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Doped and undoped compositions of Ce1-xSrxO2-δ (x = 0, 0.025, 0.05, 0.075, and 0.1) are synthesized using the sol–gel auto-combustion method. The calcined powders are sintered at 1450 °C for four hours (h). The sintered samples are characterized and tested by various experimental techniques to study their structural, microstructural, and electrical properties as electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFC). The X-ray diffraction results confirm the single-phase formation except for the x = 0.1 sample, which also exhibited a minor secondary phase, i.e., SrCeO3. X-ray photoelectron spectroscopy (XPS) reveals the mixed oxidation state of cerium (Ce4+/Ce3+) in undoped and doped CeO2. The presence of oxygen vacancies has also been verified using Raman spectroscopy. The Sr creates oxygen vacancies and acts as the sintering aid to densify the samples. The highest conductivity is 6.46 × 10–3 S.cm−1 for x = 0.075 sample at 600 °C. The power density of the sample is about 89 mW.cm−2 at 600 °C. With a relative density of ~ 97%, the x = 0.075 sample can be used as a solid electrolyte in IT-SOFC. [ABSTRACT FROM AUTHOR]

Nanocrystalline cerium (IV) oxides doped with transition metals have gained significant interest recently, mostly in the field of catalysis. Herein, we present the comprehensive studies on ceria doped with 10 mol.% of transition metals (Mn, Fe, Co, Ni or Cu) synthesized by the reverse microemulsion method. The aim of this work is to study the properties of those materials with the use of different complementary methods like XRD, SEM, TPR, and XPS and to determine the possibility of fabrication of single-phase materials with that doping level. Studies presented here prove that despite showing single-phase XRD patterns with high nanocrystallinity, in all obtained materials, the dopants are not fully incorporated in the ceria lattice. Spectroscopy studies show that additional transition metal oxides are present on the surface of all materials. Herein, we also present the analyses of L 3,2 -edges of transition metals in ceria, as well as high energy Ce K-edge to prove that 10 mol.% of any of those transition metals cannot be incorporated in the ceria host without the formation of additional phases. Using techniques presented here, it was found that the highest share of Mn can be dissolved in the lattice, while Cu is mostly present as a surficial Cu 2 O. Studies presented are an important contribution to the discussion about the solubility limits in nanocrystalline ceria and its properties which may be utilized for e.g various catalysts or as electrolytes. [ABSTRACT FROM AUTHOR]

The development of direct dimethyl ether (DME) solid oxide fuel cells (SOFCs) has several drawbacks, due to the low catalytic activity and carbon deposition of conventional Ni–zirconia-based anodes. In the present study, the insertion of 2.0 wt.% Ru-Ce0.7Zr0.3O2−δ (ruthenium–zirconium-doped ceria, Ru-CZO) as an anode catalyst layer (ACL) is proposed to be a promising solution. For this purpose, the CZO powder was prepared by the sol–gel synthesis method, and subsequently, nanoparticles of Ru (1.0–2.0 wt.%) were synthesized by the impregnation method and calcination. The catalyst powder was characterized by BET-specific surface area, X-ray diffraction (XRD), field emission scanning electron microscopy with an energy-dispersive spectroscopy detector (FESEM-EDS), and transmission electron microscopy (TEM) techniques. Afterward, the catalytic activity of Ru-CZO catalyst was studied using DME partial oxidation. Finally, button anode-supported SOFCs with Ru-CZO ACL were prepared, depositing Ru-CZO onto the anode support and using an annealing process. The effect of ACL on the electrochemical performance of cells was investigated under a DME and air mixture at 750 °C. The results showed a high dispersion of Ru in the CZO solid solution, which provided a complete DME conversion and high yields of H2 and CO at 750 °C. As a result, 2.0 wt.% Ru-CZO ACL enhanced the cell performance by more than 20% at 750 °C. The post-test analysis of cells with ACL proved a remarkable resistance of Ru-CZO ACL to carbon deposition compared to the reference cell, evidencing the potential application of Ru-CZO as a catalyst as well as an ACL for direct DME SOFCs. [ABSTRACT FROM AUTHOR]

Integration of doped ceria into fuel electrode-supported solid oxide cells is challenging due to high sintering temperatures leading to undesirable interdiffusion between the layers. We investigate the influence of the dopant in ceria X 0.1 Ce 0.9 O 1.95 (10XDC, X = Y, Gd or Sm) on the interdiffusion with yttria-stabilized zirconia (8YSZ). Powder mixtures of 8YSZ and 10XDC were sintered at temperatures between 1000 and 1400 °C to quantify the phase formation. Interdiffusion in layered systems sintered at 1400 °C was investigated by SEM. Symmetrical Ni-10XDC cells with an 8YSZ electrolyte were analyzed using impedance spectroscopy. Despite small differences in the interdiffusion behavior, different dopants do not lead to significant changes in the cell impedance. Notably, the presence of NiO in the fuel electrode leads to enhanced interdiffusion kinetics of 10XDC with 8YSZ and the formation of porosity at the electrolyte interface. The detrimental influence of these microstructural changes on the electrode performance was investigated. [Display omitted] • Dopants in ceria modify the interdiffusion kinetics with yttria-stabilized zirconia. • The presence of NiO during sintering leads to porosity at the ceria/zirconia interface. • Porosity results in drastic loss of fuel electrode performance. • Porosity at the electrolyte interface can be prevented by adding an interlayer. [ABSTRACT FROM AUTHOR]

Ni-based cermets are the most widely used anode materials for solid oxide fuel cells. Reducing the content of Ni is beneficial to anode stability but usually unfavorable for the catalytic activity. In this study, Ni-Ce0.8Sm0.2O2-δ anode with a low Ni content is synthesized through a polymer-directed evaporation-induced self-assembly strategy. Ni distributes evenly in the anode, resulting in an enlarged triple-phase boundary region and improved reactivity of lattice oxygen in the oxide phase. The anode containing 5 wt.% Ni possesses the highest amounts of oxygen vacancies and Ce3+/Ce4+ redox pairs that facilitates the charge transfer process, which is one of the rate-determining steps of anode reaction. Consequently, that anode shows the lowest polarization resistance of 0.014 Ω cm2 at 700 °C, much lower than those of other Ni-based anodes prepared through conventional techniques such as impregnation and solid-mixing. With that anode, a single cell supported by a 480-μm-thick Ce0.8Sm0.2O2-δ electrolyte layer exhibits the maximum power density of 270 mW cm−2 at 700 °C. The anode also shows a promising stability. [ABSTRACT FROM AUTHOR]

The technologically important frequency range for the application of electrostrictors and piezoelectrics is tens of Hz to tens of kHz. Sm3+- and Gd3+-doped ceria ceramics, excellent intermediate-temperature ion conductors, have been shown to exhibit very large electrostriction below 1 Hz. Why this is so is still not understood. While optimal design of ceria-based devices requires an in-depth understanding of their mechanical and electromechanical properties, systematic investigation of the influence of dopant size on frequency response is lacking. In this report, the mechanical and electromechanical properties of dense ceria ceramics doped with trivalent lanthanides (RE0.1Ce0.9O1.95, RE = Lu, Yb, Er, Gd, Sm, and Nd) were investigated. Young's, shear, and bulk moduli were obtained from ultrasound pulse echo measurements. Nanoindentation measurements revealed room-temperature creep in all samples as well as the dependence of Young's modulus on the unloading rate. Both are evidence for viscoelastic behavior, in this case anelasticity. For all samples, within the frequency range f = 0.15-150 Hz and electric field E ≤ 0.7 MV/m, the longitudinal electrostriction strain coefficient (|M33|) was 102 to 104-fold larger than expected for classical (Newnham) electrostrictors. However, electrostrictive strain in Er-, Gd-, Sm-, and Nd-doped ceramics exhibited marked frequency relaxation, with the Debye-type characteristic relaxation time τ ≤ 1 s, while for the smallest dopants-Lu and Yb-little change in electrostrictive strain was detected over the complete frequency range studied. We find that only the small, less-studied dopants continue to produce useable electrostrictive strain at the higher frequencies. We suggest that this striking difference in frequency response may be explained by postulating that introduction of a dopant induces two types of polarizable elastic dipoles and that the dopant size determines which of the two will be dominant.

