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Templated encapsulation of platinum-based catalysts promotes high-temperature stability to 1,100 °C

Nature Materials volume 21, pages 1290–1297 (2022)Cite this article

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Abstract

Stable catalysts are essential to address energy and environmental challenges, especially for applications in harsh environments (for example, high temperature, oxidizing atmosphere and steam). In such conditions, supported metal catalysts deactivate due to sintering—a process where initially small nanoparticles grow into larger ones with reduced active surface area—but strategies to stabilize them can lead to decreased performance. Here we report stable catalysts prepared through the encapsulation of platinum nanoparticles inside an alumina framework, which was formed by depositing an alumina precursor within a separately prepared porous organic framework impregnated with platinum nanoparticles. These catalysts do not sinter at 800 °C in the presence of oxygen and steam, conditions in which conventional catalysts sinter to a large extent, while showing similar reaction rates. Extending this approach to Pd–Pt bimetallic catalysts led to the small particle size being maintained at temperatures as high as 1,100 °C in air and 10% steam. This strategy can be broadly applied to other metal and metal oxides for applications where sintering is a major cause of material deactivation.

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Fig. 1: Synthesis and characterization of the encapsulated catalysts.
Fig. 2: Catalytic activity and structural characterization of the encapsulated catalyst and comparison with a supported sample.
Fig. 3: Theoretical model of the observed sintering resistance and further stability tests.
Fig. 4: Extension of the approach to Pt–Pd catalysts and demonstration of the stability to 1,100 °C.

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Data availability

Additional data that support the findings of this study are reported in the Supplementary Information. Any additional data are available from the corresponding author upon request. Source data are provided with this paper.

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Acknowledgements

We gratefully acknowledge financial support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, Catalysis Science Program to the SUNCAT Center for Interface Science and Catalysis. Additional support was provided by the Stanford Precourt Institute for Energy through a seed grant, and by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-SC0022197 to M.C. A.A. acknowledges support in the form of an American Association University Women International Fellowship and a Siebel Scholar Foundation Fellowship. M.L.S. acknowledges support in the form of a TomKat fellowship at Stanford University. Part of this work was performed at the Stanford Nano Shared Facilities, supported by the National Science Foundation under award ECCS-2026822. Part of this work was performed at the SSRL of the SLAC National Accelerator Laboratory, and use of the SSRL was supported by the US Department of Energy, Office of Science, Office of Basic Energy Science under contract no. DE-AC02-76SF00515, and by CO-ACCESS, supported by the US Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences of the US Department of Energy under contract no. DE-AC02-05CH11231. P.H. and P.N.P. acknowledge support by the state of Baden-Württemberg through bwHPC (bwunicluster and JUSTUS, RV bw17D011), and funding by the Deutsche Forschungsgemeinschaft (German Research Foundation) under project ID 434253773 and SFB 1441 project ID 426888090. The NMR study was supported by NSF EAR-1521055 to J.F.S. We thank J. Hong (SLAC National Accelerator Laboratory) for help with the XAS data collection, and G. Stewart (SLAC National Accelerator Laboratory) for the Pt@Al2O3 schematic model.

Author information

Authors and Affiliations

  1. Department of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis, Stanford University, Stanford, CA, USA

    Aisulu Aitbekova, Chengshuang Zhou, Michael L. Stone, An-Chih Yang, Emmett D. Goodman & Matteo Cargnello

  2. Department of Earth System Science, Stanford University, Stanford, CA, USA

    Juan Salvador Lezama-Pacheco

  3. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA

    Adam S. Hoffman & Simon R. Bare

  4. Institute of Catalysis Research and Technology, Karlsruhe Institute of Technology, Karlsruhe, Germany

    Philipp Huber & Philipp N. Plessow

  5. Department of Geological Sciences, Stanford University, Stanford, CA, USA

    Jonathan F. Stebbins

  6. National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

    Karen C. Bustillo, Peter Ercius & Jim Ciston

Authors
  1. Aisulu Aitbekova
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  2. Chengshuang Zhou
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Contributions

