Ceria Support Research Articles

Synthesis of Supported Nickel Nanoparticles via a Nonthermal Plasma Approach and Its Application in CO2 Reforming of Methane

A microwave plasma treatment was applied to obtain not only a desired strong metal–support interaction but also well-dispersed nickel nanoparticles supported on ceria. The catalytic properties of these supported nanoparticles were tested in CO2 reforming of methane. The plasma-treated Ni/CeO2 catalysts showed enhanced turnover frequencies (TOFs), normalized by Ni on the surface, as compared with the thermally calcined samples. The Ni/CeO2 treated under plasma with low Ni loading gave an enhanced TOF of 9.5 s–1 (700 °C, 50% CH4 and 50% CO2, and 1 atm) as compared with the thermally calcined catalyst (8.7 s–1). Increasing the Ni loading on the plasma-treated Ni/CeO2 catalysts gave an improved TOF (10.4 s–1) which was stable with time, while the TOF was observed to drop by a factor of 2 relative to the optimal TOF on the thermally calcined catalyst after 5 h. For the plasma-treated samples, concurrent treatment of both the uncalcined ceria support and the loaded metal precursor generated strong metal–support...

O2 Adsorption and Oxidative Activity on Gold-Based Catalysts with and without a Ceria Support

Understanding the O2 adsorption and oxidative activity on gold-based catalysts is of great significance for gold catalysis. According to the adsorption behaviors of O2 on Au(111)+, 3Au/Au(111)+, Au19+, and Au9/CeO2(111), the electronic nature of why O2 weakly interacts with free positively charged Au substrate while it strongly interacts with Au cluster supported on ceria is well-explained herein. The ceria support serves as an electronic repository, where it gains and stores electrons from the supported metal cluster and releases them when the metal cluster interacts with molecular O2. The possible oxygen species on gold-based catalysts have been systematically confirmed for the first time. On the Au9/CeO2 modeling catalyst, a peroxide species forms when O2 locates at the hollow site of Au9, while a superoxide forms for O2 at the top site of a Ce atom. It is very interesting to find that Ce3+ ion distributions in Aun/CeO2 catalysts have diverse possibilities. The superoxide close to Au9 has the highest oxidative activity. The interface between the Au cluster and ceria surface is the active site for Aun/CeO2 catalysts. The present work sheds light on understanding the oxidative mechanism of metal/support catalysts, as well as the development of new catalysts with high performance at relatively low temperature.

Selective hydrogenation of cinnamaldehyde in supercritical CO2 over Pt/SiO2 and Pt/HS-CeO2: An insight about the role of carbonyl interaction with supercritical CO2 or with ceria support sites in cinamyl alcohol selectivity

The catalytic hydrogenation of cinnamaldehyde employing H2 as the reductant was carried out under supercritical (sc) CO2, propane and other CO2 dense mixture, employing Pt supported on silica and high surface (HS) ceria. The phase behavior of the mixtures was found to be in good agreement with the predictions obtained from the MHV2 (modified Huron-Vidal second-order) model. In order to study the influence of scCO2 on the selectivity, the reaction was also conducted in dense propane and near-critical CO2–isopropanol mixtures. These results were compared with those corresponding to classical gas–liquid conditions with isopropanol as solvent and low H2 pressure. In scCO2, the selectivity to cinnamyl alcohol over Pt/SiO2 was 91%, quite higher than under classical conditions (38%). Such an enhancement is originated by the interaction of the CO with scCO2. For Pt/HS-CeO2 the selectivity under supercritical conditions was slightly lower (80%) than the one corresponding to Pt/SiO2 but quite higher than the one corresponding to gas–liquid conditions (54%). The interaction of the carbonyl group with ceria support predominates in this case, thus, the beneficial effect of scCO2 is not observed in the same magnitude as in the case of Pt/SiO2. A catalytic scenario is drawn for each catalyst in order to explain the different selectivity patterns.

