Monolithic Nanoporous Gold Foams with Catalytic Activity for Chemical Vapor Deposition Growth of Carbon Nanostructures

Abstract

While bulk gold is generally considered to be a catalytically inactive material, nanostructured forms of gold can in fact be highly catalytically active. However, few methods exist for preparing high-purity macroscopic forms of catalytically active gold. In this work, we describe the synthesis of catalytically active macroscopic nanoporous gold foams via combustion synthesis of gold bis­(tetrazolato)­amine complexes. The resulting metallically pure porous gold nanoarchitectures exhibit bulk densities of <0.1 g/cm3 and Brunauer–Emmett–Teller (BET) surface areas as high as 10.9 m2/g, making them among the lowest-density and highest-surface-area monolithic forms of gold produced to date. Thanks to the presence of a highly nanostructured gold surface, such gold nanofoams have also been found to be highly catalytically active toward thermal chemical vapor deposition (CVD) growth of carbon nanotubes, providing a novel method for direct synthesis of carbon nanostructures on macroscopic gold substrates. In contrast, analogous copper nanofoams were found to be catalytically inactive toward the growth of graphitic nanostructures under the same synthesis conditions, highlighting the unusually high catalytic propensity of this form factor of gold. The combustion synthesis process described herein represents a never-wet approach for directly synthesizing macroscopic catalytically active gold. Unlike sol–gel and dealloying approaches, combustion synthesis eliminates the time-consuming diffusion-mediated steps associated with previous methods and offers multiple degrees of freedom for tuning morphology, electrical conductivity, and mechanical properties.

Integrating Highly Porous and Flexible Au Hydrogels with Soft-MEMS Technologies for High-Performance Wearable Biosensing

“…This suggests a hierarchical porous structure of the Au gels, which is in good accordance with the scanning electron microscope (SEM) image (Figure G). Additionally, the specific surface area is determined to be 63.6 m 2 g –1 , which is much larger than those of other porous Au materials …”

“…Additionally, the specific surface area is determined to be 63.6 m 2 g −1 , which is much larger than those of other porous Au materials. 34 It is well reported that noble metal aero-/hydrogels including Au showed excellent electrocatalytic activities toward small molecules. 16 This is because such gels are endowed with a metallic backbone to enable rapid electron transfer, large surface area to provide more reactivity, and high porosity to facilitate the bio-recognition immobilization and accelerate mass transfer.…”

Versatile Synthesis of Nanofoams through Femtosecond Pulsed Laser Deposition

“…For all these reasons, a single technique able to produce nanofoams with controlled properties, and different materials, is of certain interest. Various techniques have been employed for the synthesis of nanofoams, each one being usually suited for specific combinations of elements, morphologies, and average density ranges: chemical vapor deposition (CVD), [27][28][29] thermal evaporation for metallic foams, [30] sol-gel method for silica nanofoams, [31] CO 2 foaming processes [32] for polymer nanofoams, and aerosolassisted chemical vapor deposition for ceramic nanofoams. [33] Among these methods, pulsed laser deposition (PLD) stands out as a versatile and promising tool for nanofoam synthesis.…”

Homogenous high enhancement surface-enhanced Raman scattering (SERS) substrates by simple hierarchical tuning of gold nanofoams

“…Compared with other anisotropic nanomaterials, applications of nanofoams have lagged, in part due to their synthetic and structural complexity compared to particle formulations. Nanofoams are porous nanomaterials typically created from copper [ 8 ], silver [ 9 ], or gold [ 10 , 11 ]. They are most commonly fabricated by chemical etching of biphasic mixtures of metals in the presence of strong acids that de-alloy the sample, leaving behind a porous phase [ 12 ].…”