Facile Self-Cross-Linking Synthesis of 3D Nanoporous Co3O4/Carbon Hybrid Electrode Materials for Supercapacitors.

A hybrid electrode material with ultrafine Co3O4 nanoparticles embedded throughout a hierarchically nanoporous graphitic carbon matrix has been obtained via a facile self-cross-linking route. Sodium alginate, a biopolymer with an ability of cross-linking with multivalent cobalt cations to form ordered microcrystalline zones, is used as a carbon source to produce nanoporous carbon frameworks of the hybrids. Ultrafine Co3O4 nanoparticles with tunable particle size (3-30 nm) are in situ grown within the nanoporous graphitic carbon frameworks by a simple carbonization of Co-cross-linked alginate. The obtained hybrid electrodes exhibit high specific capacitance of 645, 548, 486, and 347 F/g at scan rates of 5, 10, 20, and 50 mV/s, respectively, and excellent cycle performance with only 1% fading in capacitance after 10 000 cycles at a high current density of 20 A/g. Such excellent capacitive performance is ascribed to the collaborative contributions of well-dispersed ultrafine Co3O4 nanoparticles and conductive nanoporous carbon frameworks.