The development of direct dimethyl ether (DME) solid oxide fuel cells (SOFCs) has several drawbacks, due to the low catalytic activity and carbon deposition of conventional Ni–zirconia-based anodes. In the present study, the insertion of 2.0 wt.% Ru-Ce0.7Zr0.3O2−δ (ruthenium–zirconium-doped ceria, Ru-CZO) as an anode catalyst layer (ACL) is proposed to be a promising solution. For this purpose, the CZO powder was prepared by the sol–gel synthesis method, and subsequently, nanoparticles of Ru (1.0–2.0 wt.%) were synthesized by the impregnation method and calcination. The catalyst powder was characterized by BET-specific surface area, X-ray diffraction (XRD), field emission scanning electron microscopy with an energy-dispersive spectroscopy detector (FESEM-EDS), and transmission electron microscopy (TEM) techniques. Afterward, the catalytic activity of Ru-CZO catalyst was studied using DME partial oxidation. Finally, button anode-supported SOFCs with Ru-CZO ACL were prepared, depositing Ru-CZO onto the anode support and using an annealing process. The effect of ACL on the electrochemical performance of cells was investigated under a DME and air mixture at 750 °C. The results showed a high dispersion of Ru in the CZO solid solution, which provided a complete DME conversion and high yields of H2 and CO at 750 °C. As a result, 2.0 wt.% Ru-CZO ACL enhanced the cell performance by more than 20% at 750 °C. The post-test analysis of cells with ACL proved a remarkable resistance of Ru-CZO ACL to carbon deposition compared to the reference cell, evidencing the potential application of Ru-CZO as a catalyst as well as an ACL for direct DME SOFCs.

Multicomponent doping of ceria with four cations is used as a preliminary investigation into the ionic conductivity of high-entropy-doped ceria systems. Different compositions of Ce1-x(Ndx/4Prx/4Smx/4Gdx/4)O2-δ (x = 0.05, 0.10, 0.15, and 0.20) are synthesized using the oxalate co-precipitation method yielding single-phase oxalate precursors. X-ray diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy are used to characterize the precipitated oxalates. Simultaneous thermal gravimetric analysis and differential scanning calorimetry reveal a two-step decomposition of the oxalates into the doped oxide. The ionic conductivity of the samples is measured from 250 °C to 600 °C using electrochemical impedance spectroscopy. All samples exhibit similar grain conductivity values at 600 °C, comparable to singly doped samples. However, an increase in total conductivity is observed with an increase in doping concentration up to 15% followed by a decrease beyond this concentration. These findings suggest that multicomponent doping may not significantly enhance the grain conductivity of doped ceria beyond conventional single and co-doped compositions but can modulate the grain boundary conductivity and thus the total conductivity of ceria ceramics. [ABSTRACT FROM AUTHOR]

Direct methane Solid Oxide Fuel Cells (SOFCs) operated under catalytic partial oxidation (CPOX) conditions are investigated, focusing on the processing of the anode support and the anode deactivation caused by carbon deposition. Anode-supported SOFCs based on gadolinium-doped ceria (GDC) electrolyte, and NiO-GDC anode support were fabricated by the gel-casting method. Suitable aqueous slurries formulations of NiO–GDC were prepared, starting NiO-GDC nanocomposite powders, agarose as gelling agent and rice starch as pore former. Electrochemical and mechanical tests evidenced that the support of 550 ± 50 µm thickness and 10 wt% pore former is a good candidate for direct-methane SOFCs. The cells operating under stoichiometric conditions of CPOX reached a performance of 0.64 W·cm−2 at 650 ºC, a very close value to that measured under humidified hydrogen (0.71 W·cm−2). The best electrochemical stability of the cell is achieved at a CH 4 /O 2 ratio of 2.5, showing no evidence of carbon deposition and reducing nickel re-oxidation significantly. • Bending strength of gel-casted Ni-GDC support is comparable to tape-casted one. • Cell performance operating under CPOX is close to humidified hydrogen at 650 ºC. • The best electrochemical stability of the cell is achieved at a CH 4 /O 2 ratio of 2.5. • Operating at CH 4 /O 2 of 2.5, Ni re-oxidation strongly decreases without carbon deposition. [ABSTRACT FROM AUTHOR]

Electromechanically active ceramic materials, piezoelectrics and electrostrictors, provide the backbone of a variety of consumer technologies. Gd- and Sm-doped ceria are ion conducting ceramics, finding application in fuel cells, oxygen sensors, and, potentially, as memristor materials. While optimal design of ceria-based devices requires a thorough understanding of their mechanical and electromechanical properties, reports of systematic study of the effect of dopant concentration on the electromechanical behavior of ceria-based ceramics are lacking. Here we report the longitudinal electrostriction strain coefficient (M33) of dense RExCe1-xO2-x/2 (x ≤ 0.25) ceramic pellets, where RE = Gd or Sm, measured under ambient conditions as a function of dopant concentration within the frequency range f = 0.15-350 Hz and electric field amplitude E ≤ 0.5 MV/m. For >100 Hz, all ceramic pellets tested, independent of dopant concentration, exhibit longitudinal electrostriction strain coefficient with magnitude on the order of 10-18 m2/V2. The quasi-static (f < 1 Hz) electrostriction strain coefficient for undoped ceria is comparable in magnitude, while introducing 5 mol % Gd or 5 mol % Sm produces an increase in M33 by up to 2 orders of magnitude. For x ≤ 0.1 (Gd)-0.15 (Sm), the Debye-type relaxation time constant (τ) is in the range 60-300 ms. The inverse relationship between dopant concentration and quasi-static electrostrictive strain parallels the anelasticity and ionic conductivity of Gd- and Sm-doped ceria ceramics, indicating that electrostriction is partially governed by ordering of vacancies and changes in local symmetry.

