Stepwise synthesis of “Pt-on-PdAg” hybrid trigonal/hexagonal nanocrystals for efficient electroxidation of methanol: Interface engineering for trimetallic electrocatalyst

Abstract

We report the fabrication of “Pt-on-PdAg” heterogeneous nanocrystals in the form of trigonal/hexagonal plate (THNPs) and explored their applications in electroxidation of methanol (MOR) in alkaline medium. In particular, PdAg polyhedral nanoparticles are prepared in advance, followed by the addition of Pt salts to allow in situ galvanic replacement reaction (GRR) between them, leading to the formation of Pt nano-islands on PdAg particle surface and the transformation of the overall morphology into trigon/hexagon. The deliberately designed Pt-“PdAg alloy” interface arising from the hybrid structure greatly enriches the absorption sites, showing noticeable structural advantages in MOR electrocatalysis. Particularly, the carbon-supported Pt-on-PdAg THNPs exhibit nearly 30-fold increase in specific activity as compared to that of commercial Pt/C, as well as enhanced reaction kinetics and long-term durability. DFT calculations suggest that the reaction of CH 3 OH oxidation mediated by PtAgPd is energetically more favorable compared to the similar reaction promoted by Pt, which rationalizes the experimental observation that PtAgPd shows the improved catalytic performance. The present study offers a feasible route to construct trimetallic nanocrystals with successful interface engineering, and validates their promising use as fuel cell electrocatalyst from both experimental validation and fundamental insights. It may help enlighten the rational design of heterostructured electrocatalysts with regulated multiple active sites. • Stepwise synthesis of trigonal/hexagonal plate-like Pt-on-PdAg hybrid nanostructures is proved. • The density of Pt nano-islands and the overall elemental composition can be tuned. • Interface engineering, tensile strain and multimetallic synergy, contribute to enhanced MOR. • DFT calculations show that MOR mediated by PtAgPd is energetically more favorable.