Ethanol Steam Reforming on Co/CeO2: The Effect of ZnO Promoter

A series of ZnO promoted Co/CeO₂ catalysts were synthesized and characterized using XRD, TEM, H₂-TPR, CO chemisorption, O₂-TPO, IR-Py, and CO₂-TPD. The effects of ZnO on the catalytic performances of Co/CeO₂ were studied in ethanol steam reforming. It was found that the addition of ZnO facilitated the oxidation of Co⁰ via enhanced oxygen mobility of the CeO₂ support which decreased the activity of Co/CeO₂ in C–C bond cleavage of ethanol. 3 wt% ZnO promoted Co/CeO₂ exhibited minimum CO and CH₄ selectivity and maximum CO₂ selectivity. This resulted from the combined effects of the following factors with increasing ZnO loading: (1) enhanced oxygen mobility of CeO₂ facilitated the oxidation of CH _x and CO to form CO₂; (2) increased ZnO coverage on CeO₂ surface reduced the interaction between CH _x /CO and Co/CeO₂; and (3) suppressed CO adsorption on Co⁰ reduced CO oxidation rate to form CO₂. In addition, the addition of ZnO also modified the surface acidity and basicity of CeO₂, which consequently affected the C₂–C₄ product distributions.     

Active oxygen from CeO2 and its role in catalysed soot oxidation

An advanced TAP reactor is used for the first time to study CeO₂ catalysed soot oxidation using labelled oxygen. In the absence of catalyst oxidation takes place above 500°C and mainly labelled oxidation species (CO and CO₂) were observed. In the presence of catalyst it is shown that the gas-phase labelled oxygen replaces non-labelled lattice oxygen of CeO₂ creating highly active oxygen. This highly active non-labelled oxygen reacts with soot giving CO and CO₂. The creation of such active oxygen species starts from 400°C and it will decrease the soot oxidation temperature. The rate of gas-phase oxygen exchange by the CeO₂ lattice oxygen and the rate of this very active lattice oxygen with soot are much faster than the reaction rate of ¹⁸O₂ reacting with soot directly. Similarly the rate of active oxygen reaction with soot is much faster than the rate of its combination giving gas-phase O₂.     

Adsorption and reaction of CO on CuO–CeO2 catalysts prepared by the combustion method

Temperature-programmed techniques were employed to investigate the interaction of CO with CuO–CeO₂ prepared by the urea-nitrates combustion method. These catalysts exhibited high and stable CO oxidation activity at relatively low reaction temperatures (< 150 °C). The CO adsorption capacity and catalytic activity of the catalysts was analogous to the concentration of easily-reduced copper oxide surface species. TPD and TPSR results can be explained by a dual scheme of CO adsorption: (i) on oxidized sites, which get reduced with simultaneous formation of surface CO₂ and (ii) on reduced sites created by the former interaction. 10–20% of adsorbed CO desorbs molecularly in the absence of gas-phase O₂, but reacts totally towards CO₂ in the presence of gas-phase O₂. Inhibition by CO₂ observed under steady-state CO oxidation conditions is due to CO₂ adsorption as found by CO₂-TPD.     

The effect of CeO2 on Pt/CeO2/CNT catalyst for CO electrooxidation

Pt/CeO₂/CNT catalysts were prepared by adsorbing Pt nanoparticles on the supports of CNTs coated with CeO₂. The electrocatalytic performances in respect to the electrooxidation of chemisorbed CO were tested using potential step and stripping voltammetry methods under variable sweep rate and temperature conditions. At 10 mV s^–1, the CO stripping voltammogram exhibited the peak splitting phenomenon. The oxidation charge and the peak potential of the two voltammetric peaks changed regularly with the number of Pt and CeO₂ neighbours, the sweep rate, and the temperature. We considered that the low potential peak originated from the reaction of CO_ads with hydroxyl groups on CeO₂ adjacent to Pt sites, while the high potential peak came from the reaction of CO_ads with hydroxyl groups produced on pure Pt. Furthermore, the experimental results of the peak potential against the logarithm of the sweep rate and the logarithm of the current maximum time against the step potential were plotted and intersecting lines with different slopes in high and low potential regions in the plot were observed. The lines intersected at lower potentials on the Pt/CeO₂/CNT electrode than on the Pt/CNT electrode, which was attributed to the contribution of hydroxyl groups on CeO₂.     