Engineering materials with highly tunable physical properties in response to external stimuli is a cornerstone strategy for advancing energy technology. Among various approaches, engineering ionic defects and understanding their roles are essential in tailoring emergent material properties and functionalities. Here, we demonstrate an effective approach for creating and controlling ionic defects (oxygen vacancies) in epitaxial Gd-doped CeO _2− _x (CGO)(001) films grown on Nb:SrTiO _3 (001) single crystal. Our results exhibit a significant limitation in the formation of excess oxygen vacancies in the films during high-temperature film growth. However, we have discovered that managing the oxygen vacancies in the epitaxial CGO(001) films is feasible using a two-step film growth process. Subsequently, our findings show that manipulating excess oxygen vacancies is a key to the emergence of giant apparent dielectric permittivity (e.g. $\varepsilon ^{\prime}$ $ \approx $ 10 ^6 ) in the epitaxial films under electrical field control. Overall, the strategy of tuning functional ionic defects in CGO and similar oxides is beneficial for various applications such as electromechanical, sensing, and energy storage applications.

Self-assembled La 0.7 Sr 0.3 Fe 0.9 Ni 0.1 O 3-δ -Ce 0.8 Sm 0.2 O 1.9-δ (LSFN-SDC) composite cathode with a three-dimensionally ordered macroporous (3DOM) structure is synthesized using poly(methyl methacrylate) as the template for protonic ceramic fuel cells. The LSFN and SDC phases both distribute uniformly in the cathode. The SDC phase reduces the thickness of the walls of the 3DOM structure and thus hinders the bulk conduction of electrons. SDC also decreases the specific surface area and the surface oxygen reactivity of the cathode, leading to the suppression of the adsorption and dissociation of O 2. However, the SDC phase provides the conduction pathway for oxygen ions and enlarges three phase boundary consequently, which facilitates the charge transfer steps. The thickness of the walls and the specific surface area of the composite cathode are both increased with the rise of the concentration of the nitrate precursor solution, resulting in the acceleration of the cathode process. Nevertheless, an excessive precursor concentration leads to the destroy of the 3DOM structure. The 3DOM composite cathode exhibits the lowest R p of 0.039 Ω cm2, and a single cell with that cathode shows maximum power density of 1484 mW cm−2 at 700 °C. The cell exhibits a short-term stability of 120 h at 700 °C without noticeable degradation. • Self-assembled LSFN-SDC is studied as a cathode material for proton-conducting SOFC. • A three-dimensional ordered microporous structure is constructed with PMMA template. • The polarization resistance of the composite cathode is 0.039 Ω cm2 at 700 °C. • A single cell shows the P max of 1484 mW cm−2 and a promising stability at 700 °C. [ABSTRACT FROM AUTHOR]

In this paper, high-quality nanosized Ce0.8Sm0.2−xZnxO2−δ (x = 0, 0.02, 0.04, 0.08, and 0.16) powders are successfully synthesized by sol–gel process for intermediate-temperature solid oxide fuel cell (IT-SOFC) application. The thermal behavior, porosity, crystal phase, surface microstructure, and electrical properties of Ce0.8Sm0.2−xZnxO2−δ are studied by thermogravimetric-differential scanning calorimeter (TG-DSC), Archimedes drainage method, X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical impedance spectroscopy (EIS), respectively. The results show that Ce0.8Sm0.2−xZnxO2−δ electrolyte appears very high sintering activity even at sintering temperature as low as 1300 °C. The crystal phase of sample powders after sintered at 600 °C belongs to single-phase cubic fluorite structure with mean particle size of 15 nm. The lattice parameter increases first until doping 2 mol.% Zn and then decreases with more doping amount. Electrochemical performance results demonstrate that doping with appropriate amount of Zn can significantly improve the conductivity of SDC materials. The highest conductivity of 0.057 S·cm−1 at 800 °C is obtained for Ce0.8Sm0.16Zn0.04O2−δ, owing to high density, ultrafine grains, and increased grain boundaries. Furthermore, the fuel cell performance of Ce0.8Sm0.16Zn0.04O2−δ electrolyte is measured with 5 wt.% Fe-loaded activated carbon as the fuel. It delivers an outstanding performance, with an OCV of 1.02 V, a maximum power output of 408 mW·cm−2 at 850 °C, indicating that Ce0.8Sm0.16Zn0.04O2−δ may have potential application for IT-SOFC electrolyte materials. [ABSTRACT FROM AUTHOR]

Multicomponent doping of ceria with four cations is used as a preliminary investigation into the ionic conductivity of high-entropy-doped ceria systems. Different compositions of Ce1-x(Ndx/4Prx/4Smx/4Gdx/4)O2-δ (x = 0.05, 0.10, 0.15, and 0.20) are synthesized using the oxalate co-precipitation method yielding single-phase oxalate precursors. X-ray diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy are used to characterize the precipitated oxalates. Simultaneous thermal gravimetric analysis and differential scanning calorimetry reveal a two-step decomposition of the oxalates into the doped oxide. The ionic conductivity of the samples is measured from 250 °C to 600 °C using electrochemical impedance spectroscopy. All samples exhibit similar grain conductivity values at 600 °C, comparable to singly doped samples. However, an increase in total conductivity is observed with an increase in doping concentration up to 15% followed by a decrease beyond this concentration. These findings suggest that multicomponent doping may not significantly enhance the grain conductivity of doped ceria beyond conventional single and co-doped compositions but can modulate the grain boundary conductivity and thus the total conductivity of ceria ceramics.

The abundance of cerium in natural resources, its ability to absorb UV light while being transparent to visible light, as well as low photocatalytic activity make ceria (CeO2) a promising candidate for UV filter material in sunscreens. Doping with different elements can further decrease ceria catalytic and photocatalytic activity, thus preventing the degradation of other sunscreen ingredients. In this work, pure and zinc-doped ceria nanoparticles were prepared by a simple and environmentally benign hydrothermal synthesis, and characterized using various techniques. Fine ceria and doped ceria nanoparticles with particle sizes of 6.1±0.9 and 4.2±0.4 nm were prepared. In both samples, cubic ceria was the only crystalline phase, but the homogeneous distribution of zinc in the doped sample was confirmed by energy dispersive X-ray spectrometry. Nanoparticles exhibited transparency in the visible region and absorbance in the UV region with band gap of 3.23 to 3.14 eV for pure and doped sample, respectively. The oxidation stability time, determined through Castor oil oxidation process, was 23 hours for the pure and 15 hours for the doped sample, which is quite satisfactory. In vitro cytotoxicity study showed that the prepared nanoparticles were well tolerated by human skin keratinocytes (HaCaT cell line) with no significant differences in skin cells viability. However, further investigations on in vivo systems are necessary to reach a firm conclusion regarding the toxicity of ceria and doped ceria nanoparticles, and other potential dopants should be considered for improvement of ceria properties for sunscreen application.

The influence of ionic radii and valence of dopants in Ce0.9LaxYbyZr0.1−x−yO2−δ (x = 0, 0.05, 0.1, y = 0, 0.05, 0.1) on the oxidation kinetics were investigated by thermogravimetric analysis in synthetic air and were compared to undoped ceria. Samples co-doped with Zr–La and Zr–Yb exhibited moderate oxidation kinetics that were slower than undoped ceria, but much faster than 10mol% Zr-doped ceria. The extrinsic oxygen vacancy induced by the trivalent dopants improves the kinetics at oxidation temperatures below 700 °C, where the diffusion, and not the surface exchange reaction is the limiting factor. A smaller ionic radius of the substituent (i.e. r(Yb3+) < r(La3+)) in the co-doped ceria tends to facilitate lower activation energy resulting in slightly faster oxidation kinetics at temperatures below 700 °C. In contrast, additional extrinsic vacancies are rather obstructive at high temperatures (i.e. T > 700 °C) due to a change of rate limiting mechanism from bulk oxygen diffusion to surface exchange reaction. Overall, the valence of the dopant rather than the ionic radius seems to determine the oxidation kinetics primarily, and additional La or Yb doping on Zr-doped ceria is appealing especially when the applications are focused on low temperature reactions.

