Low-cost activated carbons were prepared from waste polyurethane foam by physical activation with CO₂ for the first time and chemical activation with Ca(OH)₂, NaOH, or KOH. The activation conditions were optimized to produce microporous carbons with high CO₂ adsorption capacity and CO₂/N₂ selectivity. The sample prepared by physical activation showed CO₂/N₂ selectivity of up to 24, much higher than that of chemical activation. This is mainly due to the narrower microporosity and the rich N content produced during the physical activation process. However, physical activation samples showed inferior textural properties compared to chemical activation samples and led to a lower CO₂ uptake of 3.37 mmol·g⁻¹ at 273 K. Porous carbons obtained by chemical activation showed a high CO₂ uptake of 5.85 mmol·g⁻¹ at 273 K, comparable to the optimum activated carbon materials prepared from other wastes. This is mainly attributed to large volumes of ultra-micropores (<1 nm) up to 0.212 cm³·g⁻¹ and a high surface area of 1360 m²·g⁻¹. Furthermore, in consideration of the presence of fewer contaminants, lower weight losses of physical activation samples, and the excellent recyclability of both physical- and chemical-activated samples, the waste polyurethane foam-based carbon materials exhibited potential application prospects in CO₂ capture.

Polyurethane foam is a typical commercial polymer with a large production quantity and its waste needs to be recycled. This work reports a facile method to prepare ultra-microporous carbon from the polyurethane foam (PUF) waste and use it as a reservoir to impregnate sulfur for Li-S batteries. The raw PUF was carbonized and then activated with KOH. By controlling the activation temperatures, four carbon materials (PUFC-T) with different textures and N-doping levels were obtained. PUFC-800 shows the highest BET surface area, microporous volume, and quaternary N and pyridine N-oxide species. The electrochemical test results showed that higher microporous volume is beneficial to increase the uniform distribution of sulfur, as a result, the cycle stability and rate capacity is improved significantly. A large reversible capacity of 542 mAh g-1 can be retained at a large current of 0.5 C after 200 cycles with high sulfur loading of 70%.