Development of etched SiO2@Pt@ZrO(2 )core-shell catalyst for CO and C3H6 oxidation at low temperature

Abstract

In our previous study, we conducted CO oxidation with SiO2@Pd@CeO2 catalysts. However, the limit of the CeO2 shell thickness limited the thermal stability. So, in this study, thick ZrO2 shell was introduced to improve thermal stability. SiO2@Pt@ZrO2 catalysts were examined for the simultaneous oxidation of CO and hydrocarbons. SiO2@Pt@ZrO2 catalysts had improved thermal stability compared to Pt/SiO2 or Pt/ZrO2 after aging at 750 degrees C for 25 h. However, fresh SiO2@Pt@ZrO2 catalysts showed low oxidation activity because of the low gas accessibility due to the thick ZrO2 shell. Therefore, we proposed etched SiO2@Pt@ZrO2 catalysts for enhanced gas accessibility. The selective etching of SiO2 was adjusted by varying the KOH concentration. TEM images confirmed that the void space of the core-shell catalysts increased as the concentration of KOH increased. The exposed Pt surface area increased as the void space of the core-shell catalysts was increased. On the other hand, in excessively etched 3.2 M catalysts, the core-shell structure collapsed. Etched catalysts which maintain the core-shell structure improve thermal stability after hydrothermal aging. As a result, 1.6 M catalysts showed the best simultaneous oxidation of CO and hydrocarbons, and we confirmed that properly etched catalysts enhanced the oxidation activity and thermal stability.