Search Results (13)

The activity of Co- and Ni-containing ceria-based catalysts for water–gas shift (WGS) reaction were examined in this work. The catalysts were prepared by the urea co-precipitation method. Sm and Pr dopant (5 wt.%) was used as a structural stabilizer of CeO₂, while Co or Ni was used in a small amount (1 wt.%). H₂-TPR experiments indicate that both Sm and Pr addition increased the reducibility of CeO₂. Among the studies’ catalysts, 1%Ni/Ce5%SmO exhibited the highest WGS activity. In addition, WGS rate was measured in the temperature range of 200–400 °C for Ni supported on CeO₂, Ce5%SmO, and Ce5%PrO. The activation energy of the reaction over 1%Ni/Ce5%SmO was 57 kJ/mol, while it was 61 and 66 kJ/mol, respectively, over 1%Ni/Ce5%PrO and 1%Ni/CeO₂ catalysts. A WGS reaction mechanism, CO adsorbed on the metal cluster is oxidized by oxygen supplied from the CeO₂ support at the metal–ceria interface. This oxygen is then re-oxidized by H₂O, which caps the oxygen vacancy on the ceria surface, and thereby oxygen vacancies serve as active sites for the WGS reaction. Raman experiments indicate that the presence of Sm in 1%Ni/Ce5%SmO catalyst promoted the formation of oxygen vacancies, leading to enhanced WGS performance. Full article

This study investigates the effects of samarium (Sm) promotion on the catalytic activity of 5 weight percent Ni catalysts for partial oxidation of methane (POM)-based hydrogen production supported on a Si-Al mixed oxide (10SiO₂+90Al₂O₃) system. Several 5% Ni-based catalysts supported on silica–alumina was used to test the POM at 600 °C. Sm additions ranged from 0 to 2 wt.%. Impregnation was used to create these catalysts, which were then calcined at 500 °C and examined using BET, H₂-TPR, XRD, FTIR, TEM, Raman spectroscopy, and TGA methods. Methane conversion (57.85%) and hydrogen yield (56.89%) were greatly increased with an ideal Sm loading of 1 wt.%, indicating increased catalytic activity and stability. According to catalytic tests, 1 wt.% Sm produced high CH₄ conversion and H₂ production, as well as enhanced stability and resistance to carbon deposition. Nitrogen physisorption demonstrated a progressive decrease in pore volume and surface area with the addition of Sm, while maintaining mesoporosity. At moderate Sm loadings, H₂-TPR and XRD analyses showed changes in crystallinity and increased NiO reducibility. Sm incorporation into the support and its impact on the ordering of carbon species were indicated by FTIR and Raman spectra. The optimal conditions to maximize H₂ yield were successfully identified through optimization of the best catalyst, and there was good agreement between the theoretical predictions (87.563%) and actual results (88.39%). This displays how successfully the optimization approach achieves the intended outcome. Overall, this study demonstrates that the performance and durability of Ni-based catalysts for generating syngas through POM are greatly enhanced by the addition of a moderate amount of Sm, particularly 1 wt.%. Full article

Hydrogen is a priority energy vector for energy transition. Its production from renewable feedstock like ethanol is suitable for many applications. The performance of a Ni catalyst supported on samaria-doped ceria in the production of hydrogen by the reforming of ethanol is investigated, adding Sm₂O₃ to CeO₂ in molar ratios of 1:9, 2:8, and 3:7. A CeO₂-supported Ni catalyst was also evaluated for comparative purposes. The supports were prepared by the coprecipitation method and Ni was incorporated by incipient wetness impregnation to obtain catalysts with a Ni/(Ce+Sm) molar ratio of 4/6. The catalysts were characterized by a nitrogen adsorption isotherm, X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Increasing Sm₂O₃ content leads to a more homogeneous distribution of Sm₂O₃ and Ni particles on the support, and higher oxygen mobility, favoring the catalytic properties. The catalyst with a Sm₂O₃/CeO₂ molar ratio of 3/7 showed outstanding behavior, with an average ethanol conversion of 97%, hydrogen yield of 68%, and great stability. The results suggest that the main route for hydrogen production is ethanol dehydrogenation, followed by steam reforming of acetaldehyde, and acetone and ethylene formation are promoted by increasing Sm content in the outer surface of the catalyst. Full article

