Mesoporous Y2Sn2O7 pyrochlore with exposed (111) facets: an active and stable catalyst for CO oxidation

Abstract

Pyrochlore with an A₂B₂O₇ crystal structure is a perfect mixed oxide for catalytic application for its high thermal stability. In the present manuscript, mesoporous Y₂Sn₂O₇ pyrochlore with exposed (111) facets was successfully synthesized via a simple hydrothermal method and used for CO oxidation. In comparison with Y₂Sn₂O₇ prepared by a co-precipitation method (Y₂Sn₂O₇-CP), Y₂Sn₂O₇ prepared by a hydrothermal method (Y₂Sn₂O₇-HT) showed superior catalytic performance for CO oxidation. Even after calcination at 800 °C for 4 h (Y₂Sn₂O₇-HT-800), its catalytic performance was still better than that of Y₂Sn₂O₇-CP. Y₂Sn₂O₇-HT is also a good support for Pd nanoparticles. Pd/Y₂Sn₂O₇-HT demonstrates the best performance for CO oxidation among all the catalysts. All the samples were characterized by XRD, SEM, TEM, HAADF-STEM Mapping, N₂ adsorption/desorption, H₂-TPR, CO-TPD and Raman spectra to reveal their physicochemical properties. Compared with Y₂Sn₂O₇-CP, Y₂Sn₂O₇-HT has more exposed (111) facets, possesses a higher amount of active surface oxygen species and had high mesoporous surface areas, which should be the reasons accounting for the superior CO oxidation performance of Y₂Sn₂O₇-HT and Pd/Y₂Sn₂O₇-HT. Pd/Y₂Sn₂O₇-HT also shows superior water-tolerance. In wet feed, its catalytic activity was even better than that in dry feed. Therefore, Pd/Y₂Sn₂O₇-HT may be a potential catalyst for practical vehicle emission control.