Sol–gel derived CeO2–Fe2O3 nanoparticles: Synthesis,characterization and solar thermochemical application

Synthesis of CeO₂–Fe₂O₃ nanoparticles via propylene oxide (PO) aided sol–gel method for the production of solar fuels via thermochemical H₂O/CO₂ splitting cycles is reported in this paper. For the synthesis of CeO₂–Fe₂O₃, cerium nitrate hexahydrate and iron nitrate nonahydrate were first dissolved in ethanol and then PO was added to this mixture as a proton scavenger to achieve the gel formation. Synthesized CeO₂–Fe₂O₃ gel was aged, dried, and then calcined in air to achieve the desired phase composition. Influence of different synthesis parameters on physico-chemical properties of sol-gel derived CeO₂–Fe₂O₃ was explored in detail by using various analytical methods such as powder x-ray diffraction (PXRD), BET surface area analyzer (BET), x-ray energy dispersive spectrometer (EDS), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HR–TEM). According to the findings, at all experimental conditions, phase/chemical composition of sol–gel derived CeO₂–Fe₂O₃ was observed to be unaltered. The SSA and pore volume was increased with the upsurge in the amount of PO used during sol–gel synthesis and decreased with the rise in the calcination temperature and dwell time. In contrast, the crystallite size was enlarged with the increase in the calcination temperature and dwell time. The nanoparticle morphology of the sol–gel derived CeO₂–Fe₂O₃ was verified with the help of SEM/TEM analysis. Thermochemical CO production ability of sol–gel derived CeO₂–Fe₂O₃ was investigated by performing thermogravimetric thermal reduction and CO₂ splitting experiments in the temperature range of 1000–1400 °C. Reported results indicate that the sol–gel derived CeO₂–Fe₂O₃ produced higher amounts of O₂ (69.134 μmol/g) and CO (124.013 μmol/g) as compared to previously investigated CeO₂ and CeO₂–Fe₂O₃ in multiple thermochemical cycles. It was also observed that the redox reactivity and thermal stability of sol–gel derived CeO₂–Fe₂O₃ remained unchanged as it produced constant amounts of O₂ and CO in eight successive thermochemical cycles.     

Characterization and Catalytic Properties of Combustion Synthesized Au/CeO2 Catalyst

Ceria-supported Au catalyst has been synthesized by the solution combustion method for the first time and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Au is dispersed as Au⁰ as well as Au³⁺ states on CeO₂ surface of 20-30 nm crystallites. On heating the as-prepared 1% Au/CeO₂ in air, the concentration of Au³⁺ ions on CeO₂ increases at the expense of Au⁰. Catalytic activities for CO and hydrocarbon oxidation and NO reduction over the as-prepared and the heat-treated 1% Au/CeO₂ have been carried out using a temperature-programmed reaction technique in a packed bed tubular reactor. The results are compared with nano-sized Au metal particles dispersed on -Al₂O₂ substrate prepared by the same method. All the reactions over heat-treated Au/CeO₂ occur at lower temperature in comparison with the as-prepared Au/CeO₂ and Au/Al₂O₂. The rate of NO + CO reaction over as-prepared and heat-treated 1% Au/CeO₂ are 28.3 and 54.0 mol g^-1 s^-1 at 250 and 300 °C respectively. Activation energy (E _a) values are 106 and 90 kJ mol^-1 for CO + O₂ reaction respectively over as-prepared and heat-treated 1% Au/CeO₂ respectively.     

Positive Effect of Water Vapor on CO Oxidation at Low Temperature over Pd/CeO2–TiO2 Catalyst

CO oxidation at low temperature over Pd/CeO₂–TiO₂ catalyst was carried out in the feed containing different contents of water vapor (H₂O). A positive effect of H₂O was observed on the catalytic performance of Pd/CeO₂–TiO₂ in CO oxidation at low temperature. The extent of this effect depends on the content of H₂O in the feed; with a H₂O content being 2.5 vol%, the catalyst Pd/CeO₂–TiO₂ exhibits the highest stability (longest life time for CO oxidation at 80 °C). The results of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed reaction (TPReaction) reaction illustrated that H₂O in the feed supplies sufficient OH groups in the presence of O₂, which can react with adsorbed CO on Pd species to produce CO₂. Moreover, H₂O may also enhance the adsorption of CO and suppress the formation of some carbonate species.     

