Converting inorganic–organic hybrid sulfides into oxides: A general strategy to hierarchical-porous-structured thermal-stable metal oxides with improved catalytic performance

Abstract

A facile strategy to correlate the thermal decomposition of inorganic–organic hybrid with the Kirkendall effect appearing during the oxidation process of sulfides into oxides has been developed to synthesize hierarchical-porous-structured metal oxide microspheres by using ceria as the model system. The as-prepared hierarchical-porous-structured ceria with micropores, mesopores and macropores (HC3M) possesses a very high surface area (over 290 m² g⁻¹) and high thermal stability. We have also demonstrated that the pore size of mesopores in HC3M can be modulated by controlling the oxidation and decomposition temperature of the hybrid precursors. Our preliminary results of the preferential oxidation of carbon monoxide in the H₂-rich stream (PROX) show that both the conversion and selectivity of the Cu/HC3M catalyst are obviously higher than those of Cu/CeO₂ particles. The improved catalytic activity may be attributed to the high dispersion and the smaller size of Cu on HC3M, the high specific surface area and unique hierarchical porous structure of HC3M support. Thus, the hierarchical-porous-structured ceria is expected to find promising applications in catalysis, sensors and fuel cells. In addition, the method to convert inorganic–organic hybrid sulfides into oxides can be successfully extended to the synthesis of hierarchical-porous-structured Y-doped and La-doped ceria with the modulated composition. Through the designed preparation of inorganic–organic hybrid sulfides, selenides or tellurides followed by the oxidation and thermal decomposition at suitable temperature, we believe that this conversion of hybrid materials into oxides might be extended to fabricate other hierarchical-porous-structured oxides with improved physical and/or chemical properties.