Pd-Sb Rhombohedra with an Unconventional Rhombohedral Phase as a Trifunctional Electrocatalyst.

Crystal phase engineering is an important strategy for designing noble-metal-based catalysts with optimized activity and stability. From the thermodynamic point of view, it remains a great challenge to synthesize unconventional phases of noble metals. Here, a new class of Pd-based nanostructure with unconventional rhombohedral Pd 20 Sb 7 phase is successfully synthesized. Benefiting from the high proportion of the unique exposed Pd 20 Sb 7 (003) surface, Pd 20 Sb 7 rhombohedra display much enhanced ethanol oxidation reaction (EOR) and oxygen reduction reaction performance compared with commercial Pd/C. Moreover, Pd 20 Sb 7 rhombohedra are also demonstrated as an effective air cathode in non-aqueous Li-air batteries with an overpotential of only 0.24 V. Density functional theory calculations reveal that the unique exposed facets of Pd 20 Sb 7 rhombohedra can not only reduce the excessive adsorption of CH 3 CO* to CH 3 COOH on Pd for promoting EOR process, but also weaken CO binding and CO poisoning. This work provides a new class of unconventional intermetallic nanomaterials with enhanced electrocatalytic activity.