An energy-efficient method inspired by nutrient transport during the growth of tree to prepare free-standing wood/MXene electrodes

Abstract

Wood has been increasingly used as free-standing electrodes for supercapacitors, but the urgent issues in common preparation are high energy consumption and long duration, especially destruction of wood structure, greatly limiting further development. Abundant meso−/macropores and O-containing functional groups in wood can facilitate nutrient transport by capillarity and transpiration effects. Inspired by this phenomenon, this work innovatively develops a modified energy-efficient method using Ti3C2Tx (a typical MXene) droplets to prepare free-standing wood/Ti3C2Tx (WT) electrodes. Ti3C2Tx, with ultra-high conductivity and good electrochemical activity is loaded into wood to compensate for the electrical isolation of wood and contribute large capacitance. The pores in wood not only act as capillary tubes to transport Ti3C2Tx and provide loading space for compositing abundant Ti3C2Tx, but also serve as routes for rapid ion transport during charging-discharging process. The heating panel is applied to ensure continuous absorption of Ti3C2Tx by bringing in transpiration effect by fast evaporating water and reaching unsaturated state of wood. Resultantly, an all-wood supercapacitor assembled by two WTs electrodes and one wood separator exhibits good specific capacitance (623 mF cm−2 at 0.5 mA cm−2), high rate capability (80% at 20 mA cm−2), and large energy density (15.11 μWh cm−2 at 11.70 μW cm−2).