Boosting photothermal conversion and energy storage in MXene electrodes through softened wood toward solar-enhanced flexible supercapacitor.

With the development of emerging electronics and the increasing emphasis on environmental sustainability, there is a growing interest in flexible supercapacitors enhanced through the renewable solar energy. To address this demand, MXene materials with favorable electrical conductivity and photothermal performances have emerged as a promising option for the ideal electrodes. However, their widespread application has been hindered by issues such as severe self-stacking and limited irradiated area. Herein, a porous MXene flexible electrode capable of overcoming these challenges by incorporating softened wood (SW) is proposed for the first time. The selective removal of hemicellulose/lignin from wood renders SW flexible and exposes abundant oxygen-containing groups, forming a porous framework suitable for MXene loading. The polar attraction between these oxygen-containing groups and the MXene suspension facilitates rapid swelling of the SW. Through hydrogen bonding interactions, MXene nanosheets self-assemble on the SW, creating a continuous 3D conductive network. The 3D porous structure of SW enlarges both the contact area of active materials/electrolytes and the effective irradiated area of MXene/sunlight, improving electrochemical properties and photothermal performance. The flexible symmetric supercapacitor exhibits a significant areal capacitance (2225 mF cm−2), outstanding energy density (26.4 μWh cm−2) and notable solar-driven capacitance enhancement of 36 % within only 40 seconds under 1-solar illumination. This study introduces a novel design concept for eco-friendly flexible energy storage devices by integrating MXene with SW, demonstrating a promising pathway for developing sustainable and effective energy storage solutions. [Display omitted] • A porous MXene flexible electrode enhanced by softened wood is proposed. • Partial removal of hemicellulose/lignin enables wood soft and plenty MXene loading. • 3D structure enhances electrochemistry & photothermal performances of MSW. • The FSC delivers outstanding energy density and solar-enhanced capacitance. [ABSTRACT FROM AUTHOR]