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Effect of UiO-66 precursors with different Ce/Zr ratios on the performance of Pt-based catalysts in dry methane reforming reactions
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Chen YANG, Panying JIANG, Dongyang SHEN, Yuhua ZHANG, Jinlin LI*, Lin LI*
Journal of Fuel Chemistry and Technology | 2026, 54(8) : 20250335-1671 - 20250335-1681
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Journal of Fuel Chemistry and Technology | 2026, 54(8): 20250335-1671-20250335-1681
• RESEARCH PAPER •
Effect of UiO-66 precursors with different Ce/Zr ratios on the performance of Pt-based catalysts in dry methane reforming reactions
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Chen YANG, Panying JIANG, Dongyang SHEN, Yuhua ZHANG, Jinlin LI*, Lin LI*
Affiliations
  • Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science, South-Central Minzu University, Wuhan 430074, China
Published: 2026-08-10 doi: 10.1016/S1872-5813(26)60669-X
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To address challenges of sintering and carbon deposition in the dry reforming of methane (DRM), this study employs UiO-66 as a precursor for modifying Pt-based catalysts. A series of Pt/CeO2-ZrO2 catalysts were synthesized via incipient wetness impregnation using supports with varying Ce/Zr ratios prepared through a hydrothermal method. Comprehensive characterization—including CO2-TPD, CH4-TPD, XPS, XAFS, in situ DRIFTS, TG and Raman spectroscopy—revealed a volcano type correlation between DRM performance and the Ce/Zr ratio. Optimal catalytic activity and stability were achieved with the Pt/3CeO2-ZrO2 catalyst (Ce/Zr = 3∶1). This catalyst features highly dispersed platinum, primarily existing as single atoms and thermally stable PtOx clusters. Furthermore, it exhibits the highest concentration of Ce3+ and Zr3+ species, abundant oxygen vacancies (Vo), and a high defect density, all of which are indicative of a strong metal-support interaction. Mechanistically, the continuous and stable DRM reaction is facilitated by oxygen-assisted CH4 dissociation and hydrogen-assisted CO2 dissociation. At 800 °C, this catalyst exhibited outstanding performance, with CH4 and CO2 conversion rates reaching 86% and 93%, respectively. Notably, a 10 h stability test revealed no detectable carbon deposition. These results confirm that the catalyst significantly enhances reaction kinetics while demonstrating superior activity, stability, and resistance to both coking and sintering.

dry reforming of methane  /  platinum catalysts  /  UiO-66  /  CeO2-ZrO2
杨晨, 姜潘颖, 申东阳, 张煜华, 李金林, 李琳. 不同Ce/Zr比的UiO-66前驱体对Pt基催化剂甲烷干重整反应性能的影响. 燃料化学学报（中英文）, 2026 , 54 (8) : 20250335-1671 -20250335-1681 . DOI: 10.1016/S1872-5813(26)60669-X
Chen YANG, Panying JIANG, Dongyang SHEN, Yuhua ZHANG, Jinlin LI, Lin LI. Effect of UiO-66 precursors with different Ce/Zr ratios on the performance of Pt-based catalysts in dry methane reforming reactions[J]. Journal of Fuel Chemistry and Technology, 2026 , 54 (8) : 20250335-1671 -20250335-1681 . DOI: 10.1016/S1872-5813(26)60669-X
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Global warming, driven by excessive greenhouse gas emissions, constitutes one of the most critical environmental challenges of our time. Carbon dioxide (CO2) and methane (CH4) serve as the primary contributors, accounting for approximately 71.6% and 21% of total emissions, respectively[1−2]. As climate impacts intensify, there is an urgent imperative to shift toward need to transition towards sustainable energy frameworks by converting these greenhouse gases into high-value fuels and chemicals[3−4]. Dry reforming of methane (DRM) represents a promising strategy for carbon recycling, as it simultaneously converts CH4 and CO2 into economically valuable syngas with a unity H2/CO ratio. Consequently, DRM has attracted considerable attention for its potential applications in sustainable energy and chemical synthesis[5−7].