The effect of ceria content on the properties of Pd/CeO2/Al2O3 catalysts for steam reforming of methane

The effect of CeO₂ loading on the surface properties and catalytic behaviors of CeO₂–Al₂O₃-supported Pd catalysts was studied in the process of steam reforming of methane. The catalysts were characterized by S_BET, X-ray diffraction (XRD), temperature-programmed reduction (TPR), UV–vis diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FTIR). The XRD measurements indicated that palladium particles on the surface of fresh and reduced catalysts are well dispersed. TPR experiments revealed a heterogeneous distribution of PdO species over CeO₂–Al₂O₃ supports; one fraction of large particles, reducible at room temperature, another fraction interacting with CeO₂ and Al₂O₃, reducible at higher temperatures of 347 and 423 K, respectively. The PdO species reducible at room temperature showed lower CO adsorption relative to the PdO species reducible at high temperature. In contrast to Pd/Al₂O₃, the FTIR results revealed that CeO₂-containing catalyst with CeO₂ loading ≥12 wt.% show lower ratio (LF/HF) between the intensity of the CO bands in the bridging mode at low frequency (LF) and the linear mode at high frequency (HF). This ratio was constant with increasing the temperature of reduction. The FTIR spectra and the measurement of Pd dispersion suggested that Pd surface becomes partially covered with ceria at all temperature of reduction and with increasing ceria loading in Pd/CeO₂–Al₂O₃ catalysts. Although the PdO/Al₂O₃ showed higher Pd dispersion compared to that of CeO₂-containing catalysts, the addition of ceria resulted in an increase of the turnover rate and specific rate to steam reforming of methane. The CH₄ turnover rate of Pd/CeO₂–Al₂O₃ catalysts with ceria loading ≥12 wt.% was around four orders of magnitude higher compared to that of Pd/Al₂O₃ catalyst. The increase of the activity of the catalysts was attributed to various effects of CeO₂ such as: (i) change of superficial Pd structure with blocking of Pd sites; (ii) the jumping of oxygen (O^*) from ceria to Pd surface, which can decrease the carbon formation on Pd surface. Considering that these effects of CeO₂ are opposite to changes of the reaction rate, the increase of specific reaction rate with enhancing the ceria loading suggests that net effect results in the increase of the accessibility of CH₄ to metal active sites.     

Effect of CeO2 on CO removal over CeO2-modified Ni catalyst in CO-rich syngas

A CeO₂-modified Ni catalyst has been studied as a substitute for Ni bulk catalyst in a CO removal reaction using various characterization methods. CO removal was enhanced slightly and presented at lower reaction temperatures following promotion of CeO₂ on Ni. The enhanced ability to reduce CO was mainly a result of methanation rather than WGS during a CO removal reaction. Based on X-ray diffraction and temperature-programmed reduction, CeO₂ appeared to change the Ni surface properties. Because the bond strength between C and O atoms in CO was weakened by the surface oxygen of CeO₂ on Ni, the CeO₂-promoted Ni catalyst showed higher CO conversion and lower selectivity to WGS than Ni bulk catalyst.     

The Effect of CeO2 on the Hydrodenitrogenation Performance of Bulk Ni2P

Bulk Ni₂P and CeO₂-containing bulk Ni₂P (Ce?CNi₂P(x), where x represents the Ce/Ni atomic ratio) were prepared by a co-precipitation method followed by an in situ H₂ temperature-programmed reduction procedure. The catalysts were characterized by XRD, CO chemisorption, TEM, N₂ adsorption?Cdesorption, XPS and X-ray absorption spectroscopy (XAS). Their hydrodenitrogenation performances were studied using quinoline (Q) and decahydroquinoline as the model compounds. Both the hydrogenation and C?CN bond cleavage activities of Ni₂P were improved by the introduction of CeO₂. CeO₂ mainly accelerated the denitrogenation of Q to propylcyclohexane rather than to propylbenzene. XRD and XPS measurements revealed that the Ce species in Ce?CNi₂P(x) were mainly in the oxide form and both Ce⁴⁺ and Ce³⁺ species coexisted on the surface of the catalysts. Addition of CeO₂ significantly decreased the particle size of Ni₂P, resulting in increased specific surface areas and CO uptakes, possibly due to the strong interaction between the Ce species and Ni₂P. At a Ce/Ni atomic ratio higher than 0.25, segregation of CeO₂ took place. XAS results of the passivated catalysts showed that CeO₂ not only affected the oxidability of Ni₂P but also led to the formation of metallic Ni. The promoting effect of CeO₂ was discussed by considering the electronic interactions between Ce species and Ni₂P as well as the presence of the amorphous Ni and low valence Ce³⁺ species.     

