Renewable carbon foam/δ-MnO2 composites with well-defined hierarchical microstructure as supercapacitor electrodes

Composite electrodes containing both carbon and transition metal oxides have attracted tremendous interest because of their great potential as prominent electrodes for supercapacitors. Herein, direct growth of δ-MnO2 on wheat flour-derived carbon foam (WFCF) with well-developed hierarchical microstructure is readily carried out through an easy, scalable, and reliable two-step synthesis (also referred to as "foaming and cooking" technique), thereby achieving dual goals of environmental sustainability and remarkable electrical energy storage. The unique electrode architecture closely assembled between the prepared sponge-like carbon foam and nanostructured δ-MnO2 affords not only large exposed electroactive surface area but also rapid electrons and ions transport pathway, benefiting from the 3D interconnected hierarchical porous texture as well as considerable open channels between the anchored MnO2 sheets. As a result, the symmetric supercapacitor device based on the WFCF/MnO2-2.0 composite delivers a capacitance of 146 F g−1 and an impressive energy density of 20.3 Wh kg−1 at 1 A g−1 with good cycling stability in 6 M KOH electrolyte. The kinetic analysis indicates a combination of capacitive and battery-like electrochemical response. The proposed "foaming and cooking" strategy renders a prospective way for facile construction of high-performance supercapacitor electrodes with fast kinetics, good reversibility and structure stability.