Reactive Gas Research Articles

Enhancing Photocatalytic CO2 Conversion through Oxygen-Vacancy-Mediated Topological Phase Transition.

Weak adsorption of gas reactants and strong binding of intermediates present a significant challenge for most transition metal oxides, particularly in the realm of CO2 photoreduction. Herein, we demonstrate that the adsorption can be fine-tuned by phase engineering of oxide catalysts. An oxygen vacancy mediated topological phase transition in Ni-Co oxide nanowires, supported on a hierarchical graphene aerogel (GA), is observed from a spinel phase to a rock-salt phase. Such in situ phase transition empowers the Ni-Co oxide catalyst with a strong internal electric field and the attainment of abundant oxygen vacancies. Among a series of catalysts, the in situ transformed spinel/rock-salt heterojunction supported on GA stands out for an exceptional photocatalytic CO2 reduction activity and selectivity, yielding an impressive CO production rate of 12.5 mmol g-1 h-1 and high selectivity of 96.5 %. This remarkable performance is a result of the robust interfacial coupling between two topological phases that optimizes the electronic structures through directional charge transfer across interfaces. The phase transition process induces more Co2+ in octahedral site, which can effectively enhance the Co-O covalency. This synergistic effect balances the surface activation of CO2 molecules and desorption of reaction intermediates, thereby lowering the energetic barrier of the rate-limiting step.

Revisitation of reactive direct current magnetron sputtering discharge: Investigation of Mg–CF4, Mg–O2, and Ti–O2 discharges by probe measurements

The reactive direct current (DC) magnetron sputtering discharges of Mg–CF4, Mg–O2, and Ti–O2 were investigated using probe measurements as a function of reactive gas flow ratio. The emission spectroscopy, which was conducted before the probe measurements, demonstrates that all the three DC discharges transit from nonreactive to reactive discharge mode with increasing reactive gas flow ratio. The probe measurements show that the plasma potentials of the Mg–O2 and Ti–O2 DC discharges slightly increase or remain almost constant with increasing reactive gas flow ratio, whereas that of the Mg–CF4 DC discharge drastically decreases at the mode transition. For the same change in reactive gas flow ratio, the discharge voltage of the Mg–CF4 DC discharge slightly increases and that of the Mg–O2 DC discharge drastically increases at the mode transition, whereas that of the Ti–O2 DC discharge slightly decreases at the mode transition. The changes in the cathode sheath potential difference at the mode transition differ between the Mg–CF4 and Ti–O2 DC discharges and the Mg–O2 DC discharge because of the difference in the probability of secondary electron emission at the cathode surface; furthermore, the changes in the anode sheath potential difference at the mode transition differ between the Mg–CF4 DC discharge and the Mg–O2 and Ti–O2 DC discharges because of the difference in the probability of negative-ion formation in the plasma bulk. The most informative results obtained in this study were the differences in the potential differences at the cathode and anode sheaths among the Mg–CF4, Mg–O2, and Ti–O2 DC discharges. They well demonstrated the effects of the change in secondary-emitted species at the cathode surface and the change in reactive gas concentration in the plasma on the potential configuration.

Calculation of Deflagration Appearence in Hydrogen-Air Mixtures Flows in Regions with Obstacles

Many researches devoted to deflagration appearance in hydrogen-air mixes and transition it to detonation. Preference of hydrogen as a fuel is detonation fuel cycle which is more energetic preferable in comparing with ordinary fuel cycle. In connection with this preference problem of hydrogen detonation engine constructing is extreme actual. Essential part of investigations in this field is developing and improving of mathematical methods for numerical simulation of deflagration initiation and transition it to stable detonation. In real physical experiments this deflagration initiation in flows appears via sudden hot spot appearance or near an obstacle on boarding surface. In this paper numerically investigated flows of reactive gas mixes in channels with obstacles with purpose to define regims of deflagration initiation.

Investigation of properties of novel multilayer Cr/CrN/CrTiN/CrTiAlN hard coating with four bilayers

A novel multilayer Cr/CrN/CrTiN/CrTiAlN hard coating with four bilayers was developed by reactive closed field unbalanced magnetron sputtering (CFUBMS). The substrate temperature was kept in the range of 170 °C to 200 °C. The reactive gas flow was controlled by Optical Emission Monitoring. A thickness of 1.8 μm was determined using a calotester. The morphology and chemical composition were studied by electron microscopy (SEM and EDS). Nanohardness of 34.1 GPa and a modulus of elasticity of 386 GPa were determined using the nanoindentation technique. The scratch test against a diamond Rockwell indenter did not show features indicating poor adhesion. The reciprocating wear test revealed strong resistance to wear, and a coefficient of friction of 0.19 was determined. The developed multilayered hard coating showed optimal mechanical properties for industrial applications on instruments of low-temperature materials.

