3-Dimensional (3D) composites based on a unique combination of MnO2-nanostructures, graphene oxide nanosheets and porous Diatomaceous Earth (DE) microparticles (GO-DE@MnO2) were synthesized and explored for application in high-performance supercapacitors. To explore the influence of the structural properties of MnO2 nanostructures on supercapacitor performances, several MnO2 structures with nanosheet and nanowire morphologies were synthesized and characterized. The prepared GO-DE@MnO2 composites with MnO2 nanosheets due to their higher conductivity and higher surface area showed a larger specific capacitance of 152.5 F g(-1) and a relatively better cycle stability (83.3% capacitance retention after 2000 cycles at a scan rate of 2 A g(-1)), indicating great potential for application in supercapacitors.