Cerium Nitrate Solution Research Articles

The influence of pH electrolyte on the electrochemical deposition and properties of cerium oxide thin films

Thin cerium oxide layers cathodically deposited on zinc were studied. These electrochemically deposited coatings provide effective corrosion protection and require less deposition time compared to chemical conversion coatings. The kinetics of their formation depend on various factors, such as temperature, applied current density, electrolyte composition, pH, and agitation. In this study, the effect of bath solution pH was investigated, with coatings produced at room temperature from aqueous cerium nitrate solutions. Chronopotentiometry, linear sweep voltammetry, and electrochemical impedance spectroscopy (EIS) were used to monitor the deposition process, while scanning electron microscopy and energy-dispersive spectroscopy were performed to characterize the deposits. Corrosion resistance was evaluated through potentiodynamic tests in a 3.5% NaCl solution. The results indicate that the electrolyte pH significantly influences the cerium electrodeposition process. Based on the findings, the cerium oxide coating obtained from a pH 4 solution exhibited lower corrosion current density, higher polarization resistance, and superior anti-corrosion performance.

Structural Parameters of Ion Coordination in Aqueous Solutions of Cerium Nitrate According to the X-Ray Diffraction Analysis

Structural Parameters of Ion Coordination in Aqueous Solutions of Cerium Nitrate According to the X-Ray Diffraction Analysis

Controllable synthesis of core-shell SiO2@CeO2 abrasives for chemical mechanical polishing on SiO2 film

The controllable and facile synthesis of SiO2@CeO2 core-shell (CS) composite nanoparticles is crucial for various applications, i.e., chemical mechanical polishing (CMP), nanoreactors, and photocatalysis. However, it is still a challenge to control the synthesis of homogeneous CeO2-coated SiO2 core-shell nanoparticles without additional chemicals or organic solvents. The study investigated the influence of reaction atmosphere, initial pH of the silica colloidal, and the quantity of cerium nitrate on the ceria coating process systematically. Furthermore, the synthesis mechanism of CS composite nanoparticles was ascertained by monitoring changes in pH, zeta potential, secondary size, and morphology over time. The controllable growth of 3%− 67.5% ceria on the surface of silica is realized by controlling the method and timing of adding cerium nitrate and ammonia solution. X-ray photoelectron spectroscopy revealed the Ce-O-Si chemical bonding that combined with the CeO2 at the interfaces of SiO2 core at temperature of 80 °C without post-heating. The material removal rate (MRR) of SiO2 film increased from 32.27 to 294.02 Å/min equipped with CS-7.65% composite nanoparticles as abrasives demonstrated significant improvement. These findings provide valuable insights for the development of SiO2@CeO2 composite nanoparticles in subsequent research.

Corrosion and in vitro characteristics of cerium phosphate based chemical conversion coating on AZ31 magnesium alloy

A two-stage chemical conversion coating procedure was proposed for cerium phosphate based coating on Mg alloys. Initially, a layer of magnesium phosphate was obtained and the cerium phosphate based coatings were achieved by immersing the precoated sample in a cerium nitrate solution prepared in either water or ethanol. The resultant coating obtained from water based nitrate bath consisted of oxides and hydroxides of cerium in addition to cerium phosphate. On the other hand, due to the lack of OH– ions in ethanol based nitrate bath, oxides and hydroxides were suppressed and cerium phosphate rich coating was obtained. Scratch test and scanning vibrating electrode analysis confirmed the self-healing characteristics of the water based coating due to the presence of cerium oxide and hydroxide in the coating. The detailed corrosion studies revealed that the ethanol based coating exhibited superior corrosion resistance in both 1 wt% NaCl as well as in simulated body fluid due to the high stability of cerium phosphate in both test conditions. Both the coatings displayed acceptable cell viability (MG63 cell line) under physiological conditions and hence have the potential for both engineering and biomedical applications.

Infrared spectroscopy analysis determining secondary structure change in albumin by cerium oxide nanoparticles.

