Elucidation of the Roles of Re in Aqueous-Phase Reforming of Glycerol over Pt-Re/C Catalysts

We report the investigation of surface properties of Pt/C and Pt Re/C catalysts using in situ spectroscopic tools and a fundamental understanding of their catalytic performances in glycerol aqueous-phase reforming (APR). We found that adding Re to Pt/C improves its activity significantly, which is consistent with our previous observation in glycerol steam reforming. However, the difference in reaction selectivity is much more pronounced in APR. Compared to Pt/C, Pt Re/C yielded significantly more liquid products, while the selectivity to H2 and CO2 decreased by more than 40%. In operand X-ray absorption spectroscopy and attenuated total reflectance infrared (ATR-IR) with in situ capability as well as Raman spectroscopy were employed to investigate the catalyst surface properties and the roles of Re. In operando X-ray absorption fine structure shows treatment. Additionally, ATR-IR using CO as a probe molecule demonstrated that desorption of CO from the Pt Re/C surface is more facile than that from Pt/C in the aqueous phase. We propose that well-dispersed Re oxide species in the proximity of Pt work as the active sites, providing both metal and acid functionalities, while the terminal Re-O moiety has little contribution to the overall reactivity as evidenced by Raman spectroscopy.