CO wetting on pillar-nanostructured substrates.

CO capture by dropwise CO condensation on cold solid surfaces is a promising technology. Understanding the role of the nanoscale surface and topographical features of CO droplet wetting characteristics is of importance for CO 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 CO 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 CO-philic to CO-phobic. By periodically pillared roughening of the Cu-like surfaces, however, a higher contact angle and a smaller spreading exponent of a liquid CO droplet are realized. Particularly, a critical crossover of CO-philic to CO-phobic can appear. The wetting of the pillared surfaces by a liquid CO droplet proceeds non-uniformly. A liquid CO 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 CO droplet are very different from each other. The findings will inform the ongoing design of CO-phobic solid surfaces for practical dropwise condensation-based CO capture applications.