The Effect of Tartaric Acid and Citric Acid as a Complexing Agent on Defect Structure and Conductivity of Copper Samarium Co-Doped Ceria Prepared by a Sol-Gel Auto-Combustion Method

Copper samarium co-doped ceria (CSDC) (Cu0.01Sm0.19Ce0.80O2−δ) nanoparticles were synthesized via a sol-gel auto-combustion of metal nitrates without a complexing agent (DI) and with tartaric acid (TA) or citric acid (CA). The solid oxide formation of CSDC/DI corresponds to the endothermic stage, whereas that of CSDC/TA and CSDC/CA matches the exothermic stage caused by the decomposition of the metal cross-linking and carbon combustion. The cross-linking occurs more extensively in the CA case as more heat is released in CA than in the TA route. The as-synthesized morphology of CSDC/DI reveals both layered structures and small agglomerated particles, whereas CSDC/TA and CSDC/CA show dense xerogel and porous xerogel, respectively. The cubic fluorite structure for calcined CSDCs was confirmed by XRD. From Raman analysis, calcined CSDC/CA has the lowest amount of copper segregation and the highest relative total oxygen vacancy concentration [ V O • • ]total, whereas calcined CSDC/DI has the highest amount of copper segregation and the lowest [ V O • • ]total. For all samples, copper segregation promotes densification, albeit to varying degrees. The relative densities of CSDC/DI, CSDC/TA, and CSDC/CA pellets are 82.8 ± 2.4%, 95.5 ± 1.8%, and 97.8 ± 0.9%, respectively. The sintered CSDC/DI has the lowest density because some copper segregates and liquid copper in interparticle spaces could evaporate earlier than samples containing a complexing agent, whereas sintered CSDC/CA has the highest density because Cu could slowly diffuse from the Cu-Sm-Ce solid solution to grain boundary regions and then precipitate as CuO. The specific grain boundary conductivity is predominantly influenced by CuO along grain boundaries, which reduces specific grain boundary conductivity and increases the enthalpy of association (ΔHa) at 250–350°C; however, it rarely impacts total grain boundary conductivity at temperatures higher than 400°C. CSDC/CA has slightly higher total conductivity than CSDC/TA despite having more CuO segregation because it has higher density and V O • • .

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The Effect of Tartaric and Citric Acid as a Complexing Agent on Defect Structure and Conductivity of Copper Samarium Co-doped Ceria Prepared by a Sol-Gel Auto-Combustion Method

10.21203/rs.3.rs-146185/v1 ◽

2021 ◽

Author(s):

Kornrawit Duangsa ◽

Apishok Tangtrakarn ◽

Charustporn Mongkolkachit ◽

Pavadee Aungkavattana ◽

Klitsada Moolsarn

Keyword(s):

Citric Acid ◽

Sol Gel ◽

Complexing Agents ◽

Total Conductivity ◽

Average Particle ◽

Doped Ceria ◽

Temperature Conductivity ◽

Metal Nitrates ◽

Auto Combustion ◽

Co Doped

Abstract A copper samarium co-doped ceria (CSDC) (Cu0.01Sm0.19Ce0.80O2-δ) nanoparticles were synthesized via a sol-gel auto-combustion of metal nitrates with two different complexing agents including tartaric acid (TA) and citric acid (CA). A reference sample was metal nitrates in deionized water (DI). TGA/DSC of gels reveals endothermic reaction for CSDC/DI but exothermic behavior for CSDC/TA or CSDC/CA during oxide formation. The CA route exhibits the highest energy release since it has extensive formation of metals-citrate. From SEM, the as-synthesized morphologies of DI, TA and CA routes show porous sheet-like, fluffy-like and foamy-like structure, respectively. XRD patterns of calcined CSDCs denote a cubic fluorite structure. The average particle sizes from TEM vary in the range of 30-32 nm. The relative oxygen vacancy (VO) concentrations for calcined and sintered CSDCs from Raman analysis are as follow; CSDC/CA>CSDC/TA>CSDC/DI. Moreover, segregation of (Ce and/or Sm)2O3 and CuO can be observed in Raman spectra for calcined and sintered CSDCs. The oxides of copper segregate mostly in sintered CSDC/CA. The XPS results confirm that Ce3+/Ce4+ coexist, and in addition, the Ce3+ represent Ce3+-VO and/or Ce2O3 segregation. The Ce3+ in sintered CSDCs suggest the existence of Ce3+-VO for CSDC/DI and CSDC/CA; however, Ce3+ implied coexisting of Ce3+-VO and Ce2O3 segregation for CSDC/TA. The relative densities of sintered CSDC/DI, CSDC/TA and CSDC/CA are 82.78%, 95.51% and 97.98%, respectively. The enthalpy of association increases with the increasing of porosity and metal oxide segregation. Segregation of CuO increases CSDC/CA’s association enthalpy at low temperature but it does not affect high temperature conductivity of CSDC/CA. The high total conductivity of 0.0271 S/cm was achieved for CSDC/CA at 600 °C.

