Interplay of topography, wettability, and confinement controls boiling of water over functionalized graphene interfaces

Abstract

Functionalized graphene offers tunable properties that can enhance energy efficiency in applications like heat exchangers and power generation. At the nanoscale, graphene's features may lower the energy barrier for bubble nucleation, improving heat transfer by facilitating frequent bubble formation at lower superheat. However, the interplay between nanoconfinement, surface features, temperature, and wettability is complex, influencing bubble dynamics non-trivially. We use molecular simulations to explore the boiling dynamics of water on pristine and defective graphene surfaces within confined spaces. We investigate the effects of varying substrate temperatures and wettability conditions by confining water between graphene sheets with different topographical features. On wetting surfaces, cavity features yield the highest heat transfer rates, followed by surfaces with protrusions and pristine graphene. In contrast, non-wetting surfaces exhibit a more complex relationship between surface features, wettability, and confinement. Our findings highlight the crucial role of wettability and topology in boiling on a realistic graphene surface, which is rarely atomically smooth. This offers new insights into nanoscale thermal management and energy transfer. The results suggest that functionalized graphene can be tailored to optimize heat transfer efficiency, providing a promising approach for enhancing energy efficiency in thermal systems without even having precise control over the nanoscopic architecture. By understanding these mechanisms, we can develop more effective strategies for thermal energy management using graphene-based technologies.