Bimetallic Au-Cu/CeO2 catalyst: Synthesis,structure, and catalytic properties in the CO preferential oxidation

The preparation of bimetallic Au-Cu catalysts via the decomposition of the double complex salt [Au(en)₂]₂[Cu(C₂O₄)₂]₃ · 8H₂O is considered. It is found that this method of preparation allows us to selectively obtain Au_0.4Cu_0.6 solid solution nanoparticles on the surface of a support. The composition of the particles corresponds to the stoichiometry of the double complex salt. The properties of bimetallic Au-Cu/CeO₂ catalyst and monometallic Au/CeO₂ and Cu/CeO₂ catalysts were studied during the preferential oxidation of CO in a mixture containing CO₂ and H₂O. The experiments were performed in a catalytic flow system within a temperature range of 50–250°C with a mixture of the following composition, vol %: CO, 1; O₂, 0.6; H₂O, 10; CO₂, 20; H₂, 60; and the balance, He. The weight hourly space velocity (WHSV) was 276000 cm³/(g h). The bimetallic catalyst made it possible to oxidize a considerably larger amount of CO with higher selectivity with CO₂ and H₂O in the mixture, relative to the monometallic catalysts. The preferential oxidation of carbon monoxide in the presence of hydrogen is a promising method for the deep purification of hydrogen-containing gas mixtures in order to remove carbon monoxide. The purified hydrogen-containing gas can be used to feed portable power units based on low-temperature proton-exchange membrane fuel cells, for the synthesis of ammonia, and for hydrogenation in fine organic synthesis.     

SELECTIVE CARBON MONOXIDE OXIDATION IN H2-RICH GAS STREAM OVER Co3O4/CeO2/ZrO2, Ag/CeO2/ZrO2, AND MnO2/CeO2/ZrO2 CATALYSTS

Activity and selectivity of selective CO oxidation in an H₂-rich gas stream over Co₃O₄/CeO₂/ZrO₂, Ag/CeO₂/ZrO₂, and MnO₂/CeO₂/ZrO₂ catalysts were studied. Effects of the metaloxide types and metaloxide molar ratios were investigated. XRD, SEM, and N₂ physisorption techniques were used to characterize the catalysts. All catalysts showed mesoporous structure. The best activity was obtained from 80/10/10 Co₃O₄/CeO₂/ZrO₂ catalyst, which resulted in 90% CO conversion at 200°C and selectivity greater than 80% at 125°C. Activity of the Co₃O₄/CeO₂/ZrO₂ catalyst increased with increase in Co₃O₄ molar ratio.     

Partial oxidation of ethanol over Pd/CeO2 and Pd/Y2O3 catalysts

The effect of the support nature on the performance of Pd catalysts during partial oxidation of ethanol was studied. H₂, CO₂ and acetaldehyde formation was favored on Pd/CeO₂, whereas CO production was facilitated over Pd/Y₂O₃ catalyst. According to the reaction mechanism, determined by DRIFTS analyses, some reaction pathways are favored depending on the support nature, which can explain the differences observed on products distribution. On Pd/Y₂O₃ catalyst, the production of acetate species was promoted, which explain the higher CO formation, since acetate species can be decomposed to CH₄ and CO at high temperatures. On Pd/CeO₂ catalyst, the acetaldehyde preferentially desorbs and/or decomposes to H₂, CH₄ and CO. The CO formed is further oxidized to CO₂, which seems to be promoted on Pd/CeO₂ catalyst.     

