Temperature-programmed Desorption Techniques Research Articles

A Novel Composite Material UiO-66-Br@MBC for Mercury Removal from Flue Gas: Preparation and Mechanism.

To reduce the mercury content in flue gas from coal-fired power plants and to obtain high-performance, low-cost mercury adsorbents, a novel composite material was prepared by structural design through the in situ growth method. Functionalization treatments such as the modification of functional groups and multilayer loading of polymetallic were conducted. These materials include the MOF material UiO-66 and modified biochar doped with Fe/Ce polymetallic, both of which contain unsaturated metal centrals and oxygen-containing functional groups. On the basis of obtaining the effects of adsorption temperature and composite ratio on the Hg0 removal characteristics, coupling and synergistic mechanisms between the various types of active centers included were investigated by using a variety of characterization and analysis tools. The active adsorption sites and oxidation sites were identified during this process, and the constitutive relationship between the physicochemical properties and the performance of Hg0 removal was established. The temperature-programmed desorption technique, Grand Canonical Monte Carlo simulation, and adsorption kinetic model were employed to reveal the mechanism of Hg0 removal. The results showed that the UiO-66-Br@MBC composite adsorbent possessed an excellent Hg0 removal performance at adsorption temperatures ranging from 50 to 250 °C, and targeted construction of adsorption and oxidation sites while maintaining thermal stability. The Hg0 removal by the composites is the result of both adsorption and oxidation. The micropores and small pore mesopores in the samples provide physical adsorption sites. The modified biochar acts as a carrier to facilitate the full exposure of the central metal zirconium ions, the formation of more active sites, and the process of electron transfer. The doping modification of the Br element can enhance the overall redox ability of the sample, and the introduced Fe and Ce polymetallic ions can work in concert to promote the oxidation process of Hg0. The excellent regulation of the ratio between adsorption and oxidation sites on the surface of the composite material finally led to a significant boost in the samples' capacity to remove Hg0.

Ni-Based Molecular Sieves Nanomaterials for Dry Methane Reforming: Role of Porous Structure and Active Sites Distribution on Hydrogen Production.

Global warming, driven by greenhouse gases like CH4 and CO2, necessitates efficient catalytic conversion to syngas. Herein, Ni containing different molecular sieve nanomaterials are investigated for dry reforming of methane (DRM). The reduced catalysts are characterized by surface area porosity, X-ray diffraction, Raman infrared spectroscopy, CO2 temperature-programmed desorption techniques, and transmission electron microscopy. The active sites over each molecular sieve remain stable under oxidizing gas CO2 during DRM. The reduced 5Ni/CBV10A catalyst, characterized by the lowest silica-alumina ratio, smallest surface area and pore volume, and narrow 8-ring connecting channels, generated the maximum number of active sites on its outer surface. In contrast, the reduced-5Ni/CBV3024E catalyst, with the highest silica-alumina ratio, more than double the surface area and pore volume, 12-ring sinusoidal porous channels, and smallest Ni crystallite, produced the highest H2 output (44%) after 300 min of operation at 700 °C, with a CH4:CO2 = 1:1, P = 1 atom, gas hour space velocity (GHSV) = 42 L gcat-1 h-1. This performance was achieved despite having 25% fewer initial active sites, suggesting that a larger fraction of these sites is stabilized within the pore channels, leading to sustained catalytic activity. Using central composite design and response surface methodology, we successfully optimized the process conditions for the 5Ni/CBV3024E catalyst. The optimized conditions yielded a desirable H2 to CO ratio of 1.00, with a H2 yield of 91.92% and a CO yield of 89.16%, indicating high efficiency in gas production. The experimental results closely aligned with the predicted values, demonstrating the effectiveness of the optimization approach.

Probing Pt-CeO2 interfacial interactions through adsorption characteristics of small molecules

In this study, we prepared a Pt/CeO2/Cu(111) model catalyst and investigated CO and CO2 adsorption using infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) techniques to gain insight into the interaction between Pt nanoparticles and the CeO2 support surface. Our observations revealed that the deposition of CeO2 at 700 K results in island formation on the Cu(111) surface, whereas at 520 K it leads to a more continuous film formation. Reducing the CeO2/Cu(111) surface enhances the CO and CO2 uptakes on CeO2. Pt nanoparticles deposited on these surfaces remained in a metallic form, and during CO desorption, they facilitate the oxidation of CO to form CO2 by utilizing lattice oxygen from the interface between them and CeO2.

