Effect of the surface state on the catalytic performance of a Co/CeO2 ethanol steam-reforming catalyst

• Co/CeO2 ethanol steam reforming catalyst is investigated in situ by XPS.
• The active surface state is formulated under the ESR reaction mixture and not by the pretreatment.
• Metallic cobalt and reduced ceria favor CO, while ionic cobalt is beneficial to CO2 and CH3CHO production.
• Adsorbed hydroxyl groups act as inhibitors of the ESR reaction rate.
• The cleavage of the CC ethanol bond is promoted by oxidized ceria supports.

This work examines the impact of the Co/CeO2 catalysts’ surface oxidation state and composition on the ethanol steam reforming (ESR) reaction performance. To this purpose, in situ and ex situ X-ray photoelectron spectroscopy (XPS) combined with on-line mass spectrometry were applied in a wide pressure range (0.2–20 mbar). When the reaction was performed at 0.2 mbar, metallic cobalt and partly reduced cerium oxide were found regardless of the catalysts’ pretreatment conditions. This surface state favors CO and H2 production, indicating that CC bond cleavage is the most important pathway in this pressure regime. A higher reduction degree of ceria gave rise to a larger population of adsorbed hydroxyl groups, which, contrary to the expected behavior, suppressed the activity and the CC bond cleavage yield. Under higher pressure (4–20 mbar), gradual oxidation of cobalt and ceria was noted. The presence of ionic cobalt species appears to enhance CO2 and acetaldehyde yields. On the basis of the present results and the available literature a plausible pressure-dependent reaction mechanism is proposed.

Figure optionsDownload high-quality image (141 K)Download as PowerPoint slide