Ultrathin samarium-doped palladium nanocrystals with exotic shapes for efficient electrocatalytic ethanol oxidation

We report the fabrication of PdSm bimetallic nanocrystals with controlled shapes and explore their applications as the electrocatalysts for electroxidation of ethanol (EOR) in alkaline medium. The success of current synthesis relies on the co-reduction of Pd(acac) 2 and Sm(acac) 3 in the presence of N-oleyl-1,3-propanediamine (OPDA) and Mo(CO) 6 at an elevated temperature. For the first time, ultrathin nanostructures composed of Pd-rare earth metal bimetals could be prepared in high purity, in the form of ultrathin porous nanosheets and concave tetrahedra, together with the size/edge length limited to sub-3 nm size range. When serving as electrocatalysts for EOR, the carbon-supported PdSm nanocrystals exhibited in seven-fold increase in mass activity as compared to that of Pt/C, as well as improved reaction kinetics and long-term durability. DFT calculations verify that the PdSm NCs/C catalyst modulate the reaction pathway of ethanol oxidation with lower energy barriers as compared with Pd catalyst, accounting for the improved catalytic performance. The present study provides a feasible strategy to create rare earth metal-doped bimetallic nanocrystals with controlled morphology for rational design over fuel cell catalysts and could be extended to other noble metals or alloys.