Single-atom catalysts supported on N-doped carbon: influence of synthesis parameters on selective hydrogenation performances - Archive ouverte HAL
Poster De Conférence Année : 2024

Single-atom catalysts supported on N-doped carbon: influence of synthesis parameters on selective hydrogenation performances

Résumé

Introduction Single-atom catalysts (SACs) promise unprecedented catalytic performance as they cumulate the advantages of homogenous and heterogenous catalysts, while saving expensive metals.1 However, the synthesis and characterization of SACs is challenging. The objective of this work is to synthesize efficient SACs on doped carbon materials for selective hydrogenation reactions. Herein, we focus on Pt-N-C SACs obtained with different methods for butadiene semi-hydrogenation. Materials and Methods H2PtCl6 precursor dissolved in water, ethanol or DMSO, was used to impregnate platinum (target loading 5 wt%) on several carbon supports, including commercial carbon black, nucleobase-derived N-doped carbon and pyrolyzed ZIF-8 MOF. For carbon black, 1,10-phenanthroline was used as a nitrogen source and a chelating agent for Pt.2 One-step or two-step3 pyrolysis under N2 flow was then applied to obtain the SACs. The catalysts were characterized by ICP/XRF, N2 adsorption, ADF-STEM, XRD, XPS, and Raman spectroscopy. Butadiene hydrogenation tests were performed in a flow fixed bed reactor at atmospheric pressure (C4H6:H2:He = 2:10:88%, 100 mL/min, 10 mg) from RT to 200 °C (1 °C/min) with online microGC analysis. The samples were pretreated in situ in H2 flow at 300 °C. Results and Discussion The obtention of SACs depends on the nature of the carbon source (structure, surface area, functional groups…), the nitrogen content, the impregnation solvent, and the pyrolysis temperature. A high nitrogen content in the carbonaceous support is expected to generate numerous sites for metal atom stabilization, allowing for higher metal loadings. Fig. 1 shows the key role of N-doping at the surface of carbon black through the use of phenanthroline: Pt single atoms (SAs) are obtained instead of nanoparticles (NPs). Fig. 2 depicts the influence of using ethanol vs. water as a solvent for impregnation of the same N-doped carbon support on the Pt dispersion. While water leads to a mixture of SAs and NPs (the latter are present at the external surface of the support), ethanol allows for full (and stable) SA dispersion. The latter leads to lower activity but higher (almost 100%) butene selectivity in butadiene hydrogenation. Significance This work is relevant to the development of optimized SACs for selective hydrogenation reactions. Metals like Pt, unselective in the form of NPs, become selective when atomically dispersed. Metal dispersion and coordination are highly sensitive to the carbon characteristics and the conditions of impregnation and pyrolysis. References (1) Mitchell, S. et al., Angew. Chem. Int. Ed. 2018, 57, 15316–15329. (2) Yang, H. et al., Nat. Commun. 2019, 10, 4585. (3) Hai, X. et al., Nat. Nanotechnol. 2022, 17, 174–181. Acknowledgement This work is supported by ANR-22-CE07-0007-01 “ISAC” program.
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hal-04695388 , version 1 (12-09-2024)

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  • HAL Id : hal-04695388 , version 1

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M. Marseglia, R. André, F. Morfin, L. Piccolo. Single-atom catalysts supported on N-doped carbon: influence of synthesis parameters on selective hydrogenation performances. 18th ICC - International Congress on Catalysis, Jul 2024, Lyon, France. ⟨hal-04695388⟩
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