Communication Dans Un Congrès Année : 2025

In situ XPS investigation of MXene-based catalysts under reductive treatments

Y. Yan
S. Célérier
  • Fonction : Auteur
F. Bournel
  • Fonction : Auteur
J.-J. Gallet
  • Fonction : Auteur

Résumé

MXenes are a recently discovered family of two-dimensional carbide and nitride materials with numerous potential applications in energy storage, electronic devices, and adsorption/catalysis. We have previously shown that Ti3C2Tx (Ti/C/Ti/C/Ti layer stacking) and Mo2Ti2C3Tx (Mo/C/Ti/C/Ti/C/Mo) MXenes can stabilize single platinum atoms – serving as hydrogen dissociation promotors – at their surface and thereby act as efficient catalysts for CO2 reduction to CO (Tx represents termination groups such as O, OH and F). This reaction, also called reverse water-gas shift, is a key route to liquid fuel synthesis. We have also found that a proper thermal pretreatment under hydrogen flow at 400-500 °C is crucial to activate the catalysts. In this work, with the help of near-ambient-pressure synchrotron XPS in complement to other methods (XAS, XRD, STEM…), we have investigated the thermal evolution of the materials in the presence of H2 or H2+CO2. Figure 1 reports the influence of thermal treatments on the Pt/Mo2Ti2C3Tx system. Single Pt atoms are initially 2+, but they partially reduce to ca. 1+ state in the 200-350 °C range under UHV. Hydrogen treatments have no further effect on this state. This transition is ascribed to the decomposition of the Pt(NH3)4(NO3)2 precursor, initially adsorbed at the MXene surface, followed by the diffusion of Pt atoms at Mo vacancies, as shown by EXAFS. Regarding the Mo-rich MXene surface, the UHV heating only reduces the residual surface oxides (MoOx3); solely the presence of H2 leads to reduction of the main state, Mo4+, to Mo2+, through partial desorption of Tx species, while a further treatment under 1 bar H2 enhances the phenomenon. In this communication, we will also present a chemometric analysis of NAP-XPS results integrating those obtained at variable kinetic energies, corresponding to different probing depths.

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Dates et versions

hal-05100365 , version 1 (06-06-2025)

Identifiants

  • HAL Id : hal-05100365 , version 1

Citer

Y. Yan, F. Morfin, M. Prevot, S. Célérier, F. Bournel, et al.. In situ XPS investigation of MXene-based catalysts under reductive treatments. Journées Nationales des Spectroscopies de PhotoEmission 2025, May 2025, Ecully, France. ⟨hal-05100365⟩
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