Origin of the efficient catalytic thermal decomposition of ammonium perchlorate over (2-1-10) facets of ZnO nanosheets: Surface lattice oxygen

Abstract

ZnO nanocrystals as catalysts have been widely employed in the catalytic thermal decomposition of ammonium perchlorate (AP). However, the catalytic mechanism is still controversial and the role of surface lattice oxygen is always ignored. Herein, a classical catalytic mechanism based on the surface lattice oxygen was proposed to reveal AP decomposition promoted by ZnO nanosheets. ZnO and ZnS nanosheets, both of which have the same wurtzite structure and the same (2-1-10) exposed facets, have been synthesized by the calcination of a ZnS(en)0.5 precursor in different conditions. ZnO nanosheets with a smaller surface area showed a better catalytic activity than ZnS nanosheets because the surface lattice oxygen of the ZnO nanosheets can react with NH3 (an intermediate of AP thermal decomposition) to generate oxygen vacancies that can subsequently be recovered, while the surface lattice sulfur of the ZnS nanosheets did not react with NH3. The generation and replenishment of oxygen vacancies on the (2-1-10) exposed facets of the ZnO nanosheets were confirmed by XPS and FTIR results, and thus revealed the origin of the efficient catalytic AP decomposition over (2-1-10) facets of ZnO nanosheets as surface lattice oxygen. Therefore, this work could provide a new insight into the catalytic mechanism of metal oxides to promote AP decomposition.