Shape Transformation of Ternary PtIrPd Nanocrystals with High-Index Facets via Electrodeposition and Study of Their Catalytic Activity in Alcohol Oxidation Reactions

The catalytic activities of Pt-based nanomaterials strongly depend on their structures, including their compositions, arrangements of surface atoms, and so on. Shape-controlled synthesis has proven to be an efficient route to adjust the surface structure, while alloying has been considered an effective strategy to tune the electronic structure. The former could enhance the catalytic activity by increasing the number of active sites, while the latter could promote intrinsic activity. Previous studies have shown that alloying Pt with Pd can efficiently improve the catalytic activity, while the introduction of Ir can facilitate stability. Therefore, in order to exploit the advantages of both Pd and Ir, we aimed to prepare ternary PtIrPd nanocrystals with a high-index facet structure to further promote the catalytic performance. Herein, we have synthesized PtIrPd trioctahedral (TOH) nanocrystals (NCs) with high-index (441) facets by the electrochemical square wave potential (SWP) method. Hexoctahedral (HOH) NCs with (431) facets were obtained by simply increasing the growth time ( T g ) of the SWP, while tetrahexahedral (THH) NCs enclosed with (210) facets were prepared by raising the upper limit potential ( E U ) of the SWP. The success of the shape-controlled synthesis of these well-defined nanoparticles is mainly due to the periodic adsorption/desorption of oxygen species and crystal growth dynamics. The as-prepared ternary PtIrPd NCs exhibited good catalytic performance for the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Among them, the electrocatalytic activity of PtIrPd THH NCs was 8.6 and 11.0 times greater than that of commercial Pt/C for the MOR and EOR, respectively. Density functional theory (DFT) simulations showed that the introduction of Ir would lead to a downshift of the d -band center and reduce the reaction energy barrier for the conversion of CHOH* to COH*, which made PtIrPd THH NCs exhibit enhanced electrocatalytic activity and stability.