CO₂ wetting on pillar-nanostructured substrates

CO₂ capture by dropwise CO₂ condensation on cold solid surfaces is a promising technology. Understanding the role of the nanoscale surface and topographical features of CO₂ droplet wetting characteristics is of importance for CO₂ capture by this technology, but this remains unexplored as of yet. Here, using large-scale molecular dynamics (MD) simulations, the contact angle and wetting behaviors of CO₂ droplets on pillar-structured Cu-like surfaces are investigated for the first time. Dynamic wetting simulations show that, by changing the strength of the solid-liquid attraction [Formula: see text] a smooth Cu-like surface offers a transition from CO₂-philic to CO₂-phobic. By periodically pillared roughening of the Cu-like surfaces, however, a higher contact angle and a smaller spreading exponent of a liquid CO₂ droplet are realized. Particularly, a critical crossover of CO₂-philic to CO₂-phobic can appear. The wetting of the pillared surfaces by a liquid CO₂ droplet proceeds non-uniformly. A liquid CO₂ droplet is capable of exhibiting a transition from the Cassie state to the Wenzel state with increasing [Formula: see text] increasing inter-pillar distance, and increasing pillar width. The wetting morphologies of the metastable Wenzel state of a CO₂ droplet are very different from each other. The findings will inform the ongoing design of CO₂-phobic solid surfaces for practical dropwise condensation-based CO₂ capture applications.