Freezing-Mediated Synthesis and Applications of Porous Metals

Porous metals combine the physicochemical properties of metals and structural features of porous materials, which are characterized as a special class of materials promising in various fields such as tissue engineering, energy storage and conversion, electronics, and sensing. Among diverse fabrication approaches, freezing-mediated synthesis (e.g., freeze-casting and freeze-thawing) stands out due to its strong controllability over meso-to-macroscales as well as environmental friendliness. Many efforts have been made in the past few decades, yielding a library of porous metals featuring different building blocks (feature size and dimension), morphologies, and compositions by identifying and optimizing synthetic parameters. However, a deep understanding of the ice-matter interactions is limited, which becomes more pronounced when the processed system transforms from micrometer to nanometer size. Therefore, an overview and deep analysis for the freezing-mediated fabrication of porous metals are essential. This review first introduces the history of freezing-mediated synthesis of porous metals, followed by the fundamentals of the freezing process and design strategies. Afterward, the freezing-mediated fabrication of porous metals is summarized from the aspect of their building blocks, followed by the application explorations of those special-structure metals. Finally, the challenges and opportunities are concluded to guide future research in designing advanced porous metals by freezing-based approaches.