| Description: |
SSCI-VIDE+CATREN:ING+YYN:MPR:FMO:LPI ; International audience ; In the last decades, 2D materials have gained great attention in catalysis, owing to their large specific surface area, mechanical robustness and flexibility, and unique physical and chemical properties [1]. MXenes, a bourgeoning class of 2D transition metal carbides or nitrides, have a general formula of Mn+1XnTx (n=1−4), where M is an early transition metal, X is C or N, and Tx indicates surface termination group(s) such as −O, −OH, −F or −Cl, which depend on the etchants used in the synthesis process [2]. Since their discovery in 2011 with the Ti3C2-based system [3], MXenes have shown great potential in various fields including electrocatalysis for evolution or reduction reactions [4]. However, the literature on the application of MXenes in thermal catalysis remains scarce. In this work, we have used butadiene hydrogenation under gas flow conditions as a simple model selective hydrogenation reaction, though of applied interest for polymerization.We have used two types of Ti3C2 MXenes, noted CMX and PMX, prepared with HF or LiF/HCl etchants, respectively, as supports for metal (Pt, Pd) single atoms or nanoparticles deposited by aqueous impregnation of metal salts. From SEM and STEM images, the MXenes present a multilayer structure where each layer itself contains a few stacked nanosheets. Aberration-corrected STEM analyses of the as-prepared low-loading (0.1 wt%) Pt/MXene and Pd/MXene catalysts exclusively show single atoms on both MXenes. An increase in metal loading (1 wt%) leads to a fraction of nanoparticles.Before the reaction, the catalyst was delaminated, dispersed on quartz wool, and reduced in hydrogen. The bare MXenes showed no hydrogenation capability. PMX-supported low-loading single-atom catalysts are less active than 1 wt% metal-loaded catalysts, but they exhibit a higher selectivity towards butenes, even at the same conversion. Depending on the metal, 1-butene (Pd) or 2-butenes (Pt) are the main products. Moreover, compared to ... |