Enhancing Interaction between Lanthanum Manganese Cobalt Oxide and Carbon Black through Different Approaches for Primary Zn-Air Batteries.

Due to the need for decarbonization in energy generation, it is necessary to develop electrocatalysts for the oxygen reduction reaction (ORR), a key process in energy generation systems such as fuel cells and metal-air batteries. Perovskite-carbon material composites have emerged as active and stable electrocatalysts for the ORR, and the interaction between both components is a crucial aspect for electrocatalytic activity. This work explores different mixing methods for composite preparation, including mortar mixing, ball milling, and hydrothermal and thermal treatments. Hydrothermal treatment combined with ball milling resulted in the most favorable electrocatalytic performance, promoting intimate and extensive contact between the perovskite and carbon material and improving electrocatalytic activity. Employing X-ray photoelectron spectroscopy (XPS), an increase in the number of M-O-C species was observed, indicating enhanced interaction between the perovskite and the carbon material due to the adopted mixing methods. This finding was further corroborated by temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) techniques. Interestingly, the ball milling method results in similar performance to the hydrothermal method in the zinc-air battery and, thus, is preferable because of the ease and straightforward scalability of the preparation process.

Specific adsorptive properties and anodic polarization characteristics for hydrogen and methane in the Ni1-xCox solid-solution alloy combined with yttria-stabilized zirconia

The Ni-based cermet anode of a solid oxide fuel cell is prone to deactivation for the direct supply of CH4 due to carbon deposition. Discovered are specific adsorptive properties of Ni1-xCox solid-solution alloy catalysts combined with yttria-stabilized zirconia (Ni1-xCox-YSZ) using the temperature-programmed desorption technique. Decreasing the activation energy in the thermal desorption of adsorbed CH4 and CO from Ni1-xCox-YSZ accounts for minimizing the anodic polarization of the Ni/YSZ cermet by Co alloying in the electrochemical oxidation of CH4, suppressing carbon deposition.

An efficient and robust Co-free BaFeO3-based oxygen electrode for protonic ceramic electrochemical cells

Protonic ceramic electrochemical cells (PCECs) are promising devices for sustainable energy conversion and storage with high efficiency and low cost. However, the application of PCECs is limited by the scarcity of oxygen electrode materials with excellent oxygen reduction/evolution reaction (ORR/OER) activity and robust durability. In this investigation, perovskite oxide with specific non-stoichiometric ratios, namely Ba0.9Sr0.05La0.05Fe0.8Zn0.1Y0.1O3 (BSLFZY) are synthesized using a sol-gel method, and electrochemically evaluated as oxygen electrodes for PCECs. The structural and chemical stability of the synthesized material is explored and analyzed through X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations. Surface catalytic activity is assessed using X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), and oxygen temperature-programmed desorption techniques (O2-TPD). Additionally, the electronic conductivity results demonstrate the suitability of BSLFZY for application in PCECs. The electrochemical performance of the material is estimated using a homemade Ni-BZCYYb/BZCYYb cell with a BSLFZY oxygen electrode. Electrochemical impedance spectra within a specific temperature range are analyzed using the distribution of relaxation times (DRT) method. The results offer valuable insights into the underlying reasons for long-term electrochemical performance degradation in fuel cell (FC) mode. These results present the potential of BSLFZY for practical applications in PCECs, highlighting its excellent electrochemical performance and durability.

Photothermal Synergistic Catalysis over Defective Zn3In2S6 for CO2 Fixation.