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The Role of Nitrate on the Sol-Gel Spread Self-Combustion Process and Its Effect on the NH3-SCR Activity of Magnetic Iron-Based Catalyst

Catalysts ◽

10.3390/catal10030314 ◽

2020 ◽

Vol 10 (3) ◽

pp. 314

Author(s):

Xing Ning ◽

Zhi-bo Xiong ◽

Bin Yang ◽

Wei Lu ◽

Shui-mu Wu

Keyword(s):

Nitric Acid ◽

Citric Acid ◽

Sol Gel ◽

Nox Reduction ◽

Combustion Process ◽

Catalytic Performance ◽

Metal Nitrate ◽

Acid Sites ◽

Complexing Agent ◽

Nh3 Scr

Sol-gel spread self-combustion is the burning of the complexing agent in dried gel and the oxidant. Meanwhile, high temperature takes place during the combustion process, which is harmful to the pore structure of the catalyst. The nitrate from metal nitrate precursors as an oxidant could participate in the spread of the self-combustion process. Therefore, the influence of nitrate from metal nitrate on the spread self-combustion of an iron–cerium–tungsten citric acid gel and its catalytic performance of NOx reduction were investigated by removing nitrate via the dissolution of washing co-precipitation with citric acid and re-introducing nitric acid into the former solution. It was found that the removal of nitrate contributes to enhancing the NH3–SCR activity of the magnetic mixed oxide catalyst. The NOx reduction efficiency was close to 100% for Fe85Ce10W5–CP–CA at 250 °C while the highest was only 80% for the others. The results of thermal analysis demonstrate that the spread self-combustion process of citric acid dried gel is enhanced by re-introducing nitric acid into the citric acid dissolved solution when compared with the removal of nitrate. In addition, the removal of nitrate helps in the formation of γ-Fe2O3 crystallite in the catalyst, refining the particle size of the catalyst and increasing its pore volume. The removal of nitrate also contributes to the formation of Lewis acid sites and Brønsted acid sites on the surface of the catalyst compared with the re-introduction of nitric acid. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrates that both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms exist over Fe85Ce10W5–CP–CA at 250 °C with E–R as its main mechanism.

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Synthesis and Characterization of Co-Doped Ceria Ceramics by Sol-Gel Method

Transactions of the Indian Ceramic Society ◽

10.1080/0371750x.2011.10600161 ◽

2011 ◽

Vol 70 (3) ◽

pp. 143-147 ◽

Cited By ~ 10

Author(s):

S. Ramesh ◽

K. C. James Raju ◽

C. Vishnuvardhan Reddy

Keyword(s):

Sol Gel ◽

Synthesis And Characterization ◽

Doped Ceria ◽

Gel Method ◽

Sol Gel Method ◽

Co Doped

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Synthesis and electrochemical performance of Li1+xV3O8 as cathode material prepared by citric acid and tartaric acid assisted sol–gel processes

Current Applied Physics ◽

10.1016/j.cap.2012.09.013 ◽

2013 ◽

Vol 13 (3) ◽

pp. 517-521 ◽

Cited By ~ 12

Author(s):

Miao Shui ◽

Weidong Zheng ◽

Jie Shu ◽

Qingchun Wang ◽

Shan Gao ◽

...

Keyword(s):

Citric Acid ◽

Electrochemical Performance ◽

Cathode Material ◽

Tartaric Acid ◽

Sol Gel

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Augmentation of grain boundary conductivity in Ca2+ doped ceria-carbonate-composite

Acta Materialia ◽

10.1016/j.actamat.2015.10.024 ◽

2016 ◽

Vol 103 ◽

pp. 361-369 ◽

Cited By ~ 22

Author(s):

Aditya Maheshwari ◽

Hans-Dieter Wiemhöfer

Keyword(s):

Grain Boundary ◽

Doped Ceria ◽

Boundary Conductivity

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Composition, Microstructure, and Electrical Properties Control of the Powders Synthesized by Sol–Gel Auto-Combustion Method Using Citric Acid as the Fuel