However, the highly endothermic nature of DRM requires elevated operating temperatures (typically exceeding 700 °C) to drive the reaction[8−9]. Under these harsh conditions, catalysts are prone to rapid deactivation via carbon deposition (coking) and sintering, presenting a major bottleneck for industrial implementation[10−11]. While non-noble metal catalysts, particularly nickel-based systems, exhibit reasonable considerable initial activity, they suffer from severe instability due to coking and sintering at high temperatures[12−14]. In contrast, noble metals such as platinum (Pt) offer superior activity, stability and selectivity, attributed to their unique electronic structures and adsorption properties[15−17]. Although the application of Pt is constrained by its high cost and limited abundance, cost-effective Pt-based catalysts can be engineered by maximizing atomic utilization, stabilizing active sites, enhancing metal-support interactions (MSI), and effectively suppressing carbon deposition. Notably, Jones et al.[18] demonstrated that Pt atoms can be trapped by CeO2, yielding a Pt/CeO2 catalyst stable up to 800 °C during CO oxidation. This finding provides a critical foundation for designing Pt/CeO2 catalysts capable of withstanding the rigorous thermal demands of DRM.
Metal-organic frameworks (MOFs), a class of emerging crystalline porous materials, have attracted widespread attention for DRM applications due to their abundant active sites, high specific surface areas, and tunable pore architectures[19−21]. Among these, the UiO-66 series is particularly notable for its exceptional thermal and chemical stability, as well as its robust framework, which facilitates efficient gas adsorption and dissociation[22−25]. For instance, Shao et al.[26] utilized Zr-UiO-66 as a precursor to synthesize Ni@ZrO2 catalysts via a controlled preparation strategy. Their Ni/ZrO2-B variant exhibited superior DRM performance, which was attributed to the high dispersion of Ni species and strong metal-support interactions (SMSI). Concurrently, Ceria (CeO2), an abundant and cost-effective rare-earth material with a cubic fluorite structure, is widely used in catalysis. Its rich surface oxygen vacancies play a critical role in promoting CO2 activation[27−29]. Leveraging MOF chemistry, Lammert et al.[30] successfully synthesized Ce-based UiO-66 with an octahedral cage structure via a solvothermal method, achieving excellent thermal and chemical stability. However, pure CeO2 is prone to tends to sintering under high-temperature or reducing conditions, leading to surface area loss and catalytic deactivation[31]. To address this, zirconium (Zr) doping has been proven effective due to the high compatibility between Ce and Zr[32]. Zhou et al.[33] demonstrated that substituting Ce4+ (0.092 nm) with the smaller Zr4+ ion (0.084 nm) creates a CeO2-ZrO2 solid solution, significantly enhancing thermal stability, redox properties, and oxygen storage capacity. Damyanova et al.[34] further showed that pretreatment temperature and CeO2 concentration significantly influence strongly affect Pt morphology. While their Pt/6CeO2-ZrO2 catalyst exhibited high Pt dispersion and favorable reducibility, it required a prolonged induction period to stabilize activity, indicating considerable potential for further performance optimization. Consequently, this study utilizes UiO-66 as a precursor to engineer Pt-based catalysts. A series of Pt/CeO2-ZrO2 catalysts were synthesized via impregnation, utilizing supports with varying Ce/Zr ratios prepared through a hydrothermal method. By systematically modulating the Ce/Zr ratio, this work aims to enhance thermal stability, harness the redox properties of the support, and optimize defect concentrations. Ultimately, these findings provide valuable experimental insights for the rational design and optimization of Pt-based catalysts for DRM applications.
1　Experimental
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1.1　Materials
Ammonium cerium nitrate (Ce(NH4)2(NO3)6), zirconium chloride (ZrCl4) and 2-aminoterephthalic acid were purchased from Aladdin. All reagents were of analytical grade. N, N-dimethylformamide (DMF, analytical grade) was obtained from Sinopharm Chemical Reagent Co., Ltd., while chloroplatinic acid solution (H2PtCl6, 8%) was procured from Alfa Aesar.