The electrical conductivity of fluorite-type Ce1 –x – yLaxPryO2 – δ (x = 0.29–0.40, y = 0–0.14) solid solutions was studied over the oxygen partial pressure range from 10–20 to 0.5 atm at 973–1223 K. The (Сe,La)O2 – δ was shown to possess predominant anion conductivity with the oxygen ion transference numbers above 0.99 over the entire temperature range. The decreasing of the oxygen partial pressure leads to an increase in n-type electronic conduction. The data on total conductivity as a function of the oxygen partial pressure varying from 10–8 atm down to 10–20 atm was used to model the electronic and ionic defect formation and transport processes under reductive conditions. The concentrations of point defects and their diffusivities were calculated. The concentration of electrons localized at cerium cations, their mobility and, consequently, the partial n-type electronic conductivity were all found to decrease with the increasing of the dopants concentration. The oxygen-ion conductivity and the oxygen vacancy mobility both decreased with the increasing of the La3+, Pr3+, and Ce3+ cations' total content. This behavior can be explained by the formation of point-defect clusters comprising Ln3+ and anion vacancies, which becomes more favorable with the addition of Ln3+. [ABSTRACT FROM AUTHOR]

In the present work, calcium and titanium are doped with ceria in an effort to create a unique, effective electrolyte for solid oxide fuel cell applications (Ce0.33Ca0.34Ti0.33O1.66 (CCT-33)). CCT-33 is prepared through solid state method through ball milling and calcination. XRD analysis of the CCT-33 revealed cubic fluorite crystal structure favorable for oxygen ion conduction. Electron microscopy analysis of the sintered pellets revealed good compactness of the phase pure powders and crystallinity. The conductivity studied using impedance analysis is 10−3–10−4 S cm−1 in the temperature region of 500–630 °C. At 700 °C the highest value of 2.86 × 10−2 S cm−1 in considered temperature region was obtained. The present work introduces innovative, modified material for Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFCs).

This study mainly investigates the defect interaction mediated ionic conductivity of Ce0.9Sm0.1O1.95. The ionic conductivity mainly depends on the concentration of free oxygen vacancies. The formed oxygen vacancies are bounded with dopant cations due to columbic interaction which depends on the dielectric constant of the material. With the rise in temperature dielectric constant increases and dopant–vacancy association decreases. Consequently, ionic conductivity increases with temperature due to the enhancement of concentration of free oxygen vacancies. The association and migration energy decrease at higher temperature.

Summary: By evaluating the functional modifications induced by Zr and Fe as dopants in Pt/CeO2‐MOx/Al2O3 catalysts (M = Fe and Zr), the key features for improving water gas shift (WGS) performance for these systems have been addressed. Pt/ceria intrinsic WGS activity is often related to improved H2 surface dynamics, H2O absorption, retentions and dissociation capacities which are influenced greatly by the support nature. Two metals, iron and zirconia, were chosen as ceria dopants in this work, either in separate manner or combined. Iron incorporation resulted in CO‐redox properties and oxygen storage capacities (OSC) improvement but the formation of Ce‐Fe solid solutions did not offer any catalytic benefit, while the Zr incorporation influenced in a great manner surface electron densities and shows higher catalytic activity. When combined both metals showed an important synergy evidenced by 30% higher CO conversions and attributed to greater surface electron densities population and therefore absorption and activity. This work demonstrates that for Pt/ceria catalysts OSC enhancement does not necessarily imply a catalytic promotion. [ABSTRACT FROM AUTHOR]

• - Doping atoms and oxygen vacancies are distributed randomly or as trimers. • - Thermal expansion largely depends on the defect distribution. • - The neighbour distribution (N) lead to thermal expansion in accordance with literature data. • - The thermal expansion of the two distributions (R and N) get closer with the increase of temperature. Molecular dynamics (MD) simulations are performed to obtained the evolution of Ce 1-x Gd x O 2-x/2 lattice parameter with temperature. Gd3+ and V ö are distributed randomly (R) or as Gd ′′ ce V ö Gd ′′ ce trimer (N) inside the fluorite structure. The thermal expansion coefficient (TEC) depends on both the doping ratio and the temperature. Furthermore, MD results evidence the high influence of the defect arrangement on the TEC with the N distribution more in accordance with the experimental published TEC. We also observe that TEC of the two distributions tends to get closer at high temperature. [ABSTRACT FROM AUTHOR]

Ceria is an excellent oxide catalyst to break H 2 in the absence of noble metals and has shown great promise for potential applications in diverse technological fields. The catalytic activity of ceria is critically linked to surface composition and structure. Herein, selective doping with moderate lanthanide ions is reported to regulate surface oxygen vacancies and bonded adsorbates of ceria nanorods so as to finely tune their activities toward electro-oxidation of H 2 and C 3 H 8 in reduced-temperature solid oxide fuel cells. Lanthanide doped ceria nanorods are hydrothermally synthesized, and electrochemically evaluated as the anode catalysts for reduced-temperature SOFCs. Measurements of anode polarization resistances and fuel cell power densities show a catalytic activity in the order of Ce 0.8 Pr 0.2 O 2-δ < Ce 0.8 Gd 0.2 O 2-δ < Ce 0.8 Sm 0.2 O 2-δ. Probing the surface structure with hydrogen temperature-programmed reduction, UV-Raman and XPS reveals that such catalytic activities are essentially determined by surface reducibility, availability of surface oxygen vacancies and strongly bonded hydroxyls. • CeO 2 nanorods doped with lanthanide ions are synthesized as anodes for SOFCs. • Activities of Ce 0.8 Ln 0.2 O 2-δ are related to oxygen vacancies and bonded hydroxyls. • P max of Sm-CeO 2-δ are 0.63 and 0.23 W•cm−2 in H 2 and C 3 H 8 at 600 °C, respectively. [ABSTRACT FROM AUTHOR]

The abundance of cerium in natural resources, its ability to absorb UV light while being transparent to visible light, as well as low photocatalytic activity make ceria (CeO2) a promising candidate for UV filter material in sunscreens. Doping with different elements can further decrease ceria catalytic and photocatalytic activity, thus preventing the degradation of other sunscreen ingredients. In this work, pure and zinc-doped ceria nanoparticles were prepared by a simple and environmentally benign hydrothermal synthesis, and characterized using various techniques. Fine ceria and doped ceria nanoparticles with particle sizes of 6.1±0.9 and 4.2±0.4 nm were prepared. In both samples, cubic ceria was the only crystalline phase, but the homogeneous distribution of zinc in the doped sample was confirmed by energy dispersive X-ray spectrometry. Nanoparticles exhibited transparency in the visible region and absorbance in the UV region with band gap of 3.23 to 3.14 eV for pure and doped sample, respectively. The oxidation stability time, determined through Castor oil oxidation process, was 23 hours for the pure and 15 hours for the doped sample, which is quite satisfactory. In vitro cytotoxicity study showed that the prepared nanoparticles were well tolerated by human skin keratinocytes (HaCaT cell line) with no significant differences in skin cells viability. However, further investigations on in vivo systems are necessary to reach a firm conclusion regarding the toxicity of ceria and doped ceria nanoparticles, and other potential dopants should be considered for improvement of ceria properties for sunscreen application. [ABSTRACT FROM AUTHOR]

