The facet-dependent catalytic performance of CeO2 nanocatalysts in the decomposition of ammonium perchlorate†

Abstract

CeO₂ nanocrystals are excellent catalysts for ammonium perchlorate (AP) decomposition, and investigating their catalytic performance on specific crystal facets is essential for understanding the reaction mechanism. Herein, CeO₂ nanorods (CeO₂-R) with (110) facets, octahedra (CeO₂-O) with (111) facets and cubes (CeO₂-C) with (100) facets were successfully synthesized, and their activity in AP decomposition showed an order of CeO₂-R > CeO₂-C > CeO₂-O. Specifically, the T_HTD decreased from 428.6 °C to 357.8 °C, 385.4 °C and 410.6 °C for (110), (100) and (111) facets, respectively. The XPS and EPR results confirmed a direct positive correlation between the oxygen vacancy concentration on the facets and their catalytic performance, and through detailed tracking experiments with TG-MS, the following reasonable conclusion can be drawn: oxygen vacancies can not only facilitate the adsorption of NH₃ which is the main decomposition product, but also reduce the band gap of CeO₂, and then promote the deep dissociation of NH₃. This work presents a clear facet-dependent activity of CeO₂ in the thermal decomposition of AP and comprehensively proves the supportive role of oxygen vacancies on different facets in the reaction.