Fabrication of bimodal micro-mesoporous amorphous carbon-graphitic carbon-reduced graphene oxide composite microspheres prepared by pilot-scale spray drying and their application in supercapacitors

There has been a demand for a suitable method which is applicable to mass production of electrode materials for supercapacitor. Herein, the synthesis of amorphous carbon–graphitic carbon-reduced graphene oxide (AC-GC-rGO-a) composite microspheres by pilot-scale spray drying/KOH activation is described and their performance as an electrode material is examined. Through pilot-scale spray drying in a 2 m high chamber, large-scale production of precursor (Fe nitrate-dextrin-GO composite) microspheres is realizable. Metallic Fe nanocrystals formed by carbothermal reduction play a role in the transformation of the dextrin-derived amorphous carbon into graphitic carbon layers. Micropores are then formed from the dextrin-derived amorphous carbon by KOH activation, and finally, bimodal pore-structured AC-GC-rGO-a composite microspheres are prepared. In particular, it is revealed that crumpling of the rGO increases the electrical conductivity of the composite microspheres and thus results in a large specific capacitance (408.2 F g−1) and enhanced rate performance. Additionally, AC-GC-rGO-a features improved cycling stability, exhibiting a capacity retention of 94.7% after 10,000 cycles at 10 mA g−1. Therefore, the developed composite surpasses other carbon materials and graphene oxide composites and is potentially suitable for mass production.