Role of CO2 on CO preferential oxidation over CuO/CeO2 catalyst

The inhibiting effect of the presence of CO2 (15vol.%) in the reaction mixture of CO-PROX reaction on the performance of CuO/CeO2 catalysts has been investigated; CO2 depresses CO oxidation up to 160°C, its effect being negligible at higher temperatures. The CO2 coverage of both ceria support and catalysts has been quantitatively determined by CO2 TPD experiments and the distribution of adsorbing sites has been modeled. Two sites for CeO2 (one modified by the strong interaction between Ce and Cu when copper is added) and an additional site associated to less interacting copper for CuO/CeO2 catalysts have been identified by the mathematical model. Although ceria gives a large contribution to CO2 adsorption, the sites present in larger amount rapidly desorb CO2 in the typical temperature range of CO-PROX reaction (80–150°C), especially when copper modification induces a decrease of desorption activation energy, thus suggesting that these centres are involved in CO oxidation. Adsorption sites attributed to copper less interacting with the support still keep a fraction of adsorbed CO2 in this temperature range and the higher selectivity suggested that they can be mainly related to the H2 oxidation activity.

Tuning the shape of ceria nanomaterials for catalytic applications

The design and fabrication of catalytic materials is a key issue in heterogeneous catalysis to achieve desired performance. Traditionally, the main theme is to reduce the size of the catalyst particles as small as possible for increasing the number of active sites. In recent years, the rapid advancement in materials science has enabled us to fabricate catalyst particles with tunable shape at nanometer level. Through morphology control of nanoparticles by exposing highly reactive crystal planes, their catalytic properties can be drastically enhanced. Therefore, both size modulation and shape control of catalyst nanoparticles can be achieved independently or synergistically to optimize their catalytic behavior. We highlight, in this review, the recent progress in shape control of CeO 2 materials that are widely used as crucial components or structural and electronic promoters in heterogeneous catalysts. We first summarize the major synthetic strategies and characteristics of shape-controlled CeO 2 nanomaterials. We then survey morphology-dependent nanocatalysis of CeO 2 and Au-CeO 2 catalysts. We understand now that the enhanced catalytic property of the Au-CeO 2 system is closely related to the unique interaction between the gold nanoparticles and the ceria support; such an interaction originates from the particular shape of ceria, especially the exposed facets. Finally, we present our understanding of the morphology-dependent nanocatalysis and provide our perspectives on their future potential and development. The fundamental understanding of the nature of the intrinsic active sites of the shape-tunable ceria nanostructures, enclosed by reactive crystal planes/facets with unique properties, is expected to provide highly efficient nanocatalysts for practical applications. 催化剂的设计、合成和结构调控是获得优异性能的关键. 传统的策略主要是尽量减小催化剂颗粒尺寸以增加活性中心的数目, 即尺寸效应. 近年来, 材料科学的快速发展使得在纳米尺度上调变催化剂的尺寸和形貌成为可能, 特别是通过形貌调控可暴露更多的高活性晶面, 大幅度提高催化性能, 即纳米催化中的形貌效应. 因此, 调节催化剂的尺寸与形貌可以单独或协同优化材料的性能. 氧化铈作为催化剂的重要组分与结构、电子促进剂被广泛应用于多相催化剂体系. 本文总结了近期氧化铈材料形貌可控合成的进展, 包括主要的合成策略和表征方法; 进而分析了氧化铈和金-氧化铈催化材料的形貌效应, 指出金-氧化铈之间独特的相互作用与载体形貌密切相关; 阐述了氧化铈纳米材料因暴露晶面的差异而获得不同催化性能的化学机制. The catalytic performance of CeO 2 materials can be adjusted via tuning their shape at nanometer level by exposing different crystal planes, which influences both reaction pathway and metal-support interaction.

Theoretical Studies of the Adsorption of CO and C on Ni(111) and Ni/CeO2(111): Evidence of a Strong Metal–Support Interaction

