Rational growth of various α-MnO2 hierarchical structures and β-MnO2 nanorods via a homogeneous catalytic route

Heterogeneous catalytic reactions involved in the vapor-liquid-solid (VLS) or solution-liquid-solid (SLS) growth of 1-D nanostructures have been intensively investigated in recent years. But how to control the homogeneous catalytic route and apply it to design new structures of materials has rarely been discussed. In this work, a homogeneous catalyst was successfully controlled via changing the catalyst feed way, and three novel alpha-MnO2 hierarchical structures, namely, urchin-like structures, sphere networks, and nanowire networks, were selectively synthesized at room temperature. beta-MnO2 nanorods were also prepared via this method at higher temperatures. The present work indicates that the homogeneous catalytic route not only can produce one certain structure of inorganic materials but also can be rationally controlled and therefore used to grow more new structures. On the other hand, this homogeneous catalytic method is a solution-based self-assembly route, providing a simple, mild, and template-free way to the fabrication of hierarchical structures.