Freeze-Casting Mold-Based Scalable Synthesis of Directional Graphene Aerogels with Long-Range Pore Alignment for Energy Applications

In various applications, the pore structure of a porous medium must be controlled to facilitate heat and mass transfer, which considerably influence the system performance. Freeze-casting is a versatile technique for creating aligned pores; However, because of the complexity of the associated equipment and the energy inefficiency of liquid-nitrogen-based cooling in a room-temperature environment, limits scalability for industrial applications. This study is aimed at establishing a novel freeze-casting strategy with a simple mold design combining heat-conductive and insulating materials for long-range pore alignment via directional ice growth under deep-freezing conditions, rendering it feasible for large-scale production. Using this technique, axially aligned (Axial-GA) is developed, radially aligned (Radial-GA), and randomly distributed (Random-GA) pore structures within NaBr-impregnated graphene aerogel (GA-NaBr) configurations, demonstrating enhanced ammonia adsorption for thermal energy management. The pore structure exerted notable effects on the ammonia adsorption behavior, with Radial-GA exhibiting a higher adsorption rate due to reduced ammonia transit distance. The Radial-GA-NaBr structure demonstrated unique adsorption characteristics, retaining ≈85% of the adsorption capacity and achieving a ≈270% adsorption rate gain compared with pure NaBr powder. Overall, this research demonstrates the fabrication of aerogels with various configurations and orientations using facile and scalable methods, thereby expanding their industrial applications.