Revealing the interplay between “intelligent behavior” and surface reconstruction of non-precious metal doped SrTiO3 catalysts during methane combustion

Abstract

The impact of surface reconstruction of a model perovskite, SrTiO3 (STO), on CH4 activation for combustion and oxidative coupling was previously revealed that the reaction rate was proportional to the creation of Sr-terminated step sites. Doped perovskites (SrTi1−xMxO3, M=metal dopant) present yet another form of reconstruction throughout the surface and the bulk, where the metal dopant can migrate in and out of the perovskite lattice, also known as “intelligent behavior”. In this work, understanding the interplay between perovskite surface reconstruction (surface termination) and the “intelligent behavior” is tackled for the first time, and the catalytic consequences are probed with CH4 combustion as a model reaction. A set of experimental techniques, including XRD, Raman spectroscopy, X-ray adsorption spectroscopy, kinetic measurements, as well as DFT calculations were used to understand the catalytic behavior of the reconstructed surfaces of Ni and Cu-doped STO for methane combustion. We found that during methane oxidation, the diffusion of Ni and Cu into the lattice due to the “intelligent behavior” is accompanied by Sr enrichment on the surface of the perovskite. This Sr-enrichment process is reversible when Cu or Ni species exsolute as clusters/nanoparticles upon H2 treatment. Such a surface reconstruction is found to greatly impact the catalytic activity of doped perovskites towards methane combustion.