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CO2 hydrogenation on rhodium surfaces : a study by field emission techniques

par Lambeets, Sten ;Barroo, Cédric ;Gilis, Natalia ;Kruse, Norbert ;Visart de Bocarmé, Thierry
Référence International Workshop on Surface Physics (7: 2015-06-22: Trzebnica, Poland)
Publication Non publié, 2015-06-22

Communication à un colloque

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Résumé :

This work addresses as well the adsorption of CO2 as and the interaction of H2/CO2 gas mixtures over singles nano-sized rhodium crystallitess. This system has been studied using field emission techniques including Field Ion Microscopy (FIM) and Field Emission Microscopy Microscopies (FEM). Both FEM and FIM methods are able to image in real time the surface of a conductive material,metal conditioned as a thin tip, at with the nanoscale and even atomic lateral resolution, respectively. Dynamic evolutions of the surface composition can be followed in real time.The structure of the rhodium nanocrystals hasve been characterised by FIM, whereas CO2 adsorption and dissociation have been followed by FEM. Depending of the local work function of the surface, brightness analysis is used to monitor the reaction in while it proceeds.When pure CO2 gas is introduced in the chamber, the brightness decreases with the dissociative adsorption of CO2 gas to O(ads) and CO(ads) species. Upon increase of the hydrogen pressure, reaction phenomena were observed from 650 to 700 K. The increasing brightness indicates the occurrence of a reaction between adsorbed hydrogen and adsorbed oxygen.Crossing our results withResults from the brightness analysis have been compared to literature data which allows to propose a coherent chemical scenario. explaining these observations and identify the reaction as the The Reverse Water Gas Shift reaction (CO2(g)+H2(g)→ CO(g)+H2O(g)) is most probably in operation in our case. These assumptions are in line with direct local chemical analysis performed by atom probe techniques consisting in the coupling of a FIM device with a Time of Flight mass spectrometer operated during the ongoing processes using field pulses[3].