Temperature-programmed Surface Reaction Research Articles

Effects of nitrogen vacancy sites of oxynitride support on the catalytic activity for ammonia decomposition

Nitrogen-containing compounds such as imides and amides have been reported as efficient materials that promote ammonia decomposition over nonnoble metal catalysts. However, these compounds decompose in an air atmosphere and become inactive, which leads to difficulty in handling. Here, we focused on perovskite oxynitrides as air-stable and efficient supports for ammonia decomposition catalysts. Ni-loaded oxynitrides exhibited 2.5–18 times greater catalytic activity than did the corresponding oxide-supported Ni catalysts, even without noticeable differences in the Ni particle size and surface area of the supports. The catalytic performance of the Ni-loaded oxynitrides is well correlated with the nitrogen desorption temperature during N2 temperature-programmed desorption, which suggests that the lattice nitrogen in the oxynitride support rather than the Ni surface is the active site for ammonia decomposition. Furthermore, NH3 temperature-programmed surface reactions and density functional theory (DFT) calculations revealed that NH3 molecules are preferentially adsorbed on the nitrogen vacancy sites on the support surface rather than on the Ni surface. Thus, the ammonia decomposition reaction is facilitated by a vacancy-mediated reaction mechanism.

Regulating N-Cu/MoxC interfacial effect coupling β-Mo2C/γ-MoC phase engineering to achieve efficient hydrolysis dissociation and methanol dehydrogenation for hydrogen production

Methanol steam reforming (MSR) is a promising solution for achieving the integration of hydrogen storage, transportation, and in-situ supply. However, it is limited by the slow rate of hydrogen generation and low selectivity. This study constructed a highly active N-Cu/MoxC catalyst with strong interaction between Cu and MoxC, effectively enhancing methanol activation, hydrolysis, and hydrogen production efficiency. Under optimized condition, the 2.8 N-Cu/MoxC catalyst achieved a remarkable H2 productivity of 147.9 mmol gcat−1 h−1 and H2 selectivity of 65.7 %. N induced a partial transition from β-Mo2C phase to γ-MoC phase, resulting in a doubling of H2 production rate. The interfacial N-Cu-MoxC sites facilitated highly reactive efficient CH bond dissociation to convert CO+4H and OH activation, as well as the highly efficient CO reforming. Additionally, temperature programmed surface reaction and isotope testing futher coroborated its superiority in methanol dehydrogenation and hydrolysis dissociation. These discoveries can provide guidance for the design of advanced MSR catalysts.

Direct methane utilization through benzene dehydroalkylation catalyzed by Co2+ sites in ZSM-5 intersections

Cobalt cations exchanged in ZSM-5 are active for the direct dehydromethylation of benzene with CH4. While toluene is the primary product, an alternate reaction pathway leads also to the formation of biphenyl and phenyltoluene. This not only diminishes the selectivity but also contributes to the deactivation of the catalyst. Temperature-programmed surface reactions show that benzene adsorbs strongly on the exchanged Co2+ cations, essentially blocking the sites for alkylation below 400 °C. At temperatures exceeding 400 °C, the partial desorption of benzene enables its reaction with CH4, leading to the formation of toluene. The formation of biphenyl is kinetically hindered, and its onset is only observed at temperatures above 450 °C. When CH4 is allowed to chemisorb on Co2+ sites prior to exposure to benzene, the formation of toluene is detected at temperatures below 400 °C. By infrared spectroscopy of benzene adsorption and UV–Vis spectroscopic characterization, we identified the existence of intersections in ZSM-5 where three H+ are in proximity. The ion exchange of a zeolite lattice Al3+ pair in such positions leads to the formation of a Co2+ site near a free Brønsted acid site. We observed a correlation between the concentration of this type of Co2+ sites and the catalytic activity of Co-ZSM-5 in benzene alkylation with CH4. This is further supported by the catalytic tests of Co-ZSM-5 materials with specifically a larger proportion of Co sites in sinusoidal channels, as a result of acidic conditions during ion exchange. Based on this, we propose that toluene formation takes place via heterolytic dissociation of CH4 on a Co2+ site at intersections followed by reaction with benzene strongly interacting with an adjacent BAS.

