Low-loading Pt/β-Mo2C catalyst for ethanol dissociation. Experimental and theoretical characterization

Abstract

The adsorption and dissociation of ethanol on Pt/β-Mo₂C with a low noble metal loading (0.1 wt%) is studied in the context of catalytic H₂ production from alcohols. X-ray diffraction and experimental results indicate that Pt modifies the lattice parameters of β-Mo₂C. In line with this, density functional theory calculations indicate that the Mo–Mo distances are increased due to the presence of Pt. An experimental X-ray photoelectron spectroscopy study indicates that the chemical state of both molybdenum and carbon in Pt/β-Mo₂C are very different from those in the Pt-free carbide, which is also in agreement with the DFT results, which indicate that the Pt atoms generate a redistribution of charge density in their environment. Temperature programmed reaction analysis shows that at temperatures higher than 530 K, a two-fold increase in the production of H₂, CH₄ and C₂H₆ is observed for Pt/β-Mo₂C as compared to β-Mo₂C, suggesting a higher catalytic activity for the Pt-containing carbide than for the pristine catalyst. Additionally, H₂ production from ethanol on Pt/β-Mo₂C presents a higher activation energy (0.64 eV) than that corresponding to pristine molybdenum carbide. In agreement with this experimental result, climbing image-nudged elastic band (CI-NEB) calculations indicate that the energy barrier linked to the formation of H₂ from ethanol increases with the presence of platinum. It is concluded that the low Pt loading notably modifies the catalytic pattern of molybdenum carbide, rendering it a highly active catalyst for ethanol decomposition.