Methods to Generate Structurally Hierarchical Architectures in Nanoporous Coinage Metals

The fundamental essence of material design towards creating functional materials lies in bringing together the competing aspects of a large specific surface area and rapid transport pathways. The generation of structural hierarchy on distinct and well-defined length scales has successfully solved many problems in porous materials. Important applications of these hierarchical materials in the fields of catalysis and electrochemistry are briefly discussed. This review summarizes the recent advances in the strategies to create a hierarchical bicontinuous morphology in porous metals, focusing mainly on the hierarchical architectures in nanoporous gold. Starting from the traditional dealloying method and subsequently moving to other non-traditional top-down and bottom-up manufacturing processes including templating, 3D printing, and electrodeposition, this review will thoroughly examine the chemistry of creating hierarchical nanoporous gold and other coinage metals. Finally, we conclude with a discussion about the future opportunities for the advancement in the methodologies to create bimodal structures with enhanced sensitivity