(738d) Insights into Segregation and Exsolution of Transition Metals from Host Perovskite Oxides

The use of traditional supported metal catalysts is ubiquitous in chemical processes and industry. However, they are constantly subjected to exacerbating reactions like coking, and maintaining their high metal dispersion is an ongoing challenge [1]. One promising alternative for realizing novel supported metal catalysts is through exsolution of transition metal cations from a host perovskite oxide resulting in socketed catalysts on the surface, which are sometimes referred to as ‘intelligent catalysts’ [2]. Several studies showing the exsolution of transition metals from host perovskites do exits, however, the different factors that determine segregation and exsolution are far from well understood. In this computational study, we study different factors that determine whether segregation will occur in specific dopant metal (4d metals) and host oxide (ATiO₃ with A=Ca, Sr or Ba) systems. In particular, we investigate the host oxide, facet, and strain dependence. Figure 1 shows the density functional theory calculated differences in segregation energies for a single platinum dopant with respect to some of the investigated factors. The dynamics aspects of the exsolution process is also studied in detail using ab initio molecular dynamics to further delineate the segregation mechanisms. Identifying the specific dominant factors for a given metal dopant and host oxide system will help in the development of novel catalyst materials with new activity, selectivity and stability properties.

Reference:

1. Oh, T. et al. J. Phys. Chem.: Lett. 6, 5106-5110 (2015)
2. Nishihata, Y. et al. Nature, 418, 164-167 (2002)

Figure.1 Calculated surface segregation energies of a single Pt dopant from ATiO₃ (A=Ca, Sr, Ba) perovskites for different facets and strain values.