Freeze-Thaw-Promoted Fabrication of Clean and Hierarchically-Structured Noble Metal Gels for Electrocatalysis and Photoelectrocatalysis.

Appearing as a new class of porous materials, noble metal aerogels (NMAs) have drawn tremendous attention because of their combined features including self-supported architectures, high surface areas, and numerous optically/catalytically active sites, enabling their impressive performance in diverse fields. However, the fabrication methods often suffer from tedious procedures, long preparation times, various unavoidable impurities, and uncontrolled multiscale structures, discouraging fundamental and application oriented studies. Here, by utilizing the long-term reactivity of the noble metal aggregates, the freezing-promoted salting-out behavior, and the ice-templating, a freeze-thaw method is developed capable of preparing various hierarchically structured noble metal gels within only one day directly from dilute solutions without extra additives. In light of the cleanliness, the multi-scale structures, as well as the combined catalytic/optical properties of the obtained aerogels, the intrinsic and exceptional electrocatalytic and photoelectrocatalytic performance of NMAs are accordingly demonstrated surpassing those of commercial noble metal catalysts.