Associate 2016-17

Rosa Espinosa-Marzal

Civil & Environmental Engineering

Energy Efficiency via Nano-Mosaics

Technologies to store electrical energy generated by renewable energy sources and to produce freshwater from wastewater and seawater rely on the behavior of liquids inside pores of around ten times the diameter of the molecules themselves. The behavior of liquids in such narrow spaces differs from that in the bulk. The confined molecules stick to the wall and arrange in layers. Similar to the magnets sticking on refrigerators, their strong attraction to the surface makes it difficult for the molecules to slide. This commonly labeled “solid-like” behavior of confined liquids has been observed in “model” pores composed of atomically flat and chemically homogeneous surfaces.

The goal of this project is to achieve control over the behavior of the confined molecules by decorating the pore surface either with topographic or with chemical motifs, leading to valleys and peaks in the interaction landscape between the molecules and the confining surfaces. The focus will be on a particular class of liquids called ionic liquids that have been proposed as “designer” electrolyte for energy storage systems where they are confined in the electrode’s nanopores. A high affinity between liquid molecules and pore surface is needed to achieve high values of stored energy, at the cost of serious limitation of molecular mobility and low efficiency.

Two tasks will be carried out: to design an experimental method to study the properties of the fluid nanoconfined between heterogeneous surfaces, and to evaluate new and old data in light of phenomenological models to elucidate the parameters that will increase flow rate while maintaining the affinity to the decorated surface. By correctly tuning these heterogeneities’ mosaics, it should be possible to manipulate the solid-like behavior and to achieve higher efficiencies. This work will also advance the fundamental understanding of the behavior of nanoconfined liquids in “real” (in contrast to “model”) nanopores relevant to many applications.