The x%Ni/Sm₂O₃-MnO (x = 0, 10, 15, 20) catalysts derived from SmMn₂O₅ mullite were prepared by solution combustion and impregnation method; auto-thermal reforming (ATR) of acetic acid (HAc) for hydrogen production was used to explore the metal-support effect induced by Ni loadings on the catalytic reforming activity and product distribution. The 15%Ni/Sm₂O₃-MnO catalyst exhibited optimal catalytic performance, which can be due to the appropriate Ni loading inducing a strong metal–support interaction to form a stable Ni/Sm₂O₃-MnO active center, while side reactions, such as methanation and ketonization, were well suppressed. According to characterizations, Sm₂O₃-MnO mixed oxides derived from SmMn₂O₅ mullite were formed with oxygen vacancies; nevertheless, loading of Ni metal further promoted the formation of oxygen vacancies, thus enhancing adsorption and activation of oxygen-containing intermediate species and resulting in higher reactivity with HAc conversion near 100% and hydrogen yield at 2.62 mol-H₂/mol-HAc. Full article

Large-scale hydrogen production by the steam reforming of long-chain hydrocarbon fuel is highly desirable for fuel-cell application. In this work, LaNiO₃ perovskite materials doped with different rare earth elements (Ce, Pr, Tb and Sm) were prepared by a sol-gel method, and the derivatives supported Ni-based catalysts which were successfully synthesized by hydrogen reduction. The physicochemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction, high-resolution transmission electron microscopy, N₂ adsorption–desorption isotherms, H₂ temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic performance of the as-prepared catalysts for hydrogen production was investigated via the steam reforming of n-dodecane. The results showed that the catalyst forms perovskite oxides after calcination with abundant mesopores and macropores. After reduction, Ni particles were uniformly distributed on perovskite derivatives, and can effectively reduce the particles’ sizes by doping with rare earth elements (Ce, Pr, Tb and Sm). Compared with the un-doped catalyst, the activity and hydrogen-production rate of the catalysts are greatly improved with rare earth element (Ce, Pr, Tb and Sm)-doped catalysts, as well as the anti-carbon deposition performance. This is due to the strong interaction between the uniformly distributed Ni particles and the support, as well as the abundant oxygen defects on the catalyst surface. Full article

The aim of this work is the development of a structured catalyst for the dry reforming of biogas to be used as a pre–reformer in the indirect internal reforming configuration (IIR) of solid oxide fuel cells (SOFCs). The structured catalyst is based on NiCrAl foams coated with ruthenium (nominal loading 3.0 wt%) supported on a CaZr_0.85Sm_0.15O_3−δ (CZS) perovskite oxide. The powder is produced by solution combustion synthesis and deposited on metallic foams by the wash–coating method. Catalytic tests for the dry reforming of methane (DRM) reaction are carried out at 850 °C, 700 °C and 550 °C for an overall 50 h with CH₄/CO₂ = 1 and p = 1.3 bar at different gas hourly space velocities (GHSVs). The final goal is a proof–of–concept: a laboratory validation of an IIR–SOFC fed by biogas. The carbon amount on spent structured catalysts is evaluated by thermogravimetric analysis and microstructural/compositional investigation. Full article

In this study, the formation of thin-film barrier coatings based on a highly conductive Bi_1.60Er_0.4O₃ (EDB) solid electrolyte on supporting Ce_0.8Sm_0.2O_1.9 (SDC) electrolyte substrates was implemented for the first time using electrophoretic deposition (EPD). The electrokinetic properties of EDB-based suspensions in a non-aqueous dispersion medium of isopropanol modified with small additions of polyethyleneimine (PEI, 0.26 g/L) and acetylacetone (0.15 g/L), as well as in a mixed isopropanol/acetylacetone (70/30 vol.%) medium, were studied. The dependences of the thickness of the EDB coatings on voltage and deposition time were obtained using deposition on a model Ni foil electrode. Preliminary synthesis of a conductive polypyrrole (PPy) polymer film was used to create surface conductivity on non-conductive SDC substrates. The efficiency of using a modified dispersion medium based on isopropanol to obtain a continuous EDB coating 12 μm thick, sintered at a temperature of 850 °C for 5 h, is shown. The microstructure and morphology of the surface of the EDB coating were studied. A Pt/SDC/EDB/Pt cell was used to characterize the coating’s conductivity. The EPD method is shown to be promising for the formation of barrier coatings based on doped bismuth oxide. The developed method can be used for creating cathode barrier layers in SOFC technology. Full article

