Palladium (Pd) nanoparticles enclosed by high-energy facets have displayed superior catalytic properties over that of their low-indexed counterparts. However, current methods of the synthesis are neither scalable nor cost-effective. In this study, we report a simple silver-assisted seed-mediated protocol to yield monodisperse palladium tetrahexahedral (THH) nanoparticles enclosed by the high-energy {730} facets. Additionally, their structural variants, truncated and stellated Pd THHs, with tunable size and sharpness have been synthesized. We show that introducing silver ions in the growth solution plays a key role in the growth of the nanoparticles. On the basis of kinetic studies, we find that the basis for the formation of these open structures is the underpotential deposition of Ag that stabilizes these high-energy surfaces and the overall mechanism of the growth is proposed. This study establishes a synthetic procedure that is scalable and is both chemically and economically more accessible than the existing protocols for Pd THH nanoparticles, making it possible for much wider applications of the Pd THH nanoparticles and its variants. Finally, these particles displayed higher electrocatalytic activity for ethanol oxidation reaction compared to low-indexed faceted Pd nanoparticles and commercially available Pd catalysts.