Effect of alkali (Cs) doping on the surface chemistry and CO2hydrogenation performance of CuO/CeO2catalysts

Georgios Varvoutis, Maria Lykaki, Eleni Papista, Sónia A. C. Carabineiro, Antonios C. Psarras, Georgios E. Marnellos, Michalis Konsolakis

Research output: Contribution to journalArticlepeer-review

Abstract

The reaction of captured carbon dioxide with renewable hydrogen towards the eventual indirect production of liquid hydrocarbons via CO2 reduction to CO (reverse water-gas shift reaction, rWGS) is a promising pathway in the general scheme of worldwide CO2 valorization. Copper-ceria oxides have been largely employed as rWGS catalysts owing to their unique properties linked to copper-ceria interactions. Here, we report on the fine-tuning of CuO/CeO2 composites by means of alkali promotion. In particular, this work aims at exploring the effect of cesium doping (0-4 atoms Cs per nm2) on co-precipitated CuO/CeO2 catalysts under CO2 hydrogenation conditions. The as-prepared samples were characterized by N2 physisorption, X-ray diffraction (XRD), H2erature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), CO2erature programmed desorption (CO2-TPD), Fourier-transform infrared spectroscopy (FTIR) of pyridine adsorption and CO-diffuse reflectance Fourier-transform infrared spectroscopy (CO-DRIFTS). The results demonstrated that a low amount of Cs exerted a beneficial effect on CO selectivity, inhibiting, however, CO2 conversion. Specifically, a doping of 2 atoms Cs per nm2 offers > 96 % CO selectivity and equilibrium CO2 conversion at temperatures as low as 430 °C, whereas further increase in cesium loading had no additional impact. The present findings can be mainly interpreted on a basis of the alkali effect on the textural and acid/base properties; Cs doping results in a significant reduction of the surface area and thus to a lower population of active sites for CO2 conversion, whereas it enhances the formation of basic sites and the stabilization of partially reduced Cu+ species, favoring CO selectivity.

Original languageEnglish
Article number101408
JournalJournal of CO2 Utilization
Volume44
DOIs
Publication statusPublished - Feb 2021

Keywords

  • Alkali doping
  • CO Selectivity
  • COhydrogenation
  • Copper-ceria
  • Cs promotion
  • Reverse water-gas shift reaction

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