The oxidative coupling of methane and the activation of molecular O2 on CeO2/BaF2

CeO₂/BaF₂ was used as the catalyst for the oxidative coupling of methane (OCM). At 800°C and CH₄O₂=2.71,CH₄ conversion of 34% with C₂ hydrocarbon selectivity of 54.3% was obtained. XRD measurement showed that partial anion (O^2–,F^–) and/or cation (Ce⁴⁺,Ba²⁺) exchange between CeO₂ and BaF₂ lattices occurred. ESR study showed that O^– species existed on degassed catalyst. XPS study revealed that, when BaF₂ was added to CeO₂, the binding energy of Be 3d_5/2 was 2.2 eV lower than that in CeO₂, and the electron-enriched lattice oxygen species was detected. XPS, ESR and Raman study showed that, under O₂ adsorbing conditions, O ₂ ^2– and O _– ² species were detected on CeO₂/BaF₂.This work was supported by the State Key Laboratory for Physical Chemistry of the solid surface and the National Science Foundation of China.     

The Ba-hexaaluminate doped with CeO2 nanoparticles for catalytic combustion of methane

The Ba-hexaaluminate doped with CeO₂ nanoparticles with high surface area for catalytic combustion have been prepared by using the alumina sol as the (NH₄)₂CO₃ coprecipitation precursor and supercritical drying method. The catalysts are composed of the rod-like particles and granular ones. The CeO₂/BaAl₁₂O_19−α catalyst possesses the highest surface area (83.5 m²/g) and the smallest CeO₂ mean crystallite size (24.3 nm). Introduction of transition metal ion into the Al₂O₃ spinel leads to the increase of the catalytic activity. Nevertheless the hexaaluminate cannot be obtained when further increasing the introduction, the components of the main crystalline phases are Al_2.267O₄ and CeO₂. The CeO₂/BaFeMnAl₁₀O_19−α catalyst possesses the lowest complete conversion of methane temperature, probably due to the high surface area and the excellent performance of activating oxygen.     

CeO2‐CrOy/γ‐Al2O3 redox catalyst for the oxidative dehydrogenation of propane to propylene

CeO₂‐CrO_y loaded on γ‐Al₂O₃ was investigated in this work for the oxidative dehydrogenation (ODH) of propane under oxygen‐free conditions. The ODH experiments of propane were conducted in a fluidized bed at 500°C‐600°C under 0.1 Mpa. The prepared catalyst was characterized by N₂ adsorption‐desorption measurements, H₂‐temperature‐programmed reduction, O₂‐temperature‐programmed desorption, NH₃‐temperature‐programmed desorption, x‐ray photoelectron spectroscopy, and x‐ray diffraction. The change in the selectivity of propylene resulted from the thermal cracking of the propane and the competition for lattice oxygen in the catalyst between propylene formation and propane and propylene combustion. Therefore, to achieve higher propylene yield in the industry, the reaction temperature should be 550°C‐575°C for the 17.5Cr‐2Ce/Al catalyst. The results of H₂‐TPR (from 0.2218 mmol/g‐0.3208 mmol/g) revealed that the addition of CeO₂ can enhance the oxygen capacity of CrO_y. Compared with that for 17.5Cr/Al, the conversion can be enhanced from 22.4% to 28.5% and the selectivity of propylene can be improved from 72.2% to 75.9% for the 17.5Cr‐2Ce/Al catalyst. In addition, CeO₂ can inhibit the evolution of lattice oxygen (O^2?) to electrophilic oxygen species (O₂^?), causing the average CO_x (CO and CO₂) selectivity to decrease from 9.64% to 6.31%.     

Multishell hollow CeO2/CuO microbox catalysts for preferential CO oxidation in H2-rich stream

Multishell hollow CuO microbox was synthesized by a template method and the Ce(IV) nitrate solution was impregnated into the hollow cavity of the CuO support. The as-prepared catalysts were characterized by FESEM, TEM, XRD, N₂ physisorption and H₂-TPR. It is found that the alternate CuO and CeO₂ multishell structure reduces the agglomeration of CuO species and improves the dispersion of CeO₂. The special structure ensures even distribution of the two species in the material matrix and the optimum ratio of CeO₂ to CuO provides two-component active sites with high concentration. Thus, the wider full CO conversion window and higher CO₂ selectivity are achieved over the 30CeO₂/CuO microbox catalyst.     

