RGO-templated lignin-derived porous carbon materials for renewable high-performance supercapacitors

Porous carbon materials are considered as one of the most promising electrode materials of supercapacitors. However, it is inevitable to use an expensive and high-polluting activation treatment for obtaining porous structure. Herein, we reported a scalable and sustainable approach to fabricate lignin-derived porous carbon materials by combining hydrothermal reaction and high-temperature carbonization without using any chemical or physical activating reagents. During the hydrothermal reaction, industrial waste lignin as a green reducing agent deoxidized graphene oxide (GO) effectively, while reduced GO (RGO) hydrogels as 3D templates transitioned lignin molecules from ellipsoidal to disk-like conformation via non-covalent interactions and orderly aligned them on the surface of RGO nanosheets. Through this way, the intermediate products, lignin reduced GO aerogels (LRGOs), delivered superior pseudocapacitive performance caused by the reversible phenol-quinone structural transition of lignin molecules. Results indicated a highly positive correlation between the pseudocapacitance of LRGOs and the reduction degree of RGO. After carbonization, the carbonized LRGOs (C-LRGOs) presented a hierarchical porous structure and the resulted high specific surface area rendered the material an ideal electrical double layer capacitive behavior showing high specific capacitance (330 F g−1 at 1 A g−1), high energy density (11.3 Wh kg−1) at a power density of 254 W kg−1, as well as reliable cycle performance.