Mo2Ti2C3TX MXene performance in catalytic CO2 hydrogenation and its promotion with single Pt atoms - Archive ouverte HAL
Poster De Conférence Année : 2024

Mo2Ti2C3TX MXene performance in catalytic CO2 hydrogenation and its promotion with single Pt atoms

L. Loupias
  • Fonction : Auteur
S. Célérier
  • Fonction : Auteur
F. Morfin

Résumé

Introduction Transition metal carbides are known as efficient catalysts or catalyst supports and recently discovered two-dimensional carbides (MXenes) offer renewed possibilities to anchor metal atoms and promote catalytic performances.1,2 Unlike for electro- and photocatalysis, thermal catalysis on MXenes has been little investigated so far. Herein, we report on the elaboration of Pt/MXene single-atom catalysts (SACs) and their performance in CO2 hydrogenation, which is relevant to greenhouse-gas valorization into chemical energy carriers such as CO, methane and methanol. Materials and Methods Ti3C2Tx and Mo2Ti2C3TX MXenes (Tx are surface termination groups such as −O, −OH, and −F) were elaborated from the Ti3AlC2 and Mo2Ti2AlC3 MAX phases by using LiF/HCl and HF etching solutions, respectively.3 Pt was deposited on the MXenes by aqueous impregnation with H2PtCl6 or Pt(NH3)4(NO3)2. The catalysts, pre-activated in H2 flow at 400 °C and 1 atm, were tested for CO2 hydrogenation at 3 MPa (H2:CO2=3:1) and 200-350 °C in a flow-fixed bed reactor equipped with online μGC analysis. The SACs were characterized by a range of techniques, including synchrotron-based operando X-ray absorption spectroscopy (XAS) and near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS), in situ X-ray diffraction (XRD), and aberration-corrected scanning transmission electron microscopy (STEM). Results and Discussion Compared to H2PtCl6, the Pt(NH3)4(NO3)2 precursor reverses the charge of the Pt species in solution and enables higher Pt loadings while retaining a single-atom dispersion at the MXene surface. According to XAS and XPS, Pt atoms are initially in oxidation state near 2+ and reduce to near zero state upon the H2 thermal treatment while forming bonds with surface M atoms of the MXene. This includes the probable location of Pt atoms at M vacancies or Pt-M substitution. For catalytic testing, the samples were intercalated with a silica nanopowder, which attenuates MXene stacking and thereby maximizes the reaction rates.4 While Ti3C2Tx is essentially inactive, Mo2Ti2C3TX exhibits significant activity for the reverse water-gas shift reaction (CO2 + H2 → CO + H2O). Since Mo is located at the MXene surface, this result appears consistent with computational predictions for the Mo2CTx MXene5 and experimental findings for Mo2C-derived materials.6 The addition of Pt on Ti3C2Tx leads to high activity and almost 100% selectivity to CO.4 Pt/Mo2Ti2C3TX is even more active, while methane and methanol are formed as minority products. Post-reaction STEM shows that no Pt agglomeration occurred, that is the SACs are sinter-resistant. However, the less Pt-loaded samples exhibit the higher turnover frequencies, which suggests that Pt in excess may compete with the active sites at the MXene surface. Significance This work reveals the intrinsic activity of the Mo2Ti2C3TX MXene for reverse water-gas shift. Furthermore, it demonstrates that, on this MXene, single Pt atom anchoring is favorable and increases both the activity and the CO selectivity in CO2 hydrogenation. References 1. A. VahidMohammadi, J. Rosen, Y. Gogotsi, Science 2021, 372, 1165 2. D. Zhao, Z. Chen, W. Yang, S. Liu, X. Zhang, Y. Yu, W.-C. Cheong, L. Zheng, F. Ren, G. Ying, X. Cao, D. Wang, Q. Peng, G. Wang, C. Chen, J. Am. Chem. Soc. 2019, 141, 4086 3. L. Loupias, C. Morais, S. Morisset, C. Canaff, Z. Li, F. Brette, P. Chartier, N. Guignard, L. Mazière, V. Mauchamp, T. Cabioc’h, A. Habrioux, S. Célérier, SSRN 2023 doi: 10.2139/ssrn.4529024 4. Y. Yan, D. Sall, L. Loupias, S. Célérier, M. Aouine, P. Bargiela, M. Prévot, F. Morfin, L. Piccolo, Mater. Today Catal. 2023, 2, 100010 5. A. Jurado, A. Morales-Garcia, F. Viñes, F. Illas, ACS Catal. 2022, 12, 15658 6. H. Zhou, Z. Chen, E. Kountoupi, A. Tsoukalou, P.M. Abdala, P. Florian, A. Fedorov, C. Müller, Nat. Commun. 2021, 12, 5510
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hal-04695387 , version 1 (12-09-2024)

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  • HAL Id : hal-04695387 , version 1

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Y. Yan, L. Loupias, S. Célérier, F. Morfin, L. Piccolo. Mo2Ti2C3TX MXene performance in catalytic CO2 hydrogenation and its promotion with single Pt atoms. 18th ICC - International Congress on Catalysis, Jul 2024, Lyon, France. ⟨hal-04695387⟩
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