Hardness, adhesion, and wear behavior of magnetron cosputtered Ti:Zr-O-N thin films

Reactive magnetron sputtering was used to deposit Ti:Zr-O-N thin films, by using a single Zr target, with Ti ribbons placed on the erosion track of the Zr sputtering target. Zr-O-N thin films have been also deposited in the same chamber to be used as reference films. The number of Ti ribbons, the applied sputtering current, and the reactive gas flow were the variable parameters. The films were analyzed in terms of structural development and mechanical properties (instrumented indentation, adhesion scratch testing, and wear analysis). The films are either amorphous or composed of a mixture of crystalline phases based on zirconium and titanium oxides or nitrides. Hardness values are situated between ∼10 and 11 GPa for the reference films (deposited without Ti) and up to ∼22 GPa for one of the Ti:Zr-O-N films. The films deposited without Ti behave slightly better in terms of adhesion to the substrate in comparison to the remaining samples in relation to the occurrence of first cracks (Lc1, critical load 1) and for first delamination (Lc2, critical load 2), a phenomenon probably related to the lower hardness of these films, which can accommodate the plastic deformation caused by the diamond indenter, prior to the occurrence of delamination. Adhesion to the substrate is a critical characteristic during wear tests since some of the coatings exhibit severe delamination.

Initial-Boundary Value Problems for One-Dimensional pth Power Viscous Reactive Gas with Density-Dependent Viscosity

Initial-Boundary Value Problems for One-Dimensional pth Power Viscous Reactive Gas with Density-Dependent Viscosity

Kinetics and Thermodynamics of the Phase Transformation in the Nanocrystalline Substance—Gas Phase System

This study presents a model of the reaction of a nanocrystalline substance within the gas phase, where diffusion of gas reactants in the volume of the nanocrystallites is a rate-limiting step. According to the model calculations carried out, the rate of diffusion across the phase boundary located on the nanocrystallite surface limits the rate of the process. It was stated that in chemical processes with a phase transformation, the critical concentration of absorbate depends on two factors: the specific active surface area of the adsorbent and the difference in chemical potentials between the gas phase and the equilibrium potential at which the phase transformation occurs. When the actual adsorbate potential in the gas phase is much greater than the equilibrium potential of the nanocrystallite with the largest specific active surface, nanocrystallites undergo phase changes in the order according to their specific active surfaces from the largest to the smallest. In a process where the actual adsorbate potential is close to an equilibrium one, nanocrystallites undergo phase transformation in the order of their specific active surface from the smallest to the largest.

Analysis of the Radiator Loss Safety Boundary of a Space Reactor Gas Turbine Cycle with Multiple PCU Modules

The development of space exploration technologies puts higher demand on space power systems. The space reactor gas turbine cycle (SRGTC) has the advantages of compact configuration and small mass and volume and is one of the optimal options for future high-power space power systems. The SRGTC operates in an isolated island state and the radiator is fragile if it is hit by asteroids and space debris. The transient characteristics of the SRGTC are fundamental for safe operation in radiator loss accidents. In this paper, a dynamic model for the SRGTC is established, and the performance of the SRGTC with dual power conversion unit (PCU) modules (SRGTC-DPCU) after radiator loss was investigated. The results indicated that the waste heat of the system was accumulated in the radiator after radiator loss, which increased the consumed power of the compressor and further led to speed fluctuations. The bypass valve control and the temperature negative feedback effect can ensure the safe operation of the shaft and the reactor. More radiator loss decreased the speed far below the rated speed and exceeded the safety margin of the bypass valve control, which further led to system shutdown. There is a safety boundary of radiator loss accidents. Furthermore, the coupling effects of multiple PCUs after radiator loss were analyzed. The working fluid inventory was redistributed among the PCU modules. The reduction of working fluid inventory in the accident PCU module promoted the safety boundary. This study provides a reference for the operation of the SRGTC.

