CeO2 Layer Research Articles

Intriguing CeO2–TiO2 hybrid nanostructured photoanode resulting up to 46% efficiency enhancement for dye-sensitized solar cells

The harvesting of electrical energy from sunrays with low cost, clean form and prosperity is an excellent progression. In this context, significant advancement has been made in the solar energy area in terms of cell's design to enhance efficiency. Light scattering may benefit solar cells in this aspect by extending the travelling distance of light within the photoelectrode film. In this work, dextran templating high-surface-area contained CeO2 nanoparticles (~22 nm) were employed to improve the power conversion efficiency (PCE) of a TiO2-based dye-sensitized solar cell (DSSCs). Various physicochemical techniques were investigated to characterize the synthesized CeO2 nanoparticles. Synthesized cubic CeO2 nanoparticles were further explored as an additional layer on the top of the synthesized anatase TiO2 nanocube based film to fabricate CeO2–TiO2 hybrid photoanode, encouraging light scattering in DSSCs. A comparative study was undertaken to understand the effect of the CeO2 layer on the synthesized and standard anatase TiO2. The overall power conversion efficiency obtained for hybrid photoanode-based DSSC is 8.92%, ~46% higher than that of TiO2 nanocubes-based photoanode, with a considerably improved open-circuit voltage of 0.83 V under 1 SUN AM 1.5 . In addition, the PCE enhancement is observed only ~8% using standard TiO2 based photoanode under the same condition. The photovoltaic performance highlights that dextran templating CeO2 nanoparticle exhibits a significant impact as the light scattering layer and heterojunction formation when incorporating on top of the anatase TiO2 nanocube resulting in a hybrid photoanode enhancing the PCE of DSSCs. This alternative approach could facilitate the performance of TiO2 based DSSCs towards improving efficiency.

Comparative studies of metal‐organic decomposed Ga x Ce y O z and CeO 2 based functional MOS capacitor

A comparison between metal-organic decomposed GaxCeyOz and CeO2 passivation layers subjected to post-deposition annealing at 800°C in oxygen ambient was presented. Mitigation in the formation of positively charged oxygen vacancies in GaxCeyOz layer was disclosed by the grazing incidence X-ray diffraction characterization as well as the acquisition of a lower value of positive effective oxide charge (Qeff) than CeO2 layer. In addition, GaxCeyOz layer was able to sustain a higher electric breakdown field and a lower leakage current density due to the attainment of a lower interface trap density extracted using Terman's and high-low methods, slow trap density, and Qeff when compared with CeO2 layer.

A Facile Way for Acquisition of a Nanoporous Pt–C Catalyst for Oxygen Reduction Reaction

AbstractHere, the concept of preferential leaching of cerium oxide on ternary Pt–C–CeO2 compound is demonstrated in order to develop a cost‐effective catalyst for the cathode in proton exchange membrane fuel cells. The Pt–C–CeO2 thin film catalyst is prepared by simultaneous magnetron co‐sputtering of Pt, C, and CeO2. The morphology, structure, and composition of the Pt–C–CeO2 layer are characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. Both half‐cell and single‐cell tests are performed to determine its activity and durability. During an activation electrochemical cycling procedure, CeO2 is leached from the compound, leaving behind a porous Pt–C matrix which exhibits almost 3 times higher electrochemically active surface area in comparison with pure Pt with identical loading before and even after accelerated degradation tests in the half‐cell. When used as the cathode in a single‐cell membrane electrode assembly, decomposed Pt–C–CeO2 also shows greater power density than pure Pt.

Fabrication and properties of the superhydrophobic ceria‐based composite coating on magnesium alloy

AbstractA superhydrophobic ceria‐based composite coating is developed to improve anticorrosion properties of AZ61 magnesium alloy, fabricating via chemical conversion method followed by hydrothermal treatment. The cerium conversion coating has a block structure with microcracks. After the hydrothermal treatment, a dense CeO2 layer, porous CeO2 nanorods, and stearic absorbing layers are grown stepwise on the conversion coating. And the composite coating is hydrophobic or even superhydrophobic and has almost no microcracks. As the hydrothermal reaction time increases, the water contact angle of the composite coating first increases and then decreases, and it reaches the maximum value of 152° after hydrothermal treatment for 4 h. Both the dense CeO2 layer and the superhydrophobic stearic absorbing layer can effectively prevent the electrolyte from contacting the substrate; the corrosion current density of the superhydrophobic composite coating is lower than that of the hydrophilic composite coating and the cerium conversion coating, and has the best corrosion resistance.

