Boosting Electrochemical Degradation of Water Pollutants Using Sulfur-Rich Porous Polyimide-Derived Laser-Induced Graphene Catalytic Membrane

Water pollution is an inevitable concern associated with technological advancement. To address this problem, it is necessary to significantly shorten the manufacturing process of porous materials while enabling effective pollutant removal. Herein, a facile, rapid, and scalable approach is reported to obtain sulfur-doped hierarchically porous laser-induced graphene (S-LIG) as a catalytic membrane with three-dimensional networks by localized laser irradiation, along with possible adsorption and electrochemical degradation mechanisms for pollutant removal. S-LIG is derived from sulfur-containing porous polyimide film which is prepared via thermally induced phase separation followed by stepwise thermal imidization. Methylene blue (MB) adsorption behavior on the S-LIG membrane closely fits the pseudo-second-order and Freundlich isotherm models, suggesting a complex sorption mechanism, including both strong chemical interaction and physical adsorption. Furthermore, S-doping enhances catalytic activity for generating reactive oxygen species (ROS), aiding MB degradation via indirect oxidation, and improves direct oxidation on the anode by accelerating electron transfer at the electrodes. This results in a stable 93% MB degradation at a low 1.5 V after 24 h. Additionally, the impact of solution pH reveals that electrostatic attraction forces under basic conditions and the high generation of ROS under acidic conditions favor adsorption and electrochemical oxidation.