1.2　Catalyst preparation
1.2.1　Preparation of supports
CeO2 and ZrO2 supports were prepared via the thermal decomposition of hydrothermally synthesized Ce- and Zr-based UiO-66 precursors. Specifically, 2-aminoterephthalic acid (0.688 g) was dissolved in N, N-dimethylformamide (DMF, 180 mL) under magnetic stirring, followed by the addition of 60 mL of a 0.5 mol/L metal salt solution (either Ce(NH4)2(NO3)6 or ZrCl4). The mixture was stirred at 500 r/min for 30 min at room temperature, transferred to a Teflon-lined autoclave, and heated at 180 °C for 6 h. The resulting precipitates were collected by vacuum filtration, washed and dried at 80 °C for 12 h. To obtain the final supports, the dried powders were calcined in air at 350 °C for 2 h (ramp heating rate: 2 °C/min). Mixed-oxide supports were prepared using the same procedure, substituting the single-metal solution with 60 mL of a mixed Ce(NH4)2(NO3)6 and ZrCl4 solution (total concentration: 0.5 mol/L) with Ce/Zr ratios of 6∶1, 3∶1, 2∶1, 1∶1 and 0.5∶1.
1.2.2　Preparation of catalyst
Catalysts with a nominal Pt loading of 0.8% were prepared via wet impregnation. Specifically, an aqueous H2PtCl6 solution (8%) was deposited onto the supports with varying Ce/Zr ratios using rotary evaporation. The resulting samples were dried at 80 °C for 12 h and subsequently calcined in a muffle furnace at 800 °C for 10 h (ramp rate: 2 °C/min). The final catalysts were designated as follows: Pt/6CeO2-ZrO2 (denoted as Pt/6Ce-Zr), Pt/3CeO2-ZrO2 (Pt/3Ce-Zr), Pt/2CeO2-ZrO2 (Pt/2Ce-Zr), Pt/CeO2-ZrO2 (Pt/Ce-Zr), Pt/CeO2-0.5ZrO2 (Pt/Ce-0.5Zr), Pt/CeO2 and Pt/ZrO2.
1.3　Catalytic performance evaluation
1.3.1　Catalytic activity tests
Catalytic activity tests were conducted in a stainless-steel fixed-bed reactor (12 mm inner diameter). The effluent gas composition was analyzed online using an Agilent 3000 Micro-GC. Reactions were performed at atmospheric pressure using 0.1 g of catalyst diluted with 1.0 g of inert SiC to mitigate thermal gradients. The feed gas consisted of a mixture of CH4, CO2 and N2 (1∶1∶1 molar ratio) introduced at a gas hourly space velocity (GHSV) of 36 L/(g·h). Activity data were collected over a temperature range of 600–800 °C. The conversions of CH4 and CO2, as well as the H2/CO ratio, were calculated according to the following equations[35]:
$ {{x}}_{{{\text{CH}}_{\text{4}}}}\text=\frac{\text{(}{{F}}_{{{\text{CH}}_{\text{4,in}}}}-{{F}}_{{{\text{CH}}_{\text{4,out}}}}\text{)}}{{{F}}_{{{\text{CH}}_{\text{4,in}}}}}{\times 100 \%} $
$ {{x}}_{{{\text{CO}}_{\text{2}}}}=\frac{\text{(}{{F}}_{{{\text{CO}}_{\text{2,in}}}}-{{F}}_{{{\text{CO}}_{\text{2,out}}}}\text{)}}{{{F}}_{{{\text{CO}}_{\text{2,in}}}}}{\times 100 \%} $
$ \frac{{\text{H}}_{\text{2}}}{\text{CO}}\text=\frac{{{F}}_{{{\text{H}}_{\text{2,out}}}}}{{{F}}_{{{\text{CO}}_{\text{out}}}}} $
where $ {{x}}_{\mathrm{C}{{\mathrm{H}}_{4}}} $ and $ {{x}}_{\mathrm{C}{{\mathrm{O}}_{2}}} $ denote the conversions of CH4 and CO2, respectively, and F represents the reactant flow rate (L/h).
1.3.2　Catalyst stability tests
Stability tests were conducted using the same 12 mm (i.d.) stainless steel fixed-bed reactor described previously. The evaluation was performed at 800 °C for 10 h. Conditions remained identical to the activity tests, with the exception that the catalyst bed was undiluted (no SiC). Reactant conversions (CH4, CO2) and the H2/CO ratio were calculated using the methods defined above.
