Synergistic enhancement of CO2 capture in Li4SiO4 via Cu, K co-doping and cigarette butt-templated porosity: Synthesis, performance, and mechanistic insights

The escalating CO 2 concentration in the atmosphere underscores the critical need for efficient CO 2 capture technologies. While lithium orthosilicate (Li 4 SiO 4 ) represents a promising high-temperature CO 2 sorbent due to the high theoretical capacity and cycling stability, its practical application is hindered by dense microstructure and slow reaction kinetics. In this study, a sustainable and low-cost cigarette butt-assisted combustion strategy was developed to fabricate porous Li 4 SiO 4 -based sorbents. Waste cigarette butts serve as sacrificial templates, improving the porous structure and specific surface area of Li 4 SiO 4 , which significantly facilitates CO 2 diffusion. Notably, unprecedented modification methods involving Cu doping and Cu, K co-doping were developed, which substantially enhanced both CO 2 sorption capacity and cyclic stability. Thermodynamic analyses indicated that metal doping reduced the equilibrium temperature. Kinetic modeling revealed that co-doping accelerated the reaction rate in the chemical-controlled stage and reduced the apparent activation energy. Density functional theory (DFT) calculations further corroborated that doping strengthened the interaction between CO 2 and Li 4 SiO 4 surface, generating more stable sorption configuration and lower sorption energy. This work not only demonstrates a novel synthesis route for high-performance Li 4 SiO 4 , but also reveals the performance enhancement mechanisms of metal doping from the macro level to the micro level, offering valuable guidance for the rational design and theoretical analysis of advanced CO 2 capture materials.