Cerium oxide (CeO2) nanoparticles are expected to have applications in the biomedical field because of their antioxidative properties. Inorganic nanoparticles interact with proteins at the nanoparticle surface and change their conformation when administered; however, the principle underlying this interaction is still unclear. This study aimed to investigate the secondary structural changes occurring in bovine serum albumin (BSA) mixed with CeO2 nanoparticles having different surface modifications using Fourier transform infrared spectroscopy. CeO2 nanoparticles (diameter: 240nm) were synthesized from an aqueous cerium (III) nitrate solution using a homogeneous precipitation method. The surfaces of the nanoparticles were modified by the catechol compounds dopamine and 3,4-dihydroxyhydrocinnamic acid (DHCA). In the presence of these CeO2 nanoparticles (0.11-0.43mg/mL), β-sheet formation of BSA (30mg/mL) was promoted especially on the amine-modified (positively charged) nanoparticles. The local concentration of BSA on the surface of the positively charged nanoparticles may have resulted in structural changes due to electrostatic and other interactions with BSA. Further investigations of the interaction mechanism between nanoparticles and proteins are expected to lead to the safe biomedical applications of inorganic nanoparticles.

Surface modification of Al alloy by self-assembly dodecyl phosphate/cerium composite film as relevant to offshore floating photovoltaic power

PurposeThis paper aims to prepare a composite film on LY12 aluminum (Al) alloy by immersing in dodecyl phosphate and cerium nitrate solution by self-assembling methods. The effect of dipping sequence in dodecyl phosphate and cerium nitrate solution on the corrosion resistance of the composite film is studied.Design/methodology/approachThe corrosion resistance of the dodecyl phosphate/cerium composite film is investigated by electrochemical measurement and film composition analysis.FindingsThe dipping sequence in dodecyl phosphate and cerium nitrate solutions has a significant impact on the corrosion resistance of the composite film. It shows best corrosion resistance by first dipping in dodecyl phosphate and then dipping in cerium nitrate solution.Originality/valueThe research shown in this work lays a scientific basis of the film preparation for industrial applications in the future.

Influence of Surface Preparation on Corrosion Resistance Properties of Oxide Layers Formed on Mag-nesium Alloy МА8 by Microarc Oxidation

The article presents the findings on the effect of the substrate pre-impregnation in the ceri-um (III) nitrate and glycerin aqueous solutions on the corrosion-protective properties of the coatings generated on the magnesium alloy MA8 surface by microarc oxidation. The coat-ings were formed in the A-K mode from a silicate-alkaline base electrolyte solution contain-ing compounds with fluoride ions. The corrosion resistance of the magnesium alloy ensured by oxide-ceramic coatings and without them was evaluated by the electrochemical corrosion parameters: corrosion potential, corrosion current density, and polarization resistance. The study has shown that the coatings formed on the surface of the magnesium alloy MA8 provide effective anticorrosive properties of the substrate of MA8 in the solutions containing chloride ions. It was established that the preliminary impregnation of a substrate made of magnesium alloy MA8 in aqueous solutions of cerium (III) nitrate and glycerin affects the mechanism of the resulting corrosion damage.

Synthesis of a stabilized colloidal suspension of PEGylated ceria nanoparticles for biomedical applications

In this study, a simple way to produce pegylated ceria nanoparticles (CNPs) with the use of low-cost and biofriendly starting reagents, such as low molecular Polyethylene Glycol (PEG) and Tris base buffer was attempted. Via this route, a highly stable aqueous suspension of ceria nanocrystals was synthesized. The synthesis of the suspension was performed at room temperature from a cerium nitrate solution. PEG was added as a dispersing agent and aqueous tris(hydroxymethyl)aminomethane (TRIS) solution 20% w/v was poured dropwise in order to achieve ceria precipitation. The CNPs had an average size of 5 nm and were almost monodispersed or formed loose agglomerates with short chainlike patterns of the size of 20 to 25 nm. The CNPs were characterized by TEM, XRD and DLS. PEGylation of the CNPs was confirmed via FT-IR analysis, while their surface chemistry was further investigated by XPS analysis. Finally, the stability of the ceria suspension was characterized with z-potential analysis.