Doped Ceria with abundant oxygen vacancies exhibits enhanced performance in heterogeneous oxidation. In principle, doping 50 mol% divalent cations (such as: Cu2+, Zn2+, and Mg2+) into CeO2 lattice would produce an exceptional catalyst with maximum active oxygen species. However, the huge size gap between Ce (IV) and divalent metal cations obstructs its synthesis. Here, we utilize the theory of increasing configurational entropy with five metal dopants to lower the Gibbs‐free energy, and successfully incorporate 50 mol% divalent metal cations into CeO2 lattice. This unique doping environment endows Ce0.5Zn0.1Co0.1Mg0.1Ni0.1Cu0.1Ox two features: (a) Abundant active oxygen species for excellent performance in volatile organic compounds catalytic oxidation; (b) Bring multi reactive sites, which enable the simultaneous combustion of carbon monoxide, propylene and toluene. Moreover, the increased entropy value makes Ce0.5Zn0.1Co0.1Mg0.1Ni0.1Cu0.1Ox an ultra‐stable catalyst in both thermal and hydrothermal conditions (e.g., Working >200 hr in water‐resistance experiment). [ABSTRACT FROM AUTHOR]

Ceria doped with manganese in various amounts was prepared via hydrothermal synthesis. XRD revealed that beside ceria, monoclinic birnessite (Na 0.55 Mn 2 O 4 × 1.5H 2 O) appears in the samples. The occurrence of birnessite was achieved using different synthesis conditions and precursors. SEM imaging revealed birnessite layered formations surrounded with ceria nanoparticles, while EDS confirmed the presence of both phases. Weight percentage, lattice constants and crystallite size of ceria, as well as birnessite, were obtained through whole powder pattern decomposition. Pure and Mn doped ceria samples with crystallite sizes between 3.1 and 3.4 nm, and specific surface area values between 183 and 212 m2 g−1 were obtained. It was established that the amount of Mn entering the ceria lattice or forming birnessite varies with nominal composition. Introduction of Mn in ceria is evident from the decrease of ceria lattice constant (from 5.4185 Å to 5.4002 Å). The entrance of manganese in the ceria crystal lattice was confirmed via EDS spectroscopy. Thermally induced changes were monitored via DTA/TGA, XRD and FTIR. Birnessite decomposes below 200 °C, while thermal treatment at 500 °C for 2 h yields Na 2 Mn 5 O 10. Weight percentage of birnessite was confirmed through calculations based on the loss of interlayer water during TGA analysis. HRTEM revealed nanorod morphology of Na 2 Mn 5 O 10 , while EELS gave insight into the composition of this phase. [ABSTRACT FROM AUTHOR]

The rare–earth–doped ceria overcomes the difficulties of yttria–stabilized zirconia (YSZ) as an electrolyte in Solid Oxide Fuel Cells (SOFCs) due to its superior ionic conductivity in the intermediate temperature range. However, several factors such as synthesis process, sintering condition, dopant concentration, co–doping mechanism, dopant vacancy interaction, ionic radius of dopants, grain boundary, grain size, affect the ionic conductivity of the rare earth doped ceria. It is difficult to explain the ionic conductivity of rare–earth–doped ceria in terms of a single factor because there is a complex correlation among these factors. This review tries to find the complicated relationship between these factors. This work also reviews different opinions regarding the effect of these factors on ionic conductivity. The knowledge about the factors is vital to develop a better solid electrolyte for SOFCs. This work is an overview of the ionic conductivity of rare–earth–doped ceria in terms of the several affecting factors. Image 1 • Dependency of Ionic conductivity of rare–earth–doped ceria on several factors. • Correlation between the factors. • Understanding of the factors is vital to develop best solid electrolyte for SOFCs. [ABSTRACT FROM AUTHOR]

NiFeO x is a high-active electrocatalyst for oxygen evolution reaction (OER) in alkaline media, which gradually deactivate in the long run due to Fe loss from the active sites into media solution during electrocatalysis. Herein, we propose a promising stable CeNiFeO x electrocatalyst for oxygen and hydrogen evolution reactions (OER&HER) by a facile one-pot combustion synthesis. The X-ray diffraction (XRD) results indicate that both nickel and iron ions are successfully incorporated into ceria lattices to form a pure fluorite phase of CeNiFeO x nanopowders, indicating a new achievement of as high as 20% of Ni/Fe solubility in the ceria lattice for the first time. The electrochemical measurements indicate that CeNiFeO x exhibits the high OER activity of NiFeO x electrocatalyst and the enhanced stability of oxygen evolution electrocatalysts. The Ce 0.8 Ni 0.15 Fe 0.05 O x with a single phase of cubic fluorite structure among all shows the most efficient activity with the overpotential of 325 mV for OER and 337 mV for HER at the current density of 10 mA cm−2 in 1 M KOH than the pure CeO x , NiFeO x and other CeNiFeO x nanoelectrocatalysts. After 1000 cycles, the Ce 0.8 Ni 0.15 Fe 0.05 O x nano electrocatalyst exhibits the remarkably improved stability for OER compared to NiFeO x electrocatalyst. These findings demonstrate a facile approach to develop high-active and durable electrocatalysts under alkaline conditions for overall water splitting. • A high-stable CeNiFeO x electrocatalyst is developed for alkaline water splitting. • A one-pot combustion synthesis is useful to OER and HER electrocatalysts. • A new achievement of as high as 20% of Ni/Fe solubility in ceria is reported. • Ce 0.8 Ni 0.15 Fe 0.05 O x shows superior electrocatalytic bifunctional performance. [ABSTRACT FROM AUTHOR]

Ionic conductors composed of lanthanide-doped ceria with general formula Dy y Ce 1-y O 2-δ (y = 0.05, 0.1 and 0.15) were synthesized by mechanochemistry (mechanical milling), and their electrical properties analyzed to be used as solid electrolytes in low-temperature SOFC. Starting oxide reagents were milled at different times in a planetary mill and the evolution of their structures and phases with milling time and temperature (up to 1500 °C) was followed by XRD. Just milled powders were also uniaxially pressed and sintered at different temperatures (1200, 1350 and 1500 °C), and analyzed by FE-SEM, to explore their morphologies as a function of temperature and Dy content. The electrical properties of these materials and undoped commercial CeO 2 were analyzed by impedance spectroscopy at different temperatures (200–650 °C) and frequencies (100 Hz - 1 MHz). Results showed that mechanochemistry is a suitable method to obtain the Dy y Ce 1-y O 2-δ systems after 20 h of milling, since XRD patterns of these milled powders reveal the formation of fluorite-type cubic solid solutions for all studied compositions. Increasing of temperature generates a higher crystallinity in these materials while the absence of phase transitions in them is corroborated at 1200 °C. Analysis of electrical properties of samples sintered a 1200 °C corroborates the viability of these systems to be used as solid electrolytes in the SOFC technology, being that high dc conductivities (σ dc) were obtained for all doped samples, especially for the composition Dy 0.1 Ce 0·9 O 2-δ , which showed a σ dc = 1 × 10−1.91 S cm−1 at 650 °C. This value represents an increase of almost three orders of magnitude for this composition with respect to the undoped CeO 2 sample (y = 0, σ dc = 1 × 10 −4.83 Scm−1). • CeO 2 doped with Dy was successfully synthesized by a mechanochemical reaction. • All compositions (5, 10 and 15% mol of Dy) show a cubic fluorite-type structure. • Electrical properties of the samples were measured as a function of temperature. • Conductivity (σ dc) reaches a maximum of 1 * 10−1.91 Scm−1 (650 °C) for 10% of Dy. • Increasing of σ dc is related to the creation of oxygen vacancies in the structure. [ABSTRACT FROM AUTHOR]