1.4　Catalyst characterization
1.4.1　Temperature-programmed desorption (TPD)
The chemisorption behavior of CH4 and CO2 were investigated on an AMI-300 chemisorption analyzer (Zeton Altamira, USA). Prior to testing, 50.0 mg of the catalyst was loaded into a U-shaped quartz tube. The sample was pretreated in a helium flow (30 mL/min) at 150 °C for 1 h to remove impurities, then cooled to 50 °C in the same flow. The flow was then switched to the probe gas (CH4 or CO2, 30 mL/min) for a 1 h adsorption period. Subsequently, the system was purged with helium (30 mL/min) to remove physisorbed species until a stable baseline was obtained. Finally, desorption profiles were recorded by ramping the temperature to 750 °C at a rate of 10 °C/min.
1.4.2　X-ray absorption fine structure (XAFS)
The local coordination environment of Pt was investigated using X-ray absorption fine structure (XAFS) spectroscopy. Measurements were conducted at the BL14W1 beamline of the Shanghai Synchrotron Radiation Facility (SSRF), with the storage ring operating at an electron energy of 3.5 GeV. The incident beam was monochromatized using a Si(311) double-crystal monochromator. Data were collected using an argon-filled Lytle detector. The beam spot size was defined by horizontal and vertical slits to be approximately 1 mm×4 mm.
1.4.3　X-ray photoelectron spectroscopy (XPS)
X-ray photoelectron spectroscopy (XPS) measurements were performed on a VG Multilab 2000 spectrometer equipped with a monochromatic Al Kα radiation (hv=1486.6 eV). Binding energies were calibrated using the adventitious C 1s peak at 284.8 eV to compensate for surface charging effects.
1.4.4　Raman spectroscopy
Raman spectroscopy was employed to characterize the carbon species on the spent catalysts using a Thermo Scientific DXR2 XI confocal Raman spectrometer. Spectra were collected at room temperature using a 532 nm Ar+ laser for excitation. Measurements were performed using a 50× objective lens with an exposure time of 30 s. The spectra were recorded over a range of 80–4000 cm−1 with a spectral resolution of 2 cm−1.
1.4.5　 In situ diffuse reflectance fourier transform infrared spectroscopy (in situ DRIFTS)
In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments were conducted using a Thermo Scientific Nicolet iS50 spectrometer. All spectra were acquired by accumulating 64 scans at a resolution of 4 cm−1.
For single-component adsorption experiments (CH4 or CO2), the sample was first pretreated at 250 °C for 1 h under an Ar flow (30 mL/min) with a heating rate of 5 °C/min to remove surface impurities. After cooling to room temperature (25 °C), a background spectrum was collected under the Ar atmosphere. The feed gas was then switched to a mixture of the adsorbate (CH4 or CO2) and Ar (5∶30 mL/min), and the temperature was increased to the target reaction temperature of 350 °C at a rate of 2 °C/min for data acquisition.
To investigate surface species during the isothermal DRM reaction, in situ DRIFTS measurements were performed. Prior to the reaction, the catalyst was pretreated at 250 °C for 1 h under an Ar flow (30 mL/min) with a heating rate of 5 °C/min. Subsequently, the temperature was increased to 350 °C at a rate of 5 °C/min under the same Ar flow, followed by a 30 min stabilization period to ensure thermal equilibrium. After collecting a background spectrum, the feed gas was switched to a reactant mixture of CH4, CO2 and Ar (5∶5∶30 mL/min) to initiate the DRM reaction, which was monitored for 1 h.
1.4.6　Thermogravimetric analysis (TGA)
The carbon content of the spent catalysts was determined using a simultaneous thermal analyzer (TA Instruments Q600 SDT), which records both mass loss (TG) and heat flow (DSC) signals. Analysis was conducted in an air atmosphere. The samples were heated from 50 to 800 °C at a rate of 10 °C/min.