Synthesis of surface-engineered SrFe2O4 for efficient catalytic partial oxidation of methane

In this study, a series of platinum (Pt)-doped strontium iron oxide (SrFe2O4) catalysts with varying particle sizes were synthesized through the four different catalysis synthesis methods such as solution combustion synthesis (SCS), co-precipitation (Co-PPT), oxalic acid assisted sol-gel (OXA) and, hydrothermal (HT). The objective was to investigate the impact of particle size on the catalytic activity and long-term stability of these four catalysts. The XRD and Raman results confirmed the formation of the SrFe2O4 perovskite structure. HRTEM, SEM, and other characterizations revealed a clear correlation between the synthesis conditions and the resulting particle sizes. The highest%CH4 conversion was around 95 % for the catalyst prepared through Solution combustion synthesis and the catalyst was found to be thermally stable up to. 100 h at 800 °C with a negligible variation of conversion while maintaining the H2/CO ratio at 2.0. To gain insight into catalytic activity, stability, and selectivity of catalysts we have performed Temperature-programmed surface reaction (TPSR) at a controlled temperature ramping program. This study also includes the study of coke deposition on the spent catalysts through different characterization techniques. Furthermore, we have performed a kinetic study to find the initial rate of the reaction and the activation energy of the Pt-doped SrFe2O4 catalyst and it has been found that activation energy was 35 KJ/mol for the catalyst Pt/SrFe2O4 synthesis through the solution combustion method.

IrSn Bimetallic Clusters Confined in MFI Zeolites for CO Selective Catalytic Reduction of NOx in the Presence of Excess O2.

We developed a simple strategy for preparing IrSn bimetallic clusters encapsulated in pure silicon zeolites via a one-pot hydrothermal synthesis by using diethylamine as a stabilizing agent. A series of investigations verified that metal species have been confined successfully in the inner of MFI zeolites. IrSn bimetallic cluster catalysts were efficient for the CO selective catalytic reduction of NOx in the presence of excess O2. Furthermore, the 13CO temperature-programmed surface reaction results demonstrated that NO2 and N2O could form when most of the CO was transformed into CO2 and that Sn modification could passivate CO oxidation on the IrSn bimetallic clusters, leading to more reductants that could be used for NOx reduction at high temperatures. Furthermore, SO2 can also influence the NOx conversion by inhibiting the oxidation of CO. This study provides a new strategy for preparing efficient environmental catalysts with a high dispersion of metal species.

Catalytic consequences of the identity and coverages of reactive intermediates during benzene hydrogenation on Pt, Pd, and Pt-Re catalysts

Mechanistic differences in benzene and cyclohexene hydrogenation on Pt, Pd, and Pt-Re catalysts are interrogated with kinetic assessments, temperature programmed surface reactions, infrared absorption spectroscopic study, and DFT calculations. Their effective rate constants are larger on Pt than Pd surfaces either uncovered or covered with sulfur species, due to the weaker H* adsorption and higher SH* acidity on Pt than Pd. Without sulfur species, H* is the only reactive hydrogen species—on Pt, its first insertion on the adsorbed benzene (C6H6*) and its second insertion onto the cyclohexene intermediate (C6H10+1*) restrict turnovers in benzene and cyclohexane hydrogenation, respectively. H2S treatments lead to SH* species bound irreversibly that not only decreases turnovers but also alters the elementary steps and their kinetic relevance within the catalytic cycle—SH* initially attacks C6H6*, before five successive H* additions, where the third addition limits turnovers. Incorporating isolated Re atoms onto sulfur-covered Pt surfaces increases benzene hydrogenation turnovers, because OH* associated with Re sites are more acidic and effective in initiating the reaction.

Ru/MgO catalyst with dual Ru structure sites for efficient CO production from CO2 hydrogenation

The development and comprehension of supported metal catalysts for CO2 hydrogenation is of paramount importance in mitigating the net CO2 emissions. Supported Ru catalysts have been widely recognized in facilitating CO2 methanation, on which recent findings suggest that the CO2 hydrogenation process can be manipulated to favor the reverse water–gas shift (RWGS) pathway by precisely adjusting the size of Ru particles. However, the size-dependent impact of Ru remains a topic of lively debate. In this work, Ru/MgO catalysts with Ru in the form of single atoms (Ru1) and few-atom cluster (RuFAC) structures were prepared for CO2 hydrogenation. The 1.0Ru/MgO catalyst (with 1 wt.% of Ru), featuring a mixture of Ru1 and RuFAC with a size of 0.6–1.0 nm, showed the highest CO yield (38% at 500 °C) with balanced CO2 conversion and CO selectivity. Transient CO2 hydrogenation and temperature-programmed surface reaction (TPSR) studies suggested that the adsorbed CO2 species participated in CO2 hydrogenation. On Ru1 sites, CO2 hydrogenation followed the RWGS pathway, resulting in the production of CO. In contrast, on RuFAC sites, the enhanced H2 dissociation ability, along with the presence of adsorbed bidentate and monodentate carbonate species at the Ru−MgO interfaces, facilitated the formation of CH4 through the CO2 methanation pathway. This study highlights the critical roles of Ru structure and local environment in defining the CO2 hydrogenation pathways and provides new design principles for highly active Ru-based catalysts.