Co3S4 Nanoplate Arrays Decorated with Oxygen-Deficient CeO2 Nanoparticles for Supercapacitor Applications

Cobalt sulfide is favorable for supercapacitors, but its application is inhibited by the inherent slow charge transfer kinetics and poor stability in alkaline solution. Herein, zeolitic imidazole framework (ZIF)-derived Co3S4 nanoplate arrays (NPAs) decorated with CeO2 nanoparticles (NPs) grown on Ni foam have been developed. The obtained Co3S4/CeO2-NPAs display a 2D leaf-like nanoplate morphology (average thickness of nearly 230 nm) with a large amount of oxygen vacancies and exhibits remarkably boosted specific capacity/capacitance, i.e., 1155.8 C/g (2408 F/g) at 0.5 A/g with a notable rate capability (76.5% at 10 A/g), compared to Co3S4-NPAs or CeO2 NPs. More importantly, a two-electrode cell comprising the Co3S4/CeO2-NPAs and an activated carbon electrode displays a high energy density of 45.4 Wh/kg (at a power density of 850 W/kg) with decent long-term durability. Furthermore, a red light-emitting diode can be lighted up for 10 min by two charged cells, showing great prospect of Co3S4/CeO2-NPAs. The outstanding electrochemical properties of the Co3S4/CeO2-NPAs are mainly attributed to the 2D nanoplate morphology with much accessible active sites and the introduction of CeO2 NPs. The Co3S4/CeO2-rich interfaces promote electron transfer between Co3S4 and CeO2. The abundant oxygen vacancies adhere to the surface of Co3S4 and can enhance the electronic conductivity and the capture of OH–. In addition, the CeO2 layer can protect the Co3S4-NPAs from corrosion by the KOH electrolyte during the electrochemical process. Therefore, the electrode developed by this work has great potential in electrochemical applications.

Ru/Ce/Ni Metal Foams as Structured Catalysts for the Methanation of CO2

The development of highly conductive structured catalysts with enhanced mass- and heat-transfer features is required for the intensification of the strongly exothermic catalytic hydrogenation of CO2 in which large temperature gradients should be avoided to prevent catalyst deactivation and to control selectivity. Therefore, in this work we set out to investigate the preparation of novel structured catalysts obtained from a commercial open cell Ni foam with high pore density (75 ppi) onto which a CeO2 layer was deposited via electroprecipitation, and, eventually, Ru was added by impregnation. Composite Ru/Ce/Ni foam catalysts, as well as simpler binary Ru/Ni and Ce/Ni catalysts were characterized by SEM-EDX, XRD, cyclic voltammetry, N2 physisorption, H2-temperature programmed reduction (TPR), and their CO2 methanation activity was assessed at atmospheric pressure in a fixed bed flow reactor via temperature programmed tests in the range from 200 to 450 °C. Thin porous CeO2 layers, uniformly deposited on the struts of the Ni foams, produced active catalytic sites for the hydrogenation of CO2 at the interface between the metal and the oxide. The methanation activity was further boosted by the dispersion of Ru within the pores of the CeO2 layer, whereas the direct deposition of Ru on Ni, by either impregnation or pulsed electrodeposition methods, was much less effective.