Enhancing Photocatalytic CO2 Conversion through Oxygen‐Vacancy‐Mediated Topological Phase Transition

Weak adsorption of gas reactants and strong binding of intermediates present a significant challenge for most transition metal oxides, particularly in the realm of CO2 photoreduction. Herein, we demonstrate that the adsorption can be fine‐tuned by phase engineering of oxide catalysts. An oxygen vacancy mediated topological phase transition in Ni‐Co oxide nanowires, supported on a hierarchical graphene aerogel (GA), is observed from a spinel phase to a rock‐salt phase. Such in‐situ phase transition empowers the Ni‐Co oxide catalyst with a strong internal electric field and the attainment of abundant oxygen vacancies. Among a series of catalysts, the in‐situ transformed spinel/rock‐salt heterojunction supported on GA stands out for an exceptional photocatalytic CO2 reduction activity and selectivity, yielding an impressive CO production rate of 12.5 mmol g‐1h‐1 and high selectivity of 96.5%. This remarkable performance is a result of the robust interfacial coupling between two topological phases that optimizes the electronic structures through directional charge transfer across interfaces. The phase transition process induces more Co2+ in octahedral site, which can effectively enhance the Co‐O covalency. This synergistic effect balances the surface activation of CO2 molecules and desorption of reaction intermediates, thereby lowering the energetic barrier of the rate‐limiting step.

Activatable Probes for Ratiometric Imaging of Endogenous Biomarkers In Vivo.

Dynamic variations in the concentration and abnormal distribution of endogenous biomarkers are strongly associated with multiple physiological and pathological states. Therefore, it is crucial to design imaging systems capable of real-time detection of dynamic changes in biomarkers for the accurate diagnosis and effective treatment of diseases. Recently, ratiometric imaging has emerged as a widely used technique for sensing and imaging of biomarkers due to its advantage of circumventing the limitations inherent to conventional intensity-dependent signal readout methods while also providing built-in self-calibration for signal correction. Here, the recent progress of ratiometric probes and their applications in sensing and imaging of biomarkers are outlined. Ratiometric probes are classified according to their imaging mechanisms, and ratiometric photoacoustic imaging, ratiometric optical imaging including photoluminescence imaging and self-luminescence imaging, ratiometric magnetic resonance imaging, and dual-modal ratiometric imaging are discussed. The applications of ratiometric probes in the sensing and imaging of biomarkers such as pH, reactive oxygen species (ROS), reactive nitrogen species (RNS), glutathione (GSH), gas molecules, enzymes, metal ions, and hypoxia are discussed in detail. Additionally, this Review presents an overview of challenges faced in this field along with future research directions.

Dissolution behavior and kinetic investigation of 〖Ca〗^(2+) in the dissolution of colemanite in propionic acid presence saturated with synthetic flue gas

Colemanite (〖2CaO.3B〗_2 O_3.5H_2 O) is a calcium borate mineral and can be expressed as the primary material of industrial production of boric acid. Boric acid is one of the most essential raw materials obtained by solving colemanite ore in acidic solutions and gases. The dissolution behavior and kinetics of 〖Ca〗^(2+) in a solution of colemanite in a propionic acid solution saturated with synthetic flue gas were examined. In this context; the effects of particle size, reaction temperature, acid concentration, solid-liquid ratio and synthetic flue gas flow rate parameters were investigated. According to the experimental data, it was observed that the amount of 〖Ca〗^(2+) passing to the solution increased with the increase of the reaction temperature, acid concentration and gas flow rate, and with the decrease in solid-liquid ratio and grain size. Experimental results were analyzed by homogeneous and heterogeneous models using the Statistica package program, and it was determined that the dissolution of 〖Ca〗^(2+) in solution complies with the “Avrami” model. The activation energy (E) was found as 〖26.83 kJ.mol〗^(-1) and the Arrhenius constant (A) was found as 〖8.9*10〗^3.

