Cryogel Synthesis of Hierarchical Interconnected Macro-/Mesoporous Co3O4 with Superb Electrochemical Energy Storage

In this contribution, we report a facile synthesis of ultrafine Co3O4 nanocrystals with an in situ construction of mesoporous and macroporous network for supercapacitor electrode material. The resultant ultrafine Co3O4 nanocrystals form an interconnected macroporous network with mesoporous hierarchical structure. The unique architecture is realized through a modified sol gel process to formulate highly porous cryogel using freeze-drying in the presence of a soft template. Small-angle X-ray scattering and transmission electron microscopy are used to investigate the organization of the Co3O4 porous structure. The unique channels in this hierarchical pores network provide intimate electrolyte contact with cobalt oxide and facilitate electrolyte diffusion. This hierarchical structure presents superior electrochemical performance with a specific capacitance of 742.3 F g(-1) measured at a potential window of 0.5 V, unveiling one of the highest performance for sol-gel synthesized oxides to date, to the best of our knowledge. The capacity retention was 86.2% after 2000 cycles. The synthesis strategy highlights a versatile and facile dual template approach to independently tailor the porosity and particle sizes using a spontaneous nucleation approach. This serves as a major milestone toward high-performance porous metal oxide material for supercapacitor electrodes.