd-doped CeO2 nanomaterials through soft XAS

Cited by 31 publications

References 46 publications

Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd3+‐Substituted ZnO Nanoparticles

Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd3+‐Substituted ZnO Nanoparticles

Electrokinetic Insights into the Triple Ionic and Electronic Conductivity of a Novel Nanocomposite Functional Material for Protonic Ceramic Fuel Cells

Defect Engineering on CeO2‐Based Catalysts for Heterogeneous Catalytic Applications

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Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd³⁺‐Substituted ZnO Nanoparticles

Exploring the Defects and Vacancies with Photoluminescence and XANES Studies of Gd³⁺‐Substituted ZnO Nanoparticles

Defect Engineering on CeO₂‐Based Catalysts for Heterogeneous Catalytic Applications