Carbon spheres derived from biomass residue via ultrasonic spray pyrolysis for supercapacitors

Carbon spheres have been synthesized from larch residue via ultrasonic spray pyrolysis. The morphology and porous structure of the carbon spheres can be tailored by different precursors and soft template. The carbon spheres prepared with liquefied larch show honeycomb-like morphology with a size of 0.5-1 mu m, while the carbon spheres prepared with liquefied larch-based resins exhibit smooth surface. Furthermore, the carbon spheres prepared with F127 exhibit well-developed mesoporosity with two-dimensional hexagonal structure of P6mm symmetry whereas the carbon spheres prepared in the absence of F127 show the disordered porous structure. The carbon spheres (CS-R-F) prepared with liquefied larch-based resins and F127 display a high specific capacitance of 231 F g(-1) at a current density of 0.2 A g(-1). Specially, the specific capacitance still remains 146 F g(-1) even at a current density as high as 10 A g(-1). Importantly, above 97% of the maximum capacitance can be retained after 1000 cycles under a high current density of 10 A g(-1).