A.A. and M.C. conceived the research. A.A. synthesized materials, conducted the physisorption and chemisorption experiments, TGA, XPS, DRIFTS, XAS characterization and much of the catalytic activity tests, and analysed the STEM microscopy and tomography data. M.L.S. contributed with sample preparation, catalytic activity characterization and aging tests. C.Z., A.-C.Y., E.D.G., J.C. and K.C.B. performed microscopy characterization studies. J.S.L.-P. conducted the XRF and PXRD measurements. A.S.H. and S.R.B. assisted with the XAS data collection and analysis. P.H. and P.N.P. performed DFT calculations and sintering simulations. P.E. assisted with tomography reconstruction. J.F.S. performed NMR studies and analysed the data. M.C. supervised the whole research project. A.A. and M.C. wrote the manuscript with revision and participation from all authors.

Corresponding author

Correspondence to Matteo Cargnello.

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Competing interests

Stanford University has submitted a provisional patent application entitled ‘Novel approach to make active and stable low-temperature hydrocarbon combustion catalysts’ on which A.A. and M.C. are listed as inventors (US provisional patent number 63/210,723, filed in 2022). The remaining authors declare no competing interests.

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Extended data

Extended Data Fig. 1 Characterization of Pt@Al2O3.

a, TGA upon heating the sample in air to 700 °C. b, N2 physisorption isotherm. c, Pore size distribution.

Extended Data Fig. 2 Characterization of Pt/Al2O3.

a, Transmission electron microscopy image. b, NP size distribution. c, d, XPS of (c) Pt 4d3/2 (332.2 eV) and Pt 4d5/2 (315.2 eV); (d) Al 2p (74.7 eV) and Pt 4f5/2 (71.5 eV) overlapping signals. e, XRD of Pt/Al2O3 calcined at 600 °C. Highlighted peaks are due to metallic Pt. f, TEM: upon calcination the average Pt NP size increases from 3.8 nm to 23.3 nm.

Extended Data Fig. 3 Propene combustion light off curves of Pt@Al2O3.

a, Fresh Pt@Al2O3 and metal-free Al2O3 support. Reaction mixture: 0.15 vol.% C3H6, 3 vol.% O2, and 5 vol.% steam (balance Ar). b, As-prepared Pt@Al2O3 and the aged catalyst after consecutive three cycles (aging performed at 800 °C for 2 h in the reaction mixture). 30 mg of the catalyst was mixed with 160 mg of SiC diluent. Catalyst pretreatment: 300 °C, 30 min 5 vol.% O2 (40 ml/min), 10 min Ar (40 ml/min), 30 min 5 vol.% H2 (40 ml/min). Reaction mixture: 0.15 vol.% C3H6, 3 vol.% O2, 5 vol.% H2O, balance Ar (50 ml/min total flow rate).

Extended Data Fig. 4 Catalytic activity testing and characterization of Pt/!-Al2O3.

a, Light-off curve measurements of fresh and aged Pt/!-Al2O3. Reaction conditions: 0.15 vol. % C3H6, 3 vol. % O2, and 5 vol. % steam, balance Ar (40 ml/min total flow). Aging performed in the reaction mixture at 800 °C for 2 h. b–e, Representative TEM images and particle size distributions of the fresh (b, c) and aged catalysts (d, e).

Extended Data Fig. 5 Characterization of Pt samples.

a, XRD patterns for the samples and the bare support. ^ and * represent diffractions peaks due to γ-Al2O3 and quartz diluent, respectively. Highlighted region at 40° indicates overlapping γ-Al2O3 and Pt(111) diffraction peaks. b, XPS characterization of Pt@Al2O3-800. c, Magnitude and imaginary part of the Fourier Transform. d, EXAFS of the Pt L3-edge data and best-fits characterizing the encapsulated and supported Pt catalysts before and after aging at 800 °C. Black lines indicate the fits. e, f, Pt L3-edge XANES: (e) Pt@Al2O3; (f) Pt/Al2O3.

