Polyethyleneimine Intercalated into Alkyl Layer for Superhydrophobic Interface: Low-Energy and O2 & H2O-resistant CO2 Sorbent

The major challenge that solid amine sorbents face in practical large-scale applications is their susceptibility to degradation under humid and oxygen-containing conditions. This study developed a superhydrophobic alkyl-silica by co-hydrolyzing alkyl-silane and tetraethyl orthosilicate and then immobilizing polyethyleneimine as a CO2 sorbent. By adjusting the chain length and density, the surface of the alkyl-silica has abundant alkyl chains, and the PEI molecules are intercalated into the surface alkyl layer. These alkyl chains effectively block the contact of O2 and H2O with the amine group, thereby selectively allowing the adsorption/desorption of CO2 molecules through the alkyl layer. The results showed that the working capacity of PEI/alkyl-silica was maintained at 86% by oxidation treatment and 85% by rinsing treatment, respectively, exhibiting excellent stability compared to unprotected PEI/SiO2. Meanwhile, the alkyl chain due to the steric hindrance effect weakens the interaction between CO2 and amine and does not reduce its original working capacity. The energy consumption of PEI/alkyl-silica during regeneration was lowered to 1.24 GJ·t-1-CO2. This interfacial building concept provides a new path for designing a long-term stable amine sorbent for cost-effective CO2 capture by avoiding the contact of O2 and H2O with the amine.