2　Results and discussion
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2.1　Catalytic performance evaluation
2.1.1　Catalytic activity tests
Catalytic performance was evaluated in a fixed-bed reactor, with the results presented in Figure 1. As expected for the highly endothermic DRM reaction, catalytic activity increased with rising temperature. The observed H2/CO ratio of below 1 is attributed to the concurrent reverse water-gas shift (RWGS) side reaction. The Pt/ZrO2 catalyst exhibited the lowest activity. However, incorporating Ce progressively enhanced performance; Figure 1(c) illustrates this trend, showing a positive correlation between CH4 conversion and the Ce/Zr ratio. Optimal performance was achieved at a Ce/Zr ratio of 3, which yielded the highest CH4 and CO2 conversions and H2/CO ratio. Further increasing the ratio to 6 resulted in a decline in activity. Specifically, the Pt/3CeO2-ZrO2 catalyst achieved CH4 and CO2 conversions of 86% and 93%, respectively, at 800 °C, with an H2/CO ratio close to unity.
2.1.2　Catalyst stability tests
Stability tests for the Pt/3CeO2-ZrO2, Pt/CeO2 and Pt/ZrO2 catalysts were conducted at 800 °C for 10 h (Figure 2). For all three catalysts, the H2/CO ratio remained below unity due to the concurrent reverse water-gas shift (RWGS) side reaction. Notably, the Pt/3CeO2-ZrO2 catalyst exhibited superior catalytic performance and stability. Under these conditions, it achieved initial CH4 and CO2 conversions of 57% and 70%, respectively, along with the highest H2/CO ratio among the tested samples. Its exceptional stability was evidenced by the absence of significant deactivation over the 10 h run. The robustness and high activity of Pt/3CeO2-ZrO2 at 800 °C can be attributed to several factors. First, the active Pt species are well-dispersed. Second, synchrotron radiation analysis reveals that, unlike the single-atom structure in Pt/CeO2, Pt in Pt/3CeO2-ZrO2 catalyst exists primarily as thermally stable PtOx nanoclusters. Third, XPS and CO-DRIFTS characterizations confirm that this catalyst possesses the highest concentration of surface defects, facilitating the reaction. These combined features underpin its superior stability and activity. In contrast, both Pt/CeO2 and Pt/ZrO2 catalysts suffered from varying degrees of deactivation. This is attributed to the thermal instability of Pt single atoms in Pt/CeO2, and to severe carbon deposition on Pt/ZrO2, caused by the lack of CHxO* intermediate formation and a lower oxygen vacancy concentration.
2.2　Catalyst characterization
2.2.1　Chemisorption analysis
The CO2-TPD profiles are presented in Figure 3(a). Both Pt/3CeO2-ZrO2 and Pt/CeO2 exhibited comparable desorption capacities, characterized primarily by weak adsorption peaks below 250 °C. The absence of significant medium-strength adsorption sites suggests these catalysts facilitate efficient CO2 adsorption-desorption dynamics. In contrast, Pt/ZrO2 displayed stronger CO2 binding, with desorption peaks dominated by medium-strength sites above 250 °C. This indicates that the incorporation of CeO2 effectively optimizes the CO2 adsorption properties of the zirconia support. Figure 3(b) displays the CH4-TPD profiles. The Pt/CeO2 catalyst showed the highest CH4 uptake, featuring weak adsorption sites (below 250 °C) and medium-strong adsorption sites (200–500 °C). Conversely, Pt/ZrO2 exhibited the weakest CH4 adsorption capacity, characterized by weak adsorption peak and a high-temperature desorption peak between 500 and 700 °C. The Pt/3CeO2-ZrO2 catalyst demonstrated improved CH4 adsorption capacity compared to Pt/ZrO2, with a desorption profile similar to Pt/CeO2 (weak adsorption below 250 °C and medium-strong adsorption at 200–500 °C). In summary, the TPD results confirm that Pt/3CeO2-ZrO2 and Pt/CeO2 possess superior chemisorption properties for both reactants compared to Pt/ZrO2, which is favorable for the DRM reaction.
2.2.2　Analysis of the coordination structure of active sites
Figure 4(a) displays the XANES spectra of the three catalysts alongside PtO2 and Pt foil references. The near-edge absorption features of the catalysts closely resemble those of PtO2, indicating that the Pt species exist primarily in an oxidized state. Figure 4(b) presents the Fourier-transformed EXAFS spectra. In the reference samples, the Pt−O coordination shell in PtO2 appears at approximately 1.6 Å, while the metallic Pt−Pt bond in the Pt foil is centered between 2.5 and 2.7 Å.
