Enhancing the Capacitive Performance of Carbonized Wood by Growing FeOOH Nanosheets and Poly(3,4-ethylenedioxythiophene) Coating.

Carbonized wood (CW) achieved by the pyrolysis of various nature woods has received ever-increasing attentions in energy storage and conversion. However, its charge storage capacity is rather low because of its intrinsic ion adsorption mechanism. This work reports the enhanced capacitive performance of CW by growing electroactive FeOOH nanosheets and coating conductive poly(3,4-ethylenedioxythiophene) (PEDOT) network. Those vertically grown FeOOH nanosheets on both the external surface and inside the channel of CW offer more opened active sites for Faradaic reactions, whereas the porous and conductive PEDOT network significantly boosts the electrode conductivity, facilitates the ion transport, and protects the FeOOH sheets from destruction during cycling. Accordingly, the CW-FeOOH-PEDOT ternary electrodes exhibit 4.3 times higher volumetric capacitance than the CW electrode and remain at 90% capacitance upon increasing the current density from 10 to 50 mA cm-2. Remarkably, the electrode maintains 103% of its capacitance even after 10 000 cycles of galvanostatic charge-discharge at 200 mA cm-2. Besides these unique electrochemical behaviors, the CW-FeOOH-PEDOT also preserves good mechanical strength of the pristine CW electrode. This property allows easy processing of CW-based electrodes into robust energy storage device for practical applications.