Lanthanum nickel titanate perovskites as model systems for Ni-perovskite interfacial engineering in methane dry reforming

By exploiting the lanthanum – nickel – titanate model system for methane dry reforming (DRM), we show how different (double) perovskite precursor structures can be used to tailor the structure and phase composition of specific Ni – (double) perovskite interfaces by activation in different reducing atmospheres. The key parameter for successful steering of the interface structure is the stability of the parent perovskite material in the respective hydrogen or CO 2 –CH 4 mixture. Rietveld refinements of both the precursor perovskite and the interfacial structures verify the sole presence of exsolved Ni and the respective perovskite. Hydrogen reduction of the double perovskite La 2 NiTiO 6 leads to exsolution of nm-sized Ni particles and the formation of a Ni–La 2 NiTiO 6 interface. Structure refinements based on X-ray and neutron powder diffraction, combined with temperature-programmed hydrogen adsorption, reveal that the prevailing La 2 NiTiO 6 is mostly unaffected by the hydrogen treatment and formation of reduced sites is largely suppressed. Treatment of the Ti-doped single perovskite LaNi 0.5 Ti 0.5 O 3 in a CO 2 –CH 4 mixture equally yields Ni exsolution and consequently, a Ni–LaNi 0.5 Ti 0.5 O 3 interface. Similarly, LaNi 0.5 Ti 0.5 O 3 is essentially unaffected by the treatment, with interfacial structure and phase composition remaining stable over several DRM cycles. Only hydrogen reduction of LaNi 0.5 Ti 0.5 O 3 causes complete transformation of the parent perovskite into a Ni–La 2 TiO 5 /LaTiO 3 mixture. All interfaces, including Ni particles impregnated on La 2 TiO 5 with outstanding anti-coking behavior, exhibit inherent DRM activity, rivaling or even outperforming undoped LaNiO 3 . Differences in the stability of (transient) structures during exsolution along the decomposition pathway are mainly due to the Ti dopant, which stabilizes the perovskite structures in reducing atmospheres. This enhanced stability allows us to approach specific Ni-perovskite interfaces and assess their inherent DRM activity. • Defined metal-perovskite interfaces are accessed in the La–Ni–Ti perovskite system. • The inherent DRM activity of such interfaces is accessible. • Ti is a structurally stabilizing dopant for LaNiO 3 . • Ti leads to a different DRM reaction mechanism via suppression of La-oxycarbonates • The Ni–La 2 TiO 5 interface exhibits improved coking resistance.