All three catalysts exhibited a prominent signal at ~1.6 Å, corresponding to Pt−O coordination. Wavelet transform (WT) analysis was conducted to resolve both K-space and R-space information simultaneously (Figure 4(c), (d)). In these contour plots, red regions indicate high signal intensity. For the Pt/3CeO2-ZrO2 catalyst, Pt−Pt scattering was observed, attributed to the formation of PtOx clusters. In contrast, the detection of metallic Pt−Pt bonding—consistent with Pt0 clusters—suggests that the Pt species in Pt/ZrO2 exist as a mixed phase.
2.2.3　Analysis of the electronic structure of active sites
Figure 5 presents the XPS and CO-DRIFTS spectra of the catalysts. As illustrated in Figure 5(a), the Pt/3CeO2-ZrO2 and Pt/CeO2 catalysts exhibit similar Pt 4f spectral profiles. For Pt/3CeO2-ZrO2, the characteristic peaks at 72.84 eV (Pt 4f7/2) and 76.16 eV (Pt 4f5/2) are assigned to Pt2+, while the doublets at 71.35 and 74.67 eV correspond to Pt0. Similarly, Pt/CeO2 displays Pt2+ features at 72.70 and 76.04 eV, with Pt0 signals appearing at 71.32 and 74.57 eV. These results indicate that the Pt species exist predominantly in the Pt2+ oxidation state, which is consistent with the XAFS characterization. Compared to Pt/CeO2, the Pt2+ peaks in Pt/3CeO2-ZrO2 exhibit a small but distinct positive shift of ~0.1 eV toward higher binding energy. This shift suggests that Zr incorporation facilitates electron transfer, thereby stabilizing the Pt2+ species and enhancing the electronic metal-support interaction (EMSI). In CO chemisorption, the adsorption geometry depends on the nature of the active site: linear adsorption typically occurs on oxidized Pt, while both linear and bridging configurations are observed on Pt nanoclusters or nanoparticles[36].
As shown in Figure 5(b), Pt/3CeO2-ZrO2 exhibits absorption bands at 2100, 2082 and 2067 cm−1, which are assigned to linear CO adsorption on oxidized Pt and Pt nanoclusters. A characteristic band at 1836 cm−1 is attributed to bridging CO adsorbed on Pt nanoclusters. Corroborated by the XAFS data, these results confirm that Pt/3CeO2-ZrO2 primarily consists of oxidized Pt alongside a fraction of PtOx clusters, whereas Pt/CeO2 is dominated by oxidized Pt species. In contrast, Pt/ZrO2 displays a coexistence of oxidized Pt, Pt nanoclusters, and metallic Pt. Notably, Pt/ZrO2 exhibited the lowest overall CO absorption intensity among the samples, aligning well with the XPS findings.
2.2.4　Analysis of surface defect structures
The surface defect structures of the catalysts were characterized using XPS. Figures 6(a) and 6(b) display the Ce 3d and Zr 3d spectra, respectively. It is well established that the concentrations of Ce3+ and Zr3+ are linearly correlated with the abundance of oxygen vacancies[37]. Notably, the relative proportions of Ce3+ and Zr3+ are significantly higher in Pt/3CeO2-ZrO2 than in Pt/CeO2, confirming a higher density of oxygen vacancies in the ternary catalyst. The Ce peaks in Pt/3CeO2-ZrO2 exhibit a negative shift toward lower binding energy relative to Pt/CeO2. This suggests that Zr incorporation enhances the electronic metal-support interaction (EMSI). Similarly, the Zr peaks in Pt/3CeO2-ZrO2 shift toward lower binding energy compared to Pt/ZrO2, further supporting the presence of strong electronic interactions facilitated by Ce doping. Figure 6(c) presents the O 1s spectra. The peak at 529.4 eV (OⅠ) is attributed to lattice oxygen (Olattice) in ZrO2 and CeO2, while the component at 531.4 eV (OⅡ) is ascribed to surface oxygen species associated with defect sites. Deconvolution analysis reveals that the Pt/3CeO2-ZrO2 catalyst possesses the highest relative ratio of OⅡ species. In summary, the elevated Ce3+ and Zr3+ concentrations, combined with the abundance of surface oxygen vacancies (Vo), demonstrate that Pt/3CeO2-ZrO2 possesses the highest defect density. This defect-rich structure is closely associated with the strong metal-support interactions within the catalyst.