Evaluation of the first year of Pandora NO2 measurements over Beijing and application to satellite validation

Abstract. Nitrogen dioxide (NO2) is a highly photochemically reactive gas, has a lifetime of only a few hours, and at high concentrations is harmful to human beings. Therefore, it is important to monitor NO2 with high-precision, time-resolved instruments. To this end, a Pandora spectrometer has been installed on the roof of the laboratory building of the Aerospace Information Research Institute of the Chinese Academy of Sciences in the Olympic Park, Beijing, China. The concentrations of trace gases (including NO2, HCHO, O3) measured with Pandora are made available through the open-access Pandora database (https://data.pandonia-global-network.org/Beijing-RADI/Pandora171s1/, last access: 11 July 2023). In this paper, an overview is presented of the Pandora total and tropospheric NO2 vertical column densities (VCDs) and surface concentrations collected during the first year of operation, i.e., from August 2021 to July 2022. The data show that NO2 concentrations were high in the winter and low in the summer, with a diurnal cycle where the concentrations reached a minimum during the daytime. The concentrations were significantly lower during the 2022 Winter Olympics in Beijing, showing the effectiveness of the emission control measures during that period. The Pandora observations show that during northerly winds, clean air is transported to Beijing with low NO2 concentrations, whereas during southerly winds, pollution from surrounding areas is transported to Beijing and NO2 concentrations are high. The contribution of tropospheric NO2 to the total NO2 VCD varies significantly on daily to seasonal timescales; i.e., monthly averages vary between 50 % and 60 % in the winter and between 60 % and 70 % in the spring and autumn. A comparison of Pandora-measured surface concentrations with collocated in situ measurements using a Thermo Scientific 42i-TL analyzer shows that the Pandora data are low and that the relationship between Pandora-derived surface concentrations and in situ measurements is different for low and high NO2 concentrations. Explanations for these differences are offered in terms of measurement techniques and physical (transport) phenomena. The use of Pandora total and tropospheric NO2 VCDs for validation of collocated TROPOspheric Monitoring Instrument (TROPOMI) data, resampled to 100 m × 100 m, shows that although on average the TROPOMI VCDs are slightly lower, they are well within the expected error for TROPOMI of 0.5 Pmolec.cm-2 + (0.2 to 0.5) ⋅ VCDtrop (1 Pmolec.cm-2 = 1 × 1015 molec cm−2). The location of the Pandora instrument within a sub-orbital TROPOMI pixel of 3.5 km × 5.5 km may result in an error in the TROPOMI-derived tropospheric NO2 VCD between 0.223 and 0.282 Pmolec.cm-2, i.e., between 1.7 % and 2 %. In addition, the data also show that the Pandora observations at the Beijing-RADI site are representative of an area with a radius of 10 km.

Effect of ammonia-air combustion melting on the color and physical properties of soda lime silicate

Ammonia is a carbon-free fuel; hence, it does not generate CO2 during combustion. However, ammonia has a different combustion reaction and flue gas composition from conventional city gas; therefore, its impact on the glass-melting process and glass quality is unknown. In this study, batches of soda lime silicate glass and cullet raw materials were melted using ammonia or city gas as the fuel. Furthermore, the glass melted in the combustion and exhaust gas fields was analyzed to evaluate the effects on composition and color tone. The type of fuel and combustion atmosphere were found to affect the color and glass transition temperature. The batches and cullet materials that melted in the combustion field were colored because of combustion-atmosphere-induced changes in the valence of the Fe in the raw materials, and the coloration of this glass was more affected by the cullet than by the batches. Meanwhile, the glass melted in the exhaust gas field of ammonia combustion exhibited a lower glass transition temperature owing to the higher presence of H2O in the exhaust gas. The temperature was measured by four thermocouples (TC1–4) installed inside the furnace. The glass transition temperature of the glass at the TC4 position in the exhaust gas field using ammonia as fuel was 24 and 9 °C lower than those of the reference batch and cullet, respectively. Ammonia can be used as a decarbonized fuel for glass-melting furnaces by designing raw materials for soda lime silicate glass. However, the raw materials containing carbonates emitted CO2 in the exhaust gases during ammonia combustion. Therefore, to achieve a carbon-neutral glass manufacturing process, CO2 derived from both raw materials and fuel should be reduced.

Effect of gas crossover on the cold start process of proton exchange membrane fuel cells

This study develops a transient three-dimensional model to investigate the effect of reactant gas crossover through the membrane on the cold start process of PEM fuel cells. Key operating and structure parameters such as current density, anode/cathode inlet pressure, and membrane thickness are explored. The results reveal that gas crossover enhances ice formation rate and cell temperature rise due to additional hydrogen–oxygen side reactions, increasing both heat and water generations. The dominance of the ice formation rate over the temperature rise rate by gas crossover adds complexity to successful cold starts. Notably, the influence of gas crossover is more pronounced at a lower current density. As the operating current density increases from 0.04 A cm−2 to 0.12 A cm−2, the contribution of gas crossover to the temperature rise rate and ice formation rate decrease from 31.6 % to 11.3 % and from 54.5 % to 16.8 %, respectively. The increase of anode inlet pressure accelerates ice formation and temperature rise, whereas cathode inlet pressure has minimal effect. A thicker membrane mitigates gas crossover and is beneficial to cold start success, especially under a wet initial condition. This study emphasizes the significant role of gas crossover in the PEM fuel cell cold start process, highlighting the imperative consideration of gas crossover in both cold start models and strategy developments.