Study of Ybco Superconductor Coating on Austenitic Stainless Steel By Electrophoretic Deposition Method

1. Introduction Yttrium-based superconductors（YBCO）are expected to be applied to transmission lines. But, it haven’t been widely used, one of the reason is that the substrate and the film formation are too expensive. In order to solve these problems, using stainless steel and an Electrophoretic Deposition method (EPD) method were adopted as a new system. However, it has been reported that using stainless steel has low oxidation resistance in high-temperature. It may cause to decrease the conduction performance as a wire［1］. On the other hand it is generally known that a film produced by EPD has low adhesion［2］. Therefore, we aimed to improve the above two points and create the new superconducting wires. 2. Experimental Producting the YBCO calcined powder is that mixture powder compounded by Y, Ba, and Cu in a 1:2:3 molar ratio was heated up to 880 ℃ during 10 h and then crushed. This process was performed three times in total. The powder was analyzed by X-ray diffraction (XRD).EPD method was used to form a YBCO film or a CeO2 film. A bath containing 10 g/l of YBCO or CeO2 powder and 0.1~0.2 g/l of I2 in 100 ml of acetone was stirred with a magnetic stirrer at a rotation speed of 500 rpm. Stainless steel sheet was used as both the electrodes. 600 V was applied during 30 seconds to produce the YBCO coatings on the cathode.Multilayer coatings were heated up to 950 ℃ during 6 h. After that it was analyzed by electron probe microanalysis (EPMA) to know the film thickness and diffusion behavior of elements for the interface between metal and oxide films. 3. Results and Discussion 3.1 Identification of YBCO calcine powder Calcined powder was analyzed by XRD. Obtained patterns almost match with the standard YBCO. Therefore the powder was identified as YBCO. 3.2 Examination of optimal EPD conditions At the first EPD, the YBCO film had peeled off and it was considered that hydrogen generated from the cathode is cause. This hydrogen is derived from hydrogen ions and it was generated by the catalytic action of enol type acetone and iodine present in the solution. Therefore, iodine concentration or enol type acetone concentration should be reduced than before in order to suppress the hydrogens. In this study, Iodine concentration was reduced from 0.2 g/l to 0.1 g/l. As a result of above conditions, the film didn’t peel off. From this, it was found that the cause of film peeling was generated hydrogen from the cathode, and 0.1 g/l iodine concentration is suitable for EPD when depositing the YBCO film. CeO2 film was also deposited in the same way. Fig.1 shows the electron micrograph of the CeO2 and YBCO layers on stainless steel sheet. Comparing each layers, although the CeO2 layer is densely deposited, but YBCO layer is not densely and many voids can be confirmed. It is considered that the particle size of YBCO is too large. Therefore, the size will be reduced in next time. 3.3 Examination of optimal substrate for main calcination Finally we analyzed interlayer mapping with EPMA between the stainless steel and the YBCO layers after heating up to 950 ℃. At this time, the existence of Fe was confirmed in the YBCO layer . YBCO is consisted of Y, Ba, Cu, and O. Including Fe is only stainless steel in the sample. From this, it is considered that Fe was diffused from the stainless steel layer to the YBCO layer by main calcination. While O was also detected in the stainless steel layer. However it isn’t included O. Therefore, it is considered that the diffusion of O occurred from the YBCO layer to the stainless steel layer, contrary to the diffusion of Fe. From this results, intermediate layer between the stainless steel and the YBCO layer is necessary to prevent the diffusion of Fe and O. References ［1］Tetsuo Kato, Katsushi Kusaka, Journal of the Japan Society of Powder and Powder Metallurgy, 27, 152 (1980)［2］Yoshinori Takayama, Nobuyuki Koura, Yasushi Idemoto, Hiroshi Yanagishita, Takashi Nakane, Masashi kawamura, Naotaka Tanabe, Journal of Ceramic Society of Japan, 107, 437 (1999)［3］Naotaka Minami, Nobuyuki Koura, Journal of the Surface Finishing Society of Japan, 43, 93 (1992)［4］A.K.Jha, N.Khare, Physica C, 469, 811 (2009) Figure 1

In situ observation of catalytic CeO2-nanocube (100) surface with carbon contamination by environmental TEM: a model for soot combustion

An environmental transmission electron microscopy (ETEM) was applied to the in situ observation of carbon contamination removal reaction on (100) crystal plane of catalytic CeO2 nanocubes. The distance between the surface of CeO2 and carbon layer (width) was quantitatively measured versus time at eleven points on three CeO2 nanocubes by observation at an oxygen pressure of 3.0 × 10−1 Pa at 400 °C. The carbon contamination removal rate in the time range of 100 to 460 s was 0.01 ± 0.002 nm s−1, not depending on the place. However, in the later stage, the rates of 0.057 ± 0.01 nm s−1 and 0.24 ± 0.02 nm s−1 were obtained for carbon contamination of different areas in the specimen even if the same crystal plane (100) was in contact with carbon. Carbon on the crystal surface in the inner area of the CeO2 aggregate was eliminated more quickly than contamination in the outer area. The result means that the local-environmental influence in nanoparticle aggregates is taken into account in a heterogeneous catalytic reaction as well as contamination reduction using ETEM.