CeO2 doped with various rare earth (RE) ions (Sm, Y, La and Nd) having a broom‐like hierarchical structure was successfully prepared by a template‐free hydrothermal method. The photooxidation performance of RE‐doped products was significantly better than that of pure CeO2, and comparative experiments showed that Sm‐doped CeO2 (SC) has superior photooxidation activity, resulting about 3.0‐times and 8.5‐times higher activities of bisphenol A (BPA) degradation and of acetaldehyde (CH3CHO) decomposition, respectively, than those of pure CeO2. Due to the incorporation of RE ions, the surface exposed cerium ions are partly substituted by those cations, resulting in a higher concentration of oxygen vacancies (Ov) in RE‐doped CeO2. The increased Ov can act as a trapping center for photo‐generated electrons to form a doping transition state between the conduction band (CB) and valence band (VB), which can restrict the recombination rate of electrons and holes effectively and lead to an outstanding enhancement of photooxidation performance. Furthermore, abundant highly reactive hydroxyl radicals (.OH) and superoxide radicals (.O2−), which are efficient intermediates with vivid oxidation ability, can further enhance the photocatalytic activity of RE‐doped CeO2. A cost‐effective strategy for designing CeO2‐based semiconductor photocatalysts doped with multitudinous RE ions that have enhanced photooxidation performance is presented in this paper. [ABSTRACT FROM AUTHOR]

In order to evaluate applicability of Ce0.6 –хLa0.4PrхO2 – δ (x = 0–0.2) fluorites for protective interlayers and electrode components for intermediate-temperature solid oxide fuel cells (SOFCs), their thermal expansion, chemical interaction with solid electrolyte material, tolerance towards reduction and electrochemical behavior were studied. The incorporation of praseodymium into Ce0.6La0.4O2 – δ was found to increase unit cell parameters and thermal expansion coefficients, from (13.2 ± 0.3) × 10–6 to (18.5 ± 0.8) × 10–6 К–1 at intermediate temperatures. Increasing total concentration of rare-earth cations in the fluorite-like cerium dioxide structure also correlates with decreasing thermodynamic stability under both oxidizing and reducing conditions. As a result, high-temperature chemical interaction between the Pr-doped materials and lanthanum gallate-based solid electrolyte becomes more intensive with respect to Ce0.6La0.4O2 – δ, whilst reduction of Pr-containing solid solution may leads to segregation of a secondary phase with the C-type structure. The combination of these factors deteriorates compatibility of the interlayers with other SOFC components. Consequently, the overpotentials of PrBaFe1.2Ni0.8O6 – δ cathodes in the electrochemical cells with (La0.9Sr0.1)0.98Ga0.8Mg0.2O3 – δ solid electrolyte were –42 and –143 mV in O2 atmosphere at the current density –58 mA/cm2 and 1073 K when the interlayers of Ce0.6La0.4O2 – δ or Ce0.5La0.4Pr0.1O2 – δ were used, respectively. [ABSTRACT FROM AUTHOR]

There is a renewed interest in CeO 2 for use in solar-driven, two-step thermochemical cycles for water splitting. However, despite fast reduction/oxidation kinetics and high thermal stability of ceria, the cycle capacity of CeO 2 is low due to thermodynamic limitations. In an effort to increase cycle capacity and reduce thermal reduction temperature, we have studied binary zirconium-substituted ceria (Zr x Ce 1-x O 2 , x = 0.1, 0.15, 0.25) and ternary praseodymium/gadolinium-doped Zr-ceria (M 0.1 Zr 0.25 Ce 0.65 O 2 , M = Pr, Gd). We evaluate the oxygen cycle capacity and water splitting performance of crystallographically and morphologically stable powders that are thermally reduced by laser irradiation in a stagnation flow reactor. The addition of zirconium dopant into the ceria lattice improves O 2 cycle capacity and H 2 production by approximately 30% and 11%, respectively. This improvement is independent of the Zr dopant level, up to 25%, suggesting that above 10% Zr dopant level, Zr might be displaced during the high temperature annealing process. The addition of Pr and Gd to the binary Zr-ceria mixed oxide, on the other hand, is detrimental to H 2 production. A kinetic analysis is performed using a model-based analytical approach to account for effects of mixing and dispersion, and to identify the rate controlling mechanism of the water splitting process. We find that the water splitting reaction at 1000 °C and with 30 vol% H 2 O, for all doped ceria samples, is surface limited and best described by a deceleratory power law model (F-model), similar to undoped CeO 2. Additionally, we used density functional theory (DFT) calculations to examine the role of Zr, Pr, and Gd. We find that the addition of Pr and Gd induce non-redox active sites and, therefore, are detrimental to H 2 production, in agreement with experimental work. The calculated surface H 2 formation step was found to be rate limiting, having activation barriers greater than bulk O diffusion, for all materials. This agrees with and further explains experimental findings. Image 1 • H 2 O splitting of reduced Zr, Gd/Zr, and Pr/Zr doped ceria is surface reaction limited. • Pr and Gd addition induce non-redox active sites, detrimental to H 2 production. • Surface H 2 formation is rate limiting, activation barriers > bulk O 2 diffusion. • Steam oxidation is best described by a deceleratory power law model (F-model). [ABSTRACT FROM AUTHOR]

Doped ceria is known for its high ionic conductivity which is limited by the creation of defect clusters. We investigate using Molecular Dynamics the evolution of the structure and oxygen diffusivity of the Ce 0.9 M 0.1 O 1.95 (M = Gd, Sm) doped and co-doped CeO 2 systems. Two configurations concerning the introduction of the doping ions and oxygen vacancies inside the structure are generated and compared, the random one (R) and the neighbor one (N). The pair potential parameter set is chosen among three sets by comparison with experimental data. The pair correlation function first peak is fitted by a lognormal function to take into account the asymmetry. The evolution of the coefficient of thermal expansion, the coordination number and the bond lengths of the different ion pairs with the temperature, is presented. The influence of the local C-type sesquioxide M 2 O 3 structure on those parameters is discussed. No significant positive co-doping effect on the oxygen diffusion process is revealed. The random configuration of the defects leads to the highest oxygen diffusivity and to the lower activation energy whatever the doping ion (Gd, Sm or Gd/Sm). [ABSTRACT FROM AUTHOR]

