Superior catalytic activity of Pd-based catalysts upon tuning the structure of the ceria-zirconia support for methane combustion

Abstract

Pd-based catalysts supported on CeO2-ZrO2 (CZ) mixed oxides have been universally applied toward the oxidation of methane, a strong greenhouse gas. Herein, CZ supports of different structures were prepared using hydrothermal (ST-CZ), co-precipitation (CP-CZ), and physical mixing (Mix-CZ) methods. Subsequently, the effects of the CZ support structure on the catalytic activity of the resulting Pd/CZ catalysts toward methane combustion were evaluated. ST-CZ shows the presence of cubic and tetragonal phases of CZ solid solutions, while CP-CZ is a pure tetragonal-phase solid solution and Mix-CZ is a mixture of CeO2 and ZrO2. The CZ solid solution improved the Pd dispersion and Pd2+/Pd ratio on the catalyst surface. Furthermore, CZ oxides with a two-phase composite structure resulted in higher oxygen storage capacity and oxygen mobility in the Pd/CZ catalysts than in the pure solid solution phase. Therefore, the Pd/ST-CZ catalyst shows superior catalytic activity for methane combustion than the other two catalysts.