Lignin-derived S-doped carbon-Ti_yO_x surface for electromagnetic wave shielding and wastewater remediation

Biomass-derived carbon materials, characterized by diverse surface functional groups and porous or hierarchical structures, are increasingly utilized for environmental pollution control. In this study, a one-step laser processing technique was applied to create a carbon-based composite directly on a polycarbonate (PC) substrate from a lignin-TiO₂/PVA film. This process resulted in a uniform porous structure, which incorporated S doping and Ti in various states (Ti⁴⁺, Ti³⁺, Ti²⁺, and Ti⁰). The material, named S-C-Ti_yO_x, demonstrated significant potential for electromagnetic wave shielding in the X-band. The S-C-Ti_yO_x layer effectively reflected most electromagnetic waves through its conductive carbon composition, while the porous structure absorbed the remaining waves. A total shielding effectiveness (SE_T) of 42.9 dB was achieved at 11 GHz with a three-layer configuration. Notably, the reflection effectiveness (SE_R) was consistently lower than the absorption effectiveness (SE_A) across the frequency range. Additionally, the S-C-Ti_yO_x layer represented remarkable activity for the catalytic reduction of methylene blue (MB) and potassium ferricyanide (K₃[Fe(CN)₆]) using NaBH₄, which was completed in 40 s and 5 min, respectively. These results demonstrate a fast, efficient synthesis method for designing carbon-based composites that can simultaneously address environmental pollution control and electromagnetic shielding needs.