Construction of bidirectional mass transfer channel of radial section wood electrode and application of supercapacitor

The natural low-curvature porous structure of wood, characterized by its cell cavities, creates channels and spaces conducive to the transport of electrolyte ions and the accommodation of guest materials. This property positions wood as a promising substrate for the development of self-supporting electrodes. However, the densely packed wood fibers on the surface of the radial section impede the infiltration of functional guest materials and the transport of electrolyte ions. To address this limitation, a bidirectional mass transfer channel was created in the radial section of the wood through laser drilling, providing a structural foundation for achieving a uniform and high loading mass of TiCT. Ultimately, a wood/TiCT (DWT) self-supporting electrode was developed, exhibiting high mechanical strength and favorable electrochemical performance.

Using radial section wood as the substrate, a laser engraving machine was employed to drill holes in the radial section wood (1 cm × 1 cm × 0.1 cm) according to the design specifications (DW-x×x, where x denotes the number of holes). The wood-based electrode (DWT) was then obtained by loading TiCT onto the wood using a heat-drop coating method. The impact of laser drilling on the loading of TiCT in the wood was assessed by observing the changes in the micromorphology of the wood-based electrode before and after laser drilling. Additionally, the tensile properties of the samples were tested to analyze the effects of laser drilling on the mechanical properties of the wood, and the underlying mechanisms influencing the electrochemical properties of the DWT were elucidated.

Scanning electron microscopy (SEM) images demonstrate that the additional channels created by laser drilling penetrate the wood vertically and connect with some of the natural lateral channels. These bidirectional channels facilitate the entry of TiCT into the wood and its diffusion through the lateral channels, thereby achieving a uniform loading of 5 mg·cm of TiCT and preventing the accumulation of TiCT nanosheets on the surface of the radial section. Mechanical property tests indicate that the tensile strength of DW-5×5 (8 MPa) is slightly lower than that of DW-0×0 (11 MPa) after laser drilling. However, this value remains significantly higher than that of cross section wood (0.4 MPa). Electrochemical tests reveal that as the number of drilled holes increases, the area of the cyclic voltammetry (CV) curve for DWT gradually increases, with DWT-5×5 exhibiting the largest CV area among all samples. Calculation shows that the specific capacitance of DWT-5×5 reaches 1265 mF·cm at a current density of 0.2 mA·cm, which is 80% higher than that of DWT-0×0. When the current density is increased by 100 times, the DWT-5×5 electrode retains a high capacitance of 74.4%.Conclusions: A bidirectional mass transfer channel was created in the radial section of the wood through laser drilling. Although the mechanical strength of the radial section wood decreased following the drilling process, the tensile strength of DW-5×5 (8 MPa) remained significantly higher than that of cross-section wood (0.4 MPa). The construction of the bidirectional channel effectively prevents the accumulation of TiCT on the surface of the radial section, achieving a uniform loading of 5 mg·cm of TiCT. This configuration allows more active sites on the TiCT surface to interact with electrolyte ions, thereby enhancing energy storage capabilities. Additionally, the pores created by laser drilling facilitate the rapid transfer of electrolyte ions within the electrode. As a result of these improvements, the specific capacitance of DWT-5×5 after laser drilling increased by 80% compared to DWT-0×0, reaching 1265 mF·cm, and it demonstrated a high capacitance retention of 74.4% when the current density was increased by 100 times. Furthermore, the specific capacitance and rate capability of this wood-based electrode can be further enhanced by improving its electrical conductivity and creating additional active sites on the electrode surface through carbonization.