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

Abstract

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 approximate to 85% of the adsorption capacity and achieving a approximate to 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. This publication unveils a Simple Freeze-Casting Mold-Based scalable synthesis method utilizing deep freeze-based cooling. The approach is demonstrated in fabricating aerogels with controlled pore structure and long-range alignment, and holds promise for revolutionizing the research field, requiring significant heat and mass transfer, such as thermal energy management systems, secondary batteries, and environmental remediation. image