Electrospun Poly(vinyl alcohol)-l-Arginine Nanofiber Composites for Direct Air Capture of CO₂

The low concentration of CO₂ in the atmosphere makes its capture (i.e., direct air capture or DAC) challenging. By incorporating the amino acid l-arginine (l-Arg) into a poly(vinyl alcohol) (PVA) nanofiber support structure, we created porous substrates with very high surface areas of l-Arg available for CO₂ sorption. The bio-inspired PVA-Arg nanofiber composites are flexible and show excellent DAC performance compared to that of bulk l-Arg. The nanofiber composites are fabricated from an electrospinning process using an aqueous polymer solution. After obtaining the nanofiber mats, they are physically cross-linked to improve resistance to water. Increasing l-Arg loading to 50 wt % (with respect to PVA) improves sorption performance; however, loadings above 50 wt % decrease the performance due to a reduction in porosity of the nanofiber composite. High ambient humidity levels improve sorption performance significantly. The best performing nanofiber composite collected 542 μmol of CO₂ per gram of the composite during 2 h of exposure to ambient, high-humidity (100% RH) air that had a CO₂ concentration of 400-450 ppm.