In situ XAS and FTIR studies of a multi-component Ni/Fe/Cu catalyst for hydrogen production from ethanol

• NiFeCu catalyst appears homogeneous at the mesoscale but highly heterogeneous at the nanoscale.
• Cu oxidation state changes upon exposure to ethanol but Ni remains 75% reduced without further changes in oxidation state during reaction.
• Iron is not present in metallic form under any of the conditions used.
• XPS results indicate the enrichment of surface by Fe and Cu during the reduction.
• IR results show changes in the amount and type of adsorbed species with temperature and correlates with the active role of each metal at a given temperature.

Multicomponent catalysts containing Ni, Fe, Cu active for ethanol reforming reactions, prepared by solution combustion synthesis are characterized by multiple techniques such as ex situ XRD, XPS, and in situ XAFS and FTIR. XRD results indicate copper to be present in the reduced state as CuNi bimetal while nickel and iron are observed to be partially in a spinel NiFe2O4 structure. In situ XANES and XAFS analysis show a change in Ni, Fe and Cu oxidation states during reaction. Cu, which was fully reduced before reaction, became partly oxidized upon exposure to ethanol and oxygen. Ni is mostly (75%) reduced and does not seem to change its oxidation state during the reaction. Fe is not present in metallic form after reduction and during the reaction, but some change in the oxidation state from Fe(II) to Fe(III) occurred during the reaction. XPS and SEM images indicate the formation of carbon filament on the spent catalyst. XPS results also indicate the enrichment of surface by Fe and Cu during the reduction of the catalyst. Based on the activity and characterization results obtained, and literature review, the role of predominant phases during ethanol decomposition reaction is proposed.

An active catalyst for ethanol decomposition reaction, containing nano-composites of Ni/Fe/Cu was synthesized using combustion based techniques. Different characterization results indicate that the segregated phases were active at different temperature ranges resulting in gradual change the product selectivity with temperature.Figure optionsDownload high-quality image (71 K)Download as PowerPoint slide