Bicontinuous Nanoporous Metals with Self-Organized Functionalities

The functional applications of bicontinuous nanoporous metals have been rapidly growing along with the fabrication methods of the materials. Besides the most common routes of electrochemical dealloying, liquid-metal dealloying, vapor-phase dealloying, and reduction-induced decomposition, all via similar mechanisms of interface-controlled self-organization have created a broad range of nanoporous structures made of noble metals (e.g., Au and Pt), refractory metals (e.g., Ti and Ta), and reactive metals (e.g., Al and Zn). They in turn enable new applications in catalysis, sensing, actuation, and electrochemical energy storage. Underlying the burgeoning development is the close connection between the functionalities and the structural evolution mechanism. In this perspective, I will dissect the structural complexity of bicontinuous nanoporous metal into three key features: the bicontinuity, the small length scale, and the compositional heterogeneity. I will discuss their roots in the self-organization process and their ties to properties such as mechanical strength, conductivity, and catalytic activity. The analysis will be centered around two aspects of the dealloying theory, namely, percolation and surface diffusion, showing how they can be applied to quantitatively understand the self-organized functionalities. In the end, I will also highlight emerging opportunities for structural designs to further advance the functional applications of the materials.