One-pot alkaline carbonization hydrothermal synthesis of halloysite nanotubes with amino groups over Pd@CeO2/halloysite to enhance catalysis of three-way reactions

Abstract

The three-way catalytic activity of the halloysite (Hal)-supported Pd@CeO2 (P@C) catalyst was enhanced by hydrothermal carbonization. The P@C/4–1.0C-175H catalyst (P@C was loaded with carbonized Hal with a mass ratio of cellulose/Hal = 1, the temperature was 175 °C, and t = 4 h) showed higher catalytic efficiency than P@C/H (without modification) under optimal hydrothermal carbonization conditions, which was attributed to the large proportions of carbon and oxygen-containing functional groups on carbonized Hal. The T90 (full-conversion temperature) for CO conversion was decreased from 233 °C to 210 °C. On the other hand, the efficient one-pot alkaline carbonization hydrothermal synthesis combined hydrothermal carbonization and alkaline modification without complicated steps or additional active agents. The synthesis was modified, and the cellulose carbon source was substituted by lysine to induce a negative charge on the surface of Hal. The results indicated that P@C/4–1.0NC-175H exhibited strong metal-support interactions, abundant amino and oxygen-containing functional groups, and more oxygen vacancies and CeIII species. The T90 for CO conversion with P@C/4–1.0NC-175H was significantly decreased from 461 °C (P@C) to 174 °C. This research provides a simple method for enhancing metal-support interactions and improving catalytic performance.