The catalytic CO methanation reaction on Ni/CeO2(111) systems is known to depend on Ni coverage: at medium and large coverages, Ni/CeO2(111) surfaces are able to catalyze methane production, whereas at small coverage they become efficient catalysts for the water–gas shift reaction. Electronic structure, geometries, and the adsorption of C and CO on small Nin (n = 1 and 4) particles deposited on CeO2(111) have been studied using density functional theory (DFT) with the DFT+U approach and compared with Ni(111) and CeO2(111). The most stable Ni4 cluster has a pyramidal structure (pyr-Ni4), and a planar rhombohedral structure (r-Ni4) is less stable by ∼0.2 eV. Metallic Ni particles are partially oxidized (Ni2+/Ni1+) upon deposition on the ceria support, which is partially reduced. C species are strongly bound on Ni(111), whereas on Ni/CeO2(111), and on the bare support, oxidative adsorption (C + CeO2 → CO + CeO2–x) is mostly preferred, opening a Mars–van Krevelen mechanism to prevent coke formation. The exothermicity of nonoxidative adsorption of C on nickel sites follows the trend: Ni1/CeO2(111) < pyr-Ni4/CeO2(111) < Ni(111). On these systems, CO adsorption is nonoxidative. The C–O bond strength follows the inverse trend of the nonoxidative adsorption of C: Ni(111) < pyr-Ni4/CeO2(111) < Ni1/CeO2(111). The stronger C–O bond found for the CO/Ni1/CeO2(111) system compared with CO/Ni(111) provides an explanation of the Ni coverage dependence reported for the CO methanation reaction on Ni/CeO2(111) catalysts. The strong electronic perturbations in the Ni1 adatoms produce a drastic change in their chemical properties.

Stability and migration barriers of small vanadium oxide clusters on the CeO2(111) surface studied by density functional theory

By virtue of periodic density functional theory, we investigate structure and thermodynamic stability of (VO)k and (VO2)k (k = 1, 2, 3) clusters deposited on the CeO2(111) surface, which serve as models for the very active sub-monolayer vanadia catalyst on a ceria support. We find V always completely oxidized (oxidation state +5) and coordinated to four O atoms. As a consequence, Ce4+ is (partially) reduced to Ce3+. Thus, localized Ce-4f states are populated, which requires an onsite U-term (PBE+U) to avoid over-delocalization off-electrons. Importantly, trimers of VO2 were found to be extraordinarily stable (agglomeration energy: -1.68 eV), whereas aggregation of VO species on CeO2(111) is thermodynamically clearly unfavourable (agglomeration energy: 3.45 eV). As a consequence a large area of the VnOm phase diagram (for relevant temperatures) is dominated by the VO2 trimer. The latter is less active towards reduction/oxidation than the active monomer and dimer of VO2, which are not present in the phase diagram at all, although directly observed by recent STM measurements. This suggests that kinetic effects hinder VO2 to grow into larger oligomers. The lowest migration energy barrier we found is as high as 1.95 eV, which indicates that adsorbed monomeric VO2 is "kinetically locked" at low temperatures and explains why monomers are stabilized on the ceria surface.

A computational DFT study of CO oxidation on a Au nanorod supported on CeO2(110): on the role of the support termination

Possible reaction paths for CO oxidation on ceria-supported Au nanoparticle catalysts were modeled by placing a Au nanorod on a CeO2(110) surface. The results are discussed against experimental and computational data in the literature for Au/CeO2 with emphasis on the role of the ceria surface termination and involvement of ceria lattice oxygen atoms. Three CO oxidation mechanisms were modeled using density functional theory calculations: (i) reaction of adsorbed CO with ceria lattice O atoms (Mars–van Krevelen mechanism), (2) reaction of adsorbed CO with co-adsorbed O2 (co-adsorption mechanism) and (3) dissociation of adsorbed O2 followed by CO oxidation (stepwise mechanism). All three candidate mechanisms are relevant to CO oxidation catalysis as they exhibit nearly similar overall reaction barriers. The Mars–van Krevelen mechanism is consistent with experimental findings on the involvement of lattice O atoms in CO oxidation. This mechanism is prohibitive for CeO2(111) because of too high oxygen vacancy formation energy. Besides, the specific surface termination of CeO2(111) prevents O2 adsorption at its interface with Au due to repulsive interactions with the lattice O atoms. Molecular O2 adsorption is possible on CeO2(110) because of the presence of Ce4+ ions in the top layer of the surface. O2 adsorption can occur on a defective Au/CeO2(111) surface (J. Am. Chem. Soc., 2012, 134, 1560), because exposed Ce3+ ions are available. However, it is established here that O2 dissociation will heal the vacancies and deactivate Au supported on the CeO2(111) surface. The importance of Mars–van Krevelen and stepwise mechanisms in CO oxidation by Au/CeO2 strongly depends on the surface plane of the ceria support.

