Fabrication of 3D self-supporting hierarchical poplar-based thick carbon electrode via coupling delignification and gradient carbonization for electrochemical performance

The low energy and power density of biomass-based carbon are attributed to its limited mass transfer ability owing to its powder state. Specific three-dimensional (3D) self-supporting hierarchical poplar-based carbon electrodes are constructed via coupling delignification and gradient carbonization. We fabricate a self-supporting structure by taking advantage of the natural structure of the poplar wood itself during delignification. Meanwhile, the hierarchical self-supporting porous structures are controlled effectively via gradient carbonization. The 3D self-supporting hierarchical poplar-based carbon electrode shows high specific capacitance equal to 229 F g−1 (3.7 F cm−2) on a single-electrode electrochemical system. Energy density is 11.6 Wh·kg−1, power density is 3500 W kg−1, and the rate capability is 73%, which is considered satisfactory. Specifically, both the energy density and power density of the obtained samples are superior to those of other carbon-based supercapacitors under similar processing conditions and without any activation or acid etching processes. This study provides an effective approach to creating poplar-based carbon with 3D self-supporting hierarchical structures and enhances the electrochemical performance of biomass carbon under the condition of high value-added utilization.