Optimal design of locally improved structure for enhancing mass transfer in PEMFC cathode flow field

At high current density, the mass transfer in proton exchange membrane fuel cells (PEMFC) is significantly influenced by the flow field structure. In this paper, a bilateral track flow field (BTFF) is proposed to improve the transverse and longitudinal mass transfer as well as the water removal capacity of PEMFC. The geometry of the BTFF is optimized by orthogonal tests to obtain the optimal combination of geometric parameters and levels. Then using numerical modeling, the impact of the optimized BTFF (BT6) on the efficiency of the PEMFC was examined. The results show that BT6 significantly improves the utilization of the under-rib region by shortening the reactive gas diffusion path length to obtain a more uniform oxygen distribution, and the average oxygen concentration in the midline of the under-rib of the BT6 is increased by 102.60%, furthermore, the current density is increased by 16.32% compared with that of the parallel flow field (case0). In addition, by reducing the cross-sectional area of the gas flow channel, the BT6 has a higher gas flow velocity, which accelerates the removal of cathode liquid water, and the average liquid water saturation in the midline of the under-rib of the BT6 is reduced by 15.26% compared with case0. Finally, by analyzing the net power density of PEMFC, it can be found that the net power density of BT6 is increased by 15.68% compared with case0, which has good practical application value.

Effects of nitrogen flow ratio on the mechanical and anticorrosive properties of cosputtered (TiZrHfTa)Nx films

In this study, TiZrHfTa films were cosputtered through cyclical gradient composition deposition by using four single-element targets connected to direct-current power supplies. Multilayered and columnar structures formed at low and high rotation speeds of the substrate holder (RH), respectively. (TiZrHfTa)Nx thin films were then prepared through reactive cosputtering by using Ar/N2 mixed gas. A high RH value resulted in these films having homogeneous structures. Without the addition of reactive nitrogen gas, the fabricated metallic Ti0.24Zr0.23Hf0.27Ta0.26 film exhibited a valence electron concentration of 4.26, which resulted in the formation of a body-centered cubic (bcc) phase; a hardness of 4.7 GPa; and an elastic modulus of 104 GPa. (TiZrHfTa)Nx films with stoichiometric ratios (x) ranging from 0.59 to 0.97 were obtained by adjusting the reactive gas ratio fN2 (N2/(N2 + Ar)) from 0.1 to 0.7. The introduction of N into the TiZrHfTa crystallites caused the bcc phase to transform into a face-centered cubic phase and enhanced the mechanical properties of the films, with their hardness and elastic modulus increasing to 13.8–25.5 and 235–290 GPa, respectively. Nanoindentation, scratch, Rockwell-C adhesion, and potentiodynamic polarization tests indicated that among the prepared (TiZrHfTa)Nx films, the (Ti0.17Zr0.25Hf0.20Ta0.38)N0.75 film exhibited the best mechanical and anticorrosive properties. Target poisoning accompanied by defect formation affected the mechanical properties of the (TiZrHfTa)Nx films. The anticorrosive properties of the (TiZrHfTa)Nx films were dominated by the high-entropy effect through alloying with Ta and the adhesion strength between the films and substrates.

Effects of sub-distribution zone structure of bipolar plate on the mass transport of large-area proton exchange membrane fuel cells

Sub-distribution zone of the flow field plays an important role in distributing gas reactants and removing liquid products in large-active area proton exchange membrane (PEM) fuel cells. This study evaluates the effects of sub-distribution zone of PEM fuel cells with the active area of 300 cm2 based on a three-plus-one-dimensional (3D+1D) model. A new structural design of sub-distribution zone, namely, mixed structure distribution zone (MSDZ) is proposed and compared with the classic dot matrix distribution zone (DMDZ) and forced shunt distribution zone (FSDZ) design regarding pressure drop, gas distribution uniformity and cell performance. It is found that FSDZ and MSDZ design distribution uniformities are improved by 90.4 % and 55.5 %, compared to DMDZ design. The cell with the MSDZ design reaches an optimal value of 0.647 V, attributed to the reduction in mass transport voltage loss. Subsequently, based on structure characteristics of FSDZ and MSDZ designs, the effects of the rib/channel width ratio in sub-distribution zone are explored. It is found that primary shunt affects the overall distribution and secondary shunt regulates the localization. Finally, the cell performance of the three types of sub-distribution zones is compared under different humidification conditions. Results show that the cell with MSDZ design demonstrates a power density increased by 4.0 % (0.05 W cm−2) and 7.6 % (0.09 W cm−2) compared with that with DMDZ design at high and low humidification conditions, respectively.