Boosting N2O Catalytic Decomposition by the Synergistic Effect of Multiple Elements in Cobalt-Based High-Entropy Oxides.

Nitrous oxide (N2O) has a detrimental impact on the greenhouse effect, and its efficient catalytic decomposition at low temperatures remains challenging. Herein, the cobalt-based high-entropy oxide with a spinel-type structure (Co-HEO) is successfully fabricated via a facile coprecipitation method for N2O catalytic decomposition. The obtained Co-HEO catalyst displays more remarkable catalytic performance and higher thermal stability compared with single and binary Co-based oxides, as the temperature of 90% N2O decomposition (T90) is 356 °C. A series of characterization results reveal that the synergistic effect of multiple elements enhances the reducibility and augments oxygen vacancy in the high-entropy system, thus boosting the activity of the Co-HEO catalyst. Moreover, density functional theory (DFT) calculations and the temperature-programmed surface reaction (TPSR) with isotope labeling demonstrate that N2O decomposition on the Co-HEO catalyst follows the Langmuir-Hinshelwood (L-H) mechanism with the promotion of abundant oxygen vacancies. This work provides a fundamental understanding of the synergistic catalytic effect in N2O decomposition and paves the way for the novel environmental catalytic applications of HEO.

Visualization of the Active Sites of Zinc-Chromium Oxides and the CO/H2 Activation Mechanism in Direct Syngas Conversion.

Despite wide studies demonstrating the versatility of the metal oxide-zeolite (OXZEO) catalyst concept to tackle the selectivity challenge in syngas chemistry, the active sites of metal oxides and the mechanism of CO/H2 activation remain to be elucidated. Herein, we demonstrate experimentally the role of Cr in zinc-chromium oxides and unveil visually, for the first time, the active sites for CO activation employing scanning transmission electron microscopy-electron energy loss spectroscopy using the volumetric density of surface carbon species as a descriptor. The ZnCr2O4 spinel surface with atomic ZnOx overlayer is the most active site for C-O bond dissociation, particularly at the narrow ZnCr2O4(110) facets constrained between the (311) and (111) facets, followed by the Cr-doped wurtzite ZnO surface. In comparison, the surfaces of ZnCr2O4 with aggregated ZnOx overlayers, pure ZnO, and the stoichiometric ZnCr2O4 exhibit a significantly lower activity. In situ synchrotron-based vacuum ultraviolet photoionization mass spectrometric study on different temperature programmed surface reactions with isotopes of C18O, 13CO, and D2 validates direct CO dissociation over ZnCrn oxides in CO, forming CH2 and further to hydrocarbons if H2 is present and CH2CO intermediates in syngas. The activity of CO dissociation and hydrogenation over ZnCrn oxides correlates well with the syngas-to-light-olefins activity of ZnCrn-SAPO-18 composite catalysts as a function of the Cr/Zn ratio.

In chemico methodology for engineered nanomaterial categorization according to number, nature and oxidative potential of reactive surface sites.

