Preparation of Eucommia ulmoides Oliver wood derived activated carbons by combined microwave hydrothermal pretreatment and microwave pyrolysis as electrode materials for super capacitive performance

Abstract

In this work, the activated carbon was prepared from the Eucommia ulmoides Oliver (EUO) wood by a two-step method. Firstly, the EUO wood was applied for microwave hydrothermal pretreatment (MHTP), then the obtained wood precursor was activated with phosphoric acid in a traditional tube furnace (TTACs) or microwave tube furnace (MWACs), respectively. Then the structural properties, surface characteristics and electrochemical performance were evaluated. In detail, the hemicellulose contents of the EUO wood decreased significantly from 18.23 % to 1.23 % with MHTP temperature ranging from 150 °C to 190 °C. Moreover, the activated carbon generated via MHTP at 170 °C (MWAC170) possessed an excellent specific surface area (2138.3 m2/g) with a higher proportion of mesoporous structure (76.15 %) and the degree of graphitization (0.71 of ID/IG ratio) than those of samples by traditional pyrolysis method. MHTP significantly affected the component composition of the matrix, and the effect was amplificated in the microwave pyrolysis process. In this case, MWAC170 exhibited a high specific capacitance (346.86 F/g) and remarkable long-term cycling performance. The symmetric supercapacitor (SSC) offered a maximum energy density of 30.7 Wh/kg and power density of 4481.8 W/kg. Therefore, the activated carbon prepared by a two-step process combining MHTP and microwave pyrolysis could be an ideal electrode material for application in energy storage with excellent economic feasibility.