Carbon dioxide (CO2) cycloaddition not only produces highly valued cyclic carbonate but also utilizes CO2 as C1 resources with 100% atomic efficiency. However, traditional catalytic routes still suffer from inferior catalytic efficiency and harsh reaction conditions. Developing multienergy-field catalytic technology with expected efficiency offers great opportunity for satisfied yield under mild conditions. Herein, Zn3In2S6 with sulfur vacancies (Sv) was fabricated with the assistance of cetyltrimethylammonium bromide (CTAB), which is further employed for photothermally driven CO2 cycloaddition first. Photoluminescence spectroscopy and photoelectrochemical characterization demonstrated its superior separation kinetics of photoinduced carriers induced by defect engineering. The temperature-programmed desorption (TPD) technique indicated its excellent Lewis acidity-basicity characters. Due to the combination of above merits from photocatalysis and thermal catalysis, defective Zn3In2S6-Sv achieved a yield as high as 73.2% for cyclic carbonate at 80 °C under blue LED illumination within 2 h (apparent quantum yield of 0.468% under illumination of 380 nm monochromatic light at 36 mW·cm-2), which is 2.9, 2.0, and 6.9 times higher than that in dark conditions and those of pristine Zn3In2S6 and industrial representative tetrabutylammonium bromide (TBAB) thermal-catalysis process under the same conditions, respectively. The synergistic reaction path of photocatalysis and thermal catalysis was discriminated by theoretical calculation. This work provides new insights into the photothermal synergistic catalysis CO2 cycloaddition with defective ternary metal sulfides.

Determination of characteristic properties of Co3O4 loaded LaFe x Al12−x O19 hexaaluminates

Abstract Hexaaluminates are drawing attention due to their exceptional mechanical and thermal stability. They can be proposed for applications as catalysts or catalyst support materials in high-temperature reactions. In this study, various LaFe x Al12−x O19 samples (x = 0.25, 0.5, 1, and 2) have been synthesized using the sol–gel method. Subsequently, these hexaaluminate samples were impregnated with cobalt oxide to form more active centers on the hexaaluminate support. The influence of the iron (Fe) content on the crystal structure, redox properties, and oxygen immobility has been investigated through X-ray diffraction, hydrogen temperature-programmed reduction, and oxygen temperature-programmed desorption techniques. Among the Co3O4@LaFe x Al12−x O19 samples, those with x ≥ 1 exhibited a hexaaluminate crystalline structure, demonstrating a higher lattice oxygen mobility.

Experimental H2O formation on carbonaceous dust grains at temperatures up to 85 K

ABSTRACT Water represents the main component of the icy mantles on dust grains, it is of extreme importance for the formation of new species and it represents the main component for life. Water is observed both in the gas-phase and frozen in the interstellar medium (ISM), where the solid-phase formation route has been proven essential to explain abundances in molecular clouds. So far, experiments have focused on very low temperatures (around 10 K). We present the experimental evidence of solid water formation on coronene, PAH-like surface, for a higher range of temperatures. Water is efficiently formed up to 85 K through the interaction of oxygen and hydrogen atomic beams with a carbonaceous grain analogue. The beams are aimed towards the surface connected to a cryostat exploring temperatures from 10 to 100 K. The results are obtained with a QMS and analysed through a temperature-programmed desorption technique. We observe an efficient water formation on coronene from 10 up to 85 K mimicking the temperature conditions from the dense ISM to translucent regions, where the ice mantle onset is supposed to start. The results show the catalytic nature of coronene and the role of chemisorption processes. The formation of the icy mantles could be happening in less dense and warmer environments, helping explaining oxygen depletion in the ISM. The findings have several applications such as the disappearance of PAHs in translucent regions and the snowlines of protoplanetary discs. We stress on how JWST projects characterizing PAHs can be combined with H2O observations to study water formation at warm temperatures.

Quantifying Carbon Active Sites Chemisorbing Hydrogen on Oxygen Containing Activated Carbons during Heat Treatment in Hydrogen Atmosphere.

Carbon edge sites have been widely studied because of their importance in surface reactivity and electronic properties. The surface chemistry of the carbon edge sites is relevant to various reactions, and carbon active sites are key topics in many applications. Temperature-programmed desorption (TPD) and temperature-programmed reaction (TPR) techniques are used to clarify the fate of oxygen atoms present as CO-yielding functional groups on the activated carbon during heat treatment in hydrogen with an argon balance atmosphere. It has been elucidated that CO is decomposed, H2O is released by a reduction reaction with atmospheric H2, and CO2 is evolved by secondary reactions from the CO-yielding functional groups during TPR. Atmospheric H2 consumption during TPR is observed and its rate is characterized. The amounts of carbon active sites are quantified by determining the amount of H2 chemisorbed onto the carbon surfaces. Finally, it is quantitatively determined that the active sites that chemisorb hydrogen are generated after the decomposition of CO and CO2 caused by secondary reactions between ca. 700 and 1100 K from the CO-yielding functional groups. The origin of these CO-yielding functional groups is generally attributed to phenol/ether groups. In addition to these oxygen-containing functional group decompositions, some free sites on the edge sites are activated for H2 chemisorption by heat treatment between ca. 700 and 1100 K.