Methanol probe chemisorption quantifies the number of reactive sites at the surface of engineered nanomaterials, enabling normalization per reactive site in reactivity and toxicity tests, rather than per mass or physical surface area. Subsequent temperature-programmed surface reaction (TPSR) of chemisorbed methanol identifies the reactive nature of surface sites (acidic, basic, redox or combination thereof) and their reactivity. Complementary to the methanol assay, a dithiothreitol (DTT) probe oxidation reaction is used to evaluate the oxidation capacity. These acellular approaches to quantify the number, nature, and reactivity of surface sites constitute a new approach methodology (NAM) for site-specific classification of nanomaterials. As a proof of concept, CuO, CeO2, ZnO, Fe3O4, CuFe2O4, Co3O4 and two TiO2 nanomaterials were probed. A harmonized reactive descriptor for ENMs was obtained: the DTT oxidation rate per reactive surface site, or oxidative turnover frequency (OxTOF). CuO and CuFe2O4 ENMs exhibit the largest reactive site surface density and possess the highest oxidizing ability in the series, as estimated by the DTT probe reaction, followed by CeO2 NM-211 and then titania nanomaterials (DT-51 and NM-101) and Fe3O4. DTT depletion for ZnO NM-110 was associated with dissolved zinc ions rather than the ZnO particles; however, the basic characteristics of the ZnO NM-110 particles were evidenced by methanol TPSR. These acellular assays allow ranking the eight nanomaterials into three categories with statistically different oxidative potentials: CuO, CuFe2O4 and Co3O4 are the most reactive; ceria exhibits a moderate reactivity; and iron oxide and the titanias possess a low oxidative potential.

Insight into the enhanced catalytic performance of phosphate-modified ZrO2/SBA-15 for the conversion of biobased 2,5-dimethylfuran and ethylene into p-xylene

Catalytic conversion of biomass-derived platform chemicals into bulk chemicals p-xylene (PX) is appealing yet challenging due to low catalytic efficiency and severe reaction conditions. In this work, we fabricated a series of phosphate-modified ZrO2/SBA-15 (xP-Zr/SBA-15) via adjusting the addition of phosphoric acid, and used them for the catalytic conversion biomass-derived 2,5-dimethylfuran (DMF) and ethylene to PX. Because of the enhanced adsorption capability for the reactant molecules (DMF and ethylene) and the good synergistic effect between Brønsted acid sites (P-OH) and Lewis acid sites (Zr4+), 30P-Zr/SBA-15 revealed an excellent catalytic performance in the selective conversion of DMF into PX. The DMF conversion was 98.5%, PX yield was 92.0% at 250 °C for 12 h, and the corresponding PX productivity was upto 50.5 mmolPX·gcat−1·h−1. The results are far superior to those obtained on most previously reported catalysts in the literature under similar reaction conditions. The kinetic study revealed that 30P-Zr/SBA-15 has a lower apparent activation energy for the tandem reaction including the Diels-Alder reaction (57.0 kJ·mo−1) and dehydration reaction (37.7 kJ·mo−1). Moreover, the 30P-Zr/SBA-15 catalyst exhibited the excellent recyclability and could be recycled at least six times without a significant loss of activity. On the basis of the temperature-programmed surface reaction of DMF and ethylene, a reasonable reaction mechanism was proposed.

Rb-Ni/Al2O3 as dual functional material for continuous CO2 capture and selective hydrogenation to CO

Ni-based dual-functional materials (DFMs) have been widely investigated for CO2 capture and reduction with H2 (CCR). However, controlling the selectivity of CO2 hydrogenation to CH4 or CO is a fundamental challenge. Most Ni-based DFMs favor the selectivity of CH4 over CO, although CO is more desirable than CH4 from a chemical-synthesis perspective. In this study, Rb-promoted Ni nanoparticles on Al2O3, Rb-Ni/Al2O3, are developed as an effective DFM for selective CO production through CCR with a CO2 conversion of 68% and a CO selectivity of 97% under isothermal conditions at 450 °C in the mixture of O2 during CO2 capture process. The developed Rb-Ni/Al2O3 is applicable to continuous CCR using double reactor system. The roles of Rb and Ni in CCR over Rb-Ni/Al2O3 for CO formation are also discussed based on temperature-programmed surface reactions and in situ spectroscopic studies.

Activation of dimethyl carbonate on CeO2 surface: A combined experimental and theoretical study

Dimethyl carbonate (DMC) has recently emerged as a green reagent that finds versatile applications in methoxycarbonylation, carbonylation, and methylation reactions due to its multiple functionalities. In order to optimize the activity/selectivity of DMC-mediated heterogeneous catalytic reaction, it is imperative to enhance the fundamental understanding of the activation of DMC on the catalyst surface. In this study, the chemistry of DMC on the CeO2(111) surface was investigated using in-situ infrared spectroscopy, temperature-programmed surface reaction, and density functional theory calculations. It is shown that DMC readily converts into adsorbed methoxycarbonyl and methoxy on CeO2(111) at near room temperature. Upon heating, methoxycarbonyl decomposes into methoxy and carbonyl; the formed carbonyl could react with the surface oxygen atom (OS) of CeO2(111) to form desorbed carbon dioxide (COOS), leaving a surface oxygen vacancy. The surface methoxy groups undergo intermolecular hydrogen transfer to form CH3OH and HCHO, which upon heating either desorb or dehydrogenate with OS to form adsorbed methoxy and formate (with OSH), respectively. Adsorbed formate could react with OS to form desorbed COOS at higher temperatures. These findings provide fundamental insights into the catalytic chemistry of DMC on CeO2(111) surface, which may prove informative for the CeO2-catalyzed DMC-mediated reactions.