Nanostructured Pd modified Ni/CeO2 catalyst for water gas shift and catalytic hydrogen combustion reaction

Nanostructured Pd-modified Ni/CeO2 catalyst was synthesized in a single step by solution combustion method and characterized by XRD, TEM, XPS, TPR and BET surface analyzer techniques. The catalytic performance of this compound was investigated by performing the water gas shift (WGS) and catalytic hydrogen combustion (CHC) reaction. The present compound is highly active and selective (100%) toward H2 production for the WGS reaction. A lack of CO methanation activity is an important finding of present study and this is attributed to the ionic substitution of Pd and Ni species in CeO2. The creation of oxide vacancies due to ionic substitution of aliovalent ions induces dissociation of H2O that is responsible for the improved catalytic activity for WGS reaction. The combined H2-TPR and XPS results show a synergism exists among Pd, Ni and ceria support. The redox reaction mechanism was used to correlate experimental data for the WGS reaction and a mechanism involving the interaction of adsorbed H2 and O2 through the hydroxyl species was proposed for CHC reaction. The parity plot shows a good correspondence between the experimental and predicted reaction rates.

Preferential oxidation of CO in excess H2 over CuO/CeO2 catalysts: Characterization and performance as a function of the exposed face present in the CeO2 support

A series of oxidised copper-cerium nanostructured catalysts prepared by impregnation of copper over ceria supports synthesized by different methods (hydrothermal with varying preparation parameters, microemulsion/precipitation), in order to achieve different specific morphologies (nanocubes, nanorods and nanospheres), have been examined with respect to their catalytic properties for preferential oxidation of CO in excess H2 (CO-PROX). The catalysts have been characterized in detail by XRD, Raman, SBET measurement, HREM, XPS, TPR and EPR, which allows establishing a model of structural characteristics of the catalysts. The characterization results have been correlated with analysis of CO-PROX catalytic properties by means of catalytic activity measurements complemented by operando-DRIFTS. Structural dependence of the CO oxidation reaction on the dispersed copper oxide entities as a function of the exposed face present at the surface of the different ceria supports is revealed. An important overall enhancement of the CO-PROX performance is detected for the sample supported on ceria nanocubes which is proposed to be a consequence of the interaction between copper oxide and (100) faces of the ceria support.

Metal–support interface of a novel Ni–CeO2 catalyst for dry reforming of methane

Abstract Simultaneous treatment of both the loaded metal and the ceria support under plasma led to the generation of clean metal–support interface. This novel synthesis route prevents the tendency of Ni atoms migrating into the bulk of the supports, thereby avoiding a diffused interfacial region. The plasma treated sample showed excellent stability and higher catalytic activity than the thermally calcined sample in dry reforming of methane. The high activity of the plasma treated sample is attributed to the clean metal–support interface generated by exposing both the support and the loaded metal to microwave plasma treatment.

Ethanol steam reforming over Co/CeO2 catalysts: Investigation of the effect of ceria morphology

Co catalysts supported on ceria supports with different morphologies such as nano-rods (NR) and nano-cubes (NC) were investigated in regard to their activity for ethanol steam reforming. Ceria supports were prepared using the hydrothermal method where the particle shape is manipulated by controlling the pH and pressure of the precipitation environment. Structural characterization with TEM and XRD showed the two morphologies to be similar in particle size, but different in the exposure of different crystal planes. The nano-cubes had a higher exposure of the (110) plane, which is known to have a higher affinity for creating anion vacancies and surface defects. Controlled atmosphere X-ray absorption fine structure analysis, temperature programmed reduction/oxidation, dispersion measurements and steady-state reaction performance tests showed significant differences between the two catalysts. Co catalysts supported on nanocubes showed higher reducibility compared to those supported on nanorods or commercial supports of similar particle size. These catalysts also showed high H2 and CO2 yields in the 400–500°C range whereas Co/CeO2(NR) had limited carbon cleavage activity and were only active for dehydrogenation and dehydration. The superior performance of Co/CeO2(NC) catalysts is thought to be due to a combination of factors, including improved metal dispersion, increased reducibility and higher oxygen mobility.