Water–gas shift (WGS) reaction was performed over 5% Ni/CeO₂, 5% Ni/Ce-5% Sm-O, 5% Ni/Ce-5% Gd-O, 1% Re 4% Ni/Ce-5% Sm-O and 1% Re 4% Ni/Ce-5% Gd-O catalysts to reduce CO concentration and produce extra hydrogen. CeO₂ and M-doped ceria (M = Sm and Gd) were prepared using a combustion method, and then nickel and rhenium were added onto the mixed oxide supports using an impregnation method. The influence of rhenium, samarium and gadolinium on the structural and redox properties of materials that have an effect on their water–gas shift activities was investigated. It was found that the addition of samarium and gadolinium into Ni/CeO₂ enhances the surface area, reduces the crystallite size of CeO₂, increases oxygen vacancy concentration and improves Ni dispersion on the CeO₂ surface. Moreover, the addition of rhenium leads to an increase in the WGS activity of Ni/CeMO (M = Sm and Gd) catalysts. The results indicate that 1% Re 4% Ni/Ce-5% Sm-O presents the greatest WGS activity, with the maximum of 97% carbon monoxide conversion at 350 °C. An increase in the dispersion and surface area of metallic nickel in this catalyst results in the facilitation of the reactant CO adsorption. The result of X-ray absorption near-edge structure (XANES) analysis suggests that Sm and Re in 1% Re 4% Ni/Ce-5% Sm-O catalyst donate some electrons to CeO₂, resulting in a decrease in the oxidation state of cerium. The occurrence of more Ce³⁺ at the CeO₂ surface leads to higher oxygen vacancy, which alerts the redox process at the surface, thereby increasing the efficiency of the WGS reaction. Full article

Samarium oxide (Sm₂O₃) is a versatile surface for CO₂ and H₂ interaction and conversion. Samarium oxide-supported Ni, samarium oxide-supported Co-Ni, and samarium oxide-supported Ru-Ni catalysts were tested for CO₂ methanation and were characterized by X-ray diffraction, nitrogen physisorption, infrared spectroscopy, H₂-temperature programmed reduction, and X-ray photoelectron spectroscopy. Limited H₂ dissociation and widely available surface carbonate and formate species over 20 wt.% Ni, dispersed over Sm₂O₃, resulted in ~98% CH₄ selectivity. The low selectivity for CO could be due to the reforming reaction between CH₄ (methanation product) and CO₂. Co-impregnation of cobalt with nickel over Sm₂O₃ had high surface adsorbed oxygen and higher CO selectivity. On the other hand, co-impregnation of ruthenium and nickel over Sm₂O₃ led to more than one catalytic active site, carbonate species, lack of formate species, and 94% CH₄ selectivity. It indicated the following route of CH₄ synthesis over Ru-Ni/Sm₂O₃; carbonate → unstable formate → CO → CH₄. Full article

Catalysts based on perovskite—fluorite nanocomposites with supported nickel 5%Ni/[Pr_0.15Sm_0.15Ce_0.35Zr_0.35O₂ + LaMn_0.9Ru_0.1O₃] were synthesized by three different methods. Structural and surface features of as-prepared samples were elucidated by N₂ adsorption, XRD, HR TEM with EDX; reducibility and reactivity were estimated by H₂-TPR, and catalytic properties were studied in ethanol steam reforming in the 500–700 °C temperature range. The best catalytic activity without coke accumulation was demonstrated for the 5%Ni/[Pr_0.15Sm_0.15Ce_0.35Zr_0.35O₂+ LaMn_0.9Ru_0.1O₃] catalyst with nanocomposite support obtained by a simple sequential polymeric preparation method. Highly dispersed particles of metallic nickel strongly fixed on the support after the reaction were shown by the HR-TEM and H₂ –TPR data. The catalyst provides stable full conversion of ethanol and hydrogen yield above 60% at 600 °C for at least 6 h. Full article

