ab initio modelling of materials for energy applications: IrO2 and ceria
Olivier Matz
Laboratoire de Chimie Théorique - UMR7616 UPMC & CNRS, Paris, France
Mercredi 28 Septembre 2017, 11h15
bibliothèque LCT, tour 12 - 13, 4ème étage
One of the biggest scientific and technological challenges is to convert solar energy into electricity and/or to store it into chemical fuels, i.e. producing hydrogen and oxygen from water. Because ab initio techniques allow to study properties at the atomic level, periodic DFT is a powerful tool to understand the behavior of materials at the atomic scale.
Due to its good photocatalytic properties and its high efficiency in photocatalytic devices, iridium oxide was receiving an increasing interest these last years. Indeed, IrO2 was identified as playing a key role during the water oxidation [1,2] in the photo water splitting reaction. However, despite the promising properties of IrO2, the knowledge of both structural and reactivity of this material is still very poor. In this context, we have studied the structure-property-reactivity relationships of four IrO2 surfaces. More precisely, our work [3] was focused on the structural, energetic, electronic properties and chemical reactivity towards catechol, a probe molecule mimicking common linkers in photocatalytic devices.
Most of the applications of ceria are linked to its redox properties associated to the easy formation of oxygen vacancies and so the simple change in oxidation states of cerium: Ce4+ ↔ Ce3+. Moreover, ceria is important in heterogeneous catalysis, especially in the alkyne semi-hydrogenation where it has been shown to be able to split H2 in the absence of noble metal [4]. Interestingly, the hydrogenation of ceria is found to take place through a hydride specie that plays a key role [4,5]. In this context, we have investigated the detailed mechanism for the formation of surface oxygen vacancy via H2 dissociation following by H2H2O desorption on (111)-CeO2 surface.
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References :
[1] M. Pastore and F. De Angelis J. Am. Chem. Soc. 2015, 137, 5798.
[2] M. D. Kärkäs, O. Verho, E. V. Johnston, and B. Åkermark Chem. Rev. 2014, 114,11863.
[3] O. Matz and M. Calatayud J. Phys. Chem. 2017 DOI: 10.1021/acs.jpcc.7b01990.
[4] J. Vecchietti, M. A. Baltanás, C. Gervais, S. E. Collins, G. Blanco, O. Matz, M. Calatayud, and A. Bonivardi J. Catal. 2017, 345, 258.
[5] RM. García-Melchor and N. López J. Phys. Chem. C 2014, 118, 10921.