Surface modification of carbon fibres with ammonium cerium nitrate for interfacial shear strength enhancement

An ongoing research focus in the carbon fibre (CF) field has been to identify a practical and more effective surface modification method for improving CF's interfacial adhesion and bonding capacity, which is vital for achieving high performance CF composites. In this research, carbon fibres were modified by using a new and facile treatment process in an aqueous solution of ammonium cerium nitrate (ACN) at a low temperature (20 °C–50 °C). The surface analysis results revealed that the ACN treatment imparted a combined effect of CF surface oxidation and cerium (IV)/(III) immobilisation on the oxidised CF surface through coordination bonds, leading to a significantly increased specific surface area, surface energy and surface reactivity. These new surface characteristics directly contributed to an improved CF interfacial adhesion and load transfer between the modified CFs and an epoxy matrix. The study demonstrated that under specified conditions, the new treatment method resulted in 304% increase in interfacial shear strength (IFSS) and 130% increase in interlaminar shear strength (ILSS) without any significant reduction in CF's mechanical properties. In comparison, the ACN modification yielded CFs with a much higher ILSS than the current industrial processes using electrochemical oxidation and sizing.

Facile Synthesis of Stable Cerium Dioxide Sols in Nonpolar Solvents.

A method is proposed for the preparation of stable sols of nanocrystalline cerium dioxide in nonpolar solvents, based on surface modification of CeO2 nanoparticles obtained by thermal hydrolysis of concentrated aqueous solutions of ammonium cerium(IV) nitrate with residues of 2-ethylhexanoic and octanoic acids. The synthesis was carried out at temperatures below 100 °C and did not require the use of expensive and toxic reagents. An assessment of the radical-scavenging properties of the obtained sols using the superoxide anion-radical neutralization model revealed that they demonstrate notable antioxidant activity. The results obtained indicate the potential of the nanoscale cerium dioxide sols in nonpolar solvents to be used for creating nanobiomaterials possessing antioxidant properties.

Cerium-based conversion films developed on LiAl-layered double hydroxide coatings for corrosion protection of AA7075 aluminum alloys

The paper presents several experimental results regarding the influence of various procedures applied to incorporate Ce species in hydrotalcite–type chemical conver­sion coatings on the overall corrosion performance for AA 7075 aluminum alloy as a metallic substrate. Two routes were envisaged: (i) chemical incorporation of Ce by immersion in cerium nitrate solutions and (ii) electrochemical deposition of hydro­phobic Ce - based layer involving ethanolic solutions of stearic acid and cerium nitrate. The chemical route involving immersion in cerium nitrate solutions led to the incorpo­ration of 2.46 – 6.84 wt.% Ce in the composition of the porous conversion layer. The electrochemical process facilitated the formation of a hydrophobic cerium stearate layer on porous hydrotalcite conversion coating showing water contact angles of about 132o and a higher Ce content incorporated of 6.55 – 9.73 wt.%. The corrosion performance of the Ce-based conversion coatings is also discussed.

Photochromic property of cerium oxide nanoparticles prepared by dialysis of solution of cerium nitrate

