Plane tree bark-derived mesopore-dominant hierarchical carbon for high-voltage supercapacitors

Wide potential range and high specific capacitance of electrode materials are critical to high performance supercapacitors. However, it remains challenging to simultaneously achieve both high capacitance and cell voltage, particularly in organic electrolytes. Herein, three dimensional (3D) mesopore-dominant hierarchical carbons are obtained by one-step pyrolysis-activation of seasonable biowaste, i.e., plane tree bark with nano-ZnO as a mild activator. The optimized biowaste-derived carbon shows an ultrahigh mesopore area and low oxygen content. With these merits, the carbon electrodes show both high capacitance and wide capacitive potential range in both aqueous and organic electrolyte. Particularly, a specific capacitance of 115.6F g⁻¹ and a high cell voltage of 3 V are achieved with organic electrolyte. This study also reveals a mismatch between the specific capacitance and four commonly used specific surface area values. In a symmetrical supercapacitor with organic electrolyte, the positive electrode is the voltage-determining electrode. These findings may provide new perspectives on materials and device design of high-voltage supercapacitors.