Preparation and Electrochemical Performance of Bio-Oil-Derived Hydrochar as a Supercapacitor Electrode Material.

The rapid consumption of fossil energy and the urgent demand for sustainable development have significantly promoted worldwide efforts to explore new technology for energy conversion and storage. Carbon-based supercapacitors have received increasing attention. The use of biomass and waste as a carbon precursor is environmentally friendly and economical. In this study, hydrothermal pretreatment was used to synthetize coke from bio-oil, which can create a honeycomb-like structure that is advantageous for electrolyte transport. Furthermore, hydrothermal pretreatment, which is low in temperature, can create a low graphitization degree which can make heteroatom introduction and activation easier. Then, urea and KOH were used for doping and activation, which can improve conductivity and capacitance. Compared with no heteroatom and activation hydrothermal char (HC) (58.3 F/g at 1 A/g), the prepared carbon material nitrogen doping activated hydrothermal carbon (NAHC) had a good electrochemical performance of 225.4 F/g at 1 A/g. The specific capacitance of the prepared NAHC was improved by 3.8 times compared with that of HC.