Effects of cerium addition on the corrosion resistance and biocompatibility of Mg–2Sr–1Zr Alloy

Abstract

Large artificial ferromagnetic dot arrays for the critical current enhancement in superconducting YBa2Cu3O thin films

In order to enhance and/or control critical current density (Jc) in superconducting YBa2Cu3O (YBCO) thin films, different arrays of 3 µm large ferromagnetic (iron) dots with differing configurations and shapes have been deposited on top of high-quality YBCO thin films post-buffered with a layer of CeO2. Some tremendous Jc enhancement of up to nearly 100% have been obtained at high temperatures and low fields. However, the Jc performance is strongly dependent on the array configurations, shape and amount of ferromagnetic iron involved. We show that it is possible to enhance Jc at high or low magnetic field ranges. The results are clearly different to similar non magnetic array structures used to previously manipulate Jc in YBCO films, which proves the magnetic origin of the changes in Jc we observed. The enhancement is likely due to the flux localization and magnetic pinning effects, rather than magnetic shielding alone, which is effective at relatively low fields only. The results also suggest that the observed Jc changes depend on rather minor variations in initial pinning and corresponding Jc levels of the films. At the same time a common trend for all of the various investigated magnetic arrays could not be established due to explained factors.

Negative differential resistance effect and dual bipolar resistive switching properties in a transparent Ce-based devices with opposite forming polarity

In this work, we have fabricated a transparent Ce-based device with aluminum-zinc oxide (AZO) as semiconducting electrode by radio-frequency (RF) sputtering on a transparent ITO/glass substrate at room temperature (RT). The device transmittance in the visible region of 400 to 800 nm was measured to be ~92%. Studies on the AZO/CeO2/ITO/glass device reveal a dual-mode bipolar resistive switching (RS) behavior. Transparent device is found to exhibit both positive-set/negative-reset and negative-set/positive-reset switching modes with very good repetitiveness in cycle-to-cycle (C2C) switching, excellent DC endurance (>103 cycles) and long retention (>104 s). In addition, negative differential resistance (NDR) was noted to arise during positive electroforming and set-processes, and its physical origin was explored. The physics behind the NDR and dual bipolar RS behaviors were explained by the rise and fall in the density of oxygen vacancies in the CeO2 layer, as was analyzed via x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) techniques. We believe that Ce-based transparent device presented in this work can offer robust passivation for electronic devices.

Molybdenum Nitride Electrocatalysts for Hydrogen Evolution More Efficient than Platinum/Carbon: Mo2N/CeO2@Nickel Foam.

To produce hydrogen economically by electrolysis of water, one needs to develop a non-precious-metal catalyst that is as efficient as platinum metal. Here, we prepare such a catalyst by growing a layer of Mo2N over a layer of CeO2 deposited on nickel foam (NF) [hereafter, Mo2N /CeO2@NF] and show that the activity of this self-supported catalyst for hydrogen evolution in 1.0 M KOH is more efficient than that of the Pt/C electrode, achieving a current density of 10 mA/cm2 at a fairly low overpotential of 26 mV. Furthermore, after a long-time electrochemical stability test for 24 h at a fixed current density, the overpotential needed to attain a current density of 10 mA/cm2 is increased only by 6 mV, implying the huge potential of this method to prepare a super HER activity electrode for water splitting.