Redox studies on Zr, La, Yb doped ceria (Ce 0.9 M3+/4+ 0.1 O 2-x , M3+/4+ = Zr4+, La3+, Yb3+ and CeZr 0.05 M3+ 0.05 O 1.95 , M3+ = La3+, Yb3+) ceramics were performed using dilatometry and mass change measurements to analyze the chemical and thermal volume changes depending on reduction state which can have dramatic effects on the long-term stability of these ceramics in Concentrated Solar Energy (CSE)–driven applications relevant to the synthesis of fuels. The reduction extents determined by both methods under vacuum (p = 2 × 10−5 mbar) are similar up to 1673 K. At higher temperatures, CeO 2 , which has a higher vapor pressure than the oxides of the dopant ions, evaporates. As a result, there is an accumulation of doping ions, which leads to a porous surface zone. Surface enrichment of dopants, especially that of Zr4+, is crucial for re-oxidation kinetics. Co-doping with trivalent doping ions such as La3+ and Yb3+ reduces the extent of selective evaporation materializing it into a thinner porous surface layer. Trivalent dopants and their additional oxygen vacancies also influence the chemical expansion/contraction of the Zr4+ doped ceria crystal lattice during the redox reaction and thus lead to a reduction of mechanical stresses. We assume that additional oxygen vacancies from trivalent dopant ions promote the disordering of intrinsic oxygen vacancies, while smaller tetravalent ions such as Zr4+ compensates this effect. This explains that doped ceria with trivalent and tetravalent ions show almost the same chemical expansion as pure ceria. The new results on alteration, thermal and chemical expansions/contractions at high temperature are particularly important for the development of metal oxide ceramic components exposed to cyclic reducing and oxidizing atmospheres at elevated temperatures achieved via CSE. • Surface accumulation of doping due to selective evaporation of CeO 2 influence the re-oxidation kinetics. • Chemical expansion of ceria increased with La3+ and Yb3+- and decreased with Zr4+- doping. • By combining trivalent and tetravalent doping ions, counteracting effects on chemical expansion are compensated. • Chemical contraction of Yb3+ doped ceria during re-oxidation revealed a two-step mechanism. [ABSTRACT FROM AUTHOR]

A Raman and electrochemical impedance spectroscopy (EIS) joint study was performed on the (Nd,Tm)- and (Nd,Dy)-doped ceria systems, members of a promising class of materials to be used as electrolytes in solid oxide cells operating at intermediate temperatures (IT-SOCs). Raman and EIS data were collected in the 573–1073 K temperature range, i.e. in the operating temperature range of IT-SOCs, and analyzed with the aim to correlate ionic conductivity and defect chemistry. Defect aggregates growing within the CeO 2 -based matrix tend in fact to reduce and even suppress oxygen transport. A slope change in the trend of Raman shift of the Ce O vibration, as well as of the FWHM/intensity ratio of the same signal, occurs around the temperature where also the activation energy to ionic conduction changes its value. This common evidence is discussed in the light of defect aggregates stability, and in more detail in terms of decomposition of the 1 V O • • 2 RE Ce ′ trimers. [Display omitted] • MicroRaman and impedance spectroscopy measurements were performed on doped ceria. • A lower activation energy to ionic conductivity is revealed above 750 K. • A discontinuity in the Raman shift of the CeO2 signal occurs at the same temperature. • Defects aggregates negatively affect ionic conductivity in doped ceria electrolytes. • Due to their low configurational entropy, defect trimers dissociate above 750 K. [ABSTRACT FROM AUTHOR]

Single-step inkjet printing infiltration with doped ceria Ce0.9Ye0.1O1.95 (YDC) and cobalt oxide (CoxOy) precursor inks was performed in order to modify the properties of the doped ceria interlayer in commercial (50 × 50 × 0.5 mm3 size) anode-supported SOFCs. The penetration of the inks throughout the La0.8Sr0.2Co0.5Fe0.5O3−δ porous cathode to the Gd0.1Ce0.9O2 (GDC) interlayer was achieved by optimisation of the inks’ rheology jetting parameters. The low-temperature calcination (750 °C) resulted in densification of the Gd-doped ceria porous interlayer as well as decoration of the cathode scaffold with nanoparticles (~20–50 nm in size). The I–V testing in pure hydrogen showed a maximum power density gain of ~20% at 700 °C and ~97% at 800 °C for the infiltrated cells. The latter effect was largely assigned to the improvement in the interfacial Ohmic resistance due to the densification of the interlayer. The EIS study of the polarisation losses of the reference and infiltrated cells revealed a reduction in the activation polarisations losses at 700 °C due to the nano-decoration of the La0.8Sr0.2Co0.5Fe0.5O3−δ scaffold surface. Such was not the case at 800 °C, where the drop in Ohmic losses was dominant. This work demonstrated that single-step inkjet printing infiltration, a non-disruptive, low-cost technique, can produce significant and scalable performance enhancements in commercial anode-supported SOFCs.

Exsolved nanoparticle catalysts have recently attracted broad research interest as they simultaneously combine the features of catalytic activity and chemical stability in various applications of energy conversion and storage. As the internal mechanism of in-situ exsolution is of prime significance for the optimization of its strategy, comprehensive research focused on the behaviors of in-situ segregation for metal (Mn, Fe, Co, Ni, Cu, Ag, Pt and Au)-substituted CeO2 is reported using first-principles calculations. An interesting link between the behaviors of metal growth from the ceria host and their microelectronic reconfigurations was established to understand the inherent attribute of metal self-regeneration, where a stair-stepping charge difference served as the inner driving force existing along the exsolving pathway, and the weak metal-coordinate associations synergistically facilitate the ceria’s in-situ growth. We hope that these new insights provide a microscopic insight into the physics of in-situ exsolution to gain a guideline for the design of nanoparticle socketed catalysts from bottom to top.

Ceria based electrolyte materials have shown potential application in low temperature solid oxide fuel cells (LT-SOFCs). In this paper, Sm3+ and Nd3+ co-doped CeO2 (SNDC) and pure CeO2 are synthesized via glycine-nitrate process (GNP) and the electro-chemical properties of the nanocrystalline structure electrolyte are investigated using complementary techniques. The result shows that Sm3+ and Nd3+ have been successfully doped into CeO2 lattice, and has the same cubic fluorite structure before, and after, doping. Sm3+ and Nd3+ co-doped causes the lattice distortion of CeO2 and generates more oxygen vacancies, which results in high ionic conductivity. The fuel cells with the nanocrystalline structure SNDC and CeO2 electrolytes have exhibited excellent electrochemical performances. At 450, 500 and 550 °C, the fuel cell for SNDC can achieve an extraordinary peak power densities of 406.25, 634.38, and 1070.31 mW·cm−2, which is, on average, about 1.26 times higher than those (309.38, 562.50 and 804.69 mW·cm−2) for pure CeO2 electrolyte. The outstanding performance of SNDC cell is closely related to the high ionic conductivity of SNDC electrolyte. Moreover, the encouraging findings suggest that the SNDC can be as potential candidate in LT-SOFCs application.

