Well-dispersed CeO₂ nanoparticles in Pt/SiO₂ catalysts for H₂ production

Full text: A promising route to produce H₂ is glycerol steam reforming (GSR) reaction (C₃H₈O₃ + 3H₂O ↔ 7H₂ + 3CO₂), with two main steps, glycerol decomposition (C₃H₈O₃ ↔ 4H₂ + 3CO) and water-gas shift reaction (WGS, CO + H₂O ↔ H₂ + CO₂). In GSR catalysts both metal phase and support can strongly impact on conversion, formation of byproducts, stability and H₂ selectivity. In Pt/SiO₂ systems, one challenge is to increase H₂ yield by favoring WGS step, that could be achieved by promoters such as CeO₂ [1]. This is demonstrated herein by colloidal synthesis of well-dispersed CeO₂ nanoparticles (NPs, 5-6 nm) [2] added to SiO₂ support. The CeO₂/SiO₂ support was calcined to remove ligands and noteworthy, X-ray diffraction confirmed that CeO₂ NPs retained their average size, then CeO₂/SiO₂ and bare SiO₂ were impregnated with Pt and calcined again. X-ray absorption fine structure spectroscopy (XAFS) showed that Pt-CeO₂ interaction led to more oxidized and dispersed Pt species than on Pt/SiO₂. The CeO₂ promoting effect in GSR reaction was demonstrated by the increase in glycerol conversion (from 80 to 100%) and the H2 fraction (from 54 to 67%) in the gas outlet through WGS step. Additionally, both catalysts showed no significant formation of liquid byproducts, carbon deposition and CeO₂ NPs had no apparent sintering. The relationship between the NPs size (< 20 nm) and the catalytic performance, experimentally scarce in this scale regime, is under investigation. (1) Tran, N. H.; Kannangara, G. S. K. Chem. Soc. Rev. 2013, 42 (24), 9454-9479. (2) Lee, S. S.; Zhu, H.; Contreras, E. Q.; Prakash, A.; Puppala, H. L.; Colvin, V.L. Chem. Mater. 2012, 24 (3), 424-432. (author)