"Dual-Template"-Directed Synthesis of Bowl-Shaped Mesoporous Platinum Nanostructures

Asymmetric bowl-shaped metals make up an important class of nanostructured materials that exhibit great potentials in catalysis, energy storage, and biomedical applications. Introducing the mesopores within the framework of bowl-shaped metals would further increase the surface area and thus increase the utilization efficiency of metals and the availability of the (electro)catalytically active sites. In this work, a one-pot surfactant-templated aqueous synthesis is developed to fabricate nanosized asymmetric platinum (Pt) bowl-shaped mesoporous nanospheres (BMSs) with good purity and uniformity. Amphiphilic dioctadecyldimethylammonium chloride acts as the "dual-template" surfactant that drives the anisotropic nucleation and growth of mesoporous Pt islands with cylinder micelles along the curved surface of the vesicles, resulting in the formation of the Pt BMSs with a bowl-shaped morphology and mesoporous structure. The diameter of the Pt BMSs can also be tailored by changing the reduction kinetics during the synthesis. More interestingly, the BMSs are able to interconnect into a more sophisticated structure of one-dimensional nanochains by increasing the K₂PtCl₄ amount added. This novel synthetic protocol brings a higher hierarchy into asymmetric bowl-shaped metals, rendering the metal BMSs with more accessible (electro)catalytically active sites. Because of the unique morphology and structure, the Pt BMSs show enhanced electrocatalytic activity and stability toward the hydrogen evolution reaction with respect to a commercial Pt/C catalyst.