CeO2 nanoparticles were obtained by heating 50 mL of 0.1 M Ce(NO3) 3·6H2O solution mixed with 5 mL of 1 M NH3 aq. at 368 K for 24 h. When H2O and ethanol were used as solvents for cerium nitrate hydrate, obtained CeO2 nanoparticles were aggregated. On the other hand, in case that ethylene glycol was used for the solvent, stable sol of CeO2 nanoparticles dispersed in ethylene glycol. Furthermore, dialysis of the sol with H2O successfully enabled the exchange of the dispersion solvent from ethylene glycol to H2O and the average particle size was 23 nm, which was less than those of the other solvents. UV and visible light were irradiated onto the obtained CeO2 powders to examine their photochromic characteristics. The CeO2 nanoparticles obtained with the ethylene glycol solution showed change of absorbance spectra after irradiation of light whose wavelength was less than 600 nm, that is, the visible light irradiation caused photochromism on the CeO2 nanoparticles. According to Ce 3d XPS spectra of the CeO2 nanoparticles, valence state of the Ce ions in the CeO2 nanoparticles was mixed valence state of Ce3+ and Ce4+, which causes inter valence charge transfer absorption. Therefore, the change of the optical absorption spectra, photochromism, occurred with the optical absorption due to the charge transfer absorption between Ce3+ and Ce4+. Furthermore, the photochromic characteristics depended on heat treatment of the CeO2 nanoparticles. Heating the nanoparticles at more than 473 K decreased amount of oxygen vacancies, which affected the mixed valence state of Ce ions so that the photochromism by irradiation of the light within the wavelength range from 400 nm to 600 nm was greatly affected.

Crystal Sizes and Energy Gaps of Cerium Oxide Using Co-Precipitation Method

Co-precipitation was used to prepare cerium oxide nano-particles. The effects of aging temperature and concentration of cobalt ion on the optical property, morphology, and particle size were investigated. The cerium oxide was prepared by adding ammonia solution into a mixed solution of cerium nitrate with cobalt nitrate solutions to obtain a large amount of precipitates and then aged further. Subsequently, the precipitates were kept in an oven for calcination keeping the temperature at 400?C for lasting 24 h. The average size of cerium oxide particles was obtained from the (111) peak in the X-ray diffraction pattern using the Scherrer equation. The crystal sizes obtained were found to be in the range of 11.82 - 13.47 nm. The results showed that the particle size decreased with an increase in the Co ion concentration and decreased with an increase in temperature. The SEM pictures show that the morphology for cerium oxide is granular and/or columnar. It can be seen from UV/Vis absorption spectrum that the maximum absorption peaks were in the range of 334 - 390 nm, depending on the operating conditions. The corresponding energy gaps were observed in the range of 3.18 - 3.71 eV. Subsequently, the Brus equation for the energy gap was discussed. Finally, particle size was correlated with the aging temperature and Co ion concentration.

Ion Exchange Dynamics in Cerium Nitrate Solution Regulated by Remotely Activated Industrial Ion Exchangers.

Many technological solutions contain valuable components as waste and can become an additional source of rare-earth elements to meet the needs of modern production. The development of technologies based on commercially available and cheap sorbents reveals the possibility for rare earth recovery from various solutions. This paper provides research on using a combination of KU-2-8 and AV-17-8 ion exchangers in different molar ratios for cerium ions sorption from its nitrate solution. The mutual activation of the ion exchangers in an aqueous medium provides their transformation into a highly ionized state by the conformational and electrochemical changes in properties during their remote interaction. The ion exchange dynamics of solutions were studied by the methods of electrical conductivity, pH measurements, and atomic emission analysis of the solutions. The research showed that the maximum activation of polymers was revealed within the molar ratio of KU-2-8:AV-17-8 equal to 3:3. In more detail, in comparison to AV-17-8, this interpolymer system showed an increase in the sorption degree by more than 1.5 times after 6 h of interaction. Moreover, compared with KU-2-8, the same interpolymer system showed an increase in the degree of cerium ions sorption by seven times after 24 h of interaction. As a result, the total cerium ions sorption degree after 48 h of sorption by individual KU-2-8 and AV-17-8 was 38% and 44%, respectively, whereas the cerium ions sorption degree by the same interpolymer system in the molar ratio 3:3 became 51%. An increase in the sorption degree of cerium ions by the interpolymer system in comparison with individual ion exchangers can be explained by the achievement of a high ionization degree of ion exchangers being activated in the interpolymer system by the remote interaction effect.