Physicochemical characterization of Au/CeO2 solids. Part 2: The impregnation preparation method

Au/CeO2 solids with different gold contents were prepared using the impregnation method. Electron microscopy (SEM and TEM) studies indicated the formation of both nanoparticles and large gold particles on the surface of the ceria support. SEM and XRD analyses revealed that the number and size of large particles increases with the gold content in the solid. The XPS technique showed that 90% of the total gold is in the metallic form Au0 while the remaining 10% were cationic gold species Au+. These latter were formed following calcination under dry air at 400 °C and are located in the proximity of the O2− and/or Cl− present on the support. These Au+ species are present at the edge of gold particles and they were reduced into metallic gold when the solid was vacuum treated (5–7.10−4 mbar) at 400 °C for 1 h. When air was adsorbed at room temperature on the latter vacuum treated solids, two EPR signals were obtained. The first one was assigned to O2− species whereas attributing the second signal was difficult and required a more detailed investigation that will be presented in a forthcoming work.

SO2 Decomposition on Pt/CeO2(111) Model Catalysts: On the Reaction Mechanism and the Influence of H2 and CO

We have performed a synchrotron radiation photoelectron spectroscopy (SR-PES) study on the mechanism of SO2 decomposition on Pt/CeO2(111) model catalysts prepared on Cu(111). Resonant photoemission spectroscopy (RPES) was applied to monitor changes of the cerium oxidation state. Adsorption of SO2 at 150 K on Pt/CeO2(111)/Cu(111) yields surface sulfites (SO32–) on ceria and upright standing molecular SO2 (SO2st) on Pt along with traces of atomic sulfur. Partial decomposition and desorption of the adsorbed species in the form of SO2 occur between 150 and 300 K. In this temperature region, slow accumulation of atomic sulfur is accompanied by reduction of the ceria support. Above 300 K, all surface species completely transform into atomic sulfur; this process is accompanied by a strong reoxidation of ceria. As probed by CO adsorption, the majority of the atomic sulfur species is located on the surface of the Pt particles. Possible reaction mechanisms involving spillover of numerous sulfur-derived species are considered. Finally, reverse spillover of the sulfur from Pt to the ceria support and formation of a cerium oxysulfide phase occurs above 550 K. The spillover of atomic sulfur is readily promoted under reducing conditions, e.g., in the presence of coadsorbed hydrogen or CO.

A non-acid-assisted and non-hydroxyl-radical-related catalytic ozonation with ceria supported copper oxide in efficient oxalate degradation in water

Oxalate is usually used as a refractory model compound that cannot be effectively removed by ozone and hydroxyl radical oxidation in water. In this study, we found that ceria supported CuO significantly improved oxalate degradation in reaction with ozone. The optimum CuO loading amount was 12%. The molar ratio of oxalate removed/ozone consumption reached 0.84. The catalytic ozonation was most effective in a neutral pH range (6.7–7.9) and became ineffective when the water solution was acidic or alkaline. Moreover, bicarbonate, a ubiquitous hydroxyl radical scavenger in natural waters, significantly improved the catalytic degradation of oxalate. Therefore, the degradation relies on neither hydroxyl radical oxidation nor acid assistance, two pathways usually proposed for catalytic ozonation. These special characters of the catalyst make it suitable to be potentially used for practical degradation of refractory hydrophilic organic matter and compounds in water and wastewater. With in situ characterization, the new surface Cu(II) formed from ozone oxidation of the trace Cu(I) of the catalyst was found to be an active site in coordination with oxalate forming multi-dentate surface complex. It is proposed that the complex can be further oxidized by molecular ozone and then decomposes through intra-molecular electron transfer. The ceria support enhanced the activity of the surface Cu(I)/Cu(II) in this process.

Adsorption sites, metal-support interactions, and oxygen spillover identified by vibrational spectroscopy of adsorbed CO: A model study on Pt/ceria catalysts

Vibrational spectroscopy of adsorbed CO is commonly used for the characterization of oxide-supported metal catalysts, in spite of persisting ambiguities concerning the band assignment. Here, we present reference data on well-defined Pt/CeO2(111)/Cu(111) model catalysts aiming at clear identification of the related features. Growth and morphology of the Pt particles are investigated by scanning tunneling microscopy (STM), the adsorption properties are probed by temperature programmed desorption (TPD), and the electronic structure has previously been studied by photoelectron spectroscopy (PES) and resonant photoelectron spectroscopy (RPES). Combining molecular beam (MB) methods and infrared reflection absorption spectroscopy (IRAS), we correlate this information to the interaction with CO.Two types of defect adsorption sites are identified on the ceria support (2097cm−1, 2120cm−1), which are assigned to structural defects and reduced Ce3+ centers. The relative abundance of these sites changes upon thermal treatment. On the Pt nanoparticles, CO first adsorbs on-top at step and edge sites (2066cm−1), before adsorption on the (111) facets occurs in bridging (1875cm−1) and on-top (2080–2097cm−1) geometry. For the first time, we identify vibrational CO features, which arise from electronic metal-support interactions and from oxygen reverse spillover. On reduced CeO2−x(111), a red-shifted band at 2053cm−1 appears, which is attributed to increased π-backbonding from Pt to CO, as a result of a change in electronic metal-oxide interaction. Thermal treatment also activates oxygen reverse spillover from the support to the Pt nanoparticle, which gives rise to a blue-shifted feature in the CO spectrum (2090–2105cm−1) due to coadsorbed oxygen next to CO sites.

