Controlled synthesis of noble metal aerogels mediated by salts.

Abstract

Noble metal aerogels (NMAs) are typically assembled from metal nanoparticles, thus combining the physicochemical properties of nanostructured metals with the self-standing porous architecture of aerogels. NMAs therefore have potential in catalysis, sensing and other applications where the controlled manipulation of their structure and composition facilitates their use in fundamental and applied sciences. However, their preparation remains challenging due to the particular gelation behavior displayed by metal systems. Here we detail the step-by-step instructions for the controlled synthesis of NMAs using salts, including reductive sodium borohydride and common salts such as sodium chloride. This strategy can rapidly synthesize NMAs with customizable ligament sizes (from <5 nm to >100 nm) and element distribution at room temperature (20-25 °C). The key stage of the approach is the control over the anisotropic assembly behavior of metal nanoparticles by tuning their interactions with ions/ligands. The synthesis conditions and procedures are elaborated to ensure reproducibility. We demonstrate the fabrication of seven single-component NMAs and over ten multicomponent NMAs, along with their corresponding characterizations and electrocatalytic applications. The fabrication period of noble metal hydrogels is 7-15 h, which can be shortened to a few minutes by introducing disturbances such as stirring. The subsequent purification time is ~48 h, the solvent exchange time is ~16 h and the drying time is 12-24 h. The total duration is 4-5 d. The procedure is suitable for users with expertise in chemistry, materials science and other related disciplines.