Catalytic Activity of Methane Oxidation on Nickel-doped Lanthanum Strontium Titanate Perovskite from Three Synthesis Methods

BackgroundThree perovskites of nickel-doped lanthanum strontium titanate (LSTN) were made and compared for their activity toward methane oxidation. MethodThe perovskite was synthesized separately via solid-state reaction, citrate complexation, and microwave-assisted methods. Significant FindingsThe perovskite from solid state reaction gave the highest activity of syngas production in repetitive redox cycles without any deterioration, demonstrating a great potential for use in chemical looping technology. Nevertheless, the material required activation in methane, as evidenced in studies of temperature-programmed surface reaction. On the contrary, the perovskite from the complexation method behaved completely different while the microwave-synthesized one gives the poorest activity. The variation of the activity was correlated with the distinct structure from different synthesis routes, which influences where a metal phase resides and how the metal anchors onto host oxides. The information obtained here would be of great benefit in making good material with desirable properties for catalysis and potential applications.

Mechanistic Insights into the Induction Period of Methanol-to-Olefin Conversion over ZSM-5 Catalysts: A Combined Temperature-Programmed Surface Reaction and Microkinetic Modeling Study

Mechanistic Insights into the Induction Period of Methanol-to-Olefin Conversion over ZSM-5 Catalysts: A Combined Temperature-Programmed Surface Reaction and Microkinetic Modeling Study

Advanced in situ IR spectroscopy study of anisole hydrodeoxygenation over Ni/SiO2 catalysts

Hydrodeoxygenation (HDO) of anisole was investigated over Ni/SiO2 catalysts prepared by incipient wetness impregnation (IWI) and deposition–precipitation (DP). The in situ FTIR, temperature-programmed surface reaction (TPSR-MS), as well as high pressure flow reactions were carried out to relate catalyst properties and reaction mechanism. The small-size Ni0-Ni+ species (2.0 nm) in Ni/SiO2-DP catalyst exhibits a strong hydrogenolysis activity for anisole, favouring the formation of phenol and benzene. The demethylation of anisole to phenol is a rapid step compared to the deoxygenation of phenol to benzene as indicated by in situ FTIR studies. The intensity of C–C stretching vibration in the two rings was enhanced with increasing temperature, suggesting the formation of condensed-ring products was promoted by high reaction temperature. The Ni/SiO2-IWI catalyst, which exhibits a larger Ni0 particle size (14.1 nm) and higher amount of desorbed H2 per surface Ni compared to Ni/SiO2-DP, shows a high hydrogenation but low hydrogenolysis activity, towards the formation of methoxycyclohexane under 40 bar H2 pressure flow reaction.

Ni-CeO2 nanocomposite with enhanced metal-support interaction for effective ammonia decomposition to hydrogen

Ammonia is a promising hydrogen storage material due to its ease of storage and decomposition to COx-free hydrogen. Herein, we report colloidal solution combustion synthesis (CSCS) to construct Ni-CeO2 nanocomposite catalysts for efficient ammonia decomposition to generate hydrogen. Unlike conventional supported Ni/CeO2 catalyst, the prepared Ni-CeO2 nanocomposite catalyst exhibited nickel embedded in CeO2 matrix with enhanced metal-support interaction. The physicochemical properties and metal-support interaction of the catalysts can be tuned by adjusting the amount of silica sol template. The resulted Ni-CeO2 nanocomposite catalysts exhibited outstanding catalytic performance in terms of activity and stability. The hydrogen production rate reached 32.9 mmol gcat−1 min−1 at 500 °C, which is superior to other state-of-the-art Ni-based catalysts and even comparable or better than some reported Ru-based catalysts. The systematic characterizations demonstrated that the unique Ni-CeO2 nanocomposite structure with enhanced metal-support interaction, not only provided a rich Ni-CeO2 interface to stabilize small-sized Ni nanoparticles, but also had a high concentration of oxygen vacancy to strengthen electronic metal-support interaction, making nickel surface electron-rich. The integrated studies of kinetics, temperature-programmed surface reaction, and DFT calculations corroborated that this enhanced metal-support interaction including geometric and electronic effects, favored the enrichment of NH3 on the catalyst surface and facilitated rate-determining N≡N bond formation step, thereby boosting the reaction rate. This study highlights the importance of designing new structural catalysts with enhanced metal-support interaction for boosting hydrogen production from ammonia decomposition.

