Free-standing and porous hierarchical nanoarchitectures constructed with cobalt cobaltite (Co3O4) nanowalls have been successfully synthesized in large scale by calcining three dimensional (3D) hierarchical nanostructures consisting of single crystalline cobalt carbonate hydroxide hydrate - Co(CO3)(0.5)(OH)center dot 0.11H(2)O nanowalls prepared with a solvothermal method. The step-by-step decomposition of the precursor can generate porous Co3O4 nanowalls with BET surface area of 88.34 m(2) g(-1). The as-prepared Co3O4 nanoarchitectures show superior specific capacitance to the most Co3O4 supercapacitor electrode materials to date. After continuously cycled for 1000 times of charge discharge at 4 A g(-1), the supercapacitors can retain ca 92.3% of their original specific capacitances. The excellent performances of the devices can be attributed to the porous and hierarchical 3D nanostructure of the materials. (C) 2012 Elsevier B.V. All rights reserved.