Hierarchical porous carbon materials produced from heavy bio-oil for high-performance supercapacitor electrodes

The heavy bio-oil produced by biomass pyrolysis was utilized as carbon source to synthesize hierarchical porous carbon materials for supercapacitor application. The influences of the chemical activation condition of the heavy bio-oil-derived carbon precursor on the microscopic morphology, pore structure, crystal structure and surface functional groups of the prepared carbon materials were investigated. Electrochemical measurements were performed both in three-electrode and two-electrode systems to evaluate the performance of the prepared carbon materials. The results show that the carbon material prepared at the NaOH/heavy bio-oil-derived carbon precursor ratio of 3:1 possessed the highest specific surface area (2826 m2 g−1) and largest total pore volume (1.78 cm3 g−1) with apparent hierarchical porous structure and abundant oxygen doping. At 0.5 A g−1, the specific capacitance of the single carbon electrode reached up to 287 F g−1 in three-electrode system and 259 F g−1 in two-electrode system, which is superior to many biomass-based carbon materials. The carbon electrode had a high capacitance retention of 63.8% from 0.5 A g−1 to 50 A g−1 in three-electrode system, indicating its outstanding rate performance. In addition, the energy density of the two-electrode symmetric supercapacitor reached 12.95 W h kg−1 at a power density of 300 W kg−1. This paper proposes a new way to prepare activated carbon electrode materials from heavy bio-oil.