Polymer templated production of highly porous cerium oxide in direct temperature driven transformation of cerium(III) salt

Highly porous (SBET > 160 m2/g) cerium oxide in the form of easy to handle microspheres and particles of micrometric size was produced by the low temperature (300 °C) calcination of Amberlite® XAD7HP microspheres saturated with cerium nitrate solution. The presented synthesis relies on both swelling ability and thermal stability of the polymer template. The final cerium oxide is characterized by SEM, TEM, XRD, XPS and the low temperature N2 sorption method. Additionally, the effect of temperature on the polymer microspheres saturated with cerium nitrate solution was assessed in synthetic air, in conditions resembling the calcination process in the furnace, by means of TG with the simultaneous QMS analysis of the gases evolved during their degradation and also of DSC analysis.

Bi Metal-Organic Framework (Ce/Ni-BTC) as Heterogeneous Catalyst for the Green Synthesis of Substituted Chromeno[4, 3-b]quinolone under Solvent Free Condition.

Novel bi metal organic framework (b-MOF) is synthesized and used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot and solvent-free, four-component reaction of dimedone, aromatic aldehydes, 4-hydroxycoumarin and ammonium acetate at 110°C. b-MOFs can be used as a heterogeneous catalyst in the synthesis of many organic compounds. The active and multi-purpose sites in b-MOFs provide a varied function in their catalytic applications. In this paper, reductive CES method is applied for the synthesis of Ce0.47/Ni0.53-BTC b-MOF. The resulting b-MOF was used as a heterogeneous catalyst for the synthesis of chromeno[4, 3-b]quinolone via one-pot and solvent-free, fourcomponent reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate at 110 °C. Ce0.47/Ni0.53-BTC was synthesized in an electrochemical cell composed of a stainless steel foil with a size of 5cm×5cm centered between two 5cm×5cm sized graphite plates as the anodes by the cathodic current density of 0.2 A/dm2 and placed in a solution of cerium nitrate (0.3 g), nickel nitrate (0.3 g), H3BTC (0.2 g) and NaNO3 (0.1 g) in ethanol (500 mL). Ce0.47/Ni0.53-BTC (10 mg) was added to a mixture of dimedone (1 mmol), aromatic aldehyde (1 mmol), hydroxycoumarin (1 mmol) and ammonium acetate (1.5 mmol) and stirred at 110 °C under solvent-free conditions for 45 min. The reaction evolution was controlled by the TLC (hexane:ethyl acetate, 4:1). Then, boiling ethanol was added to the reaction mixture and stirred at room temperature for 15 min. After the reaction completion, the catalyst was separated by centrifuge. Finally, the reaction mixture was placed in an ice bath, which resulted in a white solid product and recrystallized from ethanol to give the pure product. The b-MOF catalyst showed very good efficiency in the synthesis of the desired compounds and can be easily recovered by centrifuge and reused at least five times without a decrease in catalytic activity. In this report, a novel bi metal-organic framework (Ce0.47/Ni0.53-BTC) is synthesized via the cathodic electrosynthesis method. The synthesized b-MOF is fully characterized by several characterization methods. The catalytic activity of Ce0.47/Ni0.53-BTC is investigated in the synthesis of chromeno[4, 3-b]quinolone derivatives via one-pot four-component reaction of dimedone, aromatic aldehyde, 4-hydroxycoumarin and ammonium acetate. The reaction optimization results showed that the highest isolated yield was obtained when the reaction was performed in solvent-free conditions at 110 °C. The catalyst showed to be highly efficient in the synthesis of the desired compounds and performing the reaction utilizing various starting materials gave the products in good isolated yields, which proves the generality and the scope of the method. The catalyst could easily be recovered by centrifuge and reused at least five times without a decrease in catalytic activity.

