Interfacial effects in hierarchically porous α-MnO2/Mn3O4 heterostructures promote photocatalytic oxidation activity

Constructing hybrid nanocatalysts with more active surfaces/interfaces is crucial for promoting catalytic activities for oxidative removal of volatile organic compounds (VOCs). Herein, we have successfully designed and synthesized a hierarchically porous alpha-MnO2/Mn3O4 nanostructure with numerous interfaces using a simple topotactic transformation synthesis strategy. The real time observation of the growth dynamics from alpha-MnO2 to alpha-MnO2/alpha-Mn3O4 is achieved by in-situ transmission electron microscopy. The in-situ formed alpha-MnO2/Mn3O4 hybrid supplies not only numerous intimate interfaces but also a direct Z-scheme junction, greatly promoting the generation of superoxide radicals. It also forms more oxygen vacancies that brings about absorption of more O-2 molecules on the surface, thus generating more superoxide radicals in unit time. As a result, the hybrid shows much better catalytic oxidation activity for eliminating VOCs as compared to pure alpha-MnO2 and Mn3O4. The results demonstrate a feasible way to construct hierarchically porous heterostructures with improved photocatalytic activity for eliminating VOCs.