Nanoscale structural characterization of manganite thin films integrated to silicon correlated with their magnetic and electric properties

A detailed nanoscale structural characterization was performed on high-quality La0.66Sr0.33MnO3 (LSMO) thin films of different thicknesses and deposited by pulsed laser deposition onto buffered Si (100) substrates. A multilayered structure built of Y0.13Zr0.87O2 (YSZ) and CeO2 layers was used as buffer in order to optimize the manganite films growth. The stacking of the different layers, their morpholohy, composition and strains were analysed using different experimental techniques. In-situ characterization of the films, performed with reflection high-energy electron diffraction, revealed their epitaxial growth and smooth surfaces. High-resolution transmission electron microscopy (HR-TEM) images showed sharp interfaces between the constituents lattices and combined with energy-dispersive X-ray analysis allowed us to determine that there was no ion interdifussion across them. The Fourier-Fast-Transform of the HR-TEM images was used to resolve the epitaxy relationship between the layers, resulting in [100] LSMO (001) ‖ [110] CeO2 (001) ‖ [110] YSZ (001) ‖ [110] Si (001). The LSMO thin films were found to be ferromagnetic and metallic at low temperature regardless their thickness. The effect of strains and defects was only detected in films thinner than 15 nm and put in evidence by X-ray diffraction patterns and correlated with magnetic and electrical parameters.

Preparing pure C-axis oriented SrTiO3 film on CeO2 film by introducing a nano-Y0.5Gd0.5Ba2Cu3O7-δ layer

SrTiO3 films were deposited using pulsed laser deposition (PLD) at substrate temperatures ranging from 300 °C to 700 °C on a CeO2 layer and nano-Y0.5Gd0.5Ba2Cu3O7-δ buffered CeO2 layer, respectively. The effect of the substrate temperature and substrate film on the crystallinity, preferred orientation, and surface topography were investigated. On the CeO2 layer, there were two preferred SrTiO3 orientations, (00l) and (110). By introducing a nano-Y0.5Gd0.5Ba2Cu3O7-δ layer, pure c-axis oriented SrTiO3 films were obtained at each substrate temperature. Based on the lattice mismatch, three kinds of growth modes of SrTiO3 grains were proposed that were proved by scanning electron microscopy (SEM).

A million-microchannel multifuel steam reformer for hydrogen production

A functionalized silicon micromonolith of 7 mm in diameter and 210 μm-thick was evaluated for the production of hydrogen from the steam reforming (SR) of various fuels, containing different functional groups, such as ethanol, acetic acid, 2-propanol, acetone, and 2-methoxyethanol. The micromonolith consisted of 2 million regular channels of 3.3 μm in diameter, which were coated with a 100-nm RhPd/CeO2 catalytic layer. The catalytic activity was tested at temperatures between 823 and 1023 K, using overstoichiometric steam-to-carbon ratios and operating at contact times between 0.005 and 0.009 s. The best performance was obtained for the 2-methoxyethanol SR tests, where 53% H2 selectivity was recorded. A remarkable hydrogen production normalized by reactor volume of 110 LNH2·mL2-methoxyethanol, liquid−1 cm−3Reactor was recorded, leading to comparable H2 yields to those obtained with a conventional monolith coated with the same RhPd/CeO2 catalyst, owing to the large contact area. After more than 80 h under reaction conditions, the micromonolith was characterized by SEM and TEM. SEM analyses showed that no channels were blocked due to carbon deposition nor detached CeO2 layers were found. These results demonstrate the feasibility of using catalytic Si micromonoliths as microreformers to generate hydrogen from the SR of different fuels to power portable fuel cells.

Reciprocal Space Map Measurement of Ceramics Thin Films for Unequal Lattice Change at High Temperature

Ceria and zirconia are very important for their thermal, mechanical, and chemical stability, and their thin films have attracted much attention for applications such as buffer layers for growing electric devices, thermal-shield or optical coatings, corrosion-resistant coatings, oxygen sensors and ionic conductors for fuel cells. To investigate and control the thin film orientation and phase is important to improve those performances. In this study, the reciprocal space maps of CeO2/YSZ/Si(001) were obtained at high temperature by adding a heater to the sample stage. CeO2 and YSZ thin films were epitaxially grown samples. By measuring lattice constants at high temperature, it was conducted that axes of CeO2 and YSZ thin films parallel to the substrate surface showed smaller thermal coefficients than bulk reference and axes perpendicular to the surface showed larger thermal coefficients due to the underlayer and Si substrate. The distortion rate of the lattice of each film was small around at the film deposition temperature. And it could be controled the lattice parameter at the film surface by the film thickness. Therefore, when another thin film, for example, SrTiO3 is deposited on the CeO2 layer, the lattice change of CeO2 with increasing temperature may differ from that before depositing the top layer.

