Composites containing biological materials with nanostructured architecturehave become of great interest in modern materials science, yielding both interestingchemical properties and inspiration for biomimetic research. Herein, we describe thepreparation of a novel 3D nanostructured MnO2-based composite developed usinga carbonized proteinaceous spongin template by an extreme biomimetics approach. The thermal stability of the spongin-based scaffold facilitated the formation of both carbonized material (at 650 °C with exclusion of oxygen) and manganese oxide with a defined nanoscale structure under 150 °C. Remarkably, the unique network of spongin fibers was maintained after pyrolysis and hydrothermalprocessing, yielding a novel porous support. The MnO2-spongin composite shows a bimodal pore distribution, with macropores originating from the sponginnetwork and mesopores from the nanostructured oxidic coating. Interestingly,the composites also showed improved electrochemical properties compared tothose of MnO2. Voltammetry cycling demonstrated the good stability of the materialover more than 3,000 charging/discharging cycles. Additionally, electrochemicalimpedance spectroscopy revealed lower charge transfer resistance in the preparedmaterials. We demonstrate the potential of extreme biomimetics for developing a new generation of nanostructured materials with 3D centimeter-scale architecturefor the storage and conversion of energy generated from renewable natural sources. Open image in new window