A general approach to 3D porous CQDs/MxOy (M = Co, Ni) for remarkable performance hybrid supercapacitors

To date, zero-dimensional carbon quantum dots (CQDs), as a new carbon nanomaterials, have attracted attention in the improvement of the electrical conductivity for electrode materials. However, few attempts have been made to the use of CQDs as the structure-directing agent for the assembly of functional micro/nanoelectrodes. Herein, we have developed a general, and simple strategy to fabricate 3D porous hierarchical carbon quantum dots (CQDs)/M x O y (M   =   Co, Ni) composite nanostructures from thermolysis of corresponding CQDs/M(OH) y , where CQDs play crucial role as a structure-directing agent in tuning the morphologies of the M(OH) y . With the merits of the large electroactive surface area, superior electronic conductivity of CQDs, and fruitful porous structure, the as-fabricated battery-type electrode materials present amazing supercapacitor performance. For example, the as-made porous hierarchical CQDs/Co 3 O 4 nanoarchitectures exhibited remarkable electrochemical performance with 1603   F   g −1 at 1   A   g −1 , excellent rate capacity of 70.6% from 1 to 100   A   g −1 , superior cycling ability (97.0% capacity remained after 2000 cycles). Furthermore, the CQDs/Co 3 O 4 //AC hybrid supercapacitor (HSC) exhibits a high specific capacity of 210.4   F   g −1 with 74.8   W   h   kg −1 . The present work can be enlarged for the design of other functional 3D hierarchical micro-nanostructures in the fields of energy storage, catalysis, and photo/electrocatalysis.