Accelerating Metal Nanoparticle Exsolution by Exploiting Tolerance Factor of Perovskite Stannate

Perovskite oxide (ABO₃) with catalytically active metal nanoparticles (NPs) has the potential as a promising application such as solid oxide fuel cell operated at high temperature, electrochemical reaction, energy conversion, photocatalysis and syngas conversion. In particular, <i>in-situ </i>exsolution is emerging method that metal NPs are segregated from an oxide matrix to a surface under a reducing atmosphere for enhancing the interfacial adhesion between metal NPs and the perovskite support with high electrical conductivity [1, 2].<br/>In this presentation, we demonstrate a novel method to control a density of Ni metal NPs on surface of A-site deficient perovskite stannate matrix (A_0.9Sn_0.9Ni_0.1O_3-_δ, A = Ca, Sr, Ba) by manipulating distortion of SnO₆ octahedron by diffusion kinetics of Ni metal during exsolution process. Remarkably, the density of Ni NPs increases from 47 particles um^-2 (Ba_0.9Sn_0.9Ni_0.1O_3-_δ) to 304 particles um^-2 (Ca_0.9Sn_0.9Ni_0.1O_3-_δ) by decreasing the Goldschmidt tolerance factor of perovskite stannate epitaxial films. <i>Q</i>uantitative analysis using ambient pressure X-ray photoemission spectroscopy (APXPS) during <i>in-situ</i> exsolution process experimentally confirmed that Ni diffusion is enhanced with decreasing the tolerance factor of perovskite stannates. Experimental characterization combined with theoretical calculation shows that Goldschmidt tolerance factor of perovskite stannate promote the Ni diffusion kinetics from the oxide matrix to surface by manipulating the A-O bonding strength. Motivated by the high density of Ni NPs on perovskite stannate support, <i>in-situ</i> CO oxidation was also performed using APXPS to identify the effect of the catalytic activity of perovskite stannate support with exsolved Ni NPs. This new strategy on the manipulation of tolerance factor for promoting exsolved metal diffusion kinetics can be exploited to enhance the density of populated metal nanoparticles for emerging catalytic applications.<br/><br/><b>References</b><br/>[1] Neagu, D., Tsekouras, G., Miller, D. et al.<i> Nature Chem</i> <b>5</b>, 916–923 (2013)<br/>[2] Yu, S., Yoon, D., Lee, Y. et al., <i>Nano Lett.</i> <b>5</b>, 3538 (2020)