Engineering Self-Supported Noble Metal Foams Toward Electrocatalysis and Beyond

Noble metals, despite their expensiveness, display irreplaceable roles in widespread fields. To acquire novel physicochemical properties and boost the performance-to-price ratio for practical applications, one core direction is to engineer noble metals into nanostructured porous networks. Noble metal foams (NMFs), featuring self-supported, 3D interconnected networks structured from noble-metal-based building blocks, have drawn tremendous attention in the last two decades. Inheriting structural traits of foams and physicochemical properties of noble metals, NMFs showcase a variety of interesting properties and impressive prospect in diverse fields, including electrocatalysis, heterogeneous catalysis, surface-enhanced Raman scattering, sensing and actuation, etc. A number of NMFs have been created and versatile synthetic approaches have been developed. However, because of the innate limitation of specific methods and the insufficient understanding of formation mechanisms, flexible manipulation of compositions, structures, and corresponding properties of NMFs are still challenging. Thus, the correlations between composition/structure and properties are seldom established, retarding material design/optimization for specific applications. This review is devoted to a comprehensive introduction of NMFs ranging from synthesis to applications, with an emphasis on electrocatalysis. Challenges and opportunities are also included to guide possible research directions in this field and promote the interest of interdisciplinary scientists.