Extended Data Fig. 6 Catalytic activity testing and characterization of Pt@Al2O3 and Pt/Al2O3.

a, Arrhenius plots with 95% confidence intervals of Pt@Al2O3 and Pt/Al2O3 for propene combustion collected at conversions less than 5%. The data points are averages for three measurements. b, CO diffuse reflectance infrared spectroscopy. c, Arrhenius plots with 95% confidence intervals of Pt@Al2O3 and Pt/Al2O3 for CO oxidation collected at conversions less than 5%. The data points are averages for three measurements. d, 27Al MAS NMR spectra of fresh and aged Pt@Al2O3 and Pt/Al2O3. Peaks for four-, five-, and six-coordinated Al (AlO4, AlO5, AlO6) are labeled, with approximate percentages of each shown below the spectra. e, Proposed model schematic of Pt@Al2O3.

Extended Data Fig. 7 DFT and sintering models.

a, Side-on views of the atomic models optimized for the interfaces of Pt(100) and Pt(111) with the γ-Al2O3(100) surface. b, Illustration of sintering models and underlying assumptions: Left: No diffusion limitations lead to immediate equilibration within the gas phase and thus a constant background pressure. Right: Significant diffusion limitations through the encapsulating material lead to local equilibration between particle and gas phase for each particle, so that locally the equilibrium pressure is established.

Extended Data Fig. 8 Catalytic activity testing of Pt@Al2O3 and Pd@Al2O3.

a, Propene combustion activity for fresh Pt@Al2O3 and 1,100 °C aged Pt@Al2O3. Reaction mixture: 0.15 vol.% C3H6, 3 vol.% O2, and 5 vol.% steam. Aging performed at 1,100 °C for 5 h in air with 10 vol. % steam (40 ml/min total flow). b, TEM image of the 1,100 °C aged Pt@Al2O3 catalyst. c, d, TEM image and particle size distribution of as-synthesized Pd@Al2O3. e, Propene combustion activity for fresh Pd@Al2O3 and 1,100 °C aged Pd@Al2O3. Reaction mixture: 0.15 vol.% C3H6, 3 vol.% O2, and 5 vol.% steam. Aging performed at 1,100 °C for 5 h in air with 10 vol. % steam (40 ml/min total flow). f, TEM image of the 1,100 °C aged Pd@Al2O3 catalyst.

Extended Data Fig. 9 Catalytic activity and characterization of PdPt@Al2O3.

a, Propene combustion activity of the fresh and 1,100 °C aged metal-free alumina support. Reaction mixture: 0.15 vol.% C3H6, 3 vol.% O2, and 5 vol.% steam. Aging performed at 1,100 °C for 5 h in air with 10 vol. % steam (40 ml/min total flow). b, c, Characterization of the assynthesized and 1,100 °C aged PdPt@Al2O3: b, XPS. c, XRF. d, e, Representative HAADF-STEM image of 1,100 °C aged PdPt@Al2O3 and EDS spectrum showing no Pd or Pt detectable signal. Fe, Co, Cu, Zr and Sn normal signal from the TEM column/holder. f, XRD and g, 27Al NMR of as-synthesized and 1,100 °C aged PdPt@Al2O3.

Extended Data Fig. 10 XAS characterization of PdPt@Al2O3.

a–c, Magnitude and imaginary component of the Fourier Transform and EXAFS at the Pd K-edge (a, b) and Pt L3-edge (c, d) characterizing the fresh PdPt@Al2O3 and PdPt@Al2O3-1100-air samples. Black lines indicate the fits. The range in R was 1.2–3.0 Å (Pd) and 1.7–3.2 Å (Pt); the range in k was 2.7–12.5 Å−1 (Pd) and 3.1–12.0 Å−1 (Pt). e, f, PdPt@Al2O3 XANES: e, Pt L3-edge; f, Pd K-edge.

Supplementary information

Supplementary Information

Sintering simulations and Supplementary Figs. 1–16, Tables 1–9 and references.

Source data

Source Data Fig. 3

Source data file (text format) for DFT structures.

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Aitbekova, A., Zhou, C., Stone, M.L. et al. Templated encapsulation of platinum-based catalysts promotes high-temperature stability to 1,100 °C. Nat. Mater. 21, 1290–1297 (2022). https://doi.org/10.1038/s41563-022-01376-1

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