Low-temperature reforming of ethanol over CeO2-supported Ni-Rh bimetallic catalysts for hydrogen production

A new series of Ni-Rh bimetallic catalysts with different Ni and Rh loadings on a high-surface-area CeO₂ was developed for the reforming of bio-ethanol at low-temperature (below 450 °C) to produce H₂-rich gas for on-site or on-board fuel cell applications. Oxidative steam reforming of ethanol (OSRE) over a Ni-Rh/CeO₂ catalyst containing 5 wt% Ni and 1 wt% Rh was found to be more efficient offering about 100% ethanol conversion at 375 °C with high H₂ and CO₂ selectivity and low CO selectivity compared to the steam reforming of ethanol (SRE) reaction which required a higher temperature of about 450 °C to achieve 100% ethanol conversion. The high temperature SRE reaction favors the formation of large amount of CO, which would make the downsteam CO cleanup more complicated for polymer electrolyte membrane fuel cell (PEMFC). The presence of O₂ in the feed gas was found to greatly enhance the conversion of ethanol to produce H₂ and CO₂ as major products. Increase in Ni content above 5 wt% in the catalyst formulation decreased the H₂ selectivity while the selectivity of undesirable CH₄ and acetaldehyde increased. The 1 wt% Rh/CeO₂ catalyst was twice as active as 10 wt% Ni/CO₂ catalyst in terms of ethanol conversion and acetaldehyde selectivity and this indicated that Rh was more effective in C–C bond cleavage than Ni. The reaction was found to proceed through the formation of acetaldehyde intermediate, which subsequently underwent decomposition to produce a mixture of CO and CH₄ or reforming with H₂O and O₂ to produce CO, CO₂ and H₂. The role of Rh is mainly to cleave the C–C and C–H bonds of ethanol to produce H₂ and COx while Ni addition helps converting CO into CO₂ and H₂ by WGS reaction under the conditions employed.     

Role of CeAl11O18 in reinforcing Al2O3/Ti composites by adding CeO2

This work discusses the reinforcement effect of elongated CeAl₁₁O₁₈ phase on multifunctional Al₂O₃/Ti composites by adding CeO₂ to inhibit interfacial reaction and strengthen interface for inducing optimized performances. For this purpose, Al₂O₃/Ti composite with different contents of CeO₂ was fabricated and the microstructure, mechanical and electrical properties were studied. Results indicated that after CeO₂ was added, elongated CeAl₁₁O₁₈ phase was formed within these composites. Owing to inhibited interfacial reaction between Al₂O₃ and Ti, Ti content was increased and compositions of composites were calculated using Rietveld method based on X-ray diffraction patterns. Attributed to the strengthening and toughening effects of CeAl₁₁O₁₈ phase, 2 mol% CeO₂ added composite showed the highest flexural strength and fracture toughness of 576 MPa and 5.15 MPa·m^1/2, which increased by 21% and 20% compared to Al₂O₃/Ti composite without CeO₂ addition. In this case, crack bridging by both Ti and CeAl₁₁O₁₈ particles was the major toughening mechanism and the additional fracture toughness caused by CeAl₁₁O₁₈ toughening effect reached a maximum. The role (crack bridging or particle pull-out mechanism) of CeAl₁₁O₁₈ in toughening Al₂O₃/Ti composites depended on the aspect ratio of these elongated particles, which was directly related to CeO₂ content. Because of the inhibition of interfacial reaction and the increase in Ti content, excellent electrical resistivity of composites after CeO₂ addition was maintained in spite of the formation of insulated CeAl₁₁O₁₈ phase. All samples showed relatively low electrical resistivity of ~10⁻³ Ωcm.     

Effect of La2O3 on Ru/CeO2-La2O3 Catalyst for Ammonia Synthesis

A series of CeO₂-La₂O₃ supported ruthenium catalysts were prepared by co-precipitation method and the as-obtained samples were characterized by N₂ physisorption, X-ray diffraction, CO chemisorption, H₂-TPR, H₂-TPD and XPS. The activity test shows that ammonia concentration of the catalyst with 10% La is 13.9% at 10 MPa, 10,000 h^?1, 450 °C, which is 17% higher than that of Ru/CeO₂. La doping can improve the activity of Ru-ceria catalyst for ammonia synthesis by facilitating the reduction of oxygen which subsists in the cerium oxide surface. In addition, it can be realized that the test of catalyst stability proves the stability performance of Ru/CeO₂-La₂O₃ catalyst within the reaction time of 55 h.