Intrinsic carbon defect-engineered carbonized wood membrane electrodes for superior supercapacitors

Abstract

Carbonized wood membranes (CWMs) have emerged as highly promising self-supporting electrodes for supercapacitors (SCs) owing to their intrinsic vertical channel architecture and hierarchical porous structure. However, pristine CWM electrodes suffer from limited specific capacity, which is primarily derived from their intrinsically low specific surface area (SSA) and inferior electrolyte wettability. Herein, a highly defective carbonized wood membrane (hd-CWM) electrode was fabricated through CO2 thermal etching of pristine CWM. The as-prepared hd-CWM preserves the three-dimensional (3D) framework of CWM while introducing abundant carbon defects, leading to a significantly enhanced SSA (913.8 m2 g-1), increased pore volume (0.53 cm3 g-1), and superior electrolyte wettability (0° contact angle in 6 M KOH) compared to pristine CWM. Benefitting from these structural merits, the hd-CWM-based symmetric SC exhibits a remarkably high areal capacitance (Ca) of 1599.8 mF cm-2 at 1.0 mA cm-2, an energy density of 55.5 μWh cm-2 at a power density of 250.0 μW cm-2 within a potential window of 0-1.0 V, and excellent cycling stability with 100% capacitance retention after 10,000 cycles and unit coulombic efficiency at 10 mA cm-2. Notably, the operating potential window of the hd-CWM-SC can be extended to 0-1.3 V, resulting in significantly improved capacitive performance (1990.2 mF cm-2 at 1.0 mA cm-2, 80.3% retention at 50 mA cm-2, 99.8% retention after 5000 cycles, and energy densities of 116.8-93.8 μWh cm-2 at power densities of 325.0-17775.0 μW cm-2). This work offers novel insights into the design and fabrication of self-supporting carbon-based electrodes with high SSA, well-developed porosity, and superior electrolyte wettability for high-performance SCs.