2.2.5　 In situ infrared spectroscopic investigation
To investigate the individual activation, adsorption, and dissociation behaviors of reactants, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was performed using CH4 and CO2 as probe molecules. Figure 7(a) illustrates the adsorption and dissociation of CO2 at 350 °C. The bands located between 2260 and 2390 cm−1 are attributed to gas-phase CO2. Upon exposure to the catalysts, CO2 undergoes dissociative adsorption to form linearly adsorbed CO on Pt sites, characterized by a peak at approximately 2060 cm−1. The Pt/3CeO2-ZrO2 catalyst exhibits intermediate CO peak intensity. Notably, no linear or bridging CO bands were observed on the bare supports. This indicates that the interaction between Pt and the support is essential for facilitating CO2 activation and subsequent dissociation. Figure 7(b) displays the spectra for CH4 adsorption and dissociation. The peak at 3015 cm−1 corresponds to gas-phase CH4. Chemisorption and dissociation of CH4 occur on all three catalyst surfaces, yielding linearly adsorbed CO on Pt sites (observed at 2040–1950 cm−1). These results suggest the reaction pathway CH4 + O* $ \rightarrow $ CO + 4H*, where O* originates from lattice oxygen or surface oxygen species associated with defects. Consequently, this oxidation process generates oxygen vacancies (Vo). The absence of adsorbed CO on the bare supports indicates that the support oxygen alone is inactive for CH4 activation. In contrast, the introduction of Pt induces a restructuring of surface defects, thereby activating a portion of the surface oxygen. These results confirm a synergistic effect between the Pt species and the CeO2-ZrO2, CeO2 and ZrO2 supports.
To further elucidate the reaction mechanism, in situ DRIFTS measurements were conducted under reaction conditions at 350 °C. The resulting spectra are presented in Figure 8, divided into four spectral regions corresponding to: hydroxyl groups (−OH, panel a), carbonyl species (CO, panel b), carbonate/carboxylate species (OCOO−C−O, panel c), and oxygenated hydrocarbon intermediates (CHxO, panel d). An analysis of the −OH, CO and OCO bands reveals that the Pt/CeO2 catalyst exhibits the highest abundance of hydroxyl species (particularly Type III-OH), the largest amount of desorbable linear CO, and the strongest signal intensities for carbonate and bicarbonate intermediates. The Pt/3CeO2-ZrO2 catalyst shows intermediate intensities for these species, whereas Pt/ZrO2 exhibits the weakest signals. Moreover, as observed in Figure 8(d), no CHxO* intermediates were detected on the Pt/ZrO2 catalyst at 350 °C.
Based on the in situ DRIFTS results, the reaction mechanisms for the Pt/3CeO2-ZrO2 and Pt/CeO2 catalysts are illustrated in Figure 9. Methane activation occurs at the Pt−Olattice interface via an oxygen-assisted dissociation pathway, proceeding through CHxO* intermediates to form CO.
The dissociated hydrogen species (H*) primarily recombine to generate H2, while a portion migrates to adjacent oxygen atoms to form hydroxyl groups (−OH), which subsequently participate in the activation of CO2. Thus, CO2 is reduced by the H* species or −OH groups derived from methane. This process involves dissociation through formate (HCOO*), bicarbonate (${\mathrm{HCO}}_3^- $) and carbonate (${\mathrm{CO}}_3^{2-} $) intermediates, ultimately yielding CO and a small amount of H2O. Furthermore, the oxidation of CH4 consumes lattice oxygen (Olattice), resulting in the generation of oxygen vacancies (Vo). Concurrently, the dissociative reduction of CO2 produces surface oxygen species (O*) that refill these vacancies, thereby establishing a self-sustained catalytic cycle between the oxidation and reduction steps[38].
