Defect-induced precise synthesis of ultrasmall Ir1Sn1 intermetallic nanoparticles for enhanced propane dehydrogenation

Atomically ordered intermetallic nanomaterials have been considered to be one of the most promising catalysts for propane dehydrogenation due to their exceptional structural properties and thermal stability. However, the precise synthesis of ultrasmall intermetallic nanoparticles (iNPs) remains a challenge, since the aggregation of nanoparticles is unavoidable in a high-temperature annealing step. Herein, we develop a defect engineering strategy promoting the formation of uniform Ir1Sn1 iNPs (similar to 1.5 nm) by shortening the migration distance of Ir and Sn atoms during the alloying process. Detailed studies reveal that the highly dispersed tin oxide (SnOx) with abundant oxygen defects serve as anchoring sites for Ir precursor species, which remarkably reduce the energy barrier for the phase transformation, leading to the enhancement of the alloying degree and the anti-sintering ability of resulted iNPs after H-2-reduction. Systematic dehydrogenation tests and characterizations suggest that the isolated Ir sites in Ir1Sn1 iNPs are active for propane dehydrogenation, exhibiting >= 97 % of the propylene selectivity at near-equilibrium conversions. Moreover, no obvious aggregation and structural change of Ir1Sn1 iNPs, as well as catalyst deactivation are observed even after 26 h continuous propane dehydrogenation. The strategy of using defective metal oxide to confine atomically dispersed metals for the fabrication of uniform iNPs provides a novel method for developing robust alloy catalysts for high-temperature applications.