Rational design of MnO2@MnO2 hierarchical nanomaterials and their catalytic activities

Abstract

Hierarchically structured materials have special properties and possess potential in applications in the catalytic and electrochemical fields. Herein, two kinds of hierarchical core–shell nanostructures, lavender-like α-MnO₂@α-MnO₂ and balsam pear-like α-MnO₂@γ-MnO₂, were prepared by a facile room-temperature method using α-MnO₂ nanowires as a backbone under acidic and alkaline conditions, respectively. When being used as a catalyst for dimethyl ether combustion, α-MnO₂@γ-MnO₂ exhibited a better performance than α-MnO₂@α-MnO₂ (T₁₀ = 171 vs. 196 °C; T₉₀ = 220 vs. 258 °C, SV = 30, 000 mL g⁻¹ h⁻¹). It is concluded that the larger surface area, higher reducibility/oxygen mobility, richer surface oxygen species, and the relatively smaller apparent activation energy are responsible for the superior performance of α-MnO₂@γ-MnO₂.