Efficient and controlled nano-catalyst solid-oxide fuel cell electrode infiltration with poly-norepinephrine surface modification

There is a growing attention to enhance the performance of solid oxide fuel cell (SOFC) electrodes through the incorporation of nano-catalyst materials within the electrodes’ active sites. In this study, we report a technique for increased efficiency and microstructural control of the nano-catalyst infiltration process through polymerized norepinephrine (pNE) treatment. Nano-CeO2 catalysts were incorporated within both electrodes of commercial anode-supported SOFCs using a single salt solution step after a coating of pNE within the porous microstructure. The optimization of catalyst loading was performed by varying the cerium nitrate solution concentrations between 0.4 and 2.0 M. The ceria nanoparticles are distributed at the near-electrolyte region in both electrodes, but with microstructural variance due to the precursor molarity and solid loading. The time-dependent polarization resistance (Rp) variation was categorized into three zones by the nano-catalyst loading. Zone I referred to the baseline performance for the low-catalyst loading and fluctuating Rp. However, the cells in Zone II and III showed a continuous time-dependent activation as low as 0.275 Ω cm2 at 750 °C. The results suggest that the nano-CeO2 film reduces coarsening and related degradation of the backbone. In addition, the pNE-assisted dip infiltration enhanced infiltrant deposition efficiency by reducing the number of infiltration steps.

MAINTAINING STABLE NANODISPERSED CERIUM OXIDE FOR HEAT TRANSFER PROCESSES

The introduction of heat carriers progressive types causes the productivity of heat exchange systems to increase. One of the challenges in thermal applied applications is the search for heat carriers that will provide revolutionary indicators of thermal conductivity and stability over time, thereby increasing the order of the heat transfer processes efficiency magnitude. The paper describes the creation of stable colloidal solutions using cerium oxide and organic stabilizers to provide better heat exchange performance compared to true solutions. Cerium oxide colloids were obtained by precipitation of the oxide from an aqueous solution of cerium nitrate with an aqueous ammonia solution in the presence of a polymer under vigorous stirring at room temperature. A number of cerium oxide nanosized dispersions, stabilized with polyvinylpyrrolidone, with a particle size of 1–10 nm were obtained. The content of CeO2 in the obtained dispersions was 1.72.10–3, 5.15.10–3, 8.6.10–3, 1.21.10–2, 1.72.10–2 % at a polymer content of 1.10–3 mol/l, the pH of the dispersions was 8–9. Electron microscopic images of the obtained nanodispersions showed a colloidal particles narrow distribution and cerium oxide nanoparticles in size. Colloidal particles are macromolecular tangles of polyvinylpyrrolidone with oxide nanoparticles strung in them. A volume of 20–50 nm organic matrix contains 10–40 particles of 1–10 nm cerium oxide. The particle size distributions of the dispersions established by the photon-correlation spectroscopy method have two areas of maxima for each sample. The first maximum for the dispersions of all investigated concentrations refers to particles with a diameter of 5–6 nm, which, in our opinion, are particles of cerium oxide, both in polymer beads and probably free from the stabilizer. Another maximum, depending on the sample, is observed at 30–70 nm or 100–300 nm, and relates to colloidal particles of PVP with cerium oxide encapsulated particles. The static stability of the cerium oxide obtained nanodispersions with polyvinylpyrolidone for two years under standard conditions is comparable to the true polymer solution. It is proposed by the method of UV spectroscopy to control the reproducibility of the obtaining materials technology. Tests of the thermal conductivity of the obtained 1.72.10–3 % stable cerium oxide nanodispersion were performed at 50 °C relative to distilled water with a thermal conductivity coefficient of 0.65 W/(m·deg). We found an increase in the coefficient for nanodispersions by 4–6 %, which is a significant value for dilute solutions. Ref. 15, Fig. 4 .

