Activation of small molecules on perovskites
The here proposed PhD project between the ESRF, ILL, UGA and Saint-Gobain Research Provence aims to understand the active species in exsoluted Pd-Fe or Pd-Ti species from a perovskite ABO3 matrix (LaMn1-xFexO3-δ (LMF) and CaTi1-xFexO3-δ (CTF, 0<x<0.6)). Preliminary results show an important impact not only of the Pd-content, but also of the iron doping in these perovskites for methane oxidation. Exsolution of Pd prior to the catalytic test will not only impact the Pd state, but also other B-site elements, and possibly the A-site (Ca in CTF and La in LMF).
Besides the cation lattice, also the oxygen ion structure are affected. To obtain a complete picture of the different crystallographic sites, electronic structure and short- and long range order, a combination of neutron- and synchrotron techniques are used, with a special attention to in situ and operando studies. We use operando X-ray absorption and emission spectroscopy on beamline ID26 to probe the Fe, Ti and Pd sites. These experiments will at the same time give the opportunity to further develop operando cells to be compatible with the low energies (Pd-L edge, K-edge of Ca), and therefore be of use to a wider community.
Neutron scattering helps to shed light on the structural modifications of the oxygen sublattice accompanying exsolution, and give further details on the dynamics of B-site occupancy changes resulting from the growth mechanism of the Pd-nanoparticles and creation of defects in the Ti- and Fe-sublattice. The combination of these two techniques contribute to a more complete picture of the local environment of the catalytic active species in methane activation and CO oxidation.
Saint-Gobain Research Provence