In this work, a technology was developed for the formation of BaCe_0.8Sm_0.2O₃+1 wt% CuO (BCS-CuO)/Ce_0.8Sm_0.2O_1.9 (SDC) thin-film electrolyte membranes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) on porous NiO-BCS-CuO anode substrates using direct electrophoretic deposition (EPD). The effect of increasing the zeta potential when modifying the base suspension of a micro-sized SDC-gn powder (glycine–nitrate method) with the addition of a SDC-lec nanopowder (laser evaporation–condensation) was investigated. Dependences of the current strength on the deposition time and the deposited weight on the EPD voltage were obtained, and evolution of the morphology of the coatings during the modification of the SDC-gn suspension and a suspension of BCS-CuO powder was studied. The compatibility of the shrinkage kinetics of the SDC, the BCS-CuO electrolyte coatings and the NiO-BCS-CuO anode substrate was studied during the high-temperature sintering. Dense BCS-CuO/SDC films of different thicknesses were obtained for the first time on porous NiO-BCS-CuO anode substrates and comprehensive microstructural and electrochemical studies were carried out. The developed technology can be applied to the formation of anode-supported SOFCs with thin-film electrolyte membranes. Full article

The paper presents the results of an investigation into thin single- and triple-layer ZrO₂-Sc₂O₃-based electrolytes prepared using the tape-casting technique in combination with promising electrodes based on La₂NiO_4+δ and Ni-Ce_0.8Sm_0.2O_2-δ materials. It is shown that pressing and joint sintering of single electrolyte layers allows multilayer structures to be obtained that are free of defects at the layer interface. Electrical conductivity measurements of a triple-layer electrolyte carried out in longitudinal and transverse directions with both direct and alternating current showed resistance of the interface between the layers on the total resistance of the electrolyte to be minimal. Long-term tests have shown that the greatest degradation in resistance over time occurs in the case of an electrolyte with a tetragonal structure. Symmetrical electrochemical cells with electrodes fabricated using a screen-printing method were examined by means of electrochemical impedance spectroscopy. The polarization resistance of the electrodes was 0.45 and 0.16 Ohm∙cm² at 800 °C for the fuel and oxygen electrodes, respectively. The distribution of relaxation times method was applied for impedance data analysis. During tests of a single solid oxide fuel cell comprising a supporting triple-layer electrolyte having a thickness of 300 microns, a power density of about 160 mW/cm² at 850 °C was obtained using wet hydrogen as fuel and air as an oxidizing gas. Full article

In the present study, Ni/Ce-Sm-xCu (x = 5, 7, 10 at.%) catalysts were prepared using microwave radiation coupled with sol-gel and followed by wetness impregnation method for the Ni incorporation. Highly dispersed nanocrystallites of CuO and NiO on the Ce-Sm-Cu support were found. Increase of Cu content seems to facilitate the reducibility of the catalyst according to the H₂ temperature-programmed reduction (H₂-TPR). All the catalysts had a variety of weak, medium and strong acid/basic sites that regulate the reaction products. All the catalysts had very high X_C3H8O3 for the entire temperature (400–750 °C) range; from ≈84% at 400 °C to ≈94% at 750 °C. Ni/Ce-Sm-10Cu catalyst showed the lowest X_C3H8O3-gas implying the Cu content has a detrimental effect on performance, especially between 450–650 °C. In terms of H₂ selectivity (S_H2) and H₂ yield (Y_H2), both appeared to vary in the following order: Ni/Ce-Sm-10Cu > Ni/Ce-Sm-7Cu > Ni/Ce-Sm-5Cu, demonstrating the high impact of Cu content. Following stability tests, all the catalysts accumulated high amounts of carbon, following the order Ni/Ce-Sm-5Cu < Ni/Ce-Sm-7Cu < Ni/Ce-Sm-10Cu (52, 65 and 79 wt.%, respectively) based on the thermogravimetric analysis (TGA) studies. Raman studies showed that the incorporation of Cu in the support matrix controls the extent of carbon graphitization deposited during the reaction at hand. Full article