Nanoscale Research Letters ◽

10.1186/s11671-017-1976-1 ◽

2017 ◽

Vol 12 (1) ◽

Cited By ~ 5

Author(s):

Bogdan K. Ostafiychuk ◽

Larysa S. Kaykan ◽

Julia S. Kaykan ◽

Bogdan Ya. Deputat ◽

Olena V. Shevchuk

Keyword(s):

Citric Acid ◽

Electrical Properties ◽

Sol Gel ◽

Combustion Method ◽

Auto Combustion

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Structural, Optical, and Catalytic Properties of MgCr2O4 Spinel-Type Nanostructures Synthesized by Sol–Gel Auto-Combustion Method

Catalysts ◽

10.3390/catal11121476 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1476

Author(s):

Vasyl Mykhailovych ◽

Andrii Kanak ◽

Ştefana Cojocaru ◽

Elena-Daniela Chitoiu-Arsene ◽

Mircea Nicolae Palamaru ◽

...

Keyword(s):

Tartaric Acid ◽

Catalytic Properties ◽

Spinel Phase ◽

Sol Gel ◽

Combustion Method ◽

Temperature Treatment ◽

X Ray Diffraction ◽

Spinel Type ◽

X Ray ◽

Auto Combustion

Spinel chromite nanoparticles are prospective candidates for a variety of applications from catalysis to depollution. In this work, we used a sol–gel auto-combustion method to synthesize spinel-type MgCr2O4 nanoparticles by using fructose (FS), tartaric acid (TA), and hexamethylenetetramine (HMTA) as chelating/fuel agents. The optimal temperature treatment for the formation of impurity-free MgCr2O4 nanostructures was found to range from 500 to 750 °C. Fourier transform infrared (FTIR) spectroscopy was used to determine the lattice vibrations of the corresponding chemical bonds from octahedral and tetrahedral positions, and the optical band gap was calculated from UV–VIS spectrophotometry. The stabilization of the spinel phase was proved by X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) analysis. From field-emission scanning electron microscopy (FE-SEM), we found that the size of the constituent particles ranged from 10 to 40 nm. The catalytic activity of the as-prepared MgCr2O4 nanocrystals synthesized by using tartaric acid as a chelating/fuel agent was tested on the decomposition of hydrogen peroxide. In particular, we found that the nature of the chelating/fuel agent as well as the energy released during the auto-combustion played an important role on the structural, optical, and catalytic properties of MgCr2O4 nanoparticles obtained by this synthetic route.

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Microwave assisted sol-gel auto-combustion synthesis of NiCuFe2O4 nanoparticles using citric acid as an organic chelating agent: structural and optical studies

10.3390/ecsoc-19-c005 ◽

2015 ◽

Author(s):

Faranak Manteghi ◽

Mahnaz Kamel Attar Kar ◽

Mahdi Ghahari

Keyword(s):

Citric Acid ◽

Combustion Synthesis ◽

Sol Gel ◽

Chelating Agent ◽

Optical Studies ◽

Microwave Assisted ◽

Auto Combustion

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Effect of Doping Concentration on Grain Boundary Conductivity of Samaria Doped Ceria Composites

Journal of The Electrochemical Society ◽

10.1149/1945-7111/ac4371 ◽

2021 ◽

Author(s):

Prerna Vinchhi ◽

Roma Patel ◽

Indrajit Mukhopadhyay ◽

Abhijit Ray ◽

Ranjan Pati

Keyword(s):

Ionic Conductivity ◽

Grain Boundary ◽

Doping Concentration ◽

Single Phase ◽

Precipitation Method ◽

Molecular Water ◽

Doped Ceria ◽

Boundary Conductivity ◽

Co Precipitation ◽

Hydrated Oxide

Abstract This work aims to study the effect of Sm3+ doping concentration on the grain boundary ionic conductivity of ceria. The materials were prepared by a modified co-precipitation method, where molecular water associated with the precursor has been utilized to facilitate the hydroxylation process. The synthesized hydroxide / hydrated oxide materials were calcined and the green body (pellet) has been sintered at high temperature in order to achieve highly dense (~ 96 %) pellet. The structural analyses were done using XRD and Raman spectroscopy, which confirm the single phase cubic structure of samaria doped ceria (SDC) nanoparticles and the surface morphology of sintered samples was studied using FESEM. The ionic conductivity was measured by AC impedance spectroscopy of the sintered pellets in the temperature range of 400-700 °C, which shows superior grain boundary conductivity. The grain boundary ionic conductivity of around 0.111 S/cm has been obtained for 15SDC composition at 600 °C.

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