Synthesis of rhodium concave tetrahedrons by collectively manipulating the reduction kinetics, facet-selective capping, and surface diffusion.

This paper describes a facile synthesis of Rh tetrahedrons with concave side faces by collectively manipulating the reaction kinetics, facet-selective capping, and surface diffusion of atoms. Specifically, a combination of Na3RhCl6, triethylene glycol, l-ascorbic acid, and citric acid provides the right conditions for generating the concave tetrahedrons. After the formation of small Rh tetrahedral seeds through self-nucleation, the subsequently generated Rh atoms were selectively deposited onto the corner sites to generate Rh tetrapods. At the same time, the deposited atoms could diffuse from the corners to edges to generate concave side faces because the diffusion to face sites was restrained by the citric acid adsorbed on the {111} facets. This study offers deep insight into the growth mechanism involved the formation of noble-metal nanocrystals with concave surfaces. The Rh concave tetrahedrons were encased by a mix of {111} and {110} facets, showing great potential for catalytic applications.