In situ topologically prepared Co–Zn-based mixed metal oxide bimetallic catalysts for guaiacol hydrodeoxygenation

Bio-oil, derived from biomass pyrolysis, can be used as an alternative to fossil fuels after treatment through hydrodeoxygenation (HDO) reactions. In this study, a series of Co–Zn-based mixed metal oxide (Co-Zn-MMO) catalysts were synthesized using Co–Zn-based layered double hydroxide (Co-Zn-LDH) as a precursor. The catalysts were then used in the HDO reaction of guaiacol and larch wood-derived bio-oil. The Co–Zn-MMO catalysts were characterized via scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy, hydrogen-based temperature-programmed reduction, and ammonia temperature-programmed desorption techniques. Among the Co-Zn-MMO catalysts, the Co1-Zn2-MMO catalyst, with a Co-to-Zn molar ratio of 1:2, exhibited the highest acidity, the largest pore size and pore capacity, and the highest density (65.56%) of Co2+δ-Ov-Zn2-δ oxygen vacancy. These characteristics resulted from the metal–support interaction effect, leading to superior HDO activity for guaiacol. Furthermore, the Co1-Zn2-MMO catalyst effectively removed heteroatomic components from larch wood-derived bio-oil, thereby enhancing the quality of the bio-oil product.

Insight into the role of mesoporosity in the selective production of propene from methanol

Microporous ZSM-5, hierarchical ZSM-5, and hierarchical ZSM-11 zeolites with different crystalline sizes were prepared to determine the relations of mesoporosity with catalytic performance in methanol-to-propene reaction. The physicochemical properties were investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Temperature-Programmed Desorption, and sorption techniques. It was shown that the low pore tortuosity, hierarchical structure, and the reduction of the crystal size all can shorten the diffusion path and reduce the diffusion resistance, leading to the increase of propylene yield. By comparison, the propene yield increase to the increment of mesoporous volume due to the tortuosity is more effective than other aspects. For silica–alumina zeolites, the effective way to reduce the diffusion resistance and increase the selectivity of propylene is to lower the pore tortuosity degree, and then introduce the mesoporous structure and reduce the grain size.

Structural Engineering of Nanocarbons Comprising Graphene Frameworks via High-Temperature Annealing

Abstract High-temperature annealing is an effective way to heal the defects of graphene-based nanocarbons and enhance their crystallinity. However, the thermally induced vibration of the graphene building blocks often leads to unfavorable micro-, nano-structural evolution including layer stacking. Herein, the key structural factors to achieve highly crystalline graphene frameworks with desired microstructures upon annealing at 1800 °C is revealed. The structural changes of fullerenes, single-walled carbon nanotubes, and graphene-based porous frameworks are precisely analyzed by their structural parameters, such as the total number of graphene edge sites and precise graphene stacking structures, using a novel advanced vacuum temperature-programmed desorption technique up to 1800 °C. The stacked structure is differentiated into loose and tightly stacking, where the loosely stacked structure is found to induce further stacking at high-temperature. Moreover, a graphene framework with an inner space size of greater than 4–7 nm is beneficial to avoid structural change upon high-temperature annealing. These findings offer both a fundamental understanding of the solid-state chemistry of nanocarbons under high temperatures and a viable strategy for engineering edge-site free graphene frameworks with pre-designed microstructures.

Characterisation of the surface chemistry of carbon materials by temperature-programmed desorption: An assessment

The increasing role assumed by carbon materials in technological applications is intrinsically linked to a better understanding of carbon surface chemistry as a result of reliable methods of analysis. X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) techniques allow to obtain qualitative and quantitative information on individual functional groups on the carbon surface. In this context, TPD has established itself as an alternative technique to the Boehm titration methodology or XPS, being especially adequate for the characterisation of oxygen functional groups on carbon materials with extended porosity. This work reviews the fundamentals and methodology to perform a correct TPD-MS analysis and assessment (qualitatively and quantitatively) of the oxygenated functional groups. The applicability of the information obtained by TPD to correlate the properties of carbon materials with their performance in practical applications is also revised.

