Polystyrene sulfonate (PSS) stabilized polyethylenimine (PEI) membranes fabricated by spray coating for highly effective CO2/N2 separation

Abstract

Greenhouse effect, largely caused by CO2 emission, has become a major concern for global climate change. Post-combustion CO2 capture is one of the critical strategies to mitigate this issue. Membrane technology for carbon capture has drawn significant attention because of the cost and energy efficiency and scalability. Many membranes for CO2 capture are limited by the trade-off between CO2 permeability and CO2/N2 selectivity and the long-term stability under practical operating conditions. Facilitated transport membranes with efficient CO2 carriers have demonstrated potential to surpass the permeability-selectivity trade-off, but these carriers are often lost under operational conditions. Herein, we designed and fabricated a polystyrene sulfonate (PSS) stabilized polyethylenimine (PEI) membrane by a facile and scalable spray-coating method. The deposited defect-free selective layer, in which the amine carriers in PEI can be stabilized electrostatically by PSS, exhibited superior CO2 separation performance with good long-term stability under practical operating conditions. The separation performance was optimized by spray-coating cycles, CNT network loading, and PSS loading. Our membrane showed CO2 permeance ranging from 820 to 1,770 GPU and CO2/N2 selectivity varying from 395 to 460 under vacuum operation mode in the temperature range between 80 and 90 °C. Furthermore, the membrane was successfully scaled up to 200 cm2 with good uniformity. These results might suggest a novel membrane structure and a scalable approach for fabrication of highly efficient CO2 separation membranes.