Effect of nature of ceria support in CuO/CeO2 catalyst for PROX-CO reaction

In order to understand the effect of CeO2 on the preferential CO oxidation reaction (PROX-CO), the support cerium oxide was prepared by hydrothermal (CeO2-HT) and precipitation (CeO2-PP) methods. The catalyst supported on CeO2-HT exhibited higher activity than CuO/CeO2-PP. Characterization revealed that CuO was better dispersed on the CuO/CeO2-HT surface favoring the PROX-CO reaction, compared to CuO/CeO2-PP. Also, the nature of ceria was important for enhancing the metal-support interaction, which affects the catalytic activity. The CuO/CeO2-HT catalyst was less sensitive to presence of CO2 and H2O, remaining stable in a 24h run.

The hydrogen adsorption capacity of commercial Pd/Rh and Pt/Rh automotive catalysts and its relationship to their activity

Recent papers studying both fresh and aged Pt–Rh and Pd–Rh commercial catalysts reported hydrogen programmed temperature desorption (H2-TPD) results in an attempt to determine the noble metal dispersion. However, for the fresh catalysts, the total amount of adsorbed H2 was greater than the quantity of noble metals determined via chemical analysis, which indicates other processes, such as hydrogen spillover and H2 interactions with the ceria support, can contribute to the hydrogen adsorption. These results have now been reviewed, and although they cannot be used to determine the metal dispersion, a correlation between them and the catalytic activities for both propane and CO oxidation and the reduction of NO by CO was found. As catalytic activities are influenced by nearly all of the washcoat components, such as ceria–zirconia mixed oxides and nickel oxide, in addition to the noble metals, in some way, this technique appears to dose the sites (metal and support) involved in the catalytic reaction. Therefore, H2-TPD can be used for comparison of the catalytic activity of these catalysts.

Ti/CeOx(111) interfaces studied by XPS and STM

Low coverage of Ti was deposited on the well-ordered CeOx(111) (1.5<x<2) thin films grown on Ru(0001) by physical vapor deposition at room temperature. The structure and interaction of Ti/ceria interfaces were investigated with X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) techniques under ultrahigh vacuum conditions. XPS data indicate that the deposition of Ti on both oxidized and reduced ceria surfaces causes the partial reduction of Ce from +4 to +3 state. Ti is formally in the +4 state. STM data show the formation of small atomic-like titania features at 300K, which coalesce to form chain structures upon heating. It is demonstrated in the study that the deposition of Ti can form mixed metal oxides at the interface and modify both electronic and structural properties of the ceria support. The structural study of Ti/ceria interfaces can be a key for understanding the higher catalytic activity of the Ti–CeOx mixed oxide catalysts as compared with the individual pure oxides.

Interactions between CeO2 and NixPy for enhancing coking and sulfur resistance in autothermal reforming of liquid hydrocarbons

Nickel phosphide (NixPy) was grown on ceria and Gd-doped ceria (CGO) respectively and the resulting supported catalysts were examined in the autothermal reforming reaction of a surrogate diesel fuel, comprising of n-dodecane, naphthalene and thiophene. The catalytic NixPy sites could also induce generation of Ce3+ ions in the ceria support under the reducing atmosphere of ATR at 400–500°C according to TPR and XPS analysis. On the contrary, doping ceria by 10mol% Gd noticeably weakened generation of Ce3+ ions. The Ce3+ ions present at the surface of catalyst support act to sustain water–gas shift reaction as well as to enhance the stabilization of catalytic reactivity. The commercial steam reforming catalyst was adopted as benchmark and displayed weaker resistance to coking and sulfur deactivation than the ceria-supported NixPy catalyst.