Heteroatom Doping By Atomic Layer Deposition for Cathodic Interface Treatment of Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are widely studied due to its high efficiency and fuel flexibility.1,2 In SOFCs, cathodic reaction is known to be the main source of voltage losses due to the sluggishness of oxygen reduction reaction (ORR), which led intense research efforts to develop high-performance cathodes. The main approaches include surface treatments for facilitated surface exchange and surface area enhancement by various wet processes and/or vacuum-based deposition scheme.In this study, we demonstrate the significant impact of atomic layer deposition (ALD) treatment on the cathodic performance and operational durability. ALD has significant advantages in providing atomic scale surface overcoat with an accurate control over thickness and stoichiometry with excellent reproducibility. We use LaNi0.6Fe0.4O3- δ (LNF) as the cathodic backbone and CeO2 (ceria) as a priori infiltrated species. Two different oxides (CeO2 and Y2O3) were used as the atomic-scale coating materials.First, the cell with bare porous LNF cathode showed a high polarization resistance (Rp ) of 1.24 Ω cm2 at 700 °C, but with a single-step ceria infiltration (with 1 M cerium nitrate solution), a significantly lower Rp of 0.27 Ω cm2 was obtained. An ALD-coated ceria right on top of the LNF backbone also resulted in a dramatic decrease in Rp (0.54 Ω cm2) even with a nominal overcoat thickness of 6 Å (6 cycles of cerium and deionized water). A 6-cycle ALD coating of ceria on a ceria-infiltrated LNF showed a further improvement of cathodic performance (Rp = 0.19 Ω cm2). A similar effect was demonstrated with an ALD coating of different material (Y2O3; 3 cycles; nominal thickness = ~3 Å , Rp = 0.20 Ω cm2).More interestingly, a significantly enhanced operational durability was demonstrated by ALD treatments. A sample with a single-step infiltration of ceria showed an increase of Rp by 55% in 150 h at 700 ℃. However, a ceria ALD treatment on a ceria-infiltrated LNF resulted in a milder increase of Rp by 33% in 150 h at 700 ℃. An yttria (Y2O3) ALD overcoat suppressed the degradation even further; only 22% increase in Rp demonstrated in 150 h at 700 ℃.These observations suggest that an atomic scale surface coating by ALD can be an effective approach to enhance not only the kinetics of cathodic reactions but also the operational durability at high temperatures. This is conjectured to be originated from the capability of ALD overcoat in suppressing the sintering of either backbone or infiltrated oxide nanoparticles, and partially from a change in surface chemistry facilitating surface exchange. Electron microscopy and X-ray photoelectron spectroscopy results will be discussed in this respect.This work acknowledges the support from the U.S. National Science Foundation CAREER Award (DMR1753383) and NASA MIRO Program (NNX15AQ01A). SG and MHL also acknowledge NASA ASTAR fellowship (NNX15AW57H). The use of TEM at the Molecular Foundry was supported by the U.S. Department of Energy (Con- tract No. DE-AC02-05CH11231) 1 Z. Shao and S.M. Haile, Nature 431, 170 (2004). 2 H. Kang, S. Grewal, H. Li, and M.H. Lee, 166, 255 (2019).

Nickel–Ceramic Electrodes with High Nickel Content for Solid Electrolyte Electrochemical Devices

Composite powders (66 wt % NiO + 34 wt % Zr0.84Y0.16O1.92 were obtained according to the solution combustion synthesis technique by crystallization of nickel oxide particles on the surface of Zr0.84Y0.16O1.92particles. The samples pressed from powders after sintering and reduction in moist hydrogen had high electrical conductivity, more than 16 × 103 S cm–1 at room temperature. Impedance spectroscopic studies have shown that in a humid atmosphere of Ni – Zr0.84Y0.16O1.92, electrodes formed on the surface of a dense Zr0.84Y0.16O1.92 electrolyte have low electrochemical activity. The impregnation of the electrodes with a solution of cerium nitrate followed by thermolysis made it possible to increase the electrochemical activity of the electrode by two to three orders of magnitude. An analysis of the electrochemical impedance spectra through the calculation of the distribution function of the relaxation time showed that the rate of hydrogen oxidation at the electrodes is limited by surface–adsorption processes. After impregnation, the gas diffusion resistance significantly limits the electrode reaction rate.