Abstract Commercially available anode supported solid oxide fuel cells (NiO-8YSZ/8YSZ/LSCF- 20 mm in diameter) were anode infiltrated with gadolinium doped ceria (CGO) using a scalable drop-on-demand inkjet printing process. Cells were infiltrated with two different precursor solutions—water based or propionic acid based. The saturation limit of the 0.5 μm thick anode supports sintered at 1400 °C was found to be approximately 1wt%. No significant enhancement in power output was recorded at practical voltage levels. Microstructural characterisation was carried out after electrochemical performance testing using high resolution scanning electron microscopy. This work demonstrates that despite the feasibility of achieving CGO nanoparticle infiltration into thick, commercial SOFC anodes with a simple, low-cost and industrially scalable procedure other loss mechanisms were dominant. Infiltration of model symmetric anode cells with the propionic acid based ink demonstrated that significant reductions in polarisation resistance were possible.

• Gd and Mn dopants show enhanced activity for coke gasification and oxidation due to presence of oxygen vacancies. • Catalytic activity in a steam–air mixture is primarily governed by air. • Mn doped ceria is the favored catalyst for steam gasification due to its high activity and low cost. A series of α-alumina supported doped (Mn, Gd, Sr) ceria catalysts is investigated for the gasification (steam) and oxidation (air) of industrial coke that was generated during ethane pyrolysis. The catalytic activity is evaluated in the presence of pure steam, air and steam–air mixtures. Gd, Mn and Sr dopants reduce the coke gasification temperature in pure steam by 65 °C compared to the un-catalyzed coke gasification. Gd and Mn also decrease the coke oxidation temperature in air and help the dilute oxidation of coke in the presence of steam + air mixtures by decreasing the diluted oxidation temperature of coke by ∼125 °C. The Mn doped ceria catalyst is able to resist coke formation, during in-situ coking experiments. Structural characterization of the α-alumina supported doped (Gd and Mn) ceria catalysts by extended X-ray absorption fine structure (EXAFS) and Raman spectroscopy shows the presence of Ce3+ species and oxygen vacancies, respectively, in the ceria catalysts. The catalytic activity of the Gd-doped sample appears to be related to the presence of increased oxygen vacancies, the smaller crystallite size and a higher catalyst surface area compared to catalysts with other dopants. For the Mn-doped ceria catalyst, the presence of increased oxygen vacancies is suggested to be the main reason for its improved activity. Exposure to steam at high temperatures imparts a negligible effect on the crystallite sizes of the doped ceria catalysts, as evidenced from X-ray diffraction, indicating negligible sintering and good thermal stability of these catalysts. [ABSTRACT FROM AUTHOR]

In this work, two asymmetric NiO-BaZr0.1Ce0.7Y0.2O3-δ (NiO-BZCY) anode substrates were prepared via the phase-inversion tape casting method for Ce0.8Sm0.2O2-δ (SDC)-based solid oxide fuel cells. The results showed that the anode support structure significantly influenced the electrochemical properties of the cells. The cell supported on the anode substrate consisted of a finger-like layer and a sponge-like layer outputs highest electrochemical performance with a maximum power density of 823 mW cm−2 at 650 °C and shows great superiority over the cell fabricated by a typical dry-pressing method. The excellent performances demonstrate that the phase-inversion tape casting technique is a good strategy in fabricating anode supports for SOFCs, and the anode structure with the relatively dense sponge-like layer as top surface is optimal to construct the complete cell. [ABSTRACT FROM AUTHOR]

Nanorods of Ce0.85La0.15O1.925 (CLO) have been synthesized using a wet-chemical route and characterized by thermal analysis, phase, crystal structure, microstructure and electrical conductivity. Nanorods have been stabilized by adding binary eutectic mixture of Li2CO3 and Na2CO3. This hinders the grain growth of Ce0.85La0.15O1.925 nanorods. Cubic fluorite structure of ceria has been detected by X-ray diffraction. A sharp increase in the conductivity has been observed at a certain temperature, corresponding to superionic transition at the interfaces. This composition shows the highest conductivity, 1.14 × 10−1 S/cm at 500 °C with activation energy of conduction 0.19 eV. This value is about three orders of magnitude higher than that of Ce0.85La0.15O1.925 (2.02 × 10−4 S/cm at 500 °C) nanoparticles prepared by auto-combustion route. [ABSTRACT FROM AUTHOR]

Abstract NiO, CeO 2 and respective composites are extensively used in energy storage devices due to mostly their high electrochemical activity. However, the assessment of battery-like behavior of Ni-ceria based systems comprising (Ni or Gd)-doped ceria combined with NiO seems to be neglected in the literature. In this work, NiO and ceria-based solid solutions composite powders were obtained by a co-precipitation synthesis method. The structure and particle size of the calcined powders were investigated by X-ray diffractometry (XRD) and field emission scanning electron microscopy (FESEM), respectively. Oxidative states of composites were inspected by X-ray photoelectron spectroscopy (XPS). The electrochemical performance of powders was evaluated by cyclic voltammetry, galvanostatic charge-discharge and impedance spectroscopy. Refinement of the XRD patterns showed that powders have nanosized crystallites and mean size of particles within 20 – 70 nm were revealed by FESEM. The improved specific capacity of the NiO-CeO 2 electrode material (about 2.5 times higher than that of NiO-CGO at 5 mV s−1) is due to an increase in Faradic reactions taken place on its surface with a higher fraction of defects (namely Ni3+, Ce3+ and oxygen vacancies), as determined by XPS. The superior electrochemical performance of the NiO-CeO 2 electrode is also confirmed by electrochemical impedance spectroscopy. Graphical abstract fx1 Highlights • Ni-ceria based systems as battery-like materials; • (Ni or Gd)-doping effect on the performance of ceria in alkaline (3 M KOH) solution; • NiO + Ce-Ni-O solid solution with better battery-like behavior than NiO-Ce 0.9 Gd 0.1 O 1.95. • Battery-like behavior enhanced by surface defects. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A cost-effective Y-doped CeO2/PCN (YCC) heterojunction photocatalyst were fabricated for the first time. • The photocatalytic redox performance of YCC were promoted synergistically. • The establishment of built-in electric filed and separation of holes and electrons were conducive to photoredox of YCC. Abstract In this study, yttrium-doped CeO 2 was introduced into polymeric carbon nitride (PCN) through one-step hydrothermal reaction to form the Y-doped CeO 2 /PCN (YCC) nanocomposited photocatalysts. Morphology of products was observed by emission scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM). The structure of the products was characterized by X-ray diffractometer (XRD), FT-IR and Raman analysis. Optical absorption and band energy properties were investigated by UV–vis, PL and VB-XPS spectra. The X-ray photoelectron spectroscopy (XPS) results further revealed that the surface active oxygen and Ce3+ concentration of nanocomposited photocatalyst were significantly increased compared with pure CeO 2 and PCN counterparts. The YCC composites exhibited excellent photoredox performance under visible light irradiation, affording to 5.73- and 3.74-fold higher for RhB degradation and proton photoreduction to produce H 2 than that of pure CeO 2. The Y-doped nanocomposited means adopted in this study not only improve the optical utilization of visible light, but also effectively inhibit the recombination of photogenerated charge carriers, which are conducive to promote the photoredox performance synergistically. [ABSTRACT FROM AUTHOR]