Dealloyed Air- and Water-Sensitive Nanoporous Metals and Metalloids for Emerging Energy Applications
Jintao Fu, Samuel S. Welborn, Eric Detsi
Abstract
Nanoporous metals and metalloids are a broad class of materials whose fabrication involves the selective removal of one or more sacrificial elements from a parent alloy, also known as dealloying, which produces a bulk, monolithic framework with interconnected nanoscale ligaments and pores. The first reports within this field tended to focus on precious nanoporous metals (e.g., nanoporous gold) to provide an explanation of the fundamental mechanisms that underpin conventional, aqueous solution dealloying. As the community has grown, researchers have begun to explore various nonprecious metal and metalloid elements to expand the application space and versatility of nanoporous metals and metalloids. Air- and water-sensitive elements represent a particularly promising exploration for emerging energy applications; combining their chemical reactivity with the high specific surface area and unique morphology of nanoporous metals could enable significant advances in metal fuels for on-board hydrogen generation, next-generation battery electrodes, (electro)catalysts, and more. However, sensitivity to air and water imposes a significant fabrication barrier: The conventional aqueous solution dealloying approach either cannot create these materials at all or cannot create these materials without simultaneously forming a surface oxide film, which prevents them from being used in the applications mentioned above. To mitigate this issue, the community has developed several unique dealloying strategies involving various electrochemical, liquid metal, and thermal methods. In this review, we present those dealloying strategies and their reaction mechanisms, provide concrete examples of their fabrication and application in energy applications, and analyze their advantages and drawbacks with a focus on recyclability, complexity, and scalability.