Elucidation of the roles of Re in steam reforming of glycerol over Pt–Re/C catalysts

• Addition of Re to Pt/C catalyst increases the activity of glycerol steam reforming.
• Steam exposure has similar effects on Pt surface for Pt/C with and without Re.
• Pt–Re/C contains rhenium oxide that becomes even more oxidized upon steam exposure.
• Steam exposure leads to more facile CO desorption from Pt–Re/C than that from Pt/C.
• Facile CO desorption is likely due to CO spillover from Pt to neighboring Re–O(H).

In this paper, we report the fundamental surface properties of Pt/C and Pt–Re/C catalysts and their correlation with catalytic performance in steam reforming of glycerol. We found that the addition of Re increases the catalytic activity, H2/COx ratio, and CO2 selectivity. N2 physisorption, CO chemisorption, and attenuated total reflectance infrared (ATR-IR), Raman, and X-ray absorption spectroscopy (XAS) with in situ capabilities were employed to provide insight into the roles of Re. Using ATR-IR, we show that CO adsorption on reduced Pt–Re/C is stronger than on Pt/C. However, CO desorption from Pt–Re/C is much facilitated compared with that from Pt/C after steam pretreatment, which is more representative of the steam reforming conditions. In situ Raman and XAS studies suggest that oxidized rhenium species are formed in steam environments on the Pt–Re/C catalyst surface. The spillover of CO from neighboring Pt to such oxidized rhenium is likely the reason for the facile desorption of CO, which could further react to form CO2. Such facile CO desorption leads to enhanced glycerol steam reforming and water-gas shift activities over the Pt–Re/C catalyst.

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