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

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.