The Role of Fe in Ni-Fe/TiO2 Catalysts for the Dry Reforming of Methane

A series of nickel- and iron-modified titanium dioxide (Ni-Fe/TiO2) are studied for the dry reforming of methane (DRM) at 550 °C. Temperature-programmed surface reactions using CH4 and CO2 as probe molecules, as well as activity results, confirmed that both CO2 and CH4 conversion decreased with the addition of Fe. The XPS results obtained from reduced and used catalysts suggested changes in the surface nickel and iron species. Characterizations, particularly thermogravimetric analysis (TGA) and Raman spectroscopy over used catalysts, revealed that the addition of Fe can greatly inhibit the coke formation. In situ DRIFTS further identified that the addition of Fe favored the formation of carbonate species, which can facilitate the removal of coke deposited on the surface.

Crystal Plane Effect of Co3O4 on Styrene Catalytic Oxidation: Insights into the Role of Co3+ and Oxygen Mobility at Diverse Temperatures.

In the oxidation reaction of volatile organic compounds catalyzed by metal oxides, distinguishing the role of active metal sites and oxygen mobility at specific preferentially exposed crystal planes and diverse temperatures is challenging. Herein, Co3O4 catalysts with four different preferentially exposed crystal planes [(220), (222), (311), and (422)] and oxygen vacancy formation energies were synthesized and evaluated in styrene complete oxidation. It is demonstrated that the Co3O4 sheet (Co3O4-I) presents the highest C8H8 catalytic oxidation activity (R250°C = 8.26 μmol g-1 s-1 and WHSV = 120,000 mL h-1 g-1). Density functional theory studies reveal that it is difficult for the (311) and (222) crystal planes to form oxygen vacancies, but the (222) crystal plane is the most favorable for C8H8 adsorption regardless of the presence of oxygen vacancies. The combined analysis of temperature-programmed desorption and temperature-programmed surface reaction of C8H8 proves that Co3O4-I possesses the best C8H8 oxidation ability. It is proposed that specific surface area is vital at low temperature (below 250 °C) because it is related to the amount of surface-adsorbed oxygen species and low-temperature reducibility, while the ratio of surface Co3+/Co2+ plays a decisive role at higher temperature because of facile lattice oxygen mobility. In situ diffuse reflectance infrared Fourier spectroscopy and the 18O2 isotope experiment demonstrate that C8H8 oxidation over Co3O4-I, Co3O4-S, Co3O4-C, and Co3O4-F is mainly dominated by the Mars-van Krevelen mechanism. Furthermore, Co3O4-I shows superior thermal stability (57 h) and water resistance (1, 3, and 5 vol % H2O), which has the potential to be conducted in the actual industrial application.

Coke-resistant NdFe0.7Ni0.3O3 perovskite catalyst with superior stability for dry reforming of ethane

Effects of A-site cation substitution and B-site active metal doping-segregation on physicochemical properties of Ni-doped perovskite-structured LnFe0.7Ni0.3O3 (Ln = La, Nd, Sm, Eu) catalysts and their catalytic performance for dry reforming of ethane (DRE) were studied. The DRE activity follows the trend: NdFe0.7Ni0.3O3 > SmFe0.7Ni0.3O3 > EuFe0.7Ni0.3O3 > LaFe0.7Ni0.3O3. The doping-segregation process of Ni was demonstrated by in-situ X-ray Diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) measurements, which significantly improves the dispersion of Ni and enhance the interaction between metal and support. The results of temperature-programmed surface reactions (TPSR) and pulse reactions indicate that oxygen vacancies generated by the exsolution of Ni play an important role in the elimination of coke and shift the product from surface carbon to gaseous CO. According to the in-situ Raman experiments, the superior catalytic stability (no coke deposition or activity loss over 100 h) of NdFe0.7Ni0.3O3 is ascribed to its strong resistance towards carbon deposition.