Spatially resolved NMR spectroscopy of heterogeneous gas phase hydrogenation of 1,3-butadiene with parahydrogen

Glass tube reactors with Pd, Pt, Rh or Ir nanoparticles dispersed on a thin layer of TiO2, CeO2, SiO2 or Al2O3 provided mechanistic insight into the hydrogenation of 1,3-butadiene using parahydrogen.

Investigation of thermal shock resistant in three kinds thermal barrier cerium oxide coating (CeO2) with MCrAlY intermediate layer

The study aimed to compare the thermal shock behavior of three types of thermal barrier coatings (TBC) containing two and five layers. The substrate of the coatings, like as industrial samples, was selected from IN738LC superalloy. The first type was a two-layer TBC produced from CoNiCrAlY and CeO2 as a bond and top layers, respectively. The second type was a common five-layer TBC with a bond layer of CoNiCrAlY, a top layer of CeO2 and three intermediate layers composed of three mixing kinds of CeO2 + CoNiCrAlY. The third type was composed of a top layer of nano-structured CeO2, and the other four down layers were similar to the second type. To thermal shock test, the samples were kept at 1100 °C for 5 min and quenched in 20–25 °C water. The test was continued until all the samples were destructed. The sample was considered destructed when 20% of the coating surface was detached. To evaluate the microstructure of the samples, SEM and FESEM were used. Finally, the thermal shock lifetime of the five-layer TBC was 1.6 times higher than the two-layer TBC, and by making the top nano-structured layer in five-layer TBC, the lifetime was enhanced approximately 14%.

A novel CeO2/MgAl2O4 composite coating for the protection of AZ31 magnesium alloys

A novel CeO2/MgAl2O4 composite coating, fabricated via a cathode plasma electrolytic deposition (CPED) technique followed by hydrothermal synthesis, was developed in this study to explore its potential application as corrosion protection for AZ31 magnesium alloys. The microstructure observed through scanning electron microscopy indicated that reducing the duty cycle of the power source within a reasonable range during the CPED process was beneficial to form a uniform and dense MgAl2O4 coating, which served as an ideal adhesive matrix for a uniform CeO2 coating as the outermost layer. The results of electrochemical impedance spectra and neutral salt spray tests showed that the decoration of the CeO2 layer significantly improved the corrosion resistance of the CeO2/MgAl2O4 composite coating compared to the single MgAl2O4 coating and bare substrate. Cross-cut tests revealed that the adhesion of the MgAl2O4 coating and the CeO2/MgAl2O4 composite coating were both excellent due to the strong binding between the MgAl2O4 coating and the substrate.

Infiltration of Rare Earth Oxide into NiO-YSZ Anode Substrate for the High Performance Micro-Tubular SOFC Using LSGM Electrolyte Film

Tubular type solid oxide fuel cells are considered as the advantage of short gas sealing line and higher thermal stability. A micro-tubular type solid oxide cell was prepared by using a tubular type NiO-Y2O3 stabilized ZrO2 (NiO-YSZ) fuel electrode substrate and La0.9Sr0.1Ga0.8Mg0.2O3(LSGM) electrolyte film which was prepared by dip-coating and co-sintering method. Since IR loss and overpotential was still larger than those expected, the effects of insertion Ni-based fuel electrode functional layer on NiO-YSZ tubular substrate and rare earth oxide infiltration into NiO-YSZ tube was further studied. The result indicated that the cell using Ni-Fe functional layer and infiltration of CeO2 into the substrate shows a higher maximum power density. The electrolysis performance of the prepared tubular cell under reversible operation was also studied. The reasonably large current density was also realized in electrolysis mode on the optimized cell.