Dry reforming of methane over CeO2-supported Pt-Co catalysts with enhanced activity

Abstract

Dry reforming of methane provides opportunities of using CH4 and CO2 to produce syngas. The PtCo/CeO2 bimetallic catalyst shows higher activity and H2/CO ratio than the corresponding monometallic catalysts, mainly attributed to the synergistic effect of Pt-Co. Structural feature of the PtCo/CeO2 catalyst was revealed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of adsorbed CO and in situ techniques like X-ray diffraction (XRD), X-ray adsorption fine structure (XAFS) and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). Pt-Co alloy and separated Co particles co-existed in the bimetallic catalyst, whereas the former was determined as the dominant active structure with a Pt-Co-mixed-surface termination. During reaction, Pt and Co in the alloy structure nearly maintained their metallic state with slight oxygen decoration, yielding oxygen-metal site-pairs (O*-*). Combined kinetic investigations and DFT calculations reveal that the O*-modified catalytic surface of PtCo/CeO2 promotes CH bond activation with higher entropy contribution (less constraints) to compensate its higher activation barrier. Thermogravimetric analysis (TGA), transmission electron microscope (TEM) and Raman spectroscopy show that the PtCo/CeO2 catalyst is resistant to coke formation as effectively as Pt/CeO2 and can be easily regenerated by a mild CO2 treatment.