Synthesis of polymetallic oxides hollow spheres with superior activity, resistance to SO2, H2O and metal poisons for low-temperature NH3‑selective catalytic reduction of NOx

NH3‑selective catalytic reduction as the fascinating technology for complete NOx removal, the key in practical applications is to explore advanced catalysts with high catalytic reactivity and stability at low temperature. Herein, a series of hollow spherical AMnOx (A = Ce, Cu, Ni) catalysts was fabricated by using carbon nanospheres as sacrificial template. Characterization analysis including XRD, ICP, BET, SEM, TEM, H2-TPR, NH3-TPD, XPS, in situ DRIFTS together with kinetic studies were applied to acquire knowledge of the morphological structure and surface features of the catalysts as-prepared. We also performed a comparative study on three samples with regard to their SCR activity at low temperatures. Notable, the catalytic activity of the NiMnOx catalyst (95.9 %) was vastly superior to that of the CeMnOx (85.4 %) and CuMnOx (30.5 %) at 100 °C. This enhanced low-temperature activity of NiMnOx are correlated against hollow structure with more active sites, wider pore distribution, higher surface Mn content and the enhancement in surface acidity and reducibility. Even with 5 vol% H2O in the reaction gas fraction, the catalytic performance of NiMnOx hollow spheres was superior to the other two catalysts. Besides, it can be used for six consecutive runs without suffering a substantial activity loss. Additionally, the impact of various crucial process variables, including space velocity, H2O, SO2, and metal poisons, on the denitrification efficiency of NH3-SCR was examined. The current researches have a positive guiding role in the development of high-efficiency low-temperature NH3-SCR denitrification catalysts to boost NOx degradation.

Mesopore engineering of Co3O4 nanoplates for enhanced detection of toluene vapor

It remains a significant challenge for efficient detection of toluene vapor because of the low chemical reactivity. In this paper, the Co3O4 nanoplates with various mesopore widths (5.1, 12.6, and 19.8 nm) onto their surfaces have been successfully achieved using a simple hydrothermal and followed annealing route. Moreover, the sensor based on this Co3O4 nanoplate with mesopore width of 5.1 nm presents an obvious toluene-sensing response (including actual detection limit of 1 ppm, and excellent selectivity) at a low working temperature (140 °C). The improved toluene-sensing can be tracked from suitable mesopore size and specific catalytic activity of the Co3O4 nanoplates, which are advantageous for gas adsorption and diffusion, as well as facilitating the rapid oxidation of toluene gas. This work announces a reliable strategy to detect low reactive gas by constructing rational mesopores-width over the catalytic oxide.

Self-dispersed bimetallic NiRu nanoparticles on CeO2 for CO2 methanation

Redispersing bimetallic active nanoparticles in a heterogeneous catalyst can significantly improve metal utilization and catalytic performance, but it is very challenging. In this work, we report a feasible method to redisperse large bimetallic NiRu particles (30–40 nm) on the CeO2 support into small alloyed NiRu nanoparticles (3–5 nm) in an Ar gas atmosphere (NiRu/CeO2-Ar). During the high-temperature treatment, Ru metal in big bimetallic NiRu particles migrated to the surface of small alloyed nanoparticles because of the metal-phase separation, forming more Ni−Ru metal interfaces. As a result, NiRu/CeO2-Ar showed much better catalytic performance in CO2 methanation than the pristine catalyst (NiRu/CeO2) and the catalysts treated in air, H2, and reactant gases, respectively. Experimental and theoretical calculation results reveal that the newly generated Ni−Ru metal interfaces are conducive to the adsorption of CO2 and further direct dissociation into CO*, thus enhancing the catalytic performance. This work provides a reliable strategy to redisperse bimetallic NiRu nanoparticles into small ones with more intermetallic interfaces.