Esterification as well as transesterification of waste oil using potassium imbued tungstophosphoric acid supported graphene oxide as heterogeneous catalyst: Optimization and kinetic modeling

For one pot esterification as well as transesterification of waste oil (WO), K+ impregnated tungstophosphoric acid (TPA) was supported over graphene oxide (GO) and used as a heterogeneous catalyst. The structure of the catalyst was evaluated by a powder X-ray diffraction (XRD) study. The elemental oxidation state and catalyst composition was confirmed by X-ray Photoelectron Spectroscopy (XPS) analysis. The temperature-programmed desorption (TPD) technique supported the existence of acidic and basic sites on the surface of the catalyst. Being acidic, TPA probably catalyzes the esterification while K+ transesterification activity to the catalyst. Beneath the optimized reaction conditions, i.e. loading of catalyst 10 wt% (concerning oil), methanol: oil molar ratio of 9:1 with reaction temperature of 65 °C, >98.5% (±0.34) biodiesel was produced within 1.5 h of reaction period. By using centrifugation, the catalyst was extracted from the reaction mixture and recycled six times. The metal level in the reaction mixture was determined to be less than 2 ppm, supporting the stability of the catalyst. Additionally, the catalyst was found to be active even in the existence of free fatty acid (up to 8.76 wt%) and moisture (up to 4.0 wt%) contents. The positive values of enthalpy of activation (ΔH‡) and free energy of reaction (ΔG‡) highlighted the endothermic and non-spontaneous nature of the reaction. The kinetic modeling study, using MATLAB software (version R2021b), suggests that the reaction of WO with the synthesized catalyst was found to follow a (pseudo) first-order kinetic equation. A negative value of entropy of activation (ΔS‡) indicates that the reaction of triglyceride (T) to diglyceride (D) follows the associative pathway. In contrast, the diglyceride to monoglyceride (M) and monoglyceride to glycerol (G) conversion progressed via dissociative route.

Microwave treatment effect on the enhanced basicity of porous clay heterostructured composites derived from Laponite

Porous clay heterostructured composites (PCH) derived from layered hydrous magnesium silicate, Laponite, were functionalized by Fe(NO3)3x9H2O with the use of mechano-chemical impregnation followed by microwave irradiation or hydrothermal treatment to evoke new base properties, active in CO2 sorption. It resulted in the progressive leaching of the Mg2+ from the octahedral sheets of the Laponite structure and their capture on the surface of PCH composites increasing the Mg/Si ratio. The increase of Mg/Si ratio was accompanied by the decline of the (Mg3OH) absorption bands intensity attributed to Laponite and discussed regarding the formation of dispersed nanostructured MgO moieties capable of adsorbing CO2. CO2-TPD temperature-programmed desorption technique revealed that sorption and stabilization of CO2 molecules are related to the coordination of oxygen sites in the formed MgO lattice and that edge and corner sites facilitate the interaction of CO2 molecules with O2− sites on MgO. Doping of PCH resulted also in the nucleation of nanocrystalline α-Fe2O3 able to capture CO2 with strength and stability higher than MgO. Microwave irradiation resulted in significant development of the surface basicity as part of the transformation of clay structure. This study confirms the importance of clay minerals in the uptake and retention of CO2.

Mechanochemical Synthesized CaO/ZnCo2O4 Nanocomposites for Biodiesel Production

Biodiesel has been recognized as an environmentally friendly, renewable alternative to fossil fuels. In this work, CaO/ZnCo2O4 nanocomposites were successfully synthesized via simple mechanochemical reaction between ZnCo2O4 and CaO powders by varying the CaO loading from 5 to 20 wt.%. The synthesized materials were found to be highly efficient heterogeneous catalysts for transesterification of tributyrin with methanol to produce biodiesel. The nanocomposite, which contained 20 wt.% CaO and 80 wt.% ZnCo2O4 (CaO/ZnCo2O4-20), exhibited superior and stable transesterification activity (98% conversion) under optimized reaction conditions (1:12 TBT to methanol molar ratio, 5 wt.% catalyst and 180 min. reaction time). The experimental results revealed that the reaction mechanism on the CaO/ZnCo2O4 composite followed pseudo first-order kinetics. The physicochemical characteristics of the synthesized nanocomposites were measured using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier-transformed infrared spectroscopy (FTIR), X-ray photoelectron spectrometer (XPS), N2-physisorption, and CO2- temperature-programmed desorption (CO2-TPD) techniques. The results indicated the existence of coalescence between the CaO and ZnCo2O4 particles, Additionally, the CaO/ZnCo2O4-20 catalyst was found to possess the greater number of highly basic sites and high porosity, which are the key factors affecting catalytic performance in transesterification reactions.

