Atmospheric Condensation Performance of Plain Copper and Graphene Oxide Coated Copper Surfaces

Atmospheric condensation is important for multiple practical applications such as distillation/desalination of water, aerospace, dehumidification, and water harvesting etc. Graphene, an allotrope of carbon with two dimensional structure, has excellent thermal and electrical properties. Here we present condensation studies of water on plain copper and graphene oxide (GO) coated copper surface with different environmental conditions to explore the size distribution of the generated droplets and area coverage in order to characterize the surfaces for larger condensate harvesting. Later, droplet growth and size distributions were recorded for 41 minutes 20 seconds on the surfaces at 40% and 60% relative humidities with a surface temperature of 278 ± 0.5 K. The chamber was maintained at atmospheric pressure and 295 ± 0.5 K. The samples were observed via optical microscopy and videos of the condensation dynamics were captured. The droplet grew mainly by direct condensation and coalescence event. At later stages of condensation, surface coverage increased significantly compared to early stages for all the considered cases. Approximate 95% surface coverage was observed for GO coated copper surface which provides a great insight of this substrates for implementing it in the desired water harvesting applications. The pinning of droplets into the micro/nanostructures of the coated surfaces leads enough time for the first generation droplets to grow in larger size and made more preferential for subsequent coalescence events. Within the initial period of condensation, the number of droplets reduced according to power law decay. The contribution of coalescence mechanism in droplet growth was found larger for 60% RH than 40% RH. As droplet grew larger, direct growth became less significant compared to coalescence phenomenon.