“Operando” 3D Multiscale and Multi-technique Catalyst Probing – MULTIPROBE

The goal of the MULTIPROBE project is to develop a new methodology for the in situ and operando characterization of catalysts based on a unique combination of transmission electron microscopy and X-rays techniques, including 3D and environmental TEM, EELS spectroscopy, macro- and micro-scale X-ray absorption spectroscopy (XAS), and hyperspectral imaging. All these characterization tools have been already used individually for the analysis of the catalysts in working conditions, but their association on the study of a catalytic system in very similar conditions, with also a common methodology of data analysis and global conceptualization of the main findings, is unprecedented. This approach is: i) multiscale, allowing to cover scales from mm to sub-nm, by combining averaged information deduced from the macroscopic study of different zones of the catalytic bed, to that obtained locally over the catalyst nano-grain, for elucidating the role of the structural speciation and spatial heterogeneities; ii) multi-selective, providing morphological, structural and spectroscopic information on the various elements present on the catalyst; iii) in situ, time resolved and operando, as the experiments will be performed under conditions of pressure, temperature and gas concentration which are representative of the catalytic processes, with quantitative information on the activity and the selectivity of the catalysts.

This combined methodology will be used to provide a complete insight on the evolution under realistic reaction conditions of promising catalysts for light olefin synthesis from CO2 and CO. We have selected Fe-based bimetallic catalysts containing soldering metals, for which various physical or chemical phenomena have been postulated to occur during reaction, and account for the activation or deactivation of the active phase: atomic diffusion, alloying or dealloying phenomena, structural transformation, particle sintering, interaction with the support, carbidization etc. These catalysts are extremely active in the olefin synthesis and more selective to light olefins than most traditional catalysts, and they can operate with high yields even at atmospheric pressure. FeBi catalysts, that have been primarily studied by the consortium partners, will be first used for proof of concept of the methodological approach in operando characterization. Then, the developed methodology will be applied to iron catalysts promoted with other metals such as Pb or Sn, which have shown extremely high activity and stability in CO and CO2 hydrogenation reactions.

Particular efforts will be put on the analysis of the data obtained by each technique, especially using hyperspectral imaging, in order to propose an unprecedented correlative analytical method. The expertise of the consortium in the quantitative use of multivariate analysis based methods for the analysis of XAS data will be transposed to the analysis of the complementary spectroscopic EELS/EDX data for obtaining a global and unified description of the same material. The recently developed data analysis approaches based on machine learning methods will be used for the analysis of the two sets of data (TEM and XAS imaging and spectroscopic data) in order to provide reliable structural and activity descriptors of the same system at different length scales and in different conditions, and to take into account statistical variances between TEM and XAS analysis.

From a general point of view, this combined multiscale, time-resolved and multiselective approach proposed by the three partners (IPCMS, SOLEIL, UCCS), as well as the strategy of data analysis, will provide a correlation between chemical descriptors in the course of reaction and catalytic activities, in order to propose a direct relation between the microstructural properties of the catalyst and its performances, and could be subsequently applied to the in-situ study of a wide range of catalytic materials for CO and CO2 hydrogenation.