Clarification of the Effects of Oxygen Containing Functional Groups on the Pore Filling Behavior of Discharge Deposits in Lithium–Air Battery Cathodes Using Surface-Modified Carbon Gels

In lithium–air batteries (LABs), controlling the characteristics of the Li2O2 deposited during discharging can lead to the reduction of the large overpotential required for charging. The large overpotential is one of the most significant problems that needs to be solved to improve the cycle performance of LABs. Here, we focused on the effects of functional groups in the cathode carbon on the characteristics of the Li2O2 deposited during discharging and the cathode performance of LABs. In this study, 4 types of carbon gels (CGs) were prepared using different treatment methods to modify their surface properties. The types and amounts of oxygen-containing functional groups (OCFGs) existing within the CGs were clarified along with the number of edge H’s by a high-sensitivity temperature-programmed desorption (TPD) technique. The results of N2 adsorption analysis of discharged CGs suggested that, by increasing the number of OCFGs from 0.40 to 1.80 mmol g–1 through acid treatment, the ratio of Li2O2 deposited within the mesopores of the porous carbon particles can be increased from 1% to 60%. This significant change in the manner of Li2O2 deposition led to the reduction of the charging overpotential. Side reactions that are thought to deteriorate cycle performance tended to proceed in CGs having a large number of OCFGs. This negative effect could be reduced by removing carboxyl groups in the CGs through simple heat treatment at 300 °C in an inert atmosphere. Our study clarified the critical roles of OCFGs in the cathode during the discharging and charging of LABs. The obtained knowledge can be utilized for the development of a high-performance cathode for LABs.

Microcantilever-Based In Situ Temperature-Programmed Desorption (TPD) Technique.

Temperature-programmed desorption (TPD) is an essential technique for characterizing the fundamental properties of advanced catalysts like catalytic activity and kinetics. However, the available TPD instruments are bulky and use ex situ detectors to measure the probe molecules in the elution gas flow. Herein, we demonstrate an in situ TPD technique by developing a silicon microcantilever that integrates functional elements for mass measuring and programmable sample heating. An only nanogram-level sample is required to load on the microcantilever free end, where the integrated microheater provides programmed temperatures and the desorption-induced mass change can be measured in situ. In situ TPD can continuously measure the number of desorbed molecules from the catalyst during programmed heating, without the need for ex situ detectors. With a single-time in situ TPD measurement, the desorption activation energy can be directly calculated. The proposed in situ TPD method outperforms the existing TPD techniques and is expected to enable next-generation TPD applications.

Continuous CO2 capture and methanation over Ni-Ca/Al2O3 dual functional materials.

Although Ni-Ca-based dual functional materials (DFMs) have been examined for CO2 capture and reduction with H2 (CCR) for the synthesis of CH4, their performance has generally been investigated using single reactors in an oxygen-free environment. In addition, continuous CCR operations have scarcely been investigated. In this study, continuous CCR for the production of CH4 was investigated using a double reactor system over Al2O3-supported Ni-Ca DFMs in the presence of O2. We found that a high Ca loading (Ni(10)-Ca(30)/Al2O3, 10 wt% Ni, and 30 wt% CaO) was necessary for reaction efficiency under isothermal conditions at 450 °C. The optimized DFM exhibited an excellent performance (46% CO2 conversion, 45% CH4 yield, and 97% CH4 selectivity, respectively) and good stability over 24 h. The structure and CCR activity of Ni(10)-Ca(30)/Al2O3 were studied using X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectrometry (EDS), temperature-programmed desorption (TPD), and temperature-programmed surface reaction (TPSR) techniques.