Insights into the Genesis of a Selective and Coke-Resistant MXene-Based Catalyst for the Dry Reforming of Methane

We report the use of a multilayered vanadium carbide MXene (m-V2CTx) as a precursor for a robust oxy-carbide catalyst to convert CH4 and CO2 into syngas via dry reforming of methane (DRM). The in situ generated V2O3-V8C7/m-V2CTx catalyst undergoes a redox (oxidation-carburization) mechanism that results in attractive reactivity, selectivity (H-2/CO ratio close to unity), and unprecedented stability (negligible formation of coke). The oxy-carbide species (V2O3 and V8C7) growing in situ under reaction conditions decorate the layers of m-V2CTx and provide a better utilization of V sites in such a way that the resulting V2O3-V8C7/m-V2CT(x) catalyst exhibits four times higher activity than its bulk counterparts, V2AlC MAX phase and commercial vanadium carbide (VC). These kinetic findings combined with spectroscopy, microscopy, and isotopic labeling experiments reveal that while dehydrating the pristine m-V2CTx, an oxy-carbide (V2O3-V8C7/m-V2CTx) material is produced which oxidizes further in the presence of CO2 to generate additional V2O3 nanocrystals on the surface and in-between the multilayered structure. These oxide particles are further carburized in situ by reaction with CH4 and transforming into V8C7 nanocrystals. This study provides kinetic, structural, and mechanistic insights into the genesis of m-V2CTx as a selective and coke-resistant catalyst for DRM. We foresee m-V2CTx, and MXenes in general, as promising precursors, supports, and/or catalysts for various other catalytic applications at relatively high temperatures (>= 500 degrees C).