2.3　Analysis of carbon deposition on spent catalysts
Figure 10(a) presents the thermogravimetric (TG) profiles of the spent catalysts. No significant carbon deposition was observed on the Pt/3CeO2-ZrO2 and Pt/CeO2 catalysts, whereas the Pt/ZrO2 sample exhibited minor carbon accumulation. The Raman spectra shown in Figure 10(b) corroborate these findings. The absence of characteristic carbon bands for Pt/3CeO2-ZrO2 and Pt/CeO2 confirms their superior resistance to coking, consistent with the TG results. In contrast, the Pt/ZrO2 catalyst displayed distinct D and G bands with an intensity ratio (IG/ID) of 1.16, indicating a moderate degree of graphitization and confirming the formation of carbonaceous deposits during the reaction. The enhanced coking resistance of Pt/3CeO2-ZrO2 and Pt/CeO2 is attributed to their specific reaction pathways. During the dissociative adsorption of CH4 on Pt sites to form CH3* and H*, the CH3* species avoids the conventional dehydrogenation route; instead, it transforms into CHxO* intermediates, effectively inhibiting complete cracking into elemental carbon (C*). Conversely, the absence of CHxO* intermediates on Pt/ZrO2 facilitates carbon accumulation, rendering it significantly more susceptible to coking compared to the Ce-containing catalysts.
3　Conclusion
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In this study, the defect concentration of Pt/CeO2-ZrO2 catalysts was modulated by adjusting the Ce/Zr ratio within UiO-66 precursors. Based on comprehensive characterization (CO2-/CH4-TPD, XPS, XAFS, in situ DRIFTS, TG and Raman), the following conclusions were drawn: (1) Utilizing CeO2-ZrO2 supports derived from UiO-66 facilitates the high dispersion and stability of loaded platinum. Specifically, the Pt/3CeO2-ZrO2 catalyst exhibited the highest defect concentration and the strongest metal-support interaction. (2) Platinum exists predominantly in an oxidized state across all catalysts, though the specific speciation varies. Pt/3CeO2-ZrO2 consists mainly of PtOx clusters and single atoms. In contrast, Pt exists exclusively as single atoms on Pt/CeO2, whereas the Pt/ZrO2 catalyst contains a mixture of single atoms, PtOx clusters, and metallic Ptx clusters. (3) The catalytic cycles on Pt/3CeO2-ZrO2 and Pt/CeO2 are driven by a synergistic combination of oxygen-assisted CH4 dissociation and hydrogen-assisted CO2 dissociation. Notably, the Pt/3CeO2-ZrO2 catalyst (Ce/Zr = 3∶1) demonstrated superior catalytic activity, thermal stability against sintering, and resistance to coking at 800 °C. Specifically, it achieved CH4 and CO2 conversions of 86% and 93%, respectively, with a H2/CO ratio near unity. Both TG and Raman analyses confirmed the absence of significant carbon deposition. Collectively, these findings provide valuable experimental insights for the design and optimization of Pt-based catalysts for the dry reforming of methane.
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Year 2026 volume 54 Issue 8
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doi: 10.1016/S1872-5813(26)60669-X
  • Receive Date：2025-10-31
  • Online Date：2026-09-23
  • Published：2026-08-10
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  • Received：2025-10-31
  • Revised：2025-12-22
  • Accepted：2026-01-04
Affiliations
    Key Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science, South-Central Minzu University, Wuhan 430074, China

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表12种不同金属材料的力学参数
科
Family		 属数
Number of
genus		 种数
Number of
species		 占总种数比例
Percentage of
total species (%)		 属
Genus		 种数
Number of
species		 占总种数比例
Percentage of total
species (%)
鹅膏菌科Amanitaceae 2 11 5.26 鹅膏菌属 Amanita 10 4.78
小菇科 Mycenaceae 2 12 5.74 丝盖伞属 Inocybe 5 2.39
多孔菌科 Polyporaceae 8 14 6.70 蜡蘑属 Laccaria 5 2.39
红菇科 Russulaceae 3 23 11.00 小皮伞属 Marasmius 6 2.87
小菇属 Mycena 11 5.26
光柄菇属 Pluteus 5